Add LLVM libcxxabi (#1063)

* third_party: Add libcxxabi

Added libcxxabi from LLVM 17.0.6
The library implements the Itanium C++ exception handling ABI.

* third_party/libcxxabi: Enable __cxa_thread_atexit

Enable `__cxa_thread_atexit` from libcxxabi.
`__cxa_thread_atexit_impl` is still implemented by the cosmo libc.
The original `__cxa_thread_atexit` has been removed.

* third_party/libcxx: Build with exceptions

Build libcxx with exceptions enabled.

- Removed `_LIBCPP_NO_EXCEPTIONS` from `__config`.
- Switched the exception implementation to `libcxxabi`. These two files
are taken from the same `libcxx` version as mentioned in `README.cosmo`.
- Removed `new_handler_fallback` in favor of `libcxxabi` implementation.
- Enable `-fexceptions` and `-frtti` for `libcxx`.
- Removed `THIRD_PARTY_LIBCXX` dependency from `libcxxabi` and
`libunwind`. These libraries do not use any runtime `libcxx` functions,
just headers.

* libc: Remove remaining redundant cxa functions

- `__cxa_pure_virtual` in `libcxxabi` is also a stub similar to the
existing one.
- `__cxa_guard_*` from `libcxxabi` is used instead of the ones from
Android.

Now there should be no more duplicate implementations.
`__cxa_thread_atexit_impl`, `__cxa_atexit`, and related supporting
functions, are still left to other libraries as in `libcxxabi`.

`libcxxabi` is also now added to `cosmopolitan.a` to make up for the
removed functions.

Affected in-tree libraries (`third_party/double-conversion`) have been
updated.

Makefile

@@ -249,7 +249,6 @@ include libc/calls/BUILD.mk			#─┐
 include libc/irq/BUILD.mk			# ├──SYSTEMS RUNTIME
 include third_party/nsync/BUILD.mk		# │  You can issue system calls
 include libc/runtime/BUILD.mk			# │
-include third_party/double-conversion/BUILD.mk	# │
 include libc/crt/BUILD.mk			# │
 include third_party/dlmalloc/BUILD.mk		#─┘
 include libc/mem/BUILD.mk			#─┐
@@ -284,7 +283,10 @@ include third_party/stb/BUILD.mk		# │
 include third_party/mbedtls/BUILD.mk		# │
 include third_party/ncurses/BUILD.mk		# │
 include third_party/readline/BUILD.mk		# │
+include third_party/libunwind/BUILD.mk		# |
+include third_party/libcxxabi/BUILD.mk		# |
 include third_party/libcxx/BUILD.mk		# │
+include third_party/double-conversion/BUILD.mk	# │
 include third_party/pcre/BUILD.mk		# │
 include third_party/less/BUILD.mk		# │
 include net/https/BUILD.mk			# │
@@ -328,7 +330,6 @@ include third_party/python/BUILD.mk
 include tool/build/BUILD.mk
 include tool/curl/BUILD.mk
 include third_party/qemu/BUILD.mk
-include third_party/libunwind/BUILD.mk
 include examples/BUILD.mk
 include examples/pyapp/BUILD.mk
 include examples/pylife/BUILD.mk
@@ -441,6 +442,7 @@ COSMOPOLITAN_OBJECTS =			\
 	LIBC_TIME			\
 	THIRD_PARTY_MUSL		\
 	THIRD_PARTY_ZLIB_GZ		\
+	THIRD_PARTY_LIBCXXABI		\
 	THIRD_PARTY_LIBUNWIND		\
 	LIBC_STDIO			\
 	THIRD_PARTY_GDTOA		\

libc/intrin/__cxa_pure_virtual.c

@@ -1,28 +0,0 @@
-/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
-│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8                               :vi │
-╞══════════════════════════════════════════════════════════════════════════════╡
-│ Copyright 2023 Justine Alexandra Roberts Tunney                              │
-│                                                                              │
-│ Permission to use, copy, modify, and/or distribute this software for         │
-│ any purpose with or without fee is hereby granted, provided that the         │
-│ above copyright notice and this permission notice appear in all copies.      │
-│                                                                              │
-│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
-│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
-│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
-│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
-│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
-│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
-│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
-│ PERFORMANCE OF THIS SOFTWARE.                                                │
-╚─────────────────────────────────────────────────────────────────────────────*/
-#include "libc/intrin/kprintf.h"
-#include "libc/runtime/runtime.h"
-
-void __cxa_pure_virtual(void) {
-#ifndef NDEBUG
-  kprintf("__cxa_pure_virtual() called\n"
-          "Did you call a virtual method from a destructor?\n");
-#endif
-  abort();
-}

libc/runtime/cxaguard.c

@@ -1,115 +0,0 @@
-/*
- * Copyright (C) 2006 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-#include "libc/atomic.h"
-#include "libc/cxxabi.h"
-#include "libc/intrin/atomic.h"
-#include "libc/limits.h"
-#include "third_party/nsync/futex.internal.h"
-
-// This file contains C++ ABI support functions for one time
-// constructors as defined in the "Run-time ABI for the ARM Architecture"
-// section 4.4.2
-//
-// ARM C++ ABI and Itanium/x86 C++ ABI has different definition for
-// one time construction:
-//
-//    ARM C++ ABI defines the LSB of guard variable should be tested
-//    by compiler-generated code before calling __cxa_guard_acquire et al.
-//
-//    The Itanium/x86 C++ ABI defines the low-order _byte_ should be
-//    tested instead.
-//
-//    Meanwhile, guard variable are 32bit aligned for ARM, and 64bit
-//    aligned for x86.
-//
-// Reference documentation:
-//
-//    section 3.2.3 of ARM IHI 0041C (for ARM)
-//    section 3.3.2 of the Itanium C++ ABI specification v1.83 (for x86).
-//
-// There is no C++ ABI available for other ARCH. But the gcc source
-// shows all other ARCH follow the definition of Itanium/x86 C++ ABI.
-
-// The Itanium/x86 C++ ABI (used by all architectures that aren't ARM32)
-// mandates guard variables are 64-bit aligned, 64-bit values. The least
-// significant byte is tested by the compiler-generated code before it's
-// calling __cxa_guard_acquire.
-union CxaGuardValue {
-  atomic_int state;
-  int64_t aligner;
-};
-
-// Set construction state values according to reference documentation. 0
-// is the initialization value. Arm requires ((*gv & 1) == 1) after
-// __cxa_guard_release, ((*gv & 3) == 0) after __cxa_guard_abort. X86
-// requires first byte not modified by __cxa_guard_acquire, first byte
-// is non-zero after __cxa_guard_release.
-#define CONSTRUCTION_NOT_YET_STARTED         0
-#define CONSTRUCTION_COMPLETE                1
-#define CONSTRUCTION_UNDERWAY_WITHOUT_WAITER 0x100
-#define CONSTRUCTION_UNDERWAY_WITH_WAITER    0x200
-
-int __cxa_guard_acquire(union CxaGuardValue *gv) {
-  int old_value = atomic_load_explicit(&gv->state, memory_order_relaxed);
-  while (true) {
-    if (old_value == CONSTRUCTION_COMPLETE) {
-      // A load_acquire operation is needed before exiting with COMPLETE
-      // state, as we must ensure that all the stores performed by the
-      // construction function are observable on this CPU after we exit.
-      atomic_thread_fence(memory_order_acquire);
-      return 0;
-    } else if (old_value == CONSTRUCTION_NOT_YET_STARTED) {
-      if (!atomic_compare_exchange_weak_explicit(
-              &gv->state, &old_value, CONSTRUCTION_UNDERWAY_WITHOUT_WAITER,
-              memory_order_relaxed, memory_order_relaxed)) {
-        continue;
-      }
-      // The acquire fence may not be needed. But as described in section 3.3.2
-      // of the Itanium C++ ABI specification, it probably has to behave like
-      // the acquisition of a mutex, which needs an acquire fence.
-      atomic_thread_fence(memory_order_acquire);
-      return 1;
-    } else if (old_value == CONSTRUCTION_UNDERWAY_WITHOUT_WAITER) {
-      if (!atomic_compare_exchange_weak_explicit(
-              &gv->state, &old_value, CONSTRUCTION_UNDERWAY_WITH_WAITER,
-              memory_order_relaxed, memory_order_relaxed)) {
-        continue;
-      }
-    }
-    nsync_futex_wait_(&gv->state, CONSTRUCTION_UNDERWAY_WITH_WAITER, 0, 0);
-    old_value = atomic_load_explicit(&gv->state, memory_order_relaxed);
-  }
-}
-
-void __cxa_guard_release(union CxaGuardValue *gv) {
-  // Release fence is used to make all stores performed by the construction
-  // function visible in other threads.
-  int old_value = atomic_exchange_explicit(&gv->state, CONSTRUCTION_COMPLETE,
-                                           memory_order_release);
-  if (old_value == CONSTRUCTION_UNDERWAY_WITH_WAITER) {
-    nsync_futex_wake_(&gv->state, INT_MAX, 0);
-  }
-}
-
-void __cxa_guard_abort(union CxaGuardValue *gv) {
-  // Release fence is used to make all stores performed by the construction
-  // function visible in other threads.
-  int old_value = atomic_exchange_explicit(
-      &gv->state, CONSTRUCTION_NOT_YET_STARTED, memory_order_release);
-  if (old_value == CONSTRUCTION_UNDERWAY_WITH_WAITER) {
-    nsync_futex_wake_(&gv->state, INT_MAX, 0);
-  }
-}

libc/thread/__cxa_thread_atexit.c

@@ -1,23 +0,0 @@
-/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
-│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8                               :vi │
-╞══════════════════════════════════════════════════════════════════════════════╡
-│ Copyright 2023 Justine Alexandra Roberts Tunney                              │
-│                                                                              │
-│ Permission to use, copy, modify, and/or distribute this software for         │
-│ any purpose with or without fee is hereby granted, provided that the         │
-│ above copyright notice and this permission notice appear in all copies.      │
-│                                                                              │
-│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
-│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
-│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
-│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
-│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
-│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
-│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
-│ PERFORMANCE OF THIS SOFTWARE.                                                │
-╚─────────────────────────────────────────────────────────────────────────────*/
-#include "libc/intrin/cxaatexit.internal.h"
-
-int __cxa_thread_atexit(void *fun, void *arg, void *dso_symbol) {
-  return __cxa_thread_atexit_impl(fun, arg, dso_symbol);
-}

test/libc/thread/BUILD.mk

@@ -41,6 +41,7 @@ TEST_LIBC_THREAD_DIRECTDEPS =				\
 	LIBC_THREAD					\
 	LIBC_TIME					\
 	LIBC_X						\
+	THIRD_PARTY_LIBCXXABI				\
 	THIRD_PARTY_NSYNC				\
 	THIRD_PARTY_NSYNC_MEM
 

third_party/BUILD.mk

@@ -17,6 +17,7 @@ o/$(MODE)/third_party:				\
 	o/$(MODE)/third_party/hiredis		\
 	o/$(MODE)/third_party/less		\
 	o/$(MODE)/third_party/libcxx		\
+	o/$(MODE)/third_party/libcxxabi		\
 	o/$(MODE)/third_party/libunwind		\
 	o/$(MODE)/third_party/linenoise		\
 	o/$(MODE)/third_party/lua		\

third_party/double-conversion/BUILD.mk

@@ -31,10 +31,9 @@ THIRD_PARTY_DOUBLECONVERSION_A_CHECKS =						\
 
 THIRD_PARTY_DOUBLECONVERSION_A_DIRECTDEPS =					\
 	LIBC_INTRIN								\
-	LIBC_NEXGEN32E								\
-	LIBC_RUNTIME								\
 	LIBC_STR								\
-	LIBC_TINYMATH
+	LIBC_TINYMATH								\
+	THIRD_PARTY_LIBCXXABI
 
 THIRD_PARTY_DOUBLECONVERSION_A_DEPS :=						\
 	$(call uniq,$(foreach x,$(THIRD_PARTY_DOUBLECONVERSION_A_DIRECTDEPS),$($(x))))

third_party/libcxx/BUILD.mk

@@ -70,8 +70,8 @@ THIRD_PARTY_LIBCXX_A_HDRS =					\
 	third_party/libcxx/deque				\
 	third_party/libcxx/errno.h				\
 	third_party/libcxx/exception				\
-	third_party/libcxx/exception_fallback.hh		\
+	third_party/libcxx/exception_libcxxabi.hh		\
-	third_party/libcxx/exception_pointer_unimplemented.hh	\
+	third_party/libcxx/exception_pointer_cxxabi.hh		\
 	third_party/libcxx/execution				\
 	third_party/libcxx/experimental/__config		\
 	third_party/libcxx/filesystem				\
@@ -99,7 +99,6 @@ THIRD_PARTY_LIBCXX_A_HDRS =					\
 	third_party/libcxx/memory				\
 	third_party/libcxx/mutex				\
 	third_party/libcxx/new					\
-	third_party/libcxx/new_handler_fallback.hh		\
 	third_party/libcxx/numeric				\
 	third_party/libcxx/optional				\
 	third_party/libcxx/ostream				\
@@ -200,7 +199,9 @@ THIRD_PARTY_LIBCXX_A_DIRECTDEPS =				\
 	LIBC_THREAD						\
 	LIBC_TINYMATH						\
 	THIRD_PARTY_COMPILER_RT					\
-	THIRD_PARTY_GDTOA
+	THIRD_PARTY_GDTOA					\
+	THIRD_PARTY_LIBCXXABI					\
+	THIRD_PARTY_LIBUNWIND
 
 THIRD_PARTY_LIBCXX_A_DEPS :=					\
 	$(call uniq,$(foreach x,$(THIRD_PARTY_LIBCXX_A_DIRECTDEPS),$($(x))))
@@ -217,7 +218,10 @@ $(THIRD_PARTY_LIBCXX_A).pkg:					\
 $(THIRD_PARTY_LIBCXX_A_OBJS): private				\
 		CXXFLAGS +=					\
 			-ffunction-sections			\
-			-fdata-sections
+			-fdata-sections				\
+			-fexceptions				\
+			-frtti					\
+			-DLIBCXX_BUILDING_LIBCXXABI
 
 THIRD_PARTY_LIBCXX_LIBS = $(foreach x,$(THIRD_PARTY_LIBCXX_ARTIFACTS),$($(x)))
 THIRD_PARTY_LIBCXX_SRCS = $(foreach x,$(THIRD_PARTY_LIBCXX_ARTIFACTS),$($(x)_SRCS))

third_party/libcxx/__config

@@ -12,7 +12,6 @@
 #include "libc/isystem/features.h"
 
 #define _LIBCPP_ABI_UNSTABLE
-#define _LIBCPP_NO_EXCEPTIONS
 #define _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER
 #define _LIBCPP_DISABLE_DEPRECATION_WARNINGS
 #define _LIBCPP_HAS_TRIVIAL_MUTEX_DESTRUCTION

third_party/libcxx/exception.cc

@@ -11,6 +11,11 @@
 #include "third_party/libcxx/new"
 #include "third_party/libcxx/typeinfo"
 
-#include "third_party/libcxx/atomic_support.hh"
+#if defined(LIBCXXRT) || defined(LIBCXX_BUILDING_LIBCXXABI)
-#include "third_party/libcxx/exception_fallback.hh"
+  #include "third_party/libcxxabi/include/cxxabi.h"
-#include "third_party/libcxx/exception_pointer_unimplemented.hh"
+  using namespace __cxxabiv1;
+  #define HAVE_DEPENDENT_EH_ABI 1
+#endif
+
+#include "third_party/libcxx/exception_libcxxabi.hh"
+#include "third_party/libcxx/exception_pointer_cxxabi.hh"

third_party/libcxx/exception_fallback.hh

@@ -1,111 +0,0 @@
-// -*- C++ -*-
-//===----------------------------------------------------------------------===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-
-#include "third_party/libcxx/exception"
-#include "third_party/libcxx/cstdio"
-#include "third_party/libcxx/atomic_support.hh"
-
-namespace std {
-
-_LIBCPP_SAFE_STATIC static std::terminate_handler __terminate_handler;
-
-#if _LIBCPP_STD_VER <= 14 ||                                                   \
-    defined(_LIBCPP_ENABLE_CXX17_REMOVED_UNEXPECTED_FUNCTIONS) ||              \
-    defined(_LIBCPP_BUILDING_LIBRARY)
-_LIBCPP_SAFE_STATIC static std::unexpected_handler __unexpected_handler;
-// libcxxrt provides implementations of these functions itself.
-unexpected_handler set_unexpected(unexpected_handler func) _NOEXCEPT {
-  return __libcpp_atomic_exchange(&__unexpected_handler, func);
-}
-unexpected_handler get_unexpected() _NOEXCEPT {
-  return __libcpp_atomic_load(&__unexpected_handler);
-}
-_LIBCPP_NORETURN
-void unexpected() {
-  (*get_unexpected())();
-  // unexpected handler should not return
-  terminate();
-}
-#endif
-
-terminate_handler set_terminate(terminate_handler func) _NOEXCEPT {
-  return __libcpp_atomic_exchange(&__terminate_handler, func);
-}
-
-terminate_handler get_terminate() _NOEXCEPT {
-  return __libcpp_atomic_load(&__terminate_handler);
-}
-
-#ifndef __EMSCRIPTEN__ // We provide this in JS
-_LIBCPP_NORETURN
-void terminate() _NOEXCEPT {
-#ifndef _LIBCPP_NO_EXCEPTIONS
-  try {
-#endif // _LIBCPP_NO_EXCEPTIONS
-    (*get_terminate())();
-    // handler should not return
-    fprintf(stderr, "terminate_handler unexpectedly returned\n");
-    ::abort();
-#ifndef _LIBCPP_NO_EXCEPTIONS
-  } catch (...) {
-    // handler should not throw exception
-    fprintf(stderr, "terminate_handler unexpectedly threw an exception\n");
-    ::abort();
-  }
-#endif // _LIBCPP_NO_EXCEPTIONS
-}
-#endif // !__EMSCRIPTEN__
-
-#if !defined(__EMSCRIPTEN__)
-bool uncaught_exception() _NOEXCEPT { return uncaught_exceptions() > 0; }
-
-int uncaught_exceptions() _NOEXCEPT {
-  // #warning uncaught_exception not yet implemented
-  fprintf(stderr, "uncaught_exceptions not yet implemented\n");
-  ::abort();
-}
-#endif // !__EMSCRIPTEN__
-
-exception::~exception() _NOEXCEPT {}
-
-const char* exception::what() const _NOEXCEPT { return "std::exception"; }
-
-bad_exception::~bad_exception() _NOEXCEPT {}
-
-const char* bad_exception::what() const _NOEXCEPT {
-  return "std::bad_exception";
-}
-
-bad_alloc::bad_alloc() _NOEXCEPT {}
-
-bad_alloc::~bad_alloc() _NOEXCEPT {}
-
-const char* bad_alloc::what() const _NOEXCEPT { return "std::bad_alloc"; }
-
-bad_array_new_length::bad_array_new_length() _NOEXCEPT {}
-
-bad_array_new_length::~bad_array_new_length() _NOEXCEPT {}
-
-const char* bad_array_new_length::what() const _NOEXCEPT {
-  return "bad_array_new_length";
-}
-
-bad_cast::bad_cast() _NOEXCEPT {}
-
-bad_typeid::bad_typeid() _NOEXCEPT {}
-
-bad_cast::~bad_cast() _NOEXCEPT {}
-
-const char* bad_cast::what() const _NOEXCEPT { return "std::bad_cast"; }
-
-bad_typeid::~bad_typeid() _NOEXCEPT {}
-
-const char* bad_typeid::what() const _NOEXCEPT { return "std::bad_typeid"; }
-
-} // namespace std

third_party/libcxx/exception_libcxxabi.hh

@@ -7,20 +7,21 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "third_party/libcxx/__config"
+#include "third_party/libcxxabi/include/cxxabi.h"
-#include "third_party/libcxx/new"
+#include "third_party/libcxx/exception"
-#include "third_party/libcxx/atomic_support.hh"
+using namespace __cxxabiv1;
 
 namespace std {
 
-_LIBCPP_SAFE_STATIC static std::new_handler __new_handler;
+bool uncaught_exception() _NOEXCEPT { return uncaught_exceptions() > 0; }
 
-new_handler set_new_handler(new_handler handler) _NOEXCEPT {
+int uncaught_exceptions() _NOEXCEPT
-  return __libcpp_atomic_exchange(&__new_handler, handler);
+{
-}
+# if _LIBCPPABI_VERSION > 1001
-
+    return __cxa_uncaught_exceptions();
-new_handler get_new_handler() _NOEXCEPT {
+# else
-  return __libcpp_atomic_load(&__new_handler);
+    return __cxa_uncaught_exception() ? 1 : 0;
+# endif
 }
 
 } // namespace std

third_party/libcxx/exception_pointer_cxxabi.hh

@@ -0,0 +1,73 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "third_party/libcxxabi/include/cxxabi.h"
+#include "third_party/libcxx/exception"
+using namespace __cxxabiv1;
+
+namespace std {
+
+exception_ptr::~exception_ptr() _NOEXCEPT {
+  __cxa_decrement_exception_refcount(__ptr_);
+}
+
+exception_ptr::exception_ptr(const exception_ptr& other) _NOEXCEPT
+    : __ptr_(other.__ptr_)
+{
+    __cxa_increment_exception_refcount(__ptr_);
+}
+
+exception_ptr& exception_ptr::operator=(const exception_ptr& other) _NOEXCEPT
+{
+    if (__ptr_ != other.__ptr_)
+    {
+        __cxa_increment_exception_refcount(other.__ptr_);
+        __cxa_decrement_exception_refcount(__ptr_);
+        __ptr_ = other.__ptr_;
+    }
+    return *this;
+}
+
+nested_exception::nested_exception() _NOEXCEPT
+    : __ptr_(current_exception())
+{
+}
+
+nested_exception::~nested_exception() _NOEXCEPT
+{
+}
+
+_LIBCPP_NORETURN
+void
+nested_exception::rethrow_nested() const
+{
+    if (__ptr_ == nullptr)
+        terminate();
+    rethrow_exception(__ptr_);
+}
+
+exception_ptr current_exception() _NOEXCEPT
+{
+    // be nicer if there was a constructor that took a ptr, then
+    // this whole function would be just:
+    //    return exception_ptr(__cxa_current_primary_exception());
+    exception_ptr ptr;
+    ptr.__ptr_ = __cxa_current_primary_exception();
+    return ptr;
+}
+
+_LIBCPP_NORETURN
+void rethrow_exception(exception_ptr p)
+{
+    __cxa_rethrow_primary_exception(p.__ptr_);
+    // if p.__ptr_ is NULL, above returns so we terminate
+    terminate();
+}
+
+} // namespace std

third_party/libcxx/exception_pointer_unimplemented.hh

@@ -1,68 +0,0 @@
-// -*- C++ -*-
-//===----------------------------------------------------------------------===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-
-#include "third_party/libcxx/stdio.h"
-#include "third_party/libcxx/stdlib.h"
-#include "third_party/libcxx/exception"
-
-namespace std {
-
-exception_ptr::~exception_ptr() _NOEXCEPT {
-  // #warning exception_ptr not yet implemented
-  fprintf(stderr, "exception_ptr not yet implemented\n");
-  ::abort();
-}
-
-exception_ptr::exception_ptr(const exception_ptr& other) _NOEXCEPT
-    : __ptr_(other.__ptr_) {
-  // #warning exception_ptr not yet implemented
-  fprintf(stderr, "exception_ptr not yet implemented\n");
-  ::abort();
-}
-
-exception_ptr& exception_ptr::operator=(const exception_ptr& other) _NOEXCEPT {
-  // #warning exception_ptr not yet implemented
-  fprintf(stderr, "exception_ptr not yet implemented\n");
-  ::abort();
-}
-
-nested_exception::nested_exception() _NOEXCEPT : __ptr_(current_exception()) {}
-
-#if !defined(__GLIBCXX__)
-
-nested_exception::~nested_exception() _NOEXCEPT {}
-
-#endif
-
-_LIBCPP_NORETURN
-void nested_exception::rethrow_nested() const {
-  // #warning exception_ptr not yet implemented
-  fprintf(stderr, "exception_ptr not yet implemented\n");
-  ::abort();
-#if 0
-  if (__ptr_ == nullptr)
-      terminate();
-  rethrow_exception(__ptr_);
-#endif // FIXME
-}
-
-exception_ptr current_exception() _NOEXCEPT {
-  // #warning exception_ptr not yet implemented
-  fprintf(stderr, "exception_ptr not yet implemented\n");
-  ::abort();
-}
-
-_LIBCPP_NORETURN
-void rethrow_exception(exception_ptr p) {
-  // #warning exception_ptr not yet implemented
-  fprintf(stderr, "exception_ptr not yet implemented\n");
-  ::abort();
-}
-
-} // namespace std

third_party/libcxx/new.cc

@@ -10,7 +10,7 @@
 
 #include "third_party/libcxx/new"
 #include "third_party/libcxx/atomic_support.hh"
-#include "third_party/libcxx/new_handler_fallback.hh"
+#include "third_party/libcxxabi/include/cxxabi.h"
 
 namespace std {
 

third_party/libcxxabi/BUILD.mk

@@ -0,0 +1,112 @@
+#-*-mode:makefile-gmake;indent-tabs-mode:t;tab-width:8;coding:utf-8-*-┐
+#── vi: set noet ft=make ts=8 sw=8 fenc=utf-8 :vi ────────────────────┘
+
+PKGS += THIRD_PARTY_LIBCXXABI
+
+THIRD_PARTY_LIBCXXABI_ARTIFACTS += THIRD_PARTY_LIBCXXABI_A
+THIRD_PARTY_LIBCXXABI = $(THIRD_PARTY_LIBCXXABI_A_DEPS) $(THIRD_PARTY_LIBCXXABI_A)
+THIRD_PARTY_LIBCXXABI_A = o/$(MODE)/third_party/libcxxabi/libcxxabi.a
+
+THIRD_PARTY_LIBCXXABI_A_INCS =						\
+	third_party/libcxxabi/demangle/ItaniumNodes.def			\
+	third_party/libcxxabi/aix_state_tab_eh.inc			\
+	third_party/libcxxabi/cxa_exception.h				\
+	third_party/libcxxabi/cxa_guard_impl.h				\
+	third_party/libcxxabi/cxa_handlers.h
+
+# TODO: Remove this aligned_alloc header when libcxx is updated
+THIRD_PARTY_LIBCXXABI_A_HDRS =						\
+	third_party/libcxxabi/libcxx/include/__memory/aligned_alloc.h	\
+	third_party/libcxxabi/include/__cxxabi_config.h			\
+	third_party/libcxxabi/include/cxxabi.h				\
+	third_party/libcxxabi/demangle/DemangleConfig.h			\
+	third_party/libcxxabi/demangle/ItaniumDemangle.h		\
+	third_party/libcxxabi/demangle/StringViewExtras.h		\
+	third_party/libcxxabi/demangle/Utility.h			\
+	third_party/libcxxabi/abort_message.h				\
+	third_party/libcxxabi/fallback_malloc.h				\
+	third_party/libcxxabi/private_typeinfo.h
+
+THIRD_PARTY_LIBCXXABI_A_SRCS_CC =					\
+	third_party/libcxxabi/abort_message.cc				\
+	third_party/libcxxabi/cxa_aux_runtime.cc			\
+	third_party/libcxxabi/cxa_default_handlers.cc			\
+	third_party/libcxxabi/cxa_demangle.cc				\
+	third_party/libcxxabi/cxa_exception_storage.cc			\
+	third_party/libcxxabi/cxa_exception.cc				\
+	third_party/libcxxabi/cxa_guard.cc				\
+	third_party/libcxxabi/cxa_handlers.cc				\
+	third_party/libcxxabi/cxa_personality.cc			\
+	third_party/libcxxabi/cxa_thread_atexit.cc			\
+	third_party/libcxxabi/cxa_vector.cc				\
+	third_party/libcxxabi/cxa_virtual.cc				\
+	third_party/libcxxabi/fallback_malloc.cc			\
+	third_party/libcxxabi/private_typeinfo.cc			\
+	third_party/libcxxabi/stdlib_exception.cc			\
+	third_party/libcxxabi/stdlib_new_delete.cc			\
+	third_party/libcxxabi/stdlib_stdexcept.cc			\
+	third_party/libcxxabi/stdlib_typeinfo.cc
+
+THIRD_PARTY_LIBCXXABI_A_SRCS =						\
+	$(THIRD_PARTY_LIBCXXABI_A_SRCS_CC)
+
+THIRD_PARTY_LIBCXXABI_A_OBJS =						\
+	$(THIRD_PARTY_LIBCXXABI_A_SRCS_CC:%.cc=o/$(MODE)/%.o)
+
+THIRD_PARTY_LIBCXXABI_A_CHECKS =					\
+	$(THIRD_PARTY_LIBCXXABI_A).pkg					\
+	$(THIRD_PARTY_LIBCXXABI_A_HDRS:%=o/$(MODE)/%.okk)
+
+THIRD_PARTY_LIBCXXABI_A_DIRECTDEPS =					\
+	LIBC_CALLS							\
+	LIBC_INTRIN							\
+	LIBC_MEM							\
+	LIBC_NEXGEN32E							\
+	LIBC_RUNTIME							\
+	LIBC_STDIO							\
+	LIBC_STR							\
+	LIBC_THREAD							\
+	THIRD_PARTY_LIBUNWIND
+
+THIRD_PARTY_LIBCXXABI_A_DEPS :=						\
+	$(call uniq,$(foreach x,$(THIRD_PARTY_LIBCXXABI_A_DIRECTDEPS),$($(x))))
+
+$(THIRD_PARTY_LIBCXXABI_A):						\
+		third_party/libcxxabi/					\
+		$(THIRD_PARTY_LIBCXXABI_A).pkg				\
+		$(THIRD_PARTY_LIBCXXABI_A_OBJS)
+
+$(THIRD_PARTY_LIBCXXABI_A).pkg:						\
+		$(THIRD_PARTY_LIBCXXABI_A_OBJS)				\
+		$(foreach x,$(THIRD_PARTY_LIBCXXABI_A_DIRECTDEPS),$($(x)_A).pkg)
+
+# TODO: Remove constinit hacks when we have C++20
+$(THIRD_PARTY_LIBCXXABI_A_OBJS): private				\
+		CXXFLAGS +=						\
+			-ffunction-sections				\
+			-fdata-sections					\
+			-fexceptions					\
+			-frtti						\
+			-D_LIBCXXABI_BUILDING_LIBRARY			\
+			-D_LIBCPP_BUILDING_LIBRARY			\
+			-DHAVE___CXA_THREAD_ATEXIT_IMPL			\
+			-D_LIBCPP_CONSTINIT=__constinit			\
+			-Dconstinit=__constinit
+
+# ttypeIndex is initialized and used only when native_old_exception is true.
+# GCC does not seem to allow this.
+o/$(MODE)/third_party/libcxxabi/cxa_personality.o: private		\
+		CXXFLAGS +=						\
+			-Wno-error=maybe-uninitialized
+
+THIRD_PARTY_LIBCXXABI_LIBS = $(foreach x,$(THIRD_PARTY_LIBCXXABI_ARTIFACTS),$($(x)))
+THIRD_PARTY_LIBCXXABI_SRCS = $(foreach x,$(THIRD_PARTY_LIBCXXABI_ARTIFACTS),$($(x)_SRCS))
+THIRD_PARTY_LIBCXXABI_HDRS = $(foreach x,$(THIRD_PARTY_LIBCXXABI_ARTIFACTS),$($(x)_HDRS))
+THIRD_PARTY_LIBCXXABI_INCS = $(foreach x,$(THIRD_PARTY_LIBCXXABI_ARTIFACTS),$($(x)_INCS))
+THIRD_PARTY_LIBCXXABI_CHECKS = $(foreach x,$(THIRD_PARTY_LIBCXXABI_ARTIFACTS),$($(x)_CHECKS))
+THIRD_PARTY_LIBCXXABI_OBJS = $(foreach x,$(THIRD_PARTY_LIBCXXABI_ARTIFACTS),$($(x)_OBJS))
+
+.PHONY: o/$(MODE)/third_party/libcxxabi
+o/$(MODE)/third_party/libcxxabi: \
+	$(THIRD_PARTY_LIBCXXABI_CHECKS)	\
+	$(THIRD_PARTY_LIBCXXABI_A)

third_party/libcxxabi/CREDITS.TXT

@@ -0,0 +1,71 @@
+This file is a partial list of people who have contributed to the LLVM/libc++abi
+project.  If you have contributed a patch or made some other contribution to
+LLVM/libc++abi, please submit a patch to this file to add yourself, and it will be
+done!
+
+The list is sorted by surname and formatted to allow easy grepping and
+beautification by scripts.  The fields are: name (N), email (E), web-address
+(W), PGP key ID and fingerprint (P), description (D), and snail-mail address
+(S).
+
+N: Aaron Ballman
+E: aaron@aaronballman.com
+D: Minor patches
+
+N: Logan Chien
+E: logan.chien@mediatek.com
+D: ARM EHABI Unwind & Exception Handling
+
+N: Marshall Clow
+E: mclow.lists@gmail.com
+E: marshall@idio.com
+D: Architect and primary coauthor of libc++abi
+
+N: Matthew Dempsky
+E: matthew@dempsky.org
+D: Minor patches and bug fixes.
+
+N: Nowar Gu
+E: wenhan.gu@gmail.com
+D: Minor patches and fixes
+
+N: Howard Hinnant
+E: hhinnant@apple.com
+D: Architect and primary coauthor of libc++abi
+
+N: Dana Jansens
+E: danakj@chromium.org
+D: ARM EHABI Unwind & Exception Handling
+
+N: Nick Kledzik
+E: kledzik@apple.com
+
+N: Antoine Labour
+E: piman@chromium.org
+D: ARM EHABI Unwind & Exception Handling
+
+N: Bruce Mitchener, Jr.
+E: bruce.mitchener@gmail.com
+D: Minor typo fixes
+
+N: Andrew Morrow
+E: andrew.c.morrow@gmail.com
+D: Minor patches and fixes
+
+N: Erik Olofsson
+E: erik.olofsson@hansoft.se
+E: erik@olofsson.info
+D: Minor patches and fixes
+
+N: Jon Roelofs
+E: jroelofs@jroelofs.com
+D: ARM EHABI Unwind & Exception Handling, Bare-metal
+
+N: Nico Weber
+E: thakis@chromium.org
+D: ARM EHABI Unwind & Exception Handling
+
+N: Albert J. Wong
+E: ajwong@google.com
+D: ARM EHABI Unwind & Exception Handling
+

third_party/libcxxabi/LICENSE.TXT

@@ -0,0 +1,311 @@
+==============================================================================
+The LLVM Project is under the Apache License v2.0 with LLVM Exceptions:
+==============================================================================
+
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+       http://www.apache.org/licenses/LICENSE-2.0
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+    distributed under the License is distributed on an "AS IS" BASIS,
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+    limitations under the License.
+
+
+---- LLVM Exceptions to the Apache 2.0 License ----
+
+As an exception, if, as a result of your compiling your source code, portions
+of this Software are embedded into an Object form of such source code, you
+may redistribute such embedded portions in such Object form without complying
+with the conditions of Sections 4(a), 4(b) and 4(d) of the License.
+
+In addition, if you combine or link compiled forms of this Software with
+software that is licensed under the GPLv2 ("Combined Software") and if a
+court of competent jurisdiction determines that the patent provision (Section
+3), the indemnity provision (Section 9) or other Section of the License
+conflicts with the conditions of the GPLv2, you may retroactively and
+prospectively choose to deem waived or otherwise exclude such Section(s) of
+the License, but only in their entirety and only with respect to the Combined
+Software.
+
+==============================================================================
+Software from third parties included in the LLVM Project:
+==============================================================================
+The LLVM Project contains third party software which is under different license
+terms. All such code will be identified clearly using at least one of two
+mechanisms:
+1) It will be in a separate directory tree with its own `LICENSE.txt` or
+   `LICENSE` file at the top containing the specific license and restrictions
+   which apply to that software, or
+2) It will contain specific license and restriction terms at the top of every
+   file.
+
+==============================================================================
+Legacy LLVM License (https://llvm.org/docs/DeveloperPolicy.html#legacy):
+==============================================================================
+
+The libc++abi library is dual licensed under both the University of Illinois
+"BSD-Like" license and the MIT license.  As a user of this code you may choose
+to use it under either license.  As a contributor, you agree to allow your code
+to be used under both.
+
+Full text of the relevant licenses is included below.
+
+==============================================================================
+
+University of Illinois/NCSA
+Open Source License
+
+Copyright (c) 2009-2019 by the contributors listed in CREDITS.TXT
+
+All rights reserved.
+
+Developed by:
+
+    LLVM Team
+
+    University of Illinois at Urbana-Champaign
+
+    http://llvm.org
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal with
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions:
+
+    * Redistributions of source code must retain the above copyright notice,
+      this list of conditions and the following disclaimers.
+
+    * Redistributions in binary form must reproduce the above copyright notice,
+      this list of conditions and the following disclaimers in the
+      documentation and/or other materials provided with the distribution.
+
+    * Neither the names of the LLVM Team, University of Illinois at
+      Urbana-Champaign, nor the names of its contributors may be used to
+      endorse or promote products derived from this Software without specific
+      prior written permission.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
+CONTRIBUTORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS WITH THE
+SOFTWARE.
+
+==============================================================================
+
+Copyright (c) 2009-2014 by the contributors listed in CREDITS.TXT
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

third_party/libcxxabi/README.cosmo

@@ -0,0 +1,18 @@
+DESCRIPTION
+
+  libcxxabi - C++ Standard Library Support
+
+ORIGIN
+
+  Obtained from the LLVM monorepo, release 17.0.6.
+
+  https://github.com/llvm/llvm-project/tree/llvmorg-17.0.6/libunwind
+  commit 6009708b4367171ccdbf4b5905cb6a803753fe18
+  Author: Tobias Hieta <tobias@hieta.se>
+  Date:   Tue, 28 Nov 2023 09:52:28 +0100
+
+LOCAL CHANGES
+
+  - Add <__memory/aligned_alloc.h> (contains a few inline functions) from
+  upstream libcxx.
+  - Enable __cxa_thread_atexit for Cosmopolitan.

third_party/libcxxabi/abort_message.cc

@@ -0,0 +1,79 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "libc/isystem/stdlib.h"
+#include "libc/stdio/stdio.h"
+#include "libc/isystem/stdarg.h"
+#include "third_party/libcxxabi/abort_message.h"
+
+#ifdef __BIONIC__
+#   include <android/api-level.h>
+#   if __ANDROID_API__ >= 21
+#       include <syslog.h>
+        extern "C" void android_set_abort_message(const char* msg);
+#   else
+#       include <assert.h>
+#   endif // __ANDROID_API__ >= 21
+#endif // __BIONIC__
+
+#if defined(__APPLE__) && __has_include(<CrashReporterClient.h>)
+#   include <CrashReporterClient.h>
+#   define _LIBCXXABI_USE_CRASHREPORTER_CLIENT
+#endif
+
+void abort_message(const char* format, ...)
+{
+    // Write message to stderr. We do this before formatting into a
+    // variable-size buffer so that we still get some information if
+    // formatting into the variable-sized buffer fails.
+#if !defined(NDEBUG) || !defined(LIBCXXABI_BAREMETAL)
+    {
+        fprintf(stderr, "libc++abi: ");
+        va_list list;
+        va_start(list, format);
+        vfprintf(stderr, format, list);
+        va_end(list);
+        fprintf(stderr, "\n");
+    }
+#endif
+
+    // Format the arguments into an allocated buffer. We leak the buffer on
+    // purpose, since we're about to abort() anyway.
+#if defined(_LIBCXXABI_USE_CRASHREPORTER_CLIENT)
+    char* buffer;
+    va_list list;
+    va_start(list, format);
+    vasprintf(&buffer, format, list);
+    va_end(list);
+
+    CRSetCrashLogMessage(buffer);
+#elif defined(__BIONIC__)
+    char* buffer;
+    va_list list;
+    va_start(list, format);
+    vasprintf(&buffer, format, list);
+    va_end(list);
+
+#   if __ANDROID_API__ >= 21
+    // Show error in tombstone.
+    android_set_abort_message(buffer);
+
+    // Show error in logcat.
+    openlog("libc++abi", 0, 0);
+    syslog(LOG_CRIT, "%s", buffer);
+    closelog();
+#   else
+    // The good error reporting wasn't available in Android until L. Since we're
+    // about to abort anyway, just call __assert2, which will log _somewhere_
+    // (tombstone and/or logcat) in older releases.
+    __assert2(__FILE__, __LINE__, __func__, buffer);
+#   endif // __ANDROID_API__ >= 21
+#endif // __BIONIC__
+
+    abort();
+}

third_party/libcxxabi/abort_message.h

@@ -0,0 +1,17 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef __ABORT_MESSAGE_H_
+#define __ABORT_MESSAGE_H_
+
+#include "third_party/libcxxabi/include/cxxabi.h"
+
+extern "C" _LIBCXXABI_HIDDEN _LIBCXXABI_NORETURN void
+abort_message(const char *format, ...) __attribute__((format(printf, 1, 2)));
+
+#endif

third_party/libcxxabi/aix_state_tab_eh.inc

@@ -0,0 +1,745 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//
+//  This file implements the personality and helper functions for the state
+//  table based EH used by IBM legacy compilers xlC and xlclang++ on AIX.
+//
+//===----------------------------------------------------------------------===//
+
+#include <new>
+#include <stdio.h>
+#include <sys/debug.h>
+
+/*
+  The legacy IBM xlC and xlclang++ compilers use the state table for EH
+  instead of the range table. Destructors, or addresses of the possible catch
+  sites or cleanup code are specified in the state table which is a finite
+  state machine (FSM). Each function that has a state table also has an
+  autolocal state variable. The state variable represents the current state
+  of the function for EH and is found through the traceback table of the
+  function during unwinding, which is located at the end of each function.
+  The FSM is an array of state entries. Each state entry has the following
+  fields:
+
+  * offset/address/pointer - the offset used to locate the object, or the
+    address of a global object, or the address of the next state if it is an
+    old conditional state change entry;
+  * dtor/landing pad - address of the destructor function to invoke,
+    or address of the catch block or cleanup code in the user code to branch to;
+  * element count/action flag - the number of elements or the flag for actions;
+  * element size - if the object is an array this is the size of one element
+    of the array;
+  * flags - flags used to control how fields in the entry are interpreted;
+  * next state - the state to execute next after the action for this state is
+    performed. The value of zero indicates the end of the state for this
+    function.
+
+  The following is the description of 'element count/action flag' field.
++-----------------------------------------------------------------------------+
+| value |      description       |                  action                    |
++-------+------------------------+--------------------------------------------+
+| > 1   |   object is an array   | calls __cxa_vec_cleanup to run dtor for    |
+|       |                        | each member of the array                   |
++-------+------------------------+--------------------------------------------+
+| 1, 0  |   object is a scalar   | calls dtor for the object                  |
++-------+------------------------+--------------------------------------------+
+|  -1   |      begin catch       | branches to the handler which performes    |
+|       |                        | catch-match. If there is no catch that     |
+|       |                        | matches the exception it will be rethrown  |
++-------+------------------------+--------------------------------------------+
+|  -2   |       end catch        | ends current catch block and continues     |
+|       |                        | attempting to catch the exception          |
++-------+------------------------+--------------------------------------------+
+|  -3   |   delete the object    | calls the delete function of the object    |
++-------+------------------------+--------------------------------------------+
+|  -4   |      cleanup label     | branches to the user code for cleaning up  |
++-------+------------------------+--------------------------------------------+
+*/
+
+namespace __cxxabiv1 {
+
+extern "C" {
+
+// Macros for debugging the state table parsing.
+#ifdef NDEBUG
+#  define _LIBCXXABI_TRACE_STATETAB(msg, ...)
+#  define _LIBCXXABI_TRACE_STATETAB0(msg)
+#  define _LIBCXXABI_TRACE_STATETAB1(msg)
+#  define _LIBCXXABI_TRACING_STATETAB 0
+#else
+static bool state_tab_dbg() {
+  static bool checked = false;
+  static bool log = false;
+  if (!checked) {
+    log = (getenv("LIBCXXABI_PRINT_STATTAB") != NULL);
+    checked = true;
+  }
+  return log;
+}
+
+#  define _LIBCXXABI_TRACE_STATETAB(msg, ...)                                  \
+     do {                                                                      \
+       if (state_tab_dbg())                                                    \
+         fprintf(stderr, "libcxxabi: " msg, __VA_ARGS__);                      \
+     } while (0)
+#  define _LIBCXXABI_TRACE_STATETAB0(msg)                                      \
+     do {                                                                      \
+       if (state_tab_dbg())                                                    \
+         fprintf(stderr, "libcxxabi: " msg);                                   \
+     } while (0)
+#  define _LIBCXXABI_TRACE_STATETAB1(msg)                                      \
+     do {                                                                      \
+       if (state_tab_dbg())                                                    \
+         fprintf(stderr, msg);                                                 \
+     } while (0)
+
+#  define _LIBCXXABI_TRACING_STATETAB state_tab_dbg()
+#endif // NDEBUG
+
+namespace __state_table_eh {
+
+using destruct_f = void (*)(void*);
+
+// Definition of flags for the state table entry field 'action flag'.
+enum FSMEntryCount : intptr_t { beginCatch = -1, endCatch = -2, deleteObject = -3, cleanupLabel = -4, terminate = -5 };
+
+// Definition of flags for the state table entry field 'flags'.
+enum FSMEntryFlag : int16_t {
+  indirect = 0x100,                  // Object was thrown from a function where
+                                     // the return value optimization was used.
+  oldConditionalStateChange = 0x400, // State table entry is an indirect state
+                                     // change, dereference the address in
+                                     // offset as int for the target state.
+                                     // This is deprecated. This indicates
+                                     // the address is direct. (static local).
+  conditionalStateChange = 0x800,    // State table entry is an indirect state
+                                     // change, dereference the address in
+                                     // offset as int for the target state.
+                                     // The temporary is an automatic. State
+                                     // change is used in cases such as
+                                     // (b?(T1(),foo()):(T2(),foo())),throw 42;
+                                     // which causes a conditional state change
+                                     // so that we know if T1 or T2 need to be
+                                     // destroyed.
+  thisFlag = 0x01,                   // The address of the object for the
+                                     // cleanup action is based on the
+                                     // StateVariable::thisValue.
+  vBaseFlag = 0x02,                  // The object is of a virtual base class.
+  globalObj = 0x04                   // FSMEntry::address is the address of
+                                     // a global object.
+};
+
+namespace {
+// The finite state machine to be walked.
+struct FSMEntry {
+  union {
+    // Offset of the object within its stack frame or containing object.
+    intptr_t offset;
+    // Address of a global object.
+    intptr_t address;
+    // Address of the next state if it is an old conditional state change entry.
+    intptr_t nextStatePtr;
+  };
+  union {
+    // Address of the destructor function.
+    void (*destructor)(void*, size_t);
+    // The address of the catch block or cleanup code.
+    void* landingPad;
+  };
+  union {
+    // The flag for actions (when the value is negative).
+    FSMEntryCount actionFlag;
+    // The element count (when the value is positive or zero).
+    size_t elementCount;
+  };
+  size_t elemSize;
+  FSMEntryFlag flags;
+  uint16_t nextState;
+};
+
+struct FSM {
+  uint32_t magic; // Magic number of the state table.
+  int32_t numberOfStates;
+  FSMEntry table[1]; // Actually table[numberOfStates].
+};
+
+// The state variable on the stack.
+struct StateVariable {
+  int32_t state;
+  struct FSM* table;
+  intptr_t thisValue;
+  int32_t ignoreVBasePtrs;
+};
+} // namespace
+
+// State table magic number
+enum FSMMagic : uint32_t {
+  number = 0xbeefdead,  // State table generated by xlC compiler.
+  number2 = 0xbeeedead, // State table generated by early version xlC compiler.
+  number3 = 0x1cedbeef  // State table generated by xlclang++ compiler.
+};
+
+constexpr size_t dtorArgument = 0x02; // Flag to destructor indicating to free
+                                      // virtual bases, don't delete object.
+
+static void invoke_destructor(FSMEntry* fsmEntry, void* addr) {
+  _LIBCXXABI_TRACE_STATETAB("Destruct object=%p, fsmEntry=%p\n", addr, reinterpret_cast<void*>(fsmEntry));
+  try {
+    if (fsmEntry->elementCount == 1) {
+      _LIBCXXABI_TRACE_STATETAB0("calling scalar destructor\n");
+      (*fsmEntry->destructor)(addr, dtorArgument);
+      _LIBCXXABI_TRACE_STATETAB0("returned from scalar destructor\n");
+    } else {
+      _LIBCXXABI_TRACE_STATETAB0("calling vector destructor\n");
+      __cxa_vec_cleanup(addr, reinterpret_cast<size_t>(fsmEntry->elementCount), fsmEntry->elemSize,
+                        reinterpret_cast<destruct_f>(fsmEntry->destructor));
+      _LIBCXXABI_TRACE_STATETAB0("returned from vector destructor\n");
+    }
+  } catch (...) {
+    _LIBCXXABI_TRACE_STATETAB0("Uncaught exception in destructor, terminating\n");
+    std::terminate();
+  }
+}
+
+static void invoke_delete(FSMEntry* fsmEntry, void* addr) {
+  char* objectAddress = *reinterpret_cast<char**>(addr);
+
+  _LIBCXXABI_TRACE_STATETAB("Delete object=%p, fsmEntry=%p\n", reinterpret_cast<void*>(objectAddress),
+                            reinterpret_cast<void*>(fsmEntry));
+  try {
+    _LIBCXXABI_TRACE_STATETAB0("..calling delete()\n");
+    // 'destructor' holds a function pointer to delete().
+    (*fsmEntry->destructor)(objectAddress, fsmEntry->elemSize);
+    _LIBCXXABI_TRACE_STATETAB0("..returned from delete()\n");
+  } catch (...) {
+    _LIBCXXABI_TRACE_STATETAB0("Uncaught exception in delete(), terminating\n");
+    std::terminate();
+  }
+}
+
+// Get the frame address of the current function from its traceback table
+// which is at the end of each function.
+static uintptr_t get_frame_addr(_Unwind_Context* context) {
+  int framePointerReg = 1; // default frame pointer == SP.
+  uint32_t* p = reinterpret_cast<uint32_t*>(_Unwind_GetIP(context));
+
+  // Keep looking forward until a word of 0 is found. The traceback
+  // table starts at the following word.
+  while (*p)
+    ++p;
+  tbtable* TBTable = reinterpret_cast<tbtable*>(p + 1);
+
+  p = reinterpret_cast<uint32_t*>(&TBTable->tb_ext);
+
+  // Skip field parminfo if it exists.
+  if (TBTable->tb.fixedparms || TBTable->tb.floatparms)
+    ++p;
+
+  // Skip field tb_offset if it exists.
+  if (TBTable->tb.has_tboff)
+    ++p;
+
+  // Skip field hand_mask if it exists.
+  if (TBTable->tb.int_hndl)
+    ++p;
+
+  // Skip fields ctl_info and ctl_info_disp if they exist.
+  if (TBTable->tb.has_ctl)
+    p += 1 + *p;
+
+  // Skip fields name_len and name if exist.
+  if (TBTable->tb.name_present) {
+    const uint16_t name_len = *reinterpret_cast<uint16_t*>(p);
+    p = reinterpret_cast<uint32_t*>(reinterpret_cast<char*>(p) + name_len + sizeof(uint16_t));
+  }
+
+  if (TBTable->tb.uses_alloca)
+    framePointerReg = *reinterpret_cast<char*>(p);
+
+  return _Unwind_GetGR(context, framePointerReg);
+}
+
+// Calculate the object address from the FSM entry.
+static void* compute_addr_from_table(FSMEntry* fsmEntry, StateVariable* const state, _Unwind_Context* context) {
+  void* addr;
+  if (fsmEntry->flags & FSMEntryFlag::globalObj) {
+    addr = reinterpret_cast<void*>(fsmEntry->address);
+    _LIBCXXABI_TRACE_STATETAB("Address calculation (global obj) addr=fsmEntry->address=%p\n", addr);
+  } else if (fsmEntry->flags & FSMEntryFlag::thisFlag) {
+    addr = reinterpret_cast<void*>(state->thisValue + fsmEntry->offset);
+    _LIBCXXABI_TRACE_STATETAB("Address calculation (this obj) fsmEntry->offset=%ld : "
+                              "state->thisValue=%ld addr=(fsmEntry->offset+state->thisValue)=%p\n",
+                              fsmEntry->offset, state->thisValue, addr);
+  } else if (fsmEntry->flags & FSMEntryFlag::indirect) {
+    addr = reinterpret_cast<void*>(
+        *reinterpret_cast<char**>(get_frame_addr(context) + static_cast<uintptr_t>(fsmEntry->offset)));
+    _LIBCXXABI_TRACE_STATETAB("Address calculation (indirect obj) addr=%p, fsmEntry->offset=%ld \n",
+                              addr, fsmEntry->offset);
+  } else {
+    addr = reinterpret_cast<void*>(get_frame_addr(context) + static_cast<uintptr_t>(fsmEntry->offset));
+    _LIBCXXABI_TRACE_STATETAB("Address calculation. (local obj) addr=fsmEntry->offset=%p\n",
+                              addr);
+  }
+  return addr;
+}
+
+static void scan_state_tab(scan_results& results, _Unwind_Action actions, bool native_exception,
+                           _Unwind_Exception* unwind_exception, _Unwind_Context* context) {
+  // Initialize results to found nothing but an error.
+  results.ttypeIndex = 0;
+  results.actionRecord = 0;
+  results.languageSpecificData = 0;
+  results.landingPad = 0;
+  results.adjustedPtr = 0;
+  results.reason = _URC_FATAL_PHASE1_ERROR;
+
+  // Check for consistent actions.
+  if (actions & _UA_SEARCH_PHASE) {
+    // Do Phase 1
+    if (actions & (_UA_CLEANUP_PHASE | _UA_HANDLER_FRAME | _UA_FORCE_UNWIND)) {
+      // None of these flags should be set during Phase 1.
+      //   Client error
+      results.reason = _URC_FATAL_PHASE1_ERROR;
+      return;
+    }
+  } else if (actions & _UA_CLEANUP_PHASE) {
+    if ((actions & _UA_HANDLER_FRAME) && (actions & _UA_FORCE_UNWIND)) {
+      // _UA_HANDLER_FRAME should only be set if phase 1 found a handler.
+      // If _UA_FORCE_UNWIND is set, phase 1 shouldn't have happened.
+      //    Client error
+      results.reason = _URC_FATAL_PHASE2_ERROR;
+      return;
+    }
+  } else {
+    // Neither _UA_SEARCH_PHASE nor _UA_CLEANUP_PHASE is set.
+    //   Client error
+    results.reason = _URC_FATAL_PHASE1_ERROR;
+    return;
+  }
+
+  if (_LIBCXXABI_TRACING_STATETAB) {
+    _LIBCXXABI_TRACE_STATETAB1("\n");
+    _LIBCXXABI_TRACE_STATETAB("%s: actions=%d (", __func__, actions);
+
+    if (_UA_SEARCH_PHASE & actions)
+      _LIBCXXABI_TRACE_STATETAB1("_UA_SEARCH_PHASE ");
+    if (_UA_CLEANUP_PHASE & actions)
+      _LIBCXXABI_TRACE_STATETAB1("_UA_CLEANUP_PHASE ");
+    if (_UA_HANDLER_FRAME & actions)
+      _LIBCXXABI_TRACE_STATETAB1("_UA_HANDLER_FRAME ");
+    if (_UA_FORCE_UNWIND & actions)
+      _LIBCXXABI_TRACE_STATETAB1("_UA_FORCE_UNWIND ");
+    _LIBCXXABI_TRACE_STATETAB1(")\n");
+    _LIBCXXABI_TRACE_STATETAB("       unwind_exception=%p context=%p\n", reinterpret_cast<void*>(unwind_exception),
+                              reinterpret_cast<void*>(context));
+  }
+
+  // Start scan by getting state table address.
+  StateVariable* const state = reinterpret_cast<StateVariable* const>(_Unwind_GetLanguageSpecificData(context));
+  if (state->state <= 0) {
+    // The state is not correct - give up on this routine.
+    _LIBCXXABI_TRACE_STATETAB("state=%d and is <= 0), continue unwinding\n", state->state);
+    results.reason = _URC_CONTINUE_UNWIND;
+    return;
+  }
+  // Parse the state table.
+  FSM* const fsm = state->table;
+  FSMEntry* currFSMEntry;
+
+  if (fsm->magic != FSMMagic::number && fsm->magic != FSMMagic::number2 && fsm->magic != FSMMagic::number3) {
+    // Something is wrong with the state table we found.
+    if (_UA_SEARCH_PHASE & actions) {
+      _LIBCXXABI_TRACE_STATETAB0("Invalid FSM table, return _URC_FATAL_PHASE1_ERROR\n");
+      results.reason = _URC_FATAL_PHASE1_ERROR;
+    } else if (_UA_CLEANUP_PHASE & actions) {
+      _LIBCXXABI_TRACE_STATETAB0("Invalid FSM table, return _URC_FATAL_PHASE2_ERROR\n");
+      results.reason = _URC_FATAL_PHASE2_ERROR;
+    } else {
+      // We should never get here.
+      _LIBCXXABI_TRACE_STATETAB0("Invalid FSM table + RT Internal error, return _URC_FATAL_PHASE2_ERROR\n");
+      results.reason = _URC_FATAL_PHASE2_ERROR;
+    }
+    return;
+  }
+
+  if (_LIBCXXABI_TRACING_STATETAB) {
+    // Print the state table for debugging purposes.
+    _LIBCXXABI_TRACE_STATETAB("state->state=%d, state->ignoreVBasePtrs=%d\n", state->state, state->ignoreVBasePtrs);
+    _LIBCXXABI_TRACE_STATETAB("fsm->magic=%#x, fsm->numberOfStates=%d\n", fsm->magic, fsm->numberOfStates);
+    // Print out the FSM table.
+    _LIBCXXABI_TRACE_STATETAB0("FSM table:\n");
+    _LIBCXXABI_TRACE_STATETAB("%12s %10s %8s  %10s %7s %7s %7s %7s\n", "Entry Addr", "state", "Offset", "DTR/lpad",
+                              "count", "el_size", "flags", "next");
+    for (int i = 0; i < fsm->numberOfStates; i++) {
+      currFSMEntry = &fsm->table[i];
+      _LIBCXXABI_TRACE_STATETAB("%12p (%8d) %8ld  %10p %7ld "
+                                "%7ld %#7x %7d\n",
+                                reinterpret_cast<void*>(&currFSMEntry), i + 1, currFSMEntry->offset,
+                                reinterpret_cast<void*>(currFSMEntry->destructor),
+                                currFSMEntry->elementCount, currFSMEntry->elemSize, currFSMEntry->flags,
+                                currFSMEntry->nextState);
+    }
+  }
+
+  if (_UA_SEARCH_PHASE & actions) {
+    // Start walking the state table. Use a local copy of state->state so when
+    // we return from search phase we don't change the state number.
+    int currState = state->state;
+
+    while (currState > 0) {
+      currFSMEntry = &fsm->table[currState - 1];
+      _LIBCXXABI_TRACE_STATETAB("Processing state=%d, flags=0x%hx\n", currState, currFSMEntry->flags);
+
+      if (currFSMEntry->actionFlag == FSMEntryCount::beginCatch) {
+        // Found a catch handler.
+        if (fsm->magic == FSMMagic::number) {
+          _LIBCXXABI_TRACE_STATETAB0("Found a xlC catch handler, return _URC_FATAL_PHASE1_ERROR\n");
+          // xlC catch handlers cannot be entered because they use a
+          // proprietary EH runtime that is not interoperable.
+          results.reason = _URC_FATAL_PHASE1_ERROR;
+          return;
+        }
+        // xlclang++ compiled frames use CXA-abi EH calls and any catch
+        // block will include a catch(...) block so it is safe to assume that
+        // the handler is found without checking the catch match. The
+        // catch(...) block will rethrow the exception if there isn't a
+        // match.
+        _LIBCXXABI_TRACE_STATETAB0("Found a catch handler, return _URC_HANDLER_FOUND\n");
+        results.reason = _URC_HANDLER_FOUND;
+        return;
+      }
+      if (currFSMEntry->actionFlag == FSMEntryCount::terminate) {
+        _LIBCXXABI_TRACE_STATETAB0("Found the terminate state, return _URC_HANDLER_FOUND\n");
+        results.reason = _URC_HANDLER_FOUND;
+        return;
+      }
+      if (currFSMEntry->flags & FSMEntryFlag::oldConditionalStateChange) {
+        // Deprecated conditional expression.
+        currState = *reinterpret_cast<int*>(currFSMEntry->nextStatePtr);
+        _LIBCXXABI_TRACE_STATETAB("Flag: FSMEntryFlag::oldConditionalStateChange, dereference "
+                                  "currFSMEntry->nextStatePtr(%ld), set state=%d\n",
+                                  currFSMEntry->nextStatePtr, currState);
+        continue; // We are done this iteration of the loop, since
+                  // we changed a state.
+      }
+      if (currFSMEntry->flags & FSMEntryFlag::conditionalStateChange) {
+        void* addr = compute_addr_from_table(currFSMEntry, state, context);
+        currState = *reinterpret_cast<int*>(addr);
+        _LIBCXXABI_TRACE_STATETAB("Flag: FSMEntryFlag::conditionalStateChange, dereference "
+                                  "addr(%p), set state=%d\n", addr, currState);
+        continue; // We are done this iteration of the loop, since we
+                  // changed the state.
+      }
+      // Go to the next state.
+      currState = currFSMEntry->nextState;
+    }
+    _LIBCXXABI_TRACE_STATETAB0("No catch handler found, return _URC_CONTINUE_UNWIND\n");
+    results.reason = _URC_CONTINUE_UNWIND;
+    return;
+  }
+  if (_UA_CLEANUP_PHASE & actions) {
+    // Start walking the state table.
+    while (state->state > 0) {
+      currFSMEntry = &fsm->table[state->state - 1];
+
+      if (currFSMEntry->actionFlag == FSMEntryCount::terminate) {
+        _LIBCXXABI_TRACE_STATETAB0("Reached terminate state. Call terminate.\n");
+        std::terminate();
+      }
+      // Perform action according to the currFSMEntry->actionFlag,
+      // except when flag is FSMEntryFlag::conditionalStateChange or
+      // FSMEntryFlag::oldConditionalStateChange.
+      _LIBCXXABI_TRACE_STATETAB("Processing state=%d, flags=0x%hx\n", state->state, currFSMEntry->flags);
+      if (currFSMEntry->flags & FSMEntryFlag::oldConditionalStateChange) {
+        state->state = *reinterpret_cast<int*>(currFSMEntry->nextStatePtr);
+        _LIBCXXABI_TRACE_STATETAB("Flag: FSMEntryFlag::oldConditionalStateChange, dereference "
+                                  "currFSMEntry->nextStatePtr(%ld), set state=%d\n",
+                                  currFSMEntry->nextStatePtr, state->state);
+        continue; // We are done with this iteration of the loop, since we changed a state.
+      }
+      if (currFSMEntry->flags & FSMEntryFlag::conditionalStateChange) {
+        // A conditional state table entry holds the address of a local
+        // that holds the next state.
+        void* addr = compute_addr_from_table(currFSMEntry, state, context);
+        state->state = *reinterpret_cast<int*>(addr);
+        _LIBCXXABI_TRACE_STATETAB("Flag: FSMEntryFlag::conditionalStateChange, dereference "
+                                  "addr(%p), set state=%d\n", addr, state->state);
+        continue; // We are done with this iteration of the loop, since we changed a state.
+      }
+      if (currFSMEntry->actionFlag == FSMEntryCount::beginCatch || currFSMEntry->actionFlag == FSMEntryCount::endCatch ||
+          currFSMEntry->actionFlag == FSMEntryCount::cleanupLabel) {
+
+        _LIBCXXABI_TRACE_STATETAB(
+            "FSMEntryCount::%s: handler %p/%p, return _URC_HANDLER_FOUND\n",
+            (currFSMEntry->actionFlag == FSMEntryCount::beginCatch
+                 ? "beginCatch"
+                 : (currFSMEntry->actionFlag == FSMEntryCount::endCatch ? "endCatch" : "cleanupLabel")),
+            currFSMEntry->landingPad, *reinterpret_cast<void**>(currFSMEntry->landingPad));
+
+        state->state = currFSMEntry->nextState;
+        results.landingPad = reinterpret_cast<uintptr_t>(*reinterpret_cast<void**>(currFSMEntry->landingPad));
+        results.reason = _URC_HANDLER_FOUND;
+        return;
+      }
+      if (currFSMEntry->elementCount > 0) {
+        if (currFSMEntry->flags & FSMEntryFlag::vBaseFlag && state->ignoreVBasePtrs) {
+          _LIBCXXABI_TRACE_STATETAB0("Ignoring virtual base dtor.\n");
+        } else {
+          // We need to invoke the virtual base destructor. This must be
+          // a frame from the legacy xlC compiler as the xlclang++ compiler
+          // generates inline cleanup code rather than specifying
+          // the destructor via the state table.
+          void* addr = compute_addr_from_table(currFSMEntry, state, context);
+
+          // An extra indirect to get to the object according to the object
+          // model used by the xlC compiler.
+          addr = reinterpret_cast<void*>(*reinterpret_cast<char**>(addr));
+          _LIBCXXABI_TRACE_STATETAB("Invoke dtor for object=%p\n", addr);
+          invoke_destructor(currFSMEntry, addr);
+        }
+      } else if (currFSMEntry->actionFlag == FSMEntryCount::deleteObject) {
+        void* addr = compute_addr_from_table(currFSMEntry, state, context);
+        if (currFSMEntry->flags & FSMEntryFlag::vBaseFlag) {
+          // We need to invoke the virtual base delete function. This must be
+          // a frame from the legacy xlC compiler as the xlclang++ compiler
+          // generates inline cleanup code rather than specifying
+          // the delete function via the state table.
+
+          // An extra indirect to get to the object according to the object
+          // model used by the xlC compiler.
+          addr = reinterpret_cast<void*>(*reinterpret_cast<char**>(addr));
+        }
+        _LIBCXXABI_TRACE_STATETAB("Delete object at %p\n", addr);
+        invoke_delete(currFSMEntry, addr);
+      } else {
+        _LIBCXXABI_TRACE_STATETAB("Unknown entry in FSM (count=%ld), ignored\n",
+                                  currFSMEntry->elementCount);
+      } // End of action switching.
+
+      // Go to next state.
+      state->state = currFSMEntry->nextState;
+    }
+    _LIBCXXABI_TRACE_STATETAB0("No catch handler, return _URC_CONTINUE_UNWIND\n");
+    results.reason = _URC_CONTINUE_UNWIND;
+    return;
+  }
+  _LIBCXXABI_TRACE_STATETAB0("No state table entry for this exception, call_terminate()\n");
+  // It is possible that no state table entry specify how to handle
+  // this exception. By spec, terminate it immediately.
+  call_terminate(native_exception, unwind_exception);
+}
+
+// Personality routine for EH using the state table.
+_LIBCXXABI_FUNC_VIS _Unwind_Reason_Code
+__xlcxx_personality_v0(int version, _Unwind_Action actions, uint64_t exceptionClass,
+                       _Unwind_Exception* unwind_exception, _Unwind_Context* context) {
+  if (version != 1 || unwind_exception == 0 || context == 0)
+    return _URC_FATAL_PHASE1_ERROR;
+
+  bool native_exception = (exceptionClass & get_vendor_and_language) == (kOurExceptionClass & get_vendor_and_language);
+  scan_results results;
+  scan_state_tab(results, actions, native_exception, unwind_exception, context);
+  if (actions & _UA_SEARCH_PHASE) {
+    // Phase 1 search:  All we're looking for in phase 1 is a handler that
+    //   halts unwinding
+    return results.reason;
+  }
+  if (actions & _UA_CLEANUP_PHASE) {
+    // Phase 2 cleanup:
+    if (results.reason == _URC_HANDLER_FOUND) {
+      // Store the address of unwind_exception in the stack field
+      // reserved for compilers (SP + 3 * sizeof(uintptr_t)) in the stack of
+      // the caller of the function containing the landing pad (within the link
+      // area for the call to the latter) for __xlc_exception_handle()
+      // to retrieve when it is called by the landing pad.
+      uintptr_t *currentSP = reinterpret_cast<uintptr_t*>(_Unwind_GetGR(context, 1));
+      uintptr_t *callersSP = reinterpret_cast<uintptr_t*>(currentSP[0]);
+      callersSP[3] = reinterpret_cast<uintptr_t>(unwind_exception);
+      _LIBCXXABI_TRACE_STATETAB("Handshake: save unwind_exception=%p in stack=%p\n",
+                                reinterpret_cast<void*>(unwind_exception), reinterpret_cast<void*>(callersSP));
+      // Jump to the handler.
+      _Unwind_SetIP(context, results.landingPad);
+      return _URC_INSTALL_CONTEXT;
+    }
+    // Did not find a handler. Return the results of the scan. Normally
+    // _URC_CONTINUE_UNWIND, but could have been _URC_FATAL_PHASE2_ERROR.
+    return results.reason;
+  }
+  // We were called improperly: neither a phase 1 or phase 2 search.
+  return _URC_FATAL_PHASE1_ERROR;
+}
+} // namespace __state_table_eh
+
+// The following are EH helper functions for xlclang++ compiled code.
+
+// __xlc_catch_matchv2
+// Check whether the thrown object matches the catch handler's exception
+// declaration. If there is a match, the function returns true with adjusted
+// address of the thrown object. Otherwise, returns false.
+_LIBCXXABI_FUNC_VIS bool
+__xlc_catch_matchv2(_Unwind_Exception* exceptionObject, std::type_info* catchTypeInfo, void*& obj) {
+  _LIBCXXABI_TRACE_STATETAB("Entering %s, exceptionObject=%p\n", __func__, reinterpret_cast<void*>(exceptionObject));
+
+  if (!__isOurExceptionClass(exceptionObject)) {
+    _LIBCXXABI_TRACE_STATETAB0("No match, not a C++ exception\n");
+    return false;
+  }
+
+  __cxa_exception* exceptionHeader = 0;
+
+  if (__getExceptionClass(exceptionObject) == kOurDependentExceptionClass) {
+    // Walk to the __cxa_dependent_exception primary exception for the
+    // exception object and its type_info.
+    __cxa_dependent_exception* dependentExceptionHeader =
+        reinterpret_cast<__cxa_dependent_exception*>(exceptionObject + 1) - 1;
+    exceptionHeader = reinterpret_cast<__cxa_exception*>(dependentExceptionHeader->primaryException) - 1;
+    _LIBCXXABI_TRACE_STATETAB("exceptionObject 0x%p is a dependent, primary 0x%p\n",
+                              reinterpret_cast<void*>(exceptionObject),
+                              reinterpret_cast<void*>(&exceptionHeader->unwindHeader));
+    exceptionObject = &exceptionHeader->unwindHeader;
+  } else {
+    _LIBCXXABI_TRACE_STATETAB("exceptionObject %p is NOT a dependent\n", reinterpret_cast<void*>(exceptionObject));
+    exceptionHeader = reinterpret_cast<__cxa_exception*>(exceptionObject + 1) - 1;
+  }
+
+  void* thrownObject = reinterpret_cast<void*>(exceptionObject + 1);
+  std::type_info* throwTypeInfo = exceptionHeader->exceptionType;
+
+  // Get the type info for the thrown type and this catch clause and
+  // see if the catch caluse can catch that type.
+
+  __cxxabiv1::__shim_type_info* catchType = reinterpret_cast<__cxxabiv1::__shim_type_info*>(catchTypeInfo);
+  __cxxabiv1::__shim_type_info* throwType = reinterpret_cast<__cxxabiv1::__shim_type_info*>(throwTypeInfo);
+  _LIBCXXABI_TRACE_STATETAB("UnwindException=%p, thrownObject=%p, throwTypeInfo=%p(%s), catchTypeInfo=%p(%s)\n",
+                            reinterpret_cast<void*>(exceptionObject), thrownObject, reinterpret_cast<void*>(throwType),
+                            throwType->name(), reinterpret_cast<void*>(catchType), catchType->name());
+  if (catchType->can_catch(throwType, thrownObject)) {
+    exceptionHeader->adjustedPtr = thrownObject;
+    obj = thrownObject;
+    _LIBCXXABI_TRACE_STATETAB("Match found for thrownObject=%p\n", thrownObject);
+    return true;
+  }
+  _LIBCXXABI_TRACE_STATETAB0("No match\n");
+  return false;
+}
+
+// __xlc_throw_badexception
+// This function is for xlclang++. It allocates and throws a bad_exception.
+// During unwinding for this bad_exception, the previous exception which is
+// not matching the throw spec will be cleaned up. Thus having the same
+// effect as replace the top most exception (which is bad) with a bad_exception.
+_LIBCXXABI_FUNC_VIS void __xlc_throw_badexception() {
+  _LIBCXXABI_TRACE_STATETAB("Entering function: %s\n\n", __func__);
+  void* newexception = new (__cxa_allocate_exception(sizeof(std::bad_exception))) std::bad_exception;
+  __cxa_throw(newexception, const_cast<std::type_info*>(&typeid(std::bad_exception)), 0);
+}
+
+// skip_non_cxx_eh_aware_frames
+// This function skips non-C++ EH aware stack frames by unwinding from the
+// stack frame pointed by 'Sp' and returns the first C++ EH aware stack frame
+// found. 'Pc' is an instruction address inside the function that owns the
+// stack frame pointed to by 'Sp'.
+static uintptr_t* skip_non_cxx_eh_aware_frames(uint32_t* Pc, uintptr_t* Sp) {
+  uint32_t* currentPc = Pc;
+  uintptr_t* currentStack = Sp;
+
+  // Loop until a C++ EH aware frame is found or the return address is 0,
+  // which is the return address of the startup function '__start'.
+  while (currentPc != 0) {
+    uint32_t* p = currentPc;
+
+    // Keep looking forward until a word of 0 is found. The traceback
+    // table starts at the following word.
+    while (*p)
+      ++p;
+    tbtable* TBTable = reinterpret_cast<tbtable*>(p + 1);
+
+    // A stack frame with a C++ state table is C++ EH aware.
+    if (TBTable->tb.lang == TB_CPLUSPLUS && TBTable->tb.has_ctl)
+      return currentStack;
+
+    // Move up one stack frame.
+    currentStack = reinterpret_cast<uintptr_t*>(currentStack[0]);
+    // Get the value of the LR (saved, prior to incrementing the SP, by the
+    // prolog of the function just inspected) from the frame.
+    currentPc = reinterpret_cast<uint32_t*>(currentStack[2]);
+  }
+  // This should not happen.
+  _LIBCXXABI_TRACE_STATETAB0("skip_non_cxx_eh_aware_frames() reached the end of stack frames, aborting\n");
+  abort();
+}
+
+// __xlc_exception_handle
+// This function is for xlclang++. It returns the address of the exception
+// object stored in the reserved field in the stack of the caller of the
+// function that calls __xlc_exception_handle() (within the link area for the
+// call to the latter). The address is stored by the personality routine for
+// xlclang++ compiled code. If __xlc_exception_handle() is called by
+// non-C++ EH aware functions, their frames are skipped until a C++ EH aware
+// frame is found.
+// Note: make sure __xlc_excpetion_handle() is a non-leaf function. Currently
+// it calls skip_non_cxx_eh_aware_frames(), which in turn calls abort().
+_LIBCXXABI_FUNC_VIS uintptr_t __xlc_exception_handle() {
+  // Get the SP of this function, i.e., __xlc_exception_handle().
+  uintptr_t* lastStack = reinterpret_cast<uintptr_t*>(__builtin_frame_address(0));
+  // Move one frame up to the frame of the caller of __xlc_exception_handle().
+  lastStack = reinterpret_cast<uintptr_t*>(lastStack[0]);
+  // Get the return address of this function, i.e., __xlc_exception_handle().
+  uint32_t* returnAddress = reinterpret_cast<uint32_t*>(__builtin_return_address(0));
+
+  // Skip non-C++ EH aware frames and get the first C++ EH aware frame.
+  uintptr_t* callerStack = skip_non_cxx_eh_aware_frames(returnAddress, lastStack);
+
+  // Get the SP of the caller of the C++ EH aware caller.
+  callerStack = reinterpret_cast<uintptr_t*>(callerStack[0]);
+  // Retrieve the exception object in the stack slot saved by the personality.
+  uintptr_t exceptionObject = callerStack[3];
+  _LIBCXXABI_TRACE_STATETAB("Handshake: retrieve exceptionObject=%p from stack=%p\n",
+                            reinterpret_cast<void*>(exceptionObject), reinterpret_cast<void*>(callerStack));
+  return exceptionObject;
+}
+
+// xlclang++ may generate calls to __Deleted_Virtual.
+_LIBCXXABI_FUNC_VIS void __Deleted_Virtual() { abort(); }
+
+// __catchThrownException is called during AIX library initialization and
+// termination to handle exceptions.  An implementation is also provided in
+// libC.a(shrcore.o).  This implementation is provided for applications that
+// link with -lc++ (the xlclang++ or ibm-clang++ link default.)
+_LIBCXXABI_FUNC_VIS int
+__catchThrownException(void (*cdfunc)(void),   // function which may fail
+                       void (*cleanup)(void*), // cleanup function
+                       void* cleanuparg,       // parameter to cleanup function
+                       int action) {           // control exception throwing and termination
+  enum Action : int { None = 0, Rethrow = 1, Terminate = 2 };
+  if (!cdfunc)
+    return 0;
+  if (action == Action::Rethrow && !cleanup) {
+    // No cleanup and rethrow is effectively no-op.
+    // Avoid the catch handler when possible to allow exceptions generated
+    // from xlC binaries to flow through.
+    (*cdfunc)();
+    return 0;
+  }
+  try {
+    (*cdfunc)();
+  } catch (...) {
+    if (action == Action::Terminate)
+      std::terminate();
+    if (cleanup)
+      (*cleanup)(cleanuparg);
+    if (action == Action::Rethrow)
+      throw;
+    assert(action == Action::None);
+    return -1; // FAILED
+  }
+  return 0;
+}
+
+}  // extern "C"
+
+}  // __cxxabiv1

third_party/libcxxabi/cxa_aux_runtime.cc

@@ -0,0 +1,44 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//
+// This file implements the "Auxiliary Runtime APIs"
+// https://itanium-cxx-abi.github.io/cxx-abi/abi-eh.html#cxx-aux
+//===----------------------------------------------------------------------===//
+
+#include "third_party/libcxxabi/include/cxxabi.h"
+#include "third_party/libcxx/exception"
+#include "third_party/libcxx/new"
+#include "third_party/libcxx/typeinfo"
+
+namespace __cxxabiv1 {
+extern "C" {
+_LIBCXXABI_FUNC_VIS _LIBCXXABI_NORETURN void __cxa_bad_cast(void) {
+#ifndef _LIBCXXABI_NO_EXCEPTIONS
+  throw std::bad_cast();
+#else
+  std::terminate();
+#endif
+}
+
+_LIBCXXABI_FUNC_VIS _LIBCXXABI_NORETURN void __cxa_bad_typeid(void) {
+#ifndef _LIBCXXABI_NO_EXCEPTIONS
+  throw std::bad_typeid();
+#else
+  std::terminate();
+#endif
+}
+
+_LIBCXXABI_FUNC_VIS _LIBCXXABI_NORETURN void
+__cxa_throw_bad_array_new_length(void) {
+#ifndef _LIBCXXABI_NO_EXCEPTIONS
+  throw std::bad_array_new_length();
+#else
+  std::terminate();
+#endif
+}
+} // extern "C"
+} // abi

third_party/libcxxabi/cxa_default_handlers.cc

@@ -0,0 +1,141 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//
+// This file implements the default terminate_handler, unexpected_handler and
+// new_handler.
+//===----------------------------------------------------------------------===//
+
+#include "third_party/libcxx/exception"
+#include "third_party/libcxx/memory"
+#include "third_party/libcxx/stdlib.h"
+#include "third_party/libcxxabi/abort_message.h"
+#include "third_party/libcxxabi/include/cxxabi.h"
+#include "third_party/libcxxabi/cxa_handlers.h"
+#include "third_party/libcxxabi/cxa_exception.h"
+#include "third_party/libcxxabi/private_typeinfo.h"
+#include "third_party/libcxx/include/atomic_support.hh" // from libc++
+
+#if !defined(LIBCXXABI_SILENT_TERMINATE)
+
+static constinit const char* cause = "uncaught";
+
+#ifndef _LIBCXXABI_NO_EXCEPTIONS
+// Demangle the given string, or return the string as-is in case of an error.
+static std::unique_ptr<char const, void (*)(char const*)> demangle(char const* str)
+{
+#if !defined(LIBCXXABI_NON_DEMANGLING_TERMINATE)
+    if (const char* result = __cxxabiv1::__cxa_demangle(str, nullptr, nullptr, nullptr))
+        return {result, [](char const* p) { std::free(const_cast<char*>(p)); }};
+#endif
+    return {str, [](char const*) { /* nothing to free */ }};
+}
+
+__attribute__((noreturn))
+static void demangling_terminate_handler()
+{
+    using namespace __cxxabiv1;
+    __cxa_eh_globals* globals = __cxa_get_globals_fast();
+
+    // If there is no uncaught exception, just note that we're terminating
+    if (!globals)
+        abort_message("terminating");
+
+    __cxa_exception* exception_header = globals->caughtExceptions;
+    if (!exception_header)
+        abort_message("terminating");
+
+    _Unwind_Exception* unwind_exception =
+        reinterpret_cast<_Unwind_Exception*>(exception_header + 1) - 1;
+
+    // If we're terminating due to a foreign exception
+    if (!__isOurExceptionClass(unwind_exception))
+        abort_message("terminating due to %s foreign exception", cause);
+
+    void* thrown_object =
+        __getExceptionClass(unwind_exception) == kOurDependentExceptionClass ?
+            ((__cxa_dependent_exception*)exception_header)->primaryException :
+            exception_header + 1;
+    const __shim_type_info* thrown_type =
+        static_cast<const __shim_type_info*>(exception_header->exceptionType);
+    auto name = demangle(thrown_type->name());
+    // If the uncaught exception can be caught with std::exception&
+    const __shim_type_info* catch_type =
+        static_cast<const __shim_type_info*>(&typeid(std::exception));
+    if (catch_type->can_catch(thrown_type, thrown_object))
+    {
+        // Include the what() message from the exception
+        const std::exception* e = static_cast<const std::exception*>(thrown_object);
+        abort_message("terminating due to %s exception of type %s: %s", cause, name.get(), e->what());
+    }
+    else
+    {
+        // Else just note that we're terminating due to an exception
+        abort_message("terminating due to %s exception of type %s", cause, name.get());
+    }
+}
+#else // !_LIBCXXABI_NO_EXCEPTIONS
+__attribute__((noreturn))
+static void demangling_terminate_handler()
+{
+    abort_message("terminating");
+}
+#endif // !_LIBCXXABI_NO_EXCEPTIONS
+
+__attribute__((noreturn))
+static void demangling_unexpected_handler()
+{
+    cause = "unexpected";
+    std::terminate();
+}
+
+static constexpr std::terminate_handler default_terminate_handler = demangling_terminate_handler;
+static constexpr std::terminate_handler default_unexpected_handler = demangling_unexpected_handler;
+#else // !LIBCXXABI_SILENT_TERMINATE
+static constexpr std::terminate_handler default_terminate_handler = ::abort;
+static constexpr std::terminate_handler default_unexpected_handler = std::terminate;
+#endif // !LIBCXXABI_SILENT_TERMINATE
+
+//
+// Global variables that hold the pointers to the current handler
+//
+_LIBCXXABI_DATA_VIS
+constinit std::terminate_handler __cxa_terminate_handler = default_terminate_handler;
+
+_LIBCXXABI_DATA_VIS
+constinit std::unexpected_handler __cxa_unexpected_handler = default_unexpected_handler;
+
+_LIBCXXABI_DATA_VIS
+constinit std::new_handler __cxa_new_handler = nullptr;
+
+namespace std
+{
+
+unexpected_handler
+set_unexpected(unexpected_handler func) noexcept
+{
+    if (func == 0)
+        func = default_unexpected_handler;
+    return __libcpp_atomic_exchange(&__cxa_unexpected_handler, func,
+                                    _AO_Acq_Rel);
+}
+
+terminate_handler
+set_terminate(terminate_handler func) noexcept
+{
+    if (func == 0)
+        func = default_terminate_handler;
+    return __libcpp_atomic_exchange(&__cxa_terminate_handler, func,
+                                    _AO_Acq_Rel);
+}
+
+new_handler
+set_new_handler(new_handler handler) noexcept
+{
+    return __libcpp_atomic_exchange(&__cxa_new_handler, handler, _AO_Acq_Rel);
+}
+
+}

third_party/libcxxabi/cxa_demangle.cc

@@ -0,0 +1,409 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// FIXME: (possibly) incomplete list of features that clang mangles that this
+// file does not yet support:
+//   - C++ modules TS
+
+#include "third_party/libcxxabi/demangle/DemangleConfig.h"
+#include "third_party/libcxxabi/demangle/ItaniumDemangle.h"
+#include "third_party/libcxxabi/include/__cxxabi_config.h"
+#include "third_party/libcxx/cassert"
+#include "third_party/libcxx/cctype"
+#include "third_party/libcxx/cstdio"
+#include "third_party/libcxx/cstdlib"
+#include "third_party/libcxx/cstring"
+#include "third_party/libcxx/functional"
+#include "third_party/libcxx/numeric"
+#include "third_party/libcxx/string_view"
+#include "third_party/libcxx/utility"
+
+using namespace itanium_demangle;
+
+constexpr const char *itanium_demangle::FloatData<float>::spec;
+constexpr const char *itanium_demangle::FloatData<double>::spec;
+constexpr const char *itanium_demangle::FloatData<long double>::spec;
+
+// <discriminator> := _ <non-negative number>      # when number < 10
+//                 := __ <non-negative number> _   # when number >= 10
+//  extension      := decimal-digit+               # at the end of string
+const char *itanium_demangle::parse_discriminator(const char *first,
+                                                  const char *last) {
+  // parse but ignore discriminator
+  if (first != last) {
+    if (*first == '_') {
+      const char *t1 = first + 1;
+      if (t1 != last) {
+        if (std::isdigit(*t1))
+          first = t1 + 1;
+        else if (*t1 == '_') {
+          for (++t1; t1 != last && std::isdigit(*t1); ++t1)
+            ;
+          if (t1 != last && *t1 == '_')
+            first = t1 + 1;
+        }
+      }
+    } else if (std::isdigit(*first)) {
+      const char *t1 = first + 1;
+      for (; t1 != last && std::isdigit(*t1); ++t1)
+        ;
+      if (t1 == last)
+        first = last;
+    }
+  }
+  return first;
+}
+
+#ifndef NDEBUG
+namespace {
+struct DumpVisitor {
+  unsigned Depth = 0;
+  bool PendingNewline = false;
+
+  template<typename NodeT> static constexpr bool wantsNewline(const NodeT *) {
+    return true;
+  }
+  static bool wantsNewline(NodeArray A) { return !A.empty(); }
+  static constexpr bool wantsNewline(...) { return false; }
+
+  template<typename ...Ts> static bool anyWantNewline(Ts ...Vs) {
+    for (bool B : {wantsNewline(Vs)...})
+      if (B)
+        return true;
+    return false;
+  }
+
+  void printStr(const char *S) { fprintf(stderr, "%s", S); }
+  void print(std::string_view SV) {
+    fprintf(stderr, "\"%.*s\"", (int)SV.size(), &*SV.begin());
+  }
+  void print(const Node *N) {
+    if (N)
+      N->visit(std::ref(*this));
+    else
+      printStr("<null>");
+  }
+  void print(NodeArray A) {
+    ++Depth;
+    printStr("{");
+    bool First = true;
+    for (const Node *N : A) {
+      if (First)
+        print(N);
+      else
+        printWithComma(N);
+      First = false;
+    }
+    printStr("}");
+    --Depth;
+  }
+
+  // Overload used when T is exactly 'bool', not merely convertible to 'bool'.
+  void print(bool B) { printStr(B ? "true" : "false"); }
+
+  template <class T>
+  typename std::enable_if<std::is_unsigned<T>::value>::type print(T N) {
+    fprintf(stderr, "%llu", (unsigned long long)N);
+  }
+
+  template <class T>
+  typename std::enable_if<std::is_signed<T>::value>::type print(T N) {
+    fprintf(stderr, "%lld", (long long)N);
+  }
+
+  void print(ReferenceKind RK) {
+    switch (RK) {
+    case ReferenceKind::LValue:
+      return printStr("ReferenceKind::LValue");
+    case ReferenceKind::RValue:
+      return printStr("ReferenceKind::RValue");
+    }
+  }
+  void print(FunctionRefQual RQ) {
+    switch (RQ) {
+    case FunctionRefQual::FrefQualNone:
+      return printStr("FunctionRefQual::FrefQualNone");
+    case FunctionRefQual::FrefQualLValue:
+      return printStr("FunctionRefQual::FrefQualLValue");
+    case FunctionRefQual::FrefQualRValue:
+      return printStr("FunctionRefQual::FrefQualRValue");
+    }
+  }
+  void print(Qualifiers Qs) {
+    if (!Qs) return printStr("QualNone");
+    struct QualName { Qualifiers Q; const char *Name; } Names[] = {
+      {QualConst, "QualConst"},
+      {QualVolatile, "QualVolatile"},
+      {QualRestrict, "QualRestrict"},
+    };
+    for (QualName Name : Names) {
+      if (Qs & Name.Q) {
+        printStr(Name.Name);
+        Qs = Qualifiers(Qs & ~Name.Q);
+        if (Qs) printStr(" | ");
+      }
+    }
+  }
+  void print(SpecialSubKind SSK) {
+    switch (SSK) {
+    case SpecialSubKind::allocator:
+      return printStr("SpecialSubKind::allocator");
+    case SpecialSubKind::basic_string:
+      return printStr("SpecialSubKind::basic_string");
+    case SpecialSubKind::string:
+      return printStr("SpecialSubKind::string");
+    case SpecialSubKind::istream:
+      return printStr("SpecialSubKind::istream");
+    case SpecialSubKind::ostream:
+      return printStr("SpecialSubKind::ostream");
+    case SpecialSubKind::iostream:
+      return printStr("SpecialSubKind::iostream");
+    }
+  }
+  void print(TemplateParamKind TPK) {
+    switch (TPK) {
+    case TemplateParamKind::Type:
+      return printStr("TemplateParamKind::Type");
+    case TemplateParamKind::NonType:
+      return printStr("TemplateParamKind::NonType");
+    case TemplateParamKind::Template:
+      return printStr("TemplateParamKind::Template");
+    }
+  }
+  void print(Node::Prec P) {
+    switch (P) {
+    case Node::Prec::Primary:
+      return printStr("Node::Prec::Primary");
+    case Node::Prec::Postfix:
+      return printStr("Node::Prec::Postfix");
+    case Node::Prec::Unary:
+      return printStr("Node::Prec::Unary");
+    case Node::Prec::Cast:
+      return printStr("Node::Prec::Cast");
+    case Node::Prec::PtrMem:
+      return printStr("Node::Prec::PtrMem");
+    case Node::Prec::Multiplicative:
+      return printStr("Node::Prec::Multiplicative");
+    case Node::Prec::Additive:
+      return printStr("Node::Prec::Additive");
+    case Node::Prec::Shift:
+      return printStr("Node::Prec::Shift");
+    case Node::Prec::Spaceship:
+      return printStr("Node::Prec::Spaceship");
+    case Node::Prec::Relational:
+      return printStr("Node::Prec::Relational");
+    case Node::Prec::Equality:
+      return printStr("Node::Prec::Equality");
+    case Node::Prec::And:
+      return printStr("Node::Prec::And");
+    case Node::Prec::Xor:
+      return printStr("Node::Prec::Xor");
+    case Node::Prec::Ior:
+      return printStr("Node::Prec::Ior");
+    case Node::Prec::AndIf:
+      return printStr("Node::Prec::AndIf");
+    case Node::Prec::OrIf:
+      return printStr("Node::Prec::OrIf");
+    case Node::Prec::Conditional:
+      return printStr("Node::Prec::Conditional");
+    case Node::Prec::Assign:
+      return printStr("Node::Prec::Assign");
+    case Node::Prec::Comma:
+      return printStr("Node::Prec::Comma");
+    case Node::Prec::Default:
+      return printStr("Node::Prec::Default");
+    }
+  }
+
+  void newLine() {
+    printStr("\n");
+    for (unsigned I = 0; I != Depth; ++I)
+      printStr(" ");
+    PendingNewline = false;
+  }
+
+  template<typename T> void printWithPendingNewline(T V) {
+    print(V);
+    if (wantsNewline(V))
+      PendingNewline = true;
+  }
+
+  template<typename T> void printWithComma(T V) {
+    if (PendingNewline || wantsNewline(V)) {
+      printStr(",");
+      newLine();
+    } else {
+      printStr(", ");
+    }
+
+    printWithPendingNewline(V);
+  }
+
+  struct CtorArgPrinter {
+    DumpVisitor &Visitor;
+
+    template<typename T, typename ...Rest> void operator()(T V, Rest ...Vs) {
+      if (Visitor.anyWantNewline(V, Vs...))
+        Visitor.newLine();
+      Visitor.printWithPendingNewline(V);
+      int PrintInOrder[] = { (Visitor.printWithComma(Vs), 0)..., 0 };
+      (void)PrintInOrder;
+    }
+  };
+
+  template<typename NodeT> void operator()(const NodeT *Node) {
+    Depth += 2;
+    fprintf(stderr, "%s(", itanium_demangle::NodeKind<NodeT>::name());
+    Node->match(CtorArgPrinter{*this});
+    fprintf(stderr, ")");
+    Depth -= 2;
+  }
+
+  void operator()(const ForwardTemplateReference *Node) {
+    Depth += 2;
+    fprintf(stderr, "ForwardTemplateReference(");
+    if (Node->Ref && !Node->Printing) {
+      Node->Printing = true;
+      CtorArgPrinter{*this}(Node->Ref);
+      Node->Printing = false;
+    } else {
+      CtorArgPrinter{*this}(Node->Index);
+    }
+    fprintf(stderr, ")");
+    Depth -= 2;
+  }
+};
+}
+
+void itanium_demangle::Node::dump() const {
+  DumpVisitor V;
+  visit(std::ref(V));
+  V.newLine();
+}
+#endif
+
+namespace {
+class BumpPointerAllocator {
+  struct BlockMeta {
+    BlockMeta* Next;
+    size_t Current;
+  };
+
+  static constexpr size_t AllocSize = 4096;
+  static constexpr size_t UsableAllocSize = AllocSize - sizeof(BlockMeta);
+
+  alignas(long double) char InitialBuffer[AllocSize];
+  BlockMeta* BlockList = nullptr;
+
+  void grow() {
+    char* NewMeta = static_cast<char *>(std::malloc(AllocSize));
+    if (NewMeta == nullptr)
+      std::terminate();
+    BlockList = new (NewMeta) BlockMeta{BlockList, 0};
+  }
+
+  void* allocateMassive(size_t NBytes) {
+    NBytes += sizeof(BlockMeta);
+    BlockMeta* NewMeta = reinterpret_cast<BlockMeta*>(std::malloc(NBytes));
+    if (NewMeta == nullptr)
+      std::terminate();
+    BlockList->Next = new (NewMeta) BlockMeta{BlockList->Next, 0};
+    return static_cast<void*>(NewMeta + 1);
+  }
+
+public:
+  BumpPointerAllocator()
+      : BlockList(new (InitialBuffer) BlockMeta{nullptr, 0}) {}
+
+  void* allocate(size_t N) {
+    N = (N + 15u) & ~15u;
+    if (N + BlockList->Current >= UsableAllocSize) {
+      if (N > UsableAllocSize)
+        return allocateMassive(N);
+      grow();
+    }
+    BlockList->Current += N;
+    return static_cast<void*>(reinterpret_cast<char*>(BlockList + 1) +
+                              BlockList->Current - N);
+  }
+
+  void reset() {
+    while (BlockList) {
+      BlockMeta* Tmp = BlockList;
+      BlockList = BlockList->Next;
+      if (reinterpret_cast<char*>(Tmp) != InitialBuffer)
+        std::free(Tmp);
+    }
+    BlockList = new (InitialBuffer) BlockMeta{nullptr, 0};
+  }
+
+  ~BumpPointerAllocator() { reset(); }
+};
+
+class DefaultAllocator {
+  BumpPointerAllocator Alloc;
+
+public:
+  void reset() { Alloc.reset(); }
+
+  template<typename T, typename ...Args> T *makeNode(Args &&...args) {
+    return new (Alloc.allocate(sizeof(T)))
+        T(std::forward<Args>(args)...);
+  }
+
+  void *allocateNodeArray(size_t sz) {
+    return Alloc.allocate(sizeof(Node *) * sz);
+  }
+};
+}  // unnamed namespace
+
+//===----------------------------------------------------------------------===//
+// Code beyond this point should not be synchronized with LLVM.
+//===----------------------------------------------------------------------===//
+
+using Demangler = itanium_demangle::ManglingParser<DefaultAllocator>;
+
+namespace {
+enum : int {
+  demangle_invalid_args = -3,
+  demangle_invalid_mangled_name = -2,
+  demangle_memory_alloc_failure = -1,
+  demangle_success = 0,
+};
+}
+
+namespace __cxxabiv1 {
+extern "C" _LIBCXXABI_FUNC_VIS char *
+__cxa_demangle(const char *MangledName, char *Buf, size_t *N, int *Status) {
+  if (MangledName == nullptr || (Buf != nullptr && N == nullptr)) {
+    if (Status)
+      *Status = demangle_invalid_args;
+    return nullptr;
+  }
+
+  int InternalStatus = demangle_success;
+  Demangler Parser(MangledName, MangledName + std::strlen(MangledName));
+  Node *AST = Parser.parse();
+
+  if (AST == nullptr)
+    InternalStatus = demangle_invalid_mangled_name;
+  else {
+    OutputBuffer O(Buf, N);
+    assert(Parser.ForwardTemplateRefs.empty());
+    AST->print(O);
+    O += '\0';
+    if (N != nullptr)
+      *N = O.getCurrentPosition();
+    Buf = O.getBuffer();
+  }
+
+  if (Status)
+    *Status = InternalStatus;
+  return InternalStatus == demangle_success ? Buf : nullptr;
+}
+}  // __cxxabiv1

third_party/libcxxabi/cxa_exception.cc

@@ -0,0 +1,776 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//
+//  This file implements the "Exception Handling APIs"
+//  https://itanium-cxx-abi.github.io/cxx-abi/abi-eh.html
+//
+//===----------------------------------------------------------------------===//
+
+#include "third_party/libcxxabi/include/cxxabi.h"
+
+#include "third_party/libcxx/exception"        // for std::terminate
+#include "libc/isystem/string.h"         // for memset
+#include "third_party/libcxxabi/cxa_exception.h"
+#include "third_party/libcxxabi/cxa_handlers.h"
+#include "third_party/libcxxabi/fallback_malloc.h"
+#include "third_party/libcxx/include/atomic_support.hh" // from libc++
+
+#if __has_feature(address_sanitizer)
+#include <sanitizer/asan_interface.h>
+#endif
+
+// +---------------------------+-----------------------------+---------------+
+// | __cxa_exception           | _Unwind_Exception CLNGC++\0 | thrown object |
+// +---------------------------+-----------------------------+---------------+
+//                                                           ^
+//                                                           |
+//   +-------------------------------------------------------+
+//   |
+// +---------------------------+-----------------------------+
+// | __cxa_dependent_exception | _Unwind_Exception CLNGC++\1 |
+// +---------------------------+-----------------------------+
+
+namespace __cxxabiv1 {
+
+//  Utility routines
+static
+inline
+__cxa_exception*
+cxa_exception_from_thrown_object(void* thrown_object)
+{
+    return static_cast<__cxa_exception*>(thrown_object) - 1;
+}
+
+// Note:  This is never called when exception_header is masquerading as a
+//        __cxa_dependent_exception.
+static
+inline
+void*
+thrown_object_from_cxa_exception(__cxa_exception* exception_header)
+{
+    return static_cast<void*>(exception_header + 1);
+}
+
+//  Get the exception object from the unwind pointer.
+//  Relies on the structure layout, where the unwind pointer is right in
+//  front of the user's exception object
+static
+inline
+__cxa_exception*
+cxa_exception_from_exception_unwind_exception(_Unwind_Exception* unwind_exception)
+{
+    return cxa_exception_from_thrown_object(unwind_exception + 1 );
+}
+
+// Round s up to next multiple of a.
+static inline
+size_t aligned_allocation_size(size_t s, size_t a) {
+    return (s + a - 1) & ~(a - 1);
+}
+
+static inline
+size_t cxa_exception_size_from_exception_thrown_size(size_t size) {
+    return aligned_allocation_size(size + sizeof (__cxa_exception),
+                                   alignof(__cxa_exception));
+}
+
+void __setExceptionClass(_Unwind_Exception* unwind_exception, uint64_t newValue) {
+    ::memcpy(&unwind_exception->exception_class, &newValue, sizeof(newValue));
+}
+
+
+static void setOurExceptionClass(_Unwind_Exception* unwind_exception) {
+    __setExceptionClass(unwind_exception, kOurExceptionClass);
+}
+
+static void setDependentExceptionClass(_Unwind_Exception* unwind_exception) {
+    __setExceptionClass(unwind_exception, kOurDependentExceptionClass);
+}
+
+//  Is it one of ours?
+uint64_t __getExceptionClass(const _Unwind_Exception* unwind_exception) {
+    // On x86 and some ARM unwinders, unwind_exception->exception_class is
+    // a uint64_t. On other ARM unwinders, it is a char[8].
+    // See: http://infocenter.arm.com/help/topic/com.arm.doc.ihi0038b/IHI0038B_ehabi.pdf
+    // So we just copy it into a uint64_t to be sure.
+    uint64_t exClass;
+    ::memcpy(&exClass, &unwind_exception->exception_class, sizeof(exClass));
+    return exClass;
+}
+
+bool __isOurExceptionClass(const _Unwind_Exception* unwind_exception) {
+    return (__getExceptionClass(unwind_exception) & get_vendor_and_language) ==
+           (kOurExceptionClass                    & get_vendor_and_language);
+}
+
+static bool isDependentException(_Unwind_Exception* unwind_exception) {
+    return (__getExceptionClass(unwind_exception) & 0xFF) == 0x01;
+}
+
+//  This does not need to be atomic
+static inline int incrementHandlerCount(__cxa_exception *exception) {
+    return ++exception->handlerCount;
+}
+
+//  This does not need to be atomic
+static inline  int decrementHandlerCount(__cxa_exception *exception) {
+    return --exception->handlerCount;
+}
+
+/*
+    If reason isn't _URC_FOREIGN_EXCEPTION_CAUGHT, then the terminateHandler
+    stored in exc is called.  Otherwise the exceptionDestructor stored in
+    exc is called, and then the memory for the exception is deallocated.
+
+    This is never called for a __cxa_dependent_exception.
+*/
+static
+void
+exception_cleanup_func(_Unwind_Reason_Code reason, _Unwind_Exception* unwind_exception)
+{
+    __cxa_exception* exception_header = cxa_exception_from_exception_unwind_exception(unwind_exception);
+    if (_URC_FOREIGN_EXCEPTION_CAUGHT != reason)
+        std::__terminate(exception_header->terminateHandler);
+    // Just in case there exists a dependent exception that is pointing to this,
+    //    check the reference count and only destroy this if that count goes to zero.
+    __cxa_decrement_exception_refcount(unwind_exception + 1);
+}
+
+static _LIBCXXABI_NORETURN void failed_throw(__cxa_exception* exception_header) {
+//  Section 2.5.3 says:
+//      * For purposes of this ABI, several things are considered exception handlers:
+//      ** A terminate() call due to a throw.
+//  and
+//      * Upon entry, Following initialization of the catch parameter,
+//          a handler must call:
+//      * void *__cxa_begin_catch(void *exceptionObject );
+    (void) __cxa_begin_catch(&exception_header->unwindHeader);
+    std::__terminate(exception_header->terminateHandler);
+}
+
+// Return the offset of the __cxa_exception header from the start of the
+// allocated buffer. If __cxa_exception's alignment is smaller than the maximum
+// useful alignment for the target machine, padding has to be inserted before
+// the header to ensure the thrown object that follows the header is
+// sufficiently aligned. This happens if _Unwind_exception isn't double-word
+// aligned (on Darwin, for example).
+static size_t get_cxa_exception_offset() {
+  struct S {
+  } __attribute__((aligned));
+
+  // Compute the maximum alignment for the target machine.
+  constexpr size_t alignment = alignof(S);
+  constexpr size_t excp_size = sizeof(__cxa_exception);
+  constexpr size_t aligned_size =
+      (excp_size + alignment - 1) / alignment * alignment;
+  constexpr size_t offset = aligned_size - excp_size;
+  static_assert((offset == 0 || alignof(_Unwind_Exception) < alignment),
+                "offset is non-zero only if _Unwind_Exception isn't aligned");
+  return offset;
+}
+
+extern "C" {
+
+//  Allocate a __cxa_exception object, and zero-fill it.
+//  Reserve "thrown_size" bytes on the end for the user's exception
+//  object. Zero-fill the object. If memory can't be allocated, call
+//  std::terminate. Return a pointer to the memory to be used for the
+//  user's exception object.
+void *__cxa_allocate_exception(size_t thrown_size) throw() {
+    size_t actual_size = cxa_exception_size_from_exception_thrown_size(thrown_size);
+
+    // Allocate extra space before the __cxa_exception header to ensure the
+    // start of the thrown object is sufficiently aligned.
+    size_t header_offset = get_cxa_exception_offset();
+    char *raw_buffer =
+        (char *)__aligned_malloc_with_fallback(header_offset + actual_size);
+    if (NULL == raw_buffer)
+        std::terminate();
+    __cxa_exception *exception_header =
+        static_cast<__cxa_exception *>((void *)(raw_buffer + header_offset));
+    ::memset(exception_header, 0, actual_size);
+    return thrown_object_from_cxa_exception(exception_header);
+}
+
+
+//  Free a __cxa_exception object allocated with __cxa_allocate_exception.
+void __cxa_free_exception(void *thrown_object) throw() {
+    // Compute the size of the padding before the header.
+    size_t header_offset = get_cxa_exception_offset();
+    char *raw_buffer =
+        ((char *)cxa_exception_from_thrown_object(thrown_object)) - header_offset;
+    __aligned_free_with_fallback((void *)raw_buffer);
+}
+
+
+//  This function shall allocate a __cxa_dependent_exception and
+//  return a pointer to it. (Really to the object, not past its' end).
+//  Otherwise, it will work like __cxa_allocate_exception.
+void * __cxa_allocate_dependent_exception () {
+    size_t actual_size = sizeof(__cxa_dependent_exception);
+    void *ptr = __aligned_malloc_with_fallback(actual_size);
+    if (NULL == ptr)
+        std::terminate();
+    ::memset(ptr, 0, actual_size);
+    return ptr;
+}
+
+
+//  This function shall free a dependent_exception.
+//  It does not affect the reference count of the primary exception.
+void __cxa_free_dependent_exception (void * dependent_exception) {
+    __aligned_free_with_fallback(dependent_exception);
+}
+
+
+// 2.4.3 Throwing the Exception Object
+/*
+After constructing the exception object with the throw argument value,
+the generated code calls the __cxa_throw runtime library routine. This
+routine never returns.
+
+The __cxa_throw routine will do the following:
+
+* Obtain the __cxa_exception header from the thrown exception object address,
+which can be computed as follows:
+ __cxa_exception *header = ((__cxa_exception *) thrown_exception - 1);
+* Save the current unexpected_handler and terminate_handler in the __cxa_exception header.
+* Save the tinfo and dest arguments in the __cxa_exception header.
+* Set the exception_class field in the unwind header. This is a 64-bit value
+representing the ASCII string "XXXXC++\0", where "XXXX" is a
+vendor-dependent string. That is, for implementations conforming to this
+ABI, the low-order 4 bytes of this 64-bit value will be "C++\0".
+* Increment the uncaught_exception flag.
+* Call _Unwind_RaiseException in the system unwind library, Its argument is the
+pointer to the thrown exception, which __cxa_throw itself received as an argument.
+__Unwind_RaiseException begins the process of stack unwinding, described
+in Section 2.5. In special cases, such as an inability to find a
+handler, _Unwind_RaiseException may return. In that case, __cxa_throw
+will call terminate, assuming that there was no handler for the
+exception.
+*/
+void
+__cxa_throw(void *thrown_object, std::type_info *tinfo, void (_LIBCXXABI_DTOR_FUNC *dest)(void *)) {
+    __cxa_eh_globals *globals = __cxa_get_globals();
+    __cxa_exception* exception_header = cxa_exception_from_thrown_object(thrown_object);
+
+    exception_header->unexpectedHandler = std::get_unexpected();
+    exception_header->terminateHandler  = std::get_terminate();
+    exception_header->exceptionType = tinfo;
+    exception_header->exceptionDestructor = dest;
+    setOurExceptionClass(&exception_header->unwindHeader);
+    exception_header->referenceCount = 1;  // This is a newly allocated exception, no need for thread safety.
+    globals->uncaughtExceptions += 1;   // Not atomically, since globals are thread-local
+
+    exception_header->unwindHeader.exception_cleanup = exception_cleanup_func;
+
+#if __has_feature(address_sanitizer)
+    // Inform the ASan runtime that now might be a good time to clean stuff up.
+    __asan_handle_no_return();
+#endif
+
+#ifdef __USING_SJLJ_EXCEPTIONS__
+    _Unwind_SjLj_RaiseException(&exception_header->unwindHeader);
+#else
+    _Unwind_RaiseException(&exception_header->unwindHeader);
+#endif
+    //  This only happens when there is no handler, or some unexpected unwinding
+    //     error happens.
+    failed_throw(exception_header);
+}
+
+
+// 2.5.3 Exception Handlers
+/*
+The adjusted pointer is computed by the personality routine during phase 1
+  and saved in the exception header (either __cxa_exception or
+  __cxa_dependent_exception).
+
+  Requires:  exception is native
+*/
+void *__cxa_get_exception_ptr(void *unwind_exception) throw() {
+#if defined(_LIBCXXABI_ARM_EHABI)
+    return reinterpret_cast<void*>(
+        static_cast<_Unwind_Control_Block*>(unwind_exception)->barrier_cache.bitpattern[0]);
+#else
+    return cxa_exception_from_exception_unwind_exception(
+        static_cast<_Unwind_Exception*>(unwind_exception))->adjustedPtr;
+#endif
+}
+
+#if defined(_LIBCXXABI_ARM_EHABI)
+/*
+The routine to be called before the cleanup.  This will save __cxa_exception in
+__cxa_eh_globals, so that __cxa_end_cleanup() can recover later.
+*/
+bool __cxa_begin_cleanup(void *unwind_arg) throw() {
+    _Unwind_Exception* unwind_exception = static_cast<_Unwind_Exception*>(unwind_arg);
+    __cxa_eh_globals* globals = __cxa_get_globals();
+    __cxa_exception* exception_header =
+        cxa_exception_from_exception_unwind_exception(unwind_exception);
+
+    if (__isOurExceptionClass(unwind_exception))
+    {
+        if (0 == exception_header->propagationCount)
+        {
+            exception_header->nextPropagatingException = globals->propagatingExceptions;
+            globals->propagatingExceptions = exception_header;
+        }
+        ++exception_header->propagationCount;
+    }
+    else
+    {
+        // If the propagatingExceptions stack is not empty, since we can't
+        // chain the foreign exception, terminate it.
+        if (NULL != globals->propagatingExceptions)
+            std::terminate();
+        globals->propagatingExceptions = exception_header;
+    }
+    return true;
+}
+
+/*
+The routine to be called after the cleanup has been performed.  It will get the
+propagating __cxa_exception from __cxa_eh_globals, and continue the stack
+unwinding with _Unwind_Resume.
+
+According to ARM EHABI 8.4.1, __cxa_end_cleanup() should not clobber any
+register, thus we have to write this function in assembly so that we can save
+{r1, r2, r3}.  We don't have to save r0 because it is the return value and the
+first argument to _Unwind_Resume().  The function also saves/restores r4 to
+keep the stack aligned and to provide a temp register.  _Unwind_Resume never
+returns and we need to keep the original lr so just branch to it.  When
+targeting bare metal, the function also clobbers ip/r12 to hold the address of
+_Unwind_Resume, which may be too far away for an ordinary branch.
+*/
+__attribute__((used)) static _Unwind_Exception *
+__cxa_end_cleanup_impl()
+{
+    __cxa_eh_globals* globals = __cxa_get_globals();
+    __cxa_exception* exception_header = globals->propagatingExceptions;
+    if (NULL == exception_header)
+    {
+        // It seems that __cxa_begin_cleanup() is not called properly.
+        // We have no choice but terminate the program now.
+        std::terminate();
+    }
+
+    if (__isOurExceptionClass(&exception_header->unwindHeader))
+    {
+        --exception_header->propagationCount;
+        if (0 == exception_header->propagationCount)
+        {
+            globals->propagatingExceptions = exception_header->nextPropagatingException;
+            exception_header->nextPropagatingException = NULL;
+        }
+    }
+    else
+    {
+        globals->propagatingExceptions = NULL;
+    }
+    return &exception_header->unwindHeader;
+}
+
+asm("	.pushsection	.text.__cxa_end_cleanup,\"ax\",%progbits\n"
+    "	.globl	__cxa_end_cleanup\n"
+    "	.type	__cxa_end_cleanup,%function\n"
+    "__cxa_end_cleanup:\n"
+#if defined(__ARM_FEATURE_BTI_DEFAULT)
+    "	bti\n"
+#endif
+    "	push	{r1, r2, r3, r4}\n"
+    "	mov	r4, lr\n"
+    "	bl	__cxa_end_cleanup_impl\n"
+    "	mov	lr, r4\n"
+#if defined(LIBCXXABI_BAREMETAL)
+    "	ldr	r4,	=_Unwind_Resume\n"
+    "	mov	ip,	r4\n"
+#endif
+    "	pop	{r1, r2, r3, r4}\n"
+#if defined(LIBCXXABI_BAREMETAL)
+    "	bx	ip\n"
+#else
+    "	b	_Unwind_Resume\n"
+#endif
+    "	.popsection");
+#endif // defined(_LIBCXXABI_ARM_EHABI)
+
+/*
+This routine can catch foreign or native exceptions.  If native, the exception
+can be a primary or dependent variety.  This routine may remain blissfully
+ignorant of whether the native exception is primary or dependent.
+
+If the exception is native:
+* Increment's the exception's handler count.
+* Push the exception on the stack of currently-caught exceptions if it is not
+  already there (from a rethrow).
+* Decrements the uncaught_exception count.
+* Returns the adjusted pointer to the exception object, which is stored in
+  the __cxa_exception by the personality routine.
+
+If the exception is foreign, this means it did not originate from one of throw
+routines.  The foreign exception does not necessarily have a __cxa_exception
+header.  However we can catch it here with a catch (...), or with a call
+to terminate or unexpected during unwinding.
+* Do not try to increment the exception's handler count, we don't know where
+  it is.
+* Push the exception on the stack of currently-caught exceptions only if the
+  stack is empty.  The foreign exception has no way to link to the current
+  top of stack.  If the stack is not empty, call terminate.  Even with an
+  empty stack, this is hacked in by pushing a pointer to an imaginary
+  __cxa_exception block in front of the foreign exception.  It would be better
+  if the __cxa_eh_globals structure had a stack of _Unwind_Exception, but it
+  doesn't.  It has a stack of __cxa_exception (which has a next* in it).
+* Do not decrement the uncaught_exception count because we didn't increment it
+  in __cxa_throw (or one of our rethrow functions).
+* If we haven't terminated, assume the exception object is just past the
+  _Unwind_Exception and return a pointer to that.
+*/
+void*
+__cxa_begin_catch(void* unwind_arg) throw()
+{
+    _Unwind_Exception* unwind_exception = static_cast<_Unwind_Exception*>(unwind_arg);
+    bool native_exception = __isOurExceptionClass(unwind_exception);
+    __cxa_eh_globals* globals = __cxa_get_globals();
+    // exception_header is a hackish offset from a foreign exception, but it
+    //   works as long as we're careful not to try to access any __cxa_exception
+    //   parts.
+    __cxa_exception* exception_header =
+            cxa_exception_from_exception_unwind_exception
+            (
+                static_cast<_Unwind_Exception*>(unwind_exception)
+            );
+
+#if defined(__MVS__)
+    // Remove the exception object from the linked list of exceptions that the z/OS unwinder
+    // maintains before adding it to the libc++abi list of caught exceptions.
+    // The libc++abi will manage the lifetime of the exception from this point forward.
+    _UnwindZOS_PopException();
+#endif
+
+    if (native_exception)
+    {
+        // Increment the handler count, removing the flag about being rethrown
+        exception_header->handlerCount = exception_header->handlerCount < 0 ?
+            -exception_header->handlerCount + 1 : exception_header->handlerCount + 1;
+        //  place the exception on the top of the stack if it's not already
+        //    there by a previous rethrow
+        if (exception_header != globals->caughtExceptions)
+        {
+            exception_header->nextException = globals->caughtExceptions;
+            globals->caughtExceptions = exception_header;
+        }
+        globals->uncaughtExceptions -= 1;   // Not atomically, since globals are thread-local
+#if defined(_LIBCXXABI_ARM_EHABI)
+        return reinterpret_cast<void*>(exception_header->unwindHeader.barrier_cache.bitpattern[0]);
+#else
+        return exception_header->adjustedPtr;
+#endif
+    }
+    // Else this is a foreign exception
+    // If the caughtExceptions stack is not empty, terminate
+    if (globals->caughtExceptions != 0)
+        std::terminate();
+    // Push the foreign exception on to the stack
+    globals->caughtExceptions = exception_header;
+    return unwind_exception + 1;
+}
+
+
+/*
+Upon exit for any reason, a handler must call:
+    void __cxa_end_catch ();
+
+This routine can be called for either a native or foreign exception.
+For a native exception:
+* Locates the most recently caught exception and decrements its handler count.
+* Removes the exception from the caught exception stack, if the handler count goes to zero.
+* If the handler count goes down to zero, and the exception was not re-thrown
+  by throw, it locates the primary exception (which may be the same as the one
+  it's handling) and decrements its reference count. If that reference count
+  goes to zero, the function destroys the exception. In any case, if the current
+  exception is a dependent exception, it destroys that.
+
+For a foreign exception:
+* If it has been rethrown, there is nothing to do.
+* Otherwise delete the exception and pop the catch stack to empty.
+*/
+void __cxa_end_catch() {
+  static_assert(sizeof(__cxa_exception) == sizeof(__cxa_dependent_exception),
+                "sizeof(__cxa_exception) must be equal to "
+                "sizeof(__cxa_dependent_exception)");
+  static_assert(__builtin_offsetof(__cxa_exception, referenceCount) ==
+                    __builtin_offsetof(__cxa_dependent_exception,
+                                       primaryException),
+                "the layout of __cxa_exception must match the layout of "
+                "__cxa_dependent_exception");
+  static_assert(__builtin_offsetof(__cxa_exception, handlerCount) ==
+                    __builtin_offsetof(__cxa_dependent_exception, handlerCount),
+                "the layout of __cxa_exception must match the layout of "
+                "__cxa_dependent_exception");
+    __cxa_eh_globals* globals = __cxa_get_globals_fast(); // __cxa_get_globals called in __cxa_begin_catch
+    __cxa_exception* exception_header = globals->caughtExceptions;
+    // If we've rethrown a foreign exception, then globals->caughtExceptions
+    //    will have been made an empty stack by __cxa_rethrow() and there is
+    //    nothing more to be done.  Do nothing!
+    if (NULL != exception_header)
+    {
+        bool native_exception = __isOurExceptionClass(&exception_header->unwindHeader);
+        if (native_exception)
+        {
+            // This is a native exception
+            if (exception_header->handlerCount < 0)
+            {
+                //  The exception has been rethrown by __cxa_rethrow, so don't delete it
+                if (0 == incrementHandlerCount(exception_header))
+                {
+                    //  Remove from the chain of uncaught exceptions
+                    globals->caughtExceptions = exception_header->nextException;
+                    // but don't destroy
+                }
+                // Keep handlerCount negative in case there are nested catch's
+                //   that need to be told that this exception is rethrown.  Don't
+                //   erase this rethrow flag until the exception is recaught.
+            }
+            else
+            {
+                // The native exception has not been rethrown
+                if (0 == decrementHandlerCount(exception_header))
+                {
+                    //  Remove from the chain of uncaught exceptions
+                    globals->caughtExceptions = exception_header->nextException;
+                    // Destroy this exception, being careful to distinguish
+                    //    between dependent and primary exceptions
+                    if (isDependentException(&exception_header->unwindHeader))
+                    {
+                        // Reset exception_header to primaryException and deallocate the dependent exception
+                        __cxa_dependent_exception* dep_exception_header =
+                            reinterpret_cast<__cxa_dependent_exception*>(exception_header);
+                        exception_header =
+                            cxa_exception_from_thrown_object(dep_exception_header->primaryException);
+                        __cxa_free_dependent_exception(dep_exception_header);
+                    }
+                    // Destroy the primary exception only if its referenceCount goes to 0
+                    //    (this decrement must be atomic)
+                    __cxa_decrement_exception_refcount(thrown_object_from_cxa_exception(exception_header));
+                }
+            }
+        }
+        else
+        {
+            // The foreign exception has not been rethrown.  Pop the stack
+            //    and delete it.  If there are nested catch's and they try
+            //    to touch a foreign exception in any way, that is undefined
+            //     behavior.  They likely can't since the only way to catch
+            //     a foreign exception is with catch (...)!
+            _Unwind_DeleteException(&globals->caughtExceptions->unwindHeader);
+            globals->caughtExceptions = 0;
+        }
+    }
+}
+
+// Note:  exception_header may be masquerading as a __cxa_dependent_exception
+//        and that's ok.  exceptionType is there too.
+//        However watch out for foreign exceptions.  Return null for them.
+std::type_info *__cxa_current_exception_type() {
+//  get the current exception
+    __cxa_eh_globals *globals = __cxa_get_globals_fast();
+    if (NULL == globals)
+        return NULL;     //  If there have never been any exceptions, there are none now.
+    __cxa_exception *exception_header = globals->caughtExceptions;
+    if (NULL == exception_header)
+        return NULL;        //  No current exception
+    if (!__isOurExceptionClass(&exception_header->unwindHeader))
+        return NULL;
+    return exception_header->exceptionType;
+}
+
+// 2.5.4 Rethrowing Exceptions
+/*  This routine can rethrow native or foreign exceptions.
+If the exception is native:
+* marks the exception object on top of the caughtExceptions stack
+  (in an implementation-defined way) as being rethrown.
+* If the caughtExceptions stack is empty, it calls terminate()
+  (see [C++FDIS] [except.throw], 15.1.8).
+* It then calls _Unwind_RaiseException which should not return
+   (terminate if it does).
+  Note:  exception_header may be masquerading as a __cxa_dependent_exception
+         and that's ok.
+*/
+void __cxa_rethrow() {
+    __cxa_eh_globals* globals = __cxa_get_globals();
+    __cxa_exception* exception_header = globals->caughtExceptions;
+    if (NULL == exception_header)
+        std::terminate();      // throw; called outside of a exception handler
+    bool native_exception = __isOurExceptionClass(&exception_header->unwindHeader);
+    if (native_exception)
+    {
+        //  Mark the exception as being rethrown (reverse the effects of __cxa_begin_catch)
+        exception_header->handlerCount = -exception_header->handlerCount;
+        globals->uncaughtExceptions += 1;
+        //  __cxa_end_catch will remove this exception from the caughtExceptions stack if necessary
+    }
+    else  // this is a foreign exception
+    {
+        // The only way to communicate to __cxa_end_catch that we've rethrown
+        //   a foreign exception, so don't delete us, is to pop the stack here
+        //   which must be empty afterwards.  Then __cxa_end_catch will do
+        //   nothing
+        globals->caughtExceptions = 0;
+    }
+#ifdef __USING_SJLJ_EXCEPTIONS__
+    _Unwind_SjLj_RaiseException(&exception_header->unwindHeader);
+#else
+    _Unwind_RaiseException(&exception_header->unwindHeader);
+#endif
+
+    //  If we get here, some kind of unwinding error has occurred.
+    //  There is some weird code generation bug happening with
+    //     Apple clang version 4.0 (tags/Apple/clang-418.0.2) (based on LLVM 3.1svn)
+    //     If we call failed_throw here.  Turns up with -O2 or higher, and -Os.
+    __cxa_begin_catch(&exception_header->unwindHeader);
+    if (native_exception)
+        std::__terminate(exception_header->terminateHandler);
+    // Foreign exception: can't get exception_header->terminateHandler
+    std::terminate();
+}
+
+/*
+    If thrown_object is not null, atomically increment the referenceCount field
+    of the __cxa_exception header associated with the thrown object referred to
+    by thrown_object.
+
+    Requires:  If thrown_object is not NULL, it is a native exception.
+*/
+void
+__cxa_increment_exception_refcount(void *thrown_object) throw() {
+    if (thrown_object != NULL )
+    {
+        __cxa_exception* exception_header = cxa_exception_from_thrown_object(thrown_object);
+        std::__libcpp_atomic_add(&exception_header->referenceCount, size_t(1));
+    }
+}
+
+/*
+    If thrown_object is not null, atomically decrement the referenceCount field
+    of the __cxa_exception header associated with the thrown object referred to
+    by thrown_object.  If the referenceCount drops to zero, destroy and
+    deallocate the exception.
+
+    Requires:  If thrown_object is not NULL, it is a native exception.
+*/
+_LIBCXXABI_NO_CFI
+void __cxa_decrement_exception_refcount(void *thrown_object) throw() {
+    if (thrown_object != NULL )
+    {
+        __cxa_exception* exception_header = cxa_exception_from_thrown_object(thrown_object);
+        if (std::__libcpp_atomic_add(&exception_header->referenceCount, size_t(-1)) == 0)
+        {
+            if (NULL != exception_header->exceptionDestructor)
+                exception_header->exceptionDestructor(thrown_object);
+            __cxa_free_exception(thrown_object);
+        }
+    }
+}
+
+/*
+    Returns a pointer to the thrown object (if any) at the top of the
+    caughtExceptions stack.  Atomically increment the exception's referenceCount.
+    If there is no such thrown object or if the thrown object is foreign,
+    returns null.
+
+    We can use __cxa_get_globals_fast here to get the globals because if there have
+    been no exceptions thrown, ever, on this thread, we can return NULL without
+    the need to allocate the exception-handling globals.
+*/
+void *__cxa_current_primary_exception() throw() {
+//  get the current exception
+    __cxa_eh_globals* globals = __cxa_get_globals_fast();
+    if (NULL == globals)
+        return NULL;        //  If there are no globals, there is no exception
+    __cxa_exception* exception_header = globals->caughtExceptions;
+    if (NULL == exception_header)
+        return NULL;        //  No current exception
+    if (!__isOurExceptionClass(&exception_header->unwindHeader))
+        return NULL;        // Can't capture a foreign exception (no way to refcount it)
+    if (isDependentException(&exception_header->unwindHeader)) {
+        __cxa_dependent_exception* dep_exception_header =
+            reinterpret_cast<__cxa_dependent_exception*>(exception_header);
+        exception_header = cxa_exception_from_thrown_object(dep_exception_header->primaryException);
+    }
+    void* thrown_object = thrown_object_from_cxa_exception(exception_header);
+    __cxa_increment_exception_refcount(thrown_object);
+    return thrown_object;
+}
+
+/*
+    If reason isn't _URC_FOREIGN_EXCEPTION_CAUGHT, then the terminateHandler
+    stored in exc is called.  Otherwise the referenceCount stored in the
+    primary exception is decremented, destroying the primary if necessary.
+    Finally the dependent exception is destroyed.
+*/
+static
+void
+dependent_exception_cleanup(_Unwind_Reason_Code reason, _Unwind_Exception* unwind_exception)
+{
+    __cxa_dependent_exception* dep_exception_header =
+                      reinterpret_cast<__cxa_dependent_exception*>(unwind_exception + 1) - 1;
+    if (_URC_FOREIGN_EXCEPTION_CAUGHT != reason)
+        std::__terminate(dep_exception_header->terminateHandler);
+    __cxa_decrement_exception_refcount(dep_exception_header->primaryException);
+    __cxa_free_dependent_exception(dep_exception_header);
+}
+
+/*
+    If thrown_object is not null, allocate, initialize and throw a dependent
+    exception.
+*/
+void
+__cxa_rethrow_primary_exception(void* thrown_object)
+{
+    if ( thrown_object != NULL )
+    {
+        // thrown_object guaranteed to be native because
+        //   __cxa_current_primary_exception returns NULL for foreign exceptions
+        __cxa_exception* exception_header = cxa_exception_from_thrown_object(thrown_object);
+        __cxa_dependent_exception* dep_exception_header =
+            static_cast<__cxa_dependent_exception*>(__cxa_allocate_dependent_exception());
+        dep_exception_header->primaryException = thrown_object;
+        __cxa_increment_exception_refcount(thrown_object);
+        dep_exception_header->exceptionType = exception_header->exceptionType;
+        dep_exception_header->unexpectedHandler = std::get_unexpected();
+        dep_exception_header->terminateHandler = std::get_terminate();
+        setDependentExceptionClass(&dep_exception_header->unwindHeader);
+        __cxa_get_globals()->uncaughtExceptions += 1;
+        dep_exception_header->unwindHeader.exception_cleanup = dependent_exception_cleanup;
+#ifdef __USING_SJLJ_EXCEPTIONS__
+        _Unwind_SjLj_RaiseException(&dep_exception_header->unwindHeader);
+#else
+        _Unwind_RaiseException(&dep_exception_header->unwindHeader);
+#endif
+        // Some sort of unwinding error.  Note that terminate is a handler.
+        __cxa_begin_catch(&dep_exception_header->unwindHeader);
+    }
+    // If we return client will call terminate()
+}
+
+bool
+__cxa_uncaught_exception() throw() { return __cxa_uncaught_exceptions() != 0; }
+
+unsigned int
+__cxa_uncaught_exceptions() throw()
+{
+    // This does not report foreign exceptions in flight
+    __cxa_eh_globals* globals = __cxa_get_globals_fast();
+    if (globals == 0)
+        return 0;
+    return globals->uncaughtExceptions;
+}
+
+}  // extern "C"
+
+}  // abi

third_party/libcxxabi/cxa_exception.h

@@ -0,0 +1,164 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//
+//  This file implements the "Exception Handling APIs"
+//  https://itanium-cxx-abi.github.io/cxx-abi/abi-eh.html
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _CXA_EXCEPTION_H
+#define _CXA_EXCEPTION_H
+
+#include "third_party/libcxx/exception" // for std::unexpected_handler and std::terminate_handler
+#include "third_party/libcxxabi/include/cxxabi.h"
+#include "third_party/libunwind/include/unwind.h"
+
+namespace __cxxabiv1 {
+
+static const uint64_t kOurExceptionClass          = 0x434C4E47432B2B00; // CLNGC++\0
+static const uint64_t kOurDependentExceptionClass = 0x434C4E47432B2B01; // CLNGC++\1
+static const uint64_t get_vendor_and_language     = 0xFFFFFFFFFFFFFF00; // mask for CLNGC++
+
+_LIBCXXABI_HIDDEN uint64_t __getExceptionClass  (const _Unwind_Exception*);
+_LIBCXXABI_HIDDEN void     __setExceptionClass  (      _Unwind_Exception*, uint64_t);
+_LIBCXXABI_HIDDEN bool     __isOurExceptionClass(const _Unwind_Exception*);
+
+struct _LIBCXXABI_HIDDEN __cxa_exception {
+#if defined(__LP64__) || defined(_WIN64) || defined(_LIBCXXABI_ARM_EHABI)
+    // Now _Unwind_Exception is marked with __attribute__((aligned)),
+    // which implies __cxa_exception is also aligned. Insert padding
+    // in the beginning of the struct, rather than before unwindHeader.
+    void *reserve;
+
+    // This is a new field to support C++11 exception_ptr.
+    // For binary compatibility it is at the start of this
+    // struct which is prepended to the object thrown in
+    // __cxa_allocate_exception.
+    size_t referenceCount;
+#endif
+
+    //  Manage the exception object itself.
+    std::type_info *exceptionType;
+    void (_LIBCXXABI_DTOR_FUNC *exceptionDestructor)(void *);
+    std::unexpected_handler unexpectedHandler;
+    std::terminate_handler  terminateHandler;
+
+    __cxa_exception *nextException;
+
+    int handlerCount;
+
+#if defined(_LIBCXXABI_ARM_EHABI)
+    __cxa_exception* nextPropagatingException;
+    int propagationCount;
+#else
+    int handlerSwitchValue;
+    const unsigned char *actionRecord;
+    const unsigned char *languageSpecificData;
+    void *catchTemp;
+    void *adjustedPtr;
+#endif
+
+#if !defined(__LP64__) && !defined(_WIN64) && !defined(_LIBCXXABI_ARM_EHABI)
+    // This is a new field to support C++11 exception_ptr.
+    // For binary compatibility it is placed where the compiler
+    // previously added padding to 64-bit align unwindHeader.
+    size_t referenceCount;
+#endif
+    _Unwind_Exception unwindHeader;
+};
+
+// http://sourcery.mentor.com/archives/cxx-abi-dev/msg01924.html
+// The layout of this structure MUST match the layout of __cxa_exception, with
+// primaryException instead of referenceCount.
+struct _LIBCXXABI_HIDDEN __cxa_dependent_exception {
+#if defined(__LP64__) || defined(_WIN64) || defined(_LIBCXXABI_ARM_EHABI)
+    void* reserve; // padding.
+    void* primaryException;
+#endif
+
+    std::type_info *exceptionType;
+    void (_LIBCXXABI_DTOR_FUNC *exceptionDestructor)(void *);
+    std::unexpected_handler unexpectedHandler;
+    std::terminate_handler terminateHandler;
+
+    __cxa_exception *nextException;
+
+    int handlerCount;
+
+#if defined(_LIBCXXABI_ARM_EHABI)
+    __cxa_exception* nextPropagatingException;
+    int propagationCount;
+#else
+    int handlerSwitchValue;
+    const unsigned char *actionRecord;
+    const unsigned char *languageSpecificData;
+    void * catchTemp;
+    void *adjustedPtr;
+#endif
+
+#if !defined(__LP64__) && !defined(_WIN64) && !defined(_LIBCXXABI_ARM_EHABI)
+    void* primaryException;
+#endif
+    _Unwind_Exception unwindHeader;
+};
+
+// Verify the negative offsets of different fields.
+static_assert(sizeof(_Unwind_Exception) +
+                      offsetof(__cxa_exception, unwindHeader) ==
+                  sizeof(__cxa_exception),
+              "unwindHeader has wrong negative offsets");
+static_assert(sizeof(_Unwind_Exception) +
+                      offsetof(__cxa_dependent_exception, unwindHeader) ==
+                  sizeof(__cxa_dependent_exception),
+              "unwindHeader has wrong negative offsets");
+
+#if defined(_LIBCXXABI_ARM_EHABI)
+static_assert(offsetof(__cxa_exception, propagationCount) +
+                      sizeof(_Unwind_Exception) + sizeof(void*) ==
+                  sizeof(__cxa_exception),
+              "propagationCount has wrong negative offset");
+static_assert(offsetof(__cxa_dependent_exception, propagationCount) +
+                      sizeof(_Unwind_Exception) + sizeof(void*) ==
+                  sizeof(__cxa_dependent_exception),
+              "propagationCount has wrong negative offset");
+#elif defined(__LP64__) || defined(_WIN64)
+static_assert(offsetof(__cxa_exception, adjustedPtr) +
+                      sizeof(_Unwind_Exception) + sizeof(void*) ==
+                  sizeof(__cxa_exception),
+              "adjustedPtr has wrong negative offset");
+static_assert(offsetof(__cxa_dependent_exception, adjustedPtr) +
+                      sizeof(_Unwind_Exception) + sizeof(void*) ==
+                  sizeof(__cxa_dependent_exception),
+              "adjustedPtr has wrong negative offset");
+#else
+static_assert(offsetof(__cxa_exception, referenceCount) +
+                      sizeof(_Unwind_Exception) + sizeof(void*) ==
+                  sizeof(__cxa_exception),
+              "referenceCount has wrong negative offset");
+static_assert(offsetof(__cxa_dependent_exception, primaryException) +
+                      sizeof(_Unwind_Exception) + sizeof(void*) ==
+                  sizeof(__cxa_dependent_exception),
+              "primaryException has wrong negative offset");
+#endif
+
+struct _LIBCXXABI_HIDDEN __cxa_eh_globals {
+    __cxa_exception *   caughtExceptions;
+    unsigned int        uncaughtExceptions;
+#if defined(_LIBCXXABI_ARM_EHABI)
+    __cxa_exception* propagatingExceptions;
+#endif
+};
+
+extern "C" _LIBCXXABI_FUNC_VIS __cxa_eh_globals * __cxa_get_globals      ();
+extern "C" _LIBCXXABI_FUNC_VIS __cxa_eh_globals * __cxa_get_globals_fast ();
+
+extern "C" _LIBCXXABI_FUNC_VIS void * __cxa_allocate_dependent_exception ();
+extern "C" _LIBCXXABI_FUNC_VIS void __cxa_free_dependent_exception (void * dependent_exception);
+
+}  // namespace __cxxabiv1
+
+#endif // _CXA_EXCEPTION_H

third_party/libcxxabi/cxa_exception_storage.cc

@@ -0,0 +1,103 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//
+//  This file implements the storage for the "Caught Exception Stack"
+//  https://itanium-cxx-abi.github.io/cxx-abi/abi-eh.html#cxx-exc-stack
+//
+//===----------------------------------------------------------------------===//
+
+#include "third_party/libcxxabi/cxa_exception.h"
+
+#include "third_party/libcxx/__threading_support"
+
+#if defined(_LIBCXXABI_HAS_NO_THREADS)
+
+namespace __cxxabiv1 {
+extern "C" {
+    static __cxa_eh_globals eh_globals;
+    __cxa_eh_globals *__cxa_get_globals() { return &eh_globals; }
+    __cxa_eh_globals *__cxa_get_globals_fast() { return &eh_globals; }
+} // extern "C"
+} // namespace __cxxabiv1
+
+#elif defined(HAS_THREAD_LOCAL)
+
+namespace __cxxabiv1 {
+namespace {
+    __cxa_eh_globals *__globals() {
+        static thread_local __cxa_eh_globals eh_globals;
+        return &eh_globals;
+    }
+} // namespace
+
+extern "C" {
+    __cxa_eh_globals *__cxa_get_globals() { return __globals(); }
+    __cxa_eh_globals *__cxa_get_globals_fast() { return __globals(); }
+} // extern "C"
+} // namespace __cxxabiv1
+
+#else
+
+#include "third_party/libcxxabi/abort_message.h"
+#include "third_party/libcxxabi/fallback_malloc.h"
+
+#if defined(__ELF__) && defined(_LIBCXXABI_LINK_PTHREAD_LIB)
+#pragma comment(lib, "pthread")
+#endif
+
+//  In general, we treat all threading errors as fatal.
+//  We cannot call std::terminate() because that will in turn
+//  call __cxa_get_globals() and cause infinite recursion.
+
+namespace __cxxabiv1 {
+namespace {
+    std::__libcpp_tls_key key_;
+    std::__libcpp_exec_once_flag flag_ = _LIBCPP_EXEC_ONCE_INITIALIZER;
+
+    void _LIBCPP_TLS_DESTRUCTOR_CC destruct_(void *p) {
+        __free_with_fallback(p);
+        if (0 != std::__libcpp_tls_set(key_, NULL))
+            abort_message("cannot zero out thread value for __cxa_get_globals()");
+    }
+
+    void construct_() {
+        if (0 != std::__libcpp_tls_create(&key_, destruct_))
+            abort_message("cannot create thread specific key for __cxa_get_globals()");
+    }
+} // namespace
+
+extern "C" {
+    __cxa_eh_globals *__cxa_get_globals() {
+        // Try to get the globals for this thread
+        __cxa_eh_globals *retVal = __cxa_get_globals_fast();
+
+        // If this is the first time we've been asked for these globals, create them
+        if (NULL == retVal) {
+            retVal = static_cast<__cxa_eh_globals*>(
+                __calloc_with_fallback(1, sizeof(__cxa_eh_globals)));
+            if (NULL == retVal)
+                abort_message("cannot allocate __cxa_eh_globals");
+            if (0 != std::__libcpp_tls_set(key_, retVal))
+               abort_message("std::__libcpp_tls_set failure in __cxa_get_globals()");
+        }
+        return retVal;
+    }
+
+    // Note that this implementation will reliably return NULL if not
+    // preceded by a call to __cxa_get_globals().  This is an extension
+    // to the Itanium ABI and is taken advantage of in several places in
+    // libc++abi.
+    __cxa_eh_globals *__cxa_get_globals_fast() {
+        // First time through, create the key.
+        if (0 != std::__libcpp_execute_once(&flag_, construct_))
+            abort_message("execute once failure in __cxa_get_globals_fast()");
+        return static_cast<__cxa_eh_globals*>(std::__libcpp_tls_get(key_));
+    }
+} // extern "C"
+} // namespace __cxxabiv1
+
+#endif

third_party/libcxxabi/cxa_guard.cc

@@ -0,0 +1,53 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "third_party/libcxxabi/include/__cxxabi_config.h"
+#include "third_party/libcxxabi/include/cxxabi.h"
+
+// Tell the implementation that we're building the actual implementation
+// (and not testing it)
+#define BUILDING_CXA_GUARD
+#include "third_party/libcxxabi/cxa_guard_impl.h"
+
+/*
+    This implementation must be careful to not call code external to this file
+    which will turn around and try to call __cxa_guard_acquire reentrantly.
+    For this reason, the headers of this file are as restricted as possible.
+    Previous implementations of this code for __APPLE__ have used
+    std::__libcpp_mutex_lock and the abort_message utility without problem. This
+    implementation also uses std::__libcpp_condvar_wait which has tested
+    to not be a problem.
+*/
+
+namespace __cxxabiv1 {
+
+#if defined(_LIBCXXABI_GUARD_ABI_ARM)
+using guard_type = uint32_t;
+#else
+using guard_type = uint64_t;
+#endif
+
+extern "C"
+{
+_LIBCXXABI_FUNC_VIS int __cxa_guard_acquire(guard_type* raw_guard_object) {
+  SelectedImplementation imp(raw_guard_object);
+  return static_cast<int>(imp.cxa_guard_acquire());
+}
+
+_LIBCXXABI_FUNC_VIS void __cxa_guard_release(guard_type *raw_guard_object) {
+  SelectedImplementation imp(raw_guard_object);
+  imp.cxa_guard_release();
+}
+
+_LIBCXXABI_FUNC_VIS void __cxa_guard_abort(guard_type *raw_guard_object) {
+  SelectedImplementation imp(raw_guard_object);
+  imp.cxa_guard_abort();
+}
+}  // extern "C"
+
+}  // __cxxabiv1

third_party/libcxxabi/cxa_guard_impl.h

@@ -0,0 +1,674 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LIBCXXABI_SRC_INCLUDE_CXA_GUARD_IMPL_H
+#define LIBCXXABI_SRC_INCLUDE_CXA_GUARD_IMPL_H
+
+/* cxa_guard_impl.h - Implements the C++ runtime support for function local
+ * static guards.
+ * The layout of the guard object is the same across ARM and Itanium.
+ *
+ * The first "guard byte" (which is checked by the compiler) is set only upon
+ * the completion of cxa release.
+ *
+ * The second "init byte" does the rest of the bookkeeping. It tracks if
+ * initialization is complete or pending, and if there are waiting threads.
+ *
+ * If the guard variable is 64-bits and the platforms supplies a 32-bit thread
+ * identifier, it is used to detect recursive initialization. The thread ID of
+ * the thread currently performing initialization is stored in the second word.
+ *
+ *  Guard Object Layout:
+ * ---------------------------------------------------------------------------
+ * | a+0: guard byte | a+1: init byte | a+2: unused ... | a+4: thread-id ... |
+ * ---------------------------------------------------------------------------
+ *
+ * Note that we don't do what the ABI docs suggest (put a mutex in the guard
+ * object which we acquire in cxa_guard_acquire and release in
+ * cxa_guard_release). Instead we use the init byte to imitate that behaviour,
+ * but without actually holding anything mutex related between aquire and
+ * release/abort.
+ *
+ *  Access Protocol:
+ *    For each implementation the guard byte is checked and set before accessing
+ *    the init byte.
+ *
+ *  Overall Design:
+ *    The implementation was designed to allow each implementation to be tested
+ *    independent of the C++ runtime or platform support.
+ *
+ */
+
+#include "third_party/libcxxabi/include/__cxxabi_config.h"
+#include "third_party/libcxx/include/atomic_support.hh" // from libc++
+#if defined(__has_include)
+#  if __has_include(<sys/syscall.h>)
+#    include <sys/syscall.h>
+#  endif
+#  if __has_include(<unistd.h>)
+#    include <unistd.h>
+#  endif
+#endif
+
+#include "third_party/libcxx/__threading_support"
+#include "third_party/libcxx/cstdint"
+#include "third_party/libcxx/cstring"
+#include "libc/isystem/limits.h"
+#include "libc/isystem/stdlib.h"
+
+#ifndef _LIBCXXABI_HAS_NO_THREADS
+#  if defined(__ELF__) && defined(_LIBCXXABI_LINK_PTHREAD_LIB)
+#    pragma comment(lib, "pthread")
+#  endif
+#endif
+
+#if defined(__clang__)
+#  pragma clang diagnostic push
+#  pragma clang diagnostic ignored "-Wtautological-pointer-compare"
+#elif defined(__GNUC__)
+#  pragma GCC diagnostic push
+#  pragma GCC diagnostic ignored "-Waddress"
+#endif
+
+// To make testing possible, this header is included from both cxa_guard.cpp
+// and a number of tests.
+//
+// For this reason we place everything in an anonymous namespace -- even though
+// we're in a header. We want the actual implementation and the tests to have
+// unique definitions of the types in this header (since the tests may depend
+// on function local statics).
+//
+// To enforce this either `BUILDING_CXA_GUARD` or `TESTING_CXA_GUARD` must be
+// defined when including this file. Only `src/cxa_guard.cpp` should define
+// the former.
+#ifdef BUILDING_CXA_GUARD
+#  include "third_party/libcxxabi/abort_message.h"
+#  define ABORT_WITH_MESSAGE(...) ::abort_message(__VA_ARGS__)
+#elif defined(TESTING_CXA_GUARD)
+#  define ABORT_WITH_MESSAGE(...) ::abort()
+#else
+#  error "Either BUILDING_CXA_GUARD or TESTING_CXA_GUARD must be defined"
+#endif
+
+#if __has_feature(thread_sanitizer)
+extern "C" void __tsan_acquire(void*);
+extern "C" void __tsan_release(void*);
+#else
+#  define __tsan_acquire(addr) ((void)0)
+#  define __tsan_release(addr) ((void)0)
+#endif
+
+namespace __cxxabiv1 {
+// Use an anonymous namespace to ensure that the tests and actual implementation
+// have unique definitions of these symbols.
+namespace {
+
+//===----------------------------------------------------------------------===//
+//                          Misc Utilities
+//===----------------------------------------------------------------------===//
+
+template <class T, T (*Init)()>
+struct LazyValue {
+  LazyValue() : is_init(false) {}
+
+  T& get() {
+    if (!is_init) {
+      value = Init();
+      is_init = true;
+    }
+    return value;
+  }
+
+private:
+  T value;
+  bool is_init = false;
+};
+
+template <class IntType>
+class AtomicInt {
+public:
+  using MemoryOrder = std::__libcpp_atomic_order;
+
+  explicit AtomicInt(IntType* b) : b_(b) {}
+  AtomicInt(AtomicInt const&) = delete;
+  AtomicInt& operator=(AtomicInt const&) = delete;
+
+  IntType load(MemoryOrder ord) { return std::__libcpp_atomic_load(b_, ord); }
+  void store(IntType val, MemoryOrder ord) { std::__libcpp_atomic_store(b_, val, ord); }
+  IntType exchange(IntType new_val, MemoryOrder ord) { return std::__libcpp_atomic_exchange(b_, new_val, ord); }
+  bool compare_exchange(IntType* expected, IntType desired, MemoryOrder ord_success, MemoryOrder ord_failure) {
+    return std::__libcpp_atomic_compare_exchange(b_, expected, desired, ord_success, ord_failure);
+  }
+
+private:
+  IntType* b_;
+};
+
+//===----------------------------------------------------------------------===//
+//                       PlatformGetThreadID
+//===----------------------------------------------------------------------===//
+
+#if defined(__APPLE__) && defined(_LIBCPP_HAS_THREAD_API_PTHREAD)
+uint32_t PlatformThreadID() {
+  static_assert(sizeof(mach_port_t) == sizeof(uint32_t), "");
+  return static_cast<uint32_t>(pthread_mach_thread_np(std::__libcpp_thread_get_current_id()));
+}
+#elif defined(SYS_gettid) && defined(_LIBCPP_HAS_THREAD_API_PTHREAD)
+uint32_t PlatformThreadID() {
+  static_assert(sizeof(pid_t) == sizeof(uint32_t), "");
+  return static_cast<uint32_t>(syscall(SYS_gettid));
+}
+#else
+constexpr uint32_t (*PlatformThreadID)() = nullptr;
+#endif
+
+//===----------------------------------------------------------------------===//
+//                          GuardByte
+//===----------------------------------------------------------------------===//
+
+static constexpr uint8_t UNSET = 0;
+static constexpr uint8_t COMPLETE_BIT = (1 << 0);
+static constexpr uint8_t PENDING_BIT = (1 << 1);
+static constexpr uint8_t WAITING_BIT = (1 << 2);
+
+/// Manages reads and writes to the guard byte.
+struct GuardByte {
+  GuardByte() = delete;
+  GuardByte(GuardByte const&) = delete;
+  GuardByte& operator=(GuardByte const&) = delete;
+
+  explicit GuardByte(uint8_t* const guard_byte_address) : guard_byte(guard_byte_address) {}
+
+public:
+  /// The guard byte portion of cxa_guard_acquire. Returns true if
+  /// initialization has already been completed.
+  bool acquire() {
+    // if guard_byte is non-zero, we have already completed initialization
+    // (i.e. release has been called)
+    return guard_byte.load(std::_AO_Acquire) != UNSET;
+  }
+
+  /// The guard byte portion of cxa_guard_release.
+  void release() { guard_byte.store(COMPLETE_BIT, std::_AO_Release); }
+
+  /// The guard byte portion of cxa_guard_abort.
+  void abort() {} // Nothing to do
+
+private:
+  AtomicInt<uint8_t> guard_byte;
+};
+
+//===----------------------------------------------------------------------===//
+//                       InitByte Implementations
+//===----------------------------------------------------------------------===//
+//
+// Each initialization byte implementation supports the following methods:
+//
+//  InitByte(uint8_t* _init_byte_address, uint32_t* _thread_id_address)
+//    Construct the InitByte object, initializing our member variables
+//
+//  bool acquire()
+//    Called before we start the initialization. Check if someone else has already started, and if
+//    not to signal our intent to start it ourselves. We determine the current status from the init
+//    byte, which is one of 4 possible values:
+//      COMPLETE:           Initialization was finished by somebody else. Return true.
+//      PENDING:            Somebody has started the initialization already, set the WAITING bit,
+//                          then wait for the init byte to get updated with a new value.
+//      (PENDING|WAITING):  Somebody has started the initialization already, and we're not the
+//                          first one waiting. Wait for the init byte to get updated.
+//      UNSET:              Initialization hasn't successfully completed, and nobody is currently
+//                          performing the initialization. Set the PENDING bit to indicate our
+//                          intention to start the initialization, and return false.
+//    The return value indicates whether initialization has already been completed.
+//
+//  void release()
+//    Called after successfully completing the initialization. Update the init byte to reflect
+//    that, then if anybody else is waiting, wake them up.
+//
+//  void abort()
+//    Called after an error is thrown during the initialization. Reset the init byte to UNSET to
+//    indicate that we're no longer performing the initialization, then if anybody is waiting, wake
+//    them up so they can try performing the initialization.
+//
+
+//===----------------------------------------------------------------------===//
+//                    Single Threaded Implementation
+//===----------------------------------------------------------------------===//
+
+/// InitByteNoThreads - Doesn't use any inter-thread synchronization when
+/// managing reads and writes to the init byte.
+struct InitByteNoThreads {
+  InitByteNoThreads() = delete;
+  InitByteNoThreads(InitByteNoThreads const&) = delete;
+  InitByteNoThreads& operator=(InitByteNoThreads const&) = delete;
+
+  explicit InitByteNoThreads(uint8_t* _init_byte_address, uint32_t*) : init_byte_address(_init_byte_address) {}
+
+  /// The init byte portion of cxa_guard_acquire. Returns true if
+  /// initialization has already been completed.
+  bool acquire() {
+    if (*init_byte_address == COMPLETE_BIT)
+      return true;
+    if (*init_byte_address & PENDING_BIT)
+      ABORT_WITH_MESSAGE("__cxa_guard_acquire detected recursive initialization: do you have a function-local static variable whose initialization depends on that function?");
+    *init_byte_address = PENDING_BIT;
+    return false;
+  }
+
+  /// The init byte portion of cxa_guard_release.
+  void release() { *init_byte_address = COMPLETE_BIT; }
+  /// The init byte portion of cxa_guard_abort.
+  void abort() { *init_byte_address = UNSET; }
+
+private:
+  /// The address of the byte used during initialization.
+  uint8_t* const init_byte_address;
+};
+
+//===----------------------------------------------------------------------===//
+//                     Global Mutex Implementation
+//===----------------------------------------------------------------------===//
+
+struct LibcppMutex;
+struct LibcppCondVar;
+
+#ifndef _LIBCXXABI_HAS_NO_THREADS
+struct LibcppMutex {
+  LibcppMutex() = default;
+  LibcppMutex(LibcppMutex const&) = delete;
+  LibcppMutex& operator=(LibcppMutex const&) = delete;
+
+  bool lock() { return std::__libcpp_mutex_lock(&mutex); }
+  bool unlock() { return std::__libcpp_mutex_unlock(&mutex); }
+
+private:
+  friend struct LibcppCondVar;
+  std::__libcpp_mutex_t mutex = _LIBCPP_MUTEX_INITIALIZER;
+};
+
+struct LibcppCondVar {
+  LibcppCondVar() = default;
+  LibcppCondVar(LibcppCondVar const&) = delete;
+  LibcppCondVar& operator=(LibcppCondVar const&) = delete;
+
+  bool wait(LibcppMutex& mut) { return std::__libcpp_condvar_wait(&cond, &mut.mutex); }
+  bool broadcast() { return std::__libcpp_condvar_broadcast(&cond); }
+
+private:
+  std::__libcpp_condvar_t cond = _LIBCPP_CONDVAR_INITIALIZER;
+};
+#else
+struct LibcppMutex {};
+struct LibcppCondVar {};
+#endif // !defined(_LIBCXXABI_HAS_NO_THREADS)
+
+/// InitByteGlobalMutex - Uses a global mutex and condition variable (common to
+/// all static local variables) to manage reads and writes to the init byte.
+template <class Mutex, class CondVar, Mutex& global_mutex, CondVar& global_cond,
+          uint32_t (*GetThreadID)() = PlatformThreadID>
+struct InitByteGlobalMutex {
+
+  explicit InitByteGlobalMutex(uint8_t* _init_byte_address, uint32_t* _thread_id_address)
+      : init_byte_address(_init_byte_address), thread_id_address(_thread_id_address),
+        has_thread_id_support(_thread_id_address != nullptr && GetThreadID != nullptr) {}
+
+public:
+  /// The init byte portion of cxa_guard_acquire. Returns true if
+  /// initialization has already been completed.
+  bool acquire() {
+    LockGuard g("__cxa_guard_acquire");
+    // Check for possible recursive initialization.
+    if (has_thread_id_support && (*init_byte_address & PENDING_BIT)) {
+      if (*thread_id_address == current_thread_id.get())
+        ABORT_WITH_MESSAGE("__cxa_guard_acquire detected recursive initialization: do you have a function-local static variable whose initialization depends on that function?");
+    }
+
+    // Wait until the pending bit is not set.
+    while (*init_byte_address & PENDING_BIT) {
+      *init_byte_address |= WAITING_BIT;
+      global_cond.wait(global_mutex);
+    }
+
+    if (*init_byte_address == COMPLETE_BIT)
+      return true;
+
+    if (has_thread_id_support)
+      *thread_id_address = current_thread_id.get();
+
+    *init_byte_address = PENDING_BIT;
+    return false;
+  }
+
+  /// The init byte portion of cxa_guard_release.
+  void release() {
+    bool has_waiting;
+    {
+      LockGuard g("__cxa_guard_release");
+      has_waiting = *init_byte_address & WAITING_BIT;
+      *init_byte_address = COMPLETE_BIT;
+    }
+    if (has_waiting) {
+      if (global_cond.broadcast()) {
+        ABORT_WITH_MESSAGE("%s failed to broadcast", "__cxa_guard_release");
+      }
+    }
+  }
+
+  /// The init byte portion of cxa_guard_abort.
+  void abort() {
+    bool has_waiting;
+    {
+      LockGuard g("__cxa_guard_abort");
+      if (has_thread_id_support)
+        *thread_id_address = 0;
+      has_waiting = *init_byte_address & WAITING_BIT;
+      *init_byte_address = UNSET;
+    }
+    if (has_waiting) {
+      if (global_cond.broadcast()) {
+        ABORT_WITH_MESSAGE("%s failed to broadcast", "__cxa_guard_abort");
+      }
+    }
+  }
+
+private:
+  /// The address of the byte used during initialization.
+  uint8_t* const init_byte_address;
+  /// An optional address storing an identifier for the thread performing initialization.
+  /// It's used to detect recursive initialization.
+  uint32_t* const thread_id_address;
+
+  const bool has_thread_id_support;
+  LazyValue<uint32_t, GetThreadID> current_thread_id;
+
+private:
+  struct LockGuard {
+    LockGuard() = delete;
+    LockGuard(LockGuard const&) = delete;
+    LockGuard& operator=(LockGuard const&) = delete;
+
+    explicit LockGuard(const char* calling_func) : calling_func_(calling_func) {
+      if (global_mutex.lock())
+        ABORT_WITH_MESSAGE("%s failed to acquire mutex", calling_func_);
+    }
+
+    ~LockGuard() {
+      if (global_mutex.unlock())
+        ABORT_WITH_MESSAGE("%s failed to release mutex", calling_func_);
+    }
+
+  private:
+    const char* const calling_func_;
+  };
+};
+
+//===----------------------------------------------------------------------===//
+//                         Futex Implementation
+//===----------------------------------------------------------------------===//
+
+#if defined(SYS_futex)
+void PlatformFutexWait(int* addr, int expect) {
+  constexpr int WAIT = 0;
+  syscall(SYS_futex, addr, WAIT, expect, 0);
+  __tsan_acquire(addr);
+}
+void PlatformFutexWake(int* addr) {
+  constexpr int WAKE = 1;
+  __tsan_release(addr);
+  syscall(SYS_futex, addr, WAKE, INT_MAX);
+}
+#else
+constexpr void (*PlatformFutexWait)(int*, int) = nullptr;
+constexpr void (*PlatformFutexWake)(int*) = nullptr;
+#endif
+
+constexpr bool PlatformSupportsFutex() { return +PlatformFutexWait != nullptr; }
+
+/// InitByteFutex - Uses a futex to manage reads and writes to the init byte.
+template <void (*Wait)(int*, int) = PlatformFutexWait, void (*Wake)(int*) = PlatformFutexWake,
+          uint32_t (*GetThreadIDArg)() = PlatformThreadID>
+struct InitByteFutex {
+
+  explicit InitByteFutex(uint8_t* _init_byte_address, uint32_t* _thread_id_address)
+      : init_byte(_init_byte_address),
+        has_thread_id_support(_thread_id_address != nullptr && GetThreadIDArg != nullptr),
+        thread_id(_thread_id_address),
+        base_address(reinterpret_cast<int*>(/*_init_byte_address & ~0x3*/ _init_byte_address - 1)) {}
+
+public:
+  /// The init byte portion of cxa_guard_acquire. Returns true if
+  /// initialization has already been completed.
+  bool acquire() {
+    while (true) {
+      uint8_t last_val = UNSET;
+      if (init_byte.compare_exchange(&last_val, PENDING_BIT, std::_AO_Acq_Rel, std::_AO_Acquire)) {
+        if (has_thread_id_support) {
+          thread_id.store(current_thread_id.get(), std::_AO_Relaxed);
+        }
+        return false;
+      }
+
+      if (last_val == COMPLETE_BIT)
+        return true;
+
+      if (last_val & PENDING_BIT) {
+
+        // Check for recursive initialization
+        if (has_thread_id_support && thread_id.load(std::_AO_Relaxed) == current_thread_id.get()) {
+          ABORT_WITH_MESSAGE("__cxa_guard_acquire detected recursive initialization: do you have a function-local static variable whose initialization depends on that function?");
+        }
+
+        if ((last_val & WAITING_BIT) == 0) {
+          // This compare exchange can fail for several reasons
+          // (1) another thread finished the whole thing before we got here
+          // (2) another thread set the waiting bit we were trying to thread
+          // (3) another thread had an exception and failed to finish
+          if (!init_byte.compare_exchange(&last_val, PENDING_BIT | WAITING_BIT, std::_AO_Acq_Rel, std::_AO_Release)) {
+            // (1) success, via someone else's work!
+            if (last_val == COMPLETE_BIT)
+              return true;
+
+            // (3) someone else, bailed on doing the work, retry from the start!
+            if (last_val == UNSET)
+              continue;
+
+            // (2) the waiting bit got set, so we are happy to keep waiting
+          }
+        }
+        wait_on_initialization();
+      }
+    }
+  }
+
+  /// The init byte portion of cxa_guard_release.
+  void release() {
+    uint8_t old = init_byte.exchange(COMPLETE_BIT, std::_AO_Acq_Rel);
+    if (old & WAITING_BIT)
+      wake_all();
+  }
+
+  /// The init byte portion of cxa_guard_abort.
+  void abort() {
+    if (has_thread_id_support)
+      thread_id.store(0, std::_AO_Relaxed);
+
+    uint8_t old = init_byte.exchange(UNSET, std::_AO_Acq_Rel);
+    if (old & WAITING_BIT)
+      wake_all();
+  }
+
+private:
+  /// Use the futex to wait on the current guard variable. Futex expects a
+  /// 32-bit 4-byte aligned address as the first argument, so we use the 4-byte
+  /// aligned address that encompasses the init byte (i.e. the address of the
+  /// raw guard object that was passed to __cxa_guard_acquire/release/abort).
+  void wait_on_initialization() { Wait(base_address, expected_value_for_futex(PENDING_BIT | WAITING_BIT)); }
+  void wake_all() { Wake(base_address); }
+
+private:
+  AtomicInt<uint8_t> init_byte;
+
+  const bool has_thread_id_support;
+  // Unsafe to use unless has_thread_id_support
+  AtomicInt<uint32_t> thread_id;
+  LazyValue<uint32_t, GetThreadIDArg> current_thread_id;
+
+  /// the 4-byte-aligned address that encompasses the init byte (i.e. the
+  /// address of the raw guard object).
+  int* const base_address;
+
+  /// Create the expected integer value for futex `wait(int* addr, int expected)`.
+  /// We pass the base address as the first argument, So this function creates
+  /// an zero-initialized integer  with `b` copied at the correct offset.
+  static int expected_value_for_futex(uint8_t b) {
+    int dest_val = 0;
+    std::memcpy(reinterpret_cast<char*>(&dest_val) + 1, &b, 1);
+    return dest_val;
+  }
+
+  static_assert(Wait != nullptr && Wake != nullptr, "");
+};
+
+//===----------------------------------------------------------------------===//
+//                          GuardObject
+//===----------------------------------------------------------------------===//
+
+enum class AcquireResult {
+  INIT_IS_DONE,
+  INIT_IS_PENDING,
+};
+constexpr AcquireResult INIT_IS_DONE = AcquireResult::INIT_IS_DONE;
+constexpr AcquireResult INIT_IS_PENDING = AcquireResult::INIT_IS_PENDING;
+
+/// Co-ordinates between GuardByte and InitByte.
+template <class InitByteT>
+struct GuardObject {
+  GuardObject() = delete;
+  GuardObject(GuardObject const&) = delete;
+  GuardObject& operator=(GuardObject const&) = delete;
+
+private:
+  GuardByte guard_byte;
+  InitByteT init_byte;
+
+public:
+  /// ARM Constructor
+  explicit GuardObject(uint32_t* raw_guard_object)
+      : guard_byte(reinterpret_cast<uint8_t*>(raw_guard_object)),
+        init_byte(reinterpret_cast<uint8_t*>(raw_guard_object) + 1, nullptr) {}
+
+  /// Itanium Constructor
+  explicit GuardObject(uint64_t* raw_guard_object)
+      : guard_byte(reinterpret_cast<uint8_t*>(raw_guard_object)),
+        init_byte(reinterpret_cast<uint8_t*>(raw_guard_object) + 1, reinterpret_cast<uint32_t*>(raw_guard_object) + 1) {
+  }
+
+  /// Implements __cxa_guard_acquire.
+  AcquireResult cxa_guard_acquire() {
+    // Use short-circuit evaluation to avoid calling init_byte.acquire when
+    // guard_byte.acquire returns true. (i.e. don't call it when we know from
+    // the guard byte that initialization has already been completed)
+    if (guard_byte.acquire() || init_byte.acquire())
+      return INIT_IS_DONE;
+    return INIT_IS_PENDING;
+  }
+
+  /// Implements __cxa_guard_release.
+  void cxa_guard_release() {
+    // Update guard byte first, so if somebody is woken up by init_byte.release
+    // and comes all the way back around to __cxa_guard_acquire again, they see
+    // it as having completed initialization.
+    guard_byte.release();
+    init_byte.release();
+  }
+
+  /// Implements __cxa_guard_abort.
+  void cxa_guard_abort() {
+    guard_byte.abort();
+    init_byte.abort();
+  }
+};
+
+//===----------------------------------------------------------------------===//
+//                          Convenience Classes
+//===----------------------------------------------------------------------===//
+
+/// NoThreadsGuard - Manages initialization without performing any inter-thread
+/// synchronization.
+using NoThreadsGuard = GuardObject<InitByteNoThreads>;
+
+/// GlobalMutexGuard - Manages initialization using a global mutex and
+/// condition variable.
+template <class Mutex, class CondVar, Mutex& global_mutex, CondVar& global_cond,
+          uint32_t (*GetThreadID)() = PlatformThreadID>
+using GlobalMutexGuard = GuardObject<InitByteGlobalMutex<Mutex, CondVar, global_mutex, global_cond, GetThreadID>>;
+
+/// FutexGuard - Manages initialization using atomics and the futex syscall for
+/// waiting and waking.
+template <void (*Wait)(int*, int) = PlatformFutexWait, void (*Wake)(int*) = PlatformFutexWake,
+          uint32_t (*GetThreadIDArg)() = PlatformThreadID>
+using FutexGuard = GuardObject<InitByteFutex<Wait, Wake, GetThreadIDArg>>;
+
+//===----------------------------------------------------------------------===//
+//
+//===----------------------------------------------------------------------===//
+
+template <class T>
+struct GlobalStatic {
+  static T instance;
+};
+template <class T>
+_LIBCPP_CONSTINIT T GlobalStatic<T>::instance = {};
+
+enum class Implementation { NoThreads, GlobalMutex, Futex };
+
+template <Implementation Impl>
+struct SelectImplementation;
+
+template <>
+struct SelectImplementation<Implementation::NoThreads> {
+  using type = NoThreadsGuard;
+};
+
+template <>
+struct SelectImplementation<Implementation::GlobalMutex> {
+  using type = GlobalMutexGuard<LibcppMutex, LibcppCondVar, GlobalStatic<LibcppMutex>::instance,
+                                GlobalStatic<LibcppCondVar>::instance, PlatformThreadID>;
+};
+
+template <>
+struct SelectImplementation<Implementation::Futex> {
+  using type = FutexGuard<PlatformFutexWait, PlatformFutexWake, PlatformThreadID>;
+};
+
+// TODO(EricWF): We should prefer the futex implementation when available. But
+// it should be done in a separate step from adding the implementation.
+constexpr Implementation CurrentImplementation =
+#if defined(_LIBCXXABI_HAS_NO_THREADS)
+    Implementation::NoThreads;
+#elif defined(_LIBCXXABI_USE_FUTEX)
+    Implementation::Futex;
+#else
+    Implementation::GlobalMutex;
+#endif
+
+static_assert(CurrentImplementation != Implementation::Futex || PlatformSupportsFutex(),
+              "Futex selected but not supported");
+
+using SelectedImplementation = SelectImplementation<CurrentImplementation>::type;
+
+} // end namespace
+} // end namespace __cxxabiv1
+
+#if defined(__clang__)
+#  pragma clang diagnostic pop
+#elif defined(__GNUC__)
+#  pragma GCC diagnostic pop
+#endif
+
+#endif // LIBCXXABI_SRC_INCLUDE_CXA_GUARD_IMPL_H

third_party/libcxxabi/cxa_handlers.cc

@@ -0,0 +1,101 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//
+// This file implements the functionality associated with the terminate_handler,
+// unexpected_handler, and new_handler.
+//===----------------------------------------------------------------------===//
+
+#include "third_party/libcxx/stdexcept"
+#include "third_party/libcxx/new"
+#include "third_party/libcxx/exception"
+#include "third_party/libcxxabi/abort_message.h"
+#include "third_party/libcxxabi/include/cxxabi.h"
+#include "third_party/libcxxabi/cxa_handlers.h"
+#include "third_party/libcxxabi/cxa_exception.h"
+#include "third_party/libcxxabi/private_typeinfo.h"
+#include "third_party/libcxx/include/atomic_support.hh" // from libc++
+
+namespace std
+{
+
+unexpected_handler
+get_unexpected() noexcept
+{
+    return __libcpp_atomic_load(&__cxa_unexpected_handler, _AO_Acquire);
+}
+
+void
+__unexpected(unexpected_handler func)
+{
+    func();
+    // unexpected handler should not return
+    abort_message("unexpected_handler unexpectedly returned");
+}
+
+__attribute__((noreturn))
+void
+unexpected()
+{
+    __unexpected(get_unexpected());
+}
+
+terminate_handler
+get_terminate() noexcept
+{
+    return __libcpp_atomic_load(&__cxa_terminate_handler, _AO_Acquire);
+}
+
+void
+__terminate(terminate_handler func) noexcept
+{
+#ifndef _LIBCXXABI_NO_EXCEPTIONS
+    try
+    {
+#endif // _LIBCXXABI_NO_EXCEPTIONS
+        func();
+        // handler should not return
+        abort_message("terminate_handler unexpectedly returned");
+#ifndef _LIBCXXABI_NO_EXCEPTIONS
+    }
+    catch (...)
+    {
+        // handler should not throw exception
+        abort_message("terminate_handler unexpectedly threw an exception");
+    }
+#endif // _LIBCXXABI_NO_EXCEPTIONS
+}
+
+__attribute__((noreturn))
+void
+terminate() noexcept
+{
+#ifndef _LIBCXXABI_NO_EXCEPTIONS
+    // If there might be an uncaught exception
+    using namespace __cxxabiv1;
+    __cxa_eh_globals* globals = __cxa_get_globals_fast();
+    if (globals)
+    {
+        __cxa_exception* exception_header = globals->caughtExceptions;
+        if (exception_header)
+        {
+            _Unwind_Exception* unwind_exception =
+                reinterpret_cast<_Unwind_Exception*>(exception_header + 1) - 1;
+            if (__isOurExceptionClass(unwind_exception))
+                __terminate(exception_header->terminateHandler);
+        }
+    }
+#endif
+    __terminate(get_terminate());
+}
+
+new_handler
+get_new_handler() noexcept
+{
+    return __libcpp_atomic_load(&__cxa_new_handler, _AO_Acquire);
+}
+
+}  // std

third_party/libcxxabi/cxa_handlers.h

@@ -0,0 +1,55 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//
+// This file implements the functionality associated with the terminate_handler,
+//   unexpected_handler, and new_handler.
+//===----------------------------------------------------------------------===//
+
+#ifndef _CXA_HANDLERS_H
+#define _CXA_HANDLERS_H
+
+#include "third_party/libcxxabi/include/__cxxabi_config.h"
+
+#include "third_party/libcxx/exception"
+
+namespace std
+{
+
+_LIBCXXABI_HIDDEN _LIBCXXABI_NORETURN
+void
+__unexpected(unexpected_handler func);
+
+_LIBCXXABI_HIDDEN _LIBCXXABI_NORETURN
+void
+__terminate(terminate_handler func) noexcept;
+
+}  // std
+
+extern "C"
+{
+
+_LIBCXXABI_DATA_VIS extern void (*__cxa_terminate_handler)();
+_LIBCXXABI_DATA_VIS extern void (*__cxa_unexpected_handler)();
+_LIBCXXABI_DATA_VIS extern void (*__cxa_new_handler)();
+
+/*
+
+    At some point in the future these three symbols will become
+    C++11 atomic variables:
+
+    extern std::atomic<std::terminate_handler>  __cxa_terminate_handler;
+    extern std::atomic<std::unexpected_handler> __cxa_unexpected_handler;
+    extern std::atomic<std::new_handler>        __cxa_new_handler;
+
+    This change will not impact their ABI.  But it will allow for a
+    portable performance optimization.
+
+*/
+
+} // extern "C"
+
+#endif // _CXA_HANDLERS_H

third_party/libcxxabi/cxa_thread_atexit.cc

@@ -0,0 +1,145 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "third_party/libcxxabi/abort_message.h"
+#include "third_party/libcxxabi/include/cxxabi.h"
+#include "third_party/libcxx/__threading_support"
+#ifndef _LIBCXXABI_HAS_NO_THREADS
+#if defined(__ELF__) && defined(_LIBCXXABI_LINK_PTHREAD_LIB)
+#pragma comment(lib, "pthread")
+#endif
+#endif
+
+#include "libc/isystem/stdlib.h"
+
+namespace __cxxabiv1 {
+
+  using Dtor = void(*)(void*);
+
+  extern "C"
+#ifndef HAVE___CXA_THREAD_ATEXIT_IMPL
+  // A weak symbol is used to detect this function's presence in the C library
+  // at runtime, even if libc++ is built against an older libc
+  _LIBCXXABI_WEAK
+#endif
+  int __cxa_thread_atexit_impl(Dtor, void*, void*);
+
+#ifndef HAVE___CXA_THREAD_ATEXIT_IMPL
+
+namespace {
+  // This implementation is used if the C library does not provide
+  // __cxa_thread_atexit_impl() for us.  It has a number of limitations that are
+  // difficult to impossible to address without ..._impl():
+  //
+  // - dso_symbol is ignored.  This means that a shared library may be unloaded
+  //   (via dlclose()) before its thread_local destructors have run.
+  //
+  // - thread_local destructors for the main thread are run by the destructor of
+  //   a static object.  This is later than expected; they should run before the
+  //   destructors of any objects with static storage duration.
+  //
+  // - thread_local destructors on non-main threads run on the first iteration
+  //   through the __libccpp_tls_key destructors.
+  //   std::notify_all_at_thread_exit() and similar functions must be careful to
+  //   wait until the second iteration to provide their intended ordering
+  //   guarantees.
+  //
+  // Another limitation, though one shared with ..._impl(), is that any
+  // thread_locals that are first initialized after non-thread_local global
+  // destructors begin to run will not be destroyed.  [basic.start.term] states
+  // that all thread_local destructors are sequenced before the destruction of
+  // objects with static storage duration, resulting in a contradiction if a
+  // thread_local is constructed after that point.  Thus we consider such
+  // programs ill-formed, and don't bother to run those destructors.  (If the
+  // program terminates abnormally after such a thread_local is constructed,
+  // the destructor is not expected to run and thus there is no contradiction.
+  // So construction still has to work.)
+
+  struct DtorList {
+    Dtor dtor;
+    void* obj;
+    DtorList* next;
+  };
+
+  // The linked list of thread-local destructors to run
+  __thread DtorList* dtors = nullptr;
+  // True if the destructors are currently scheduled to run on this thread
+  __thread bool dtors_alive = false;
+  // Used to trigger destructors on thread exit; value is ignored
+  std::__libcpp_tls_key dtors_key;
+
+  void run_dtors(void*) {
+    while (auto head = dtors) {
+      dtors = head->next;
+      head->dtor(head->obj);
+      ::free(head);
+    }
+
+    dtors_alive = false;
+  }
+
+  struct DtorsManager {
+    DtorsManager() {
+      // There is intentionally no matching std::__libcpp_tls_delete call, as
+      // __cxa_thread_atexit() may be called arbitrarily late (for example, from
+      // global destructors or atexit() handlers).
+      if (std::__libcpp_tls_create(&dtors_key, run_dtors) != 0) {
+        abort_message("std::__libcpp_tls_create() failed in __cxa_thread_atexit()");
+      }
+    }
+
+    ~DtorsManager() {
+      // std::__libcpp_tls_key destructors do not run on threads that call exit()
+      // (including when the main thread returns from main()), so we explicitly
+      // call the destructor here.  This runs at exit time (potentially earlier
+      // if libc++abi is dlclose()'d).  Any thread_locals initialized after this
+      // point will not be destroyed.
+      run_dtors(nullptr);
+    }
+  };
+} // namespace
+
+#endif // HAVE___CXA_THREAD_ATEXIT_IMPL
+
+extern "C" {
+
+  _LIBCXXABI_FUNC_VIS int __cxa_thread_atexit(Dtor dtor, void* obj, void* dso_symbol) throw() {
+#ifdef HAVE___CXA_THREAD_ATEXIT_IMPL
+    return __cxa_thread_atexit_impl(dtor, obj, dso_symbol);
+#else
+    if (__cxa_thread_atexit_impl) {
+      return __cxa_thread_atexit_impl(dtor, obj, dso_symbol);
+    } else {
+      // Initialize the dtors std::__libcpp_tls_key (uses __cxa_guard_*() for
+      // one-time initialization and __cxa_atexit() for destruction)
+      static DtorsManager manager;
+
+      if (!dtors_alive) {
+        if (std::__libcpp_tls_set(dtors_key, &dtors_key) != 0) {
+          return -1;
+        }
+        dtors_alive = true;
+      }
+
+      auto head = static_cast<DtorList*>(::malloc(sizeof(DtorList)));
+      if (!head) {
+        return -1;
+      }
+
+      head->dtor = dtor;
+      head->obj = obj;
+      head->next = dtors;
+      dtors = head;
+
+      return 0;
+    }
+#endif // HAVE___CXA_THREAD_ATEXIT_IMPL
+  }
+
+} // extern "C"
+} // namespace __cxxabiv1

third_party/libcxxabi/cxa_vector.cc

@@ -0,0 +1,421 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//
+//  This file implements the "Array Construction and Destruction APIs"
+//  https://itanium-cxx-abi.github.io/cxx-abi/abi.html#array-ctor
+//
+//===----------------------------------------------------------------------===//
+
+#include "third_party/libcxxabi/include/cxxabi.h"
+#include "third_party/libcxxabi/include/__cxxabi_config.h"
+
+#include "third_party/libcxx/exception"        // for std::terminate
+#include "third_party/libcxx/new"              // for std::bad_array_new_length
+
+#include "third_party/libcxxabi/abort_message.h"
+
+#ifndef __has_builtin
+#define __has_builtin(x) 0
+#endif
+
+namespace __cxxabiv1 {
+
+//
+// Helper routines and classes
+//
+
+namespace {
+    inline static size_t __get_element_count ( void *p ) {
+        return static_cast <size_t *> (p)[-1];
+        }
+
+    inline static void __set_element_count ( void *p, size_t element_count ) {
+        static_cast <size_t *> (p)[-1] = element_count;
+        }
+
+
+//  A pair of classes to simplify exception handling and control flow.
+//  They get passed a block of memory in the constructor, and unless the
+//  'release' method is called, they deallocate the memory in the destructor.
+//  Preferred usage is to allocate some memory, attach it to one of these objects,
+//  and then, when all the operations to set up the memory block have succeeded,
+//  call 'release'. If any of the setup operations fail, or an exception is
+//  thrown, then the block is automatically deallocated.
+//
+//  The only difference between these two classes is the signature for the
+//  deallocation function (to match new2/new3 and delete2/delete3.
+    class st_heap_block2 {
+    public:
+        typedef void (*dealloc_f)(void *);
+
+        st_heap_block2 ( dealloc_f dealloc, void *ptr )
+            : dealloc_ ( dealloc ), ptr_ ( ptr ), enabled_ ( true ) {}
+        ~st_heap_block2 () { if ( enabled_ ) dealloc_ ( ptr_ ) ; }
+        void release () { enabled_ = false; }
+
+    private:
+        dealloc_f dealloc_;
+        void *ptr_;
+        bool enabled_;
+    };
+
+    class st_heap_block3 {
+    public:
+        typedef void (*dealloc_f)(void *, size_t);
+
+        st_heap_block3 ( dealloc_f dealloc, void *ptr, size_t size )
+            : dealloc_ ( dealloc ), ptr_ ( ptr ), size_ ( size ), enabled_ ( true ) {}
+        ~st_heap_block3 () { if ( enabled_ ) dealloc_ ( ptr_, size_ ) ; }
+        void release () { enabled_ = false; }
+
+    private:
+        dealloc_f dealloc_;
+        void *ptr_;
+        size_t size_;
+        bool enabled_;
+    };
+
+    class st_cxa_cleanup {
+    public:
+        typedef void (*destruct_f)(void *);
+
+        st_cxa_cleanup ( void *ptr, size_t &idx, size_t element_size, destruct_f destructor )
+            : ptr_ ( ptr ), idx_ ( idx ), element_size_ ( element_size ),
+                destructor_ ( destructor ), enabled_ ( true ) {}
+        ~st_cxa_cleanup () {
+            if ( enabled_ )
+                __cxa_vec_cleanup ( ptr_, idx_, element_size_, destructor_ );
+            }
+
+        void release () { enabled_ = false; }
+
+    private:
+        void *ptr_;
+        size_t &idx_;
+        size_t element_size_;
+        destruct_f destructor_;
+        bool enabled_;
+    };
+
+    class st_terminate {
+    public:
+        st_terminate ( bool enabled = true ) : enabled_ ( enabled ) {}
+        ~st_terminate () { if ( enabled_ ) std::terminate (); }
+        void release () { enabled_ = false; }
+    private:
+        bool enabled_ ;
+    };
+}
+
+//
+// Externally visible routines
+//
+
+namespace {
+_LIBCXXABI_NORETURN
+void throw_bad_array_new_length() {
+#ifndef _LIBCXXABI_NO_EXCEPTIONS
+  throw std::bad_array_new_length();
+#else
+  abort_message("__cxa_vec_new failed to allocate memory");
+#endif
+}
+
+bool mul_overflow(size_t x, size_t y, size_t *res) {
+#if (defined(_LIBCXXABI_COMPILER_CLANG) && __has_builtin(__builtin_mul_overflow)) \
+    || defined(_LIBCXXABI_COMPILER_GCC)
+    return __builtin_mul_overflow(x, y, res);
+#else
+    *res = x * y;
+    return x && ((*res / x) != y);
+#endif
+}
+
+bool add_overflow(size_t x, size_t y, size_t *res) {
+#if (defined(_LIBCXXABI_COMPILER_CLANG) && __has_builtin(__builtin_add_overflow)) \
+    || defined(_LIBCXXABI_COMPILER_GCC)
+  return __builtin_add_overflow(x, y, res);
+#else
+  *res = x + y;
+  return *res < y;
+#endif
+}
+
+size_t calculate_allocation_size_or_throw(size_t element_count,
+                                          size_t element_size,
+                                          size_t padding_size) {
+  size_t element_heap_size;
+  if (mul_overflow(element_count, element_size, &element_heap_size))
+    throw_bad_array_new_length();
+
+  size_t allocation_size;
+  if (add_overflow(element_heap_size, padding_size, &allocation_size))
+    throw_bad_array_new_length();
+
+  return allocation_size;
+}
+
+} // namespace
+
+extern "C" {
+
+// Equivalent to
+//
+//   __cxa_vec_new2(element_count, element_size, padding_size, constructor,
+//                  destructor, &::operator new[], &::operator delete[])
+_LIBCXXABI_FUNC_VIS void *
+__cxa_vec_new(size_t element_count, size_t element_size, size_t padding_size,
+              void (*constructor)(void *), void (*destructor)(void *)) {
+    return __cxa_vec_new2 ( element_count, element_size, padding_size,
+        constructor, destructor, &::operator new [], &::operator delete [] );
+}
+
+
+// Given the number and size of elements for an array and the non-negative
+// size of prefix padding for a cookie, allocate space (using alloc) for
+// the array preceded by the specified padding, initialize the cookie if
+// the padding is non-zero, and call the given constructor on each element.
+// Return the address of the array proper, after the padding.
+//
+// If alloc throws an exception, rethrow the exception. If alloc returns
+// NULL, return NULL. If the constructor throws an exception, call
+// destructor for any already constructed elements, and rethrow the
+// exception. If the destructor throws an exception, call std::terminate.
+//
+// The constructor may be NULL, in which case it must not be called. If the
+// padding_size is zero, the destructor may be NULL; in that case it must
+// not be called.
+//
+// Neither alloc nor dealloc may be NULL.
+_LIBCXXABI_FUNC_VIS void *
+__cxa_vec_new2(size_t element_count, size_t element_size, size_t padding_size,
+               void (*constructor)(void *), void (*destructor)(void *),
+               void *(*alloc)(size_t), void (*dealloc)(void *)) {
+  const size_t heap_size = calculate_allocation_size_or_throw(
+      element_count, element_size, padding_size);
+  char* const heap_block = static_cast<char*>(alloc(heap_size));
+  char* vec_base = heap_block;
+
+  if (NULL != vec_base) {
+    st_heap_block2 heap(dealloc, heap_block);
+
+    //  put the padding before the array elements
+        if ( 0 != padding_size ) {
+            vec_base += padding_size;
+            __set_element_count ( vec_base, element_count );
+        }
+
+    //  Construct the elements
+        __cxa_vec_ctor ( vec_base, element_count, element_size, constructor, destructor );
+        heap.release ();    // We're good!
+    }
+
+    return vec_base;
+}
+
+
+// Same as __cxa_vec_new2 except that the deallocation function takes both
+// the object address and its size.
+_LIBCXXABI_FUNC_VIS void *
+__cxa_vec_new3(size_t element_count, size_t element_size, size_t padding_size,
+               void (*constructor)(void *), void (*destructor)(void *),
+               void *(*alloc)(size_t), void (*dealloc)(void *, size_t)) {
+  const size_t heap_size = calculate_allocation_size_or_throw(
+      element_count, element_size, padding_size);
+  char* const heap_block = static_cast<char*>(alloc(heap_size));
+  char* vec_base = heap_block;
+
+  if (NULL != vec_base) {
+    st_heap_block3 heap(dealloc, heap_block, heap_size);
+
+    //  put the padding before the array elements
+        if ( 0 != padding_size ) {
+            vec_base += padding_size;
+            __set_element_count ( vec_base, element_count );
+        }
+
+    //  Construct the elements
+        __cxa_vec_ctor ( vec_base, element_count, element_size, constructor, destructor );
+        heap.release ();    // We're good!
+    }
+
+    return vec_base;
+}
+
+
+// Given the (data) addresses of a destination and a source array, an
+// element count and an element size, call the given copy constructor to
+// copy each element from the source array to the destination array. The
+// copy constructor's arguments are the destination address and source
+// address, respectively. If an exception occurs, call the given destructor
+// (if non-NULL) on each copied element and rethrow. If the destructor
+// throws an exception, call terminate(). The constructor and or destructor
+// pointers may be NULL. If either is NULL, no action is taken when it
+// would have been called.
+
+_LIBCXXABI_FUNC_VIS void __cxa_vec_cctor(void *dest_array, void *src_array,
+                                         size_t element_count,
+                                         size_t element_size,
+                                         void (*constructor)(void *, void *),
+                                         void (*destructor)(void *)) {
+    if ( NULL != constructor ) {
+        size_t idx = 0;
+        char *src_ptr  = static_cast<char *>(src_array);
+        char *dest_ptr = static_cast<char *>(dest_array);
+        st_cxa_cleanup cleanup ( dest_array, idx, element_size, destructor );
+
+        for ( idx = 0; idx < element_count;
+                    ++idx, src_ptr += element_size, dest_ptr += element_size )
+            constructor ( dest_ptr, src_ptr );
+        cleanup.release ();     // We're good!
+    }
+}
+
+
+// Given the (data) address of an array, not including any cookie padding,
+// and the number and size of its elements, call the given constructor on
+// each element. If the constructor throws an exception, call the given
+// destructor for any already-constructed elements, and rethrow the
+// exception. If the destructor throws an exception, call terminate(). The
+// constructor and/or destructor pointers may be NULL. If either is NULL,
+// no action is taken when it would have been called.
+_LIBCXXABI_FUNC_VIS void
+__cxa_vec_ctor(void *array_address, size_t element_count, size_t element_size,
+               void (*constructor)(void *), void (*destructor)(void *)) {
+    if ( NULL != constructor ) {
+        size_t idx;
+        char *ptr = static_cast <char *> ( array_address );
+        st_cxa_cleanup cleanup ( array_address, idx, element_size, destructor );
+
+    //  Construct the elements
+        for ( idx = 0; idx < element_count; ++idx, ptr += element_size )
+            constructor ( ptr );
+        cleanup.release ();     // We're good!
+    }
+}
+
+// Given the (data) address of an array, the number of elements, and the
+// size of its elements, call the given destructor on each element. If the
+// destructor throws an exception, rethrow after destroying the remaining
+// elements if possible. If the destructor throws a second exception, call
+// terminate(). The destructor pointer may be NULL, in which case this
+// routine does nothing.
+_LIBCXXABI_FUNC_VIS void __cxa_vec_dtor(void *array_address,
+                                        size_t element_count,
+                                        size_t element_size,
+                                        void (*destructor)(void *)) {
+    if ( NULL != destructor ) {
+        char *ptr = static_cast <char *> (array_address);
+        size_t idx = element_count;
+        st_cxa_cleanup cleanup ( array_address, idx, element_size, destructor );
+        {
+            st_terminate exception_guard (__cxa_uncaught_exception ());
+            ptr +=  element_count * element_size;   // one past the last element
+
+            while ( idx-- > 0 ) {
+                ptr -= element_size;
+                destructor ( ptr );
+            }
+            exception_guard.release (); //  We're good !
+        }
+        cleanup.release ();     // We're still good!
+    }
+}
+
+// Given the (data) address of an array, the number of elements, and the
+// size of its elements, call the given destructor on each element. If the
+// destructor throws an exception, call terminate(). The destructor pointer
+// may be NULL, in which case this routine does nothing.
+_LIBCXXABI_FUNC_VIS void __cxa_vec_cleanup(void *array_address,
+                                           size_t element_count,
+                                           size_t element_size,
+                                           void (*destructor)(void *)) {
+    if ( NULL != destructor ) {
+        char *ptr = static_cast <char *> (array_address);
+        size_t idx = element_count;
+        st_terminate exception_guard;
+
+        ptr += element_count * element_size;    // one past the last element
+        while ( idx-- > 0 ) {
+            ptr -= element_size;
+            destructor ( ptr );
+            }
+        exception_guard.release ();     // We're done!
+    }
+}
+
+
+// If the array_address is NULL, return immediately. Otherwise, given the
+// (data) address of an array, the non-negative size of prefix padding for
+// the cookie, and the size of its elements, call the given destructor on
+// each element, using the cookie to determine the number of elements, and
+// then delete the space by calling ::operator delete[](void *). If the
+// destructor throws an exception, rethrow after (a) destroying the
+// remaining elements, and (b) deallocating the storage. If the destructor
+// throws a second exception, call terminate(). If padding_size is 0, the
+// destructor pointer must be NULL. If the destructor pointer is NULL, no
+// destructor call is to be made.
+//
+// The intent of this function is to permit an implementation to call this
+// function when confronted with an expression of the form delete[] p in
+// the source code, provided that the default deallocation function can be
+// used. Therefore, the semantics of this function are consistent with
+// those required by the standard. The requirement that the deallocation
+// function be called even if the destructor throws an exception derives
+// from the resolution to DR 353 to the C++ standard, which was adopted in
+// April, 2003.
+_LIBCXXABI_FUNC_VIS void __cxa_vec_delete(void *array_address,
+                                          size_t element_size,
+                                          size_t padding_size,
+                                          void (*destructor)(void *)) {
+    __cxa_vec_delete2 ( array_address, element_size, padding_size,
+               destructor, &::operator delete [] );
+}
+
+// Same as __cxa_vec_delete, except that the given function is used for
+// deallocation instead of the default delete function. If dealloc throws
+// an exception, the result is undefined. The dealloc pointer may not be
+// NULL.
+_LIBCXXABI_FUNC_VIS void
+__cxa_vec_delete2(void *array_address, size_t element_size, size_t padding_size,
+                  void (*destructor)(void *), void (*dealloc)(void *)) {
+    if ( NULL != array_address ) {
+        char *vec_base   = static_cast <char *> (array_address);
+        char *heap_block = vec_base - padding_size;
+        st_heap_block2 heap ( dealloc, heap_block );
+
+        if ( 0 != padding_size && NULL != destructor ) // call the destructors
+            __cxa_vec_dtor ( array_address, __get_element_count ( vec_base ),
+                                    element_size, destructor );
+    }
+}
+
+
+// Same as __cxa_vec_delete, except that the given function is used for
+// deallocation instead of the default delete function. The deallocation
+// function takes both the object address and its size. If dealloc throws
+// an exception, the result is undefined. The dealloc pointer may not be
+// NULL.
+_LIBCXXABI_FUNC_VIS void
+__cxa_vec_delete3(void *array_address, size_t element_size, size_t padding_size,
+                  void (*destructor)(void *), void (*dealloc)(void *, size_t)) {
+    if ( NULL != array_address ) {
+        char *vec_base   = static_cast <char *> (array_address);
+        char *heap_block = vec_base - padding_size;
+        const size_t element_count = padding_size ? __get_element_count ( vec_base ) : 0;
+        const size_t heap_block_size = element_size * element_count + padding_size;
+        st_heap_block3 heap ( dealloc, heap_block, heap_block_size );
+
+        if ( 0 != padding_size && NULL != destructor ) // call the destructors
+            __cxa_vec_dtor ( array_address, element_count, element_size, destructor );
+    }
+}
+
+
+}  // extern "C"
+
+}  // abi

third_party/libcxxabi/cxa_virtual.cc

@@ -0,0 +1,24 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "third_party/libcxxabi/include/cxxabi.h"
+#include "third_party/libcxxabi/abort_message.h"
+
+namespace __cxxabiv1 {
+extern "C" {
+_LIBCXXABI_FUNC_VIS _LIBCXXABI_NORETURN
+void __cxa_pure_virtual(void) {
+  abort_message("Pure virtual function called!");
+}
+
+_LIBCXXABI_FUNC_VIS _LIBCXXABI_NORETURN
+void __cxa_deleted_virtual(void) {
+  abort_message("Deleted virtual function called!");
+}
+} // extern "C"
+} // abi

third_party/libcxxabi/demangle/DemangleConfig.h

@@ -0,0 +1,105 @@
+//===--- DemangleConfig.h --------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+// This file is contains a subset of macros copied from
+// llvm/include/llvm/Demangle/DemangleConfig.h
+//===----------------------------------------------------------------------===//
+
+#ifndef LIBCXXABI_DEMANGLE_DEMANGLE_CONFIG_H
+#define LIBCXXABI_DEMANGLE_DEMANGLE_CONFIG_H
+
+// Must be defined before pulling in headers from libc++. Allow downstream
+// build systems to override this value.
+// https://libcxx.llvm.org/UsingLibcxx.html#enabling-the-safe-libc-mode
+#ifndef _LIBCPP_VERBOSE_ABORT
+#define _LIBCPP_VERBOSE_ABORT(...) abort_message(__VA_ARGS__)
+#include "third_party/libcxxabi/abort_message.h"
+#endif
+
+#include "third_party/libcxx/ciso646"
+
+#ifdef _MSC_VER
+// snprintf is implemented in VS 2015
+#if _MSC_VER < 1900
+#define snprintf _snprintf_s
+#endif
+#endif
+
+#ifndef __has_feature
+#define __has_feature(x) 0
+#endif
+
+#ifndef __has_cpp_attribute
+#define __has_cpp_attribute(x) 0
+#endif
+
+#ifndef __has_attribute
+#define __has_attribute(x) 0
+#endif
+
+#ifndef __has_builtin
+#define __has_builtin(x) 0
+#endif
+
+#ifndef DEMANGLE_GNUC_PREREQ
+#if defined(__GNUC__) && defined(__GNUC_MINOR__) && defined(__GNUC_PATCHLEVEL__)
+#define DEMANGLE_GNUC_PREREQ(maj, min, patch)                           \
+  ((__GNUC__ << 20) + (__GNUC_MINOR__ << 10) + __GNUC_PATCHLEVEL__ >=          \
+   ((maj) << 20) + ((min) << 10) + (patch))
+#elif defined(__GNUC__) && defined(__GNUC_MINOR__)
+#define DEMANGLE_GNUC_PREREQ(maj, min, patch)                           \
+  ((__GNUC__ << 20) + (__GNUC_MINOR__ << 10) >= ((maj) << 20) + ((min) << 10))
+#else
+#define DEMANGLE_GNUC_PREREQ(maj, min, patch) 0
+#endif
+#endif
+
+#if __has_attribute(used) || DEMANGLE_GNUC_PREREQ(3, 1, 0)
+#define DEMANGLE_ATTRIBUTE_USED __attribute__((__used__))
+#else
+#define DEMANGLE_ATTRIBUTE_USED
+#endif
+
+#if __has_builtin(__builtin_unreachable) || DEMANGLE_GNUC_PREREQ(4, 5, 0)
+#define DEMANGLE_UNREACHABLE __builtin_unreachable()
+#elif defined(_MSC_VER)
+#define DEMANGLE_UNREACHABLE __assume(false)
+#else
+#define DEMANGLE_UNREACHABLE
+#endif
+
+#if __has_attribute(noinline) || DEMANGLE_GNUC_PREREQ(3, 4, 0)
+#define DEMANGLE_ATTRIBUTE_NOINLINE __attribute__((noinline))
+#elif defined(_MSC_VER)
+#define DEMANGLE_ATTRIBUTE_NOINLINE __declspec(noinline)
+#else
+#define DEMANGLE_ATTRIBUTE_NOINLINE
+#endif
+
+#if !defined(NDEBUG)
+#define DEMANGLE_DUMP_METHOD DEMANGLE_ATTRIBUTE_NOINLINE DEMANGLE_ATTRIBUTE_USED
+#else
+#define DEMANGLE_DUMP_METHOD DEMANGLE_ATTRIBUTE_NOINLINE
+#endif
+
+#if __cplusplus > 201402L && __has_cpp_attribute(fallthrough)
+#define DEMANGLE_FALLTHROUGH [[fallthrough]]
+#elif __has_cpp_attribute(gnu::fallthrough)
+#define DEMANGLE_FALLTHROUGH [[gnu::fallthrough]]
+#elif !__cplusplus
+// Workaround for llvm.org/PR23435, since clang 3.6 and below emit a spurious
+// error when __has_cpp_attribute is given a scoped attribute in C mode.
+#define DEMANGLE_FALLTHROUGH
+#elif __has_cpp_attribute(clang::fallthrough)
+#define DEMANGLE_FALLTHROUGH [[clang::fallthrough]]
+#else
+#define DEMANGLE_FALLTHROUGH
+#endif
+
+#define DEMANGLE_NAMESPACE_BEGIN namespace { namespace itanium_demangle {
+#define DEMANGLE_NAMESPACE_END } }
+
+#endif // LIBCXXABI_DEMANGLE_DEMANGLE_CONFIG_H

third_party/libcxxabi/demangle/ItaniumNodes.def

@@ -0,0 +1,95 @@
+//===------------------------- ItaniumNodes.def ----------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Define the demangler's node names
+
+#ifndef NODE
+#error Define NODE to handle nodes
+#endif
+
+NODE(NodeArrayNode)
+NODE(DotSuffix)
+NODE(VendorExtQualType)
+NODE(QualType)
+NODE(ConversionOperatorType)
+NODE(PostfixQualifiedType)
+NODE(ElaboratedTypeSpefType)
+NODE(NameType)
+NODE(AbiTagAttr)
+NODE(EnableIfAttr)
+NODE(ObjCProtoName)
+NODE(PointerType)
+NODE(ReferenceType)
+NODE(PointerToMemberType)
+NODE(ArrayType)
+NODE(FunctionType)
+NODE(NoexceptSpec)
+NODE(DynamicExceptionSpec)
+NODE(FunctionEncoding)
+NODE(LiteralOperator)
+NODE(SpecialName)
+NODE(CtorVtableSpecialName)
+NODE(QualifiedName)
+NODE(NestedName)
+NODE(LocalName)
+NODE(ModuleName)
+NODE(ModuleEntity)
+NODE(VectorType)
+NODE(PixelVectorType)
+NODE(BinaryFPType)
+NODE(BitIntType)
+NODE(SyntheticTemplateParamName)
+NODE(TypeTemplateParamDecl)
+NODE(NonTypeTemplateParamDecl)
+NODE(TemplateTemplateParamDecl)
+NODE(TemplateParamPackDecl)
+NODE(ParameterPack)
+NODE(TemplateArgumentPack)
+NODE(ParameterPackExpansion)
+NODE(TemplateArgs)
+NODE(ForwardTemplateReference)
+NODE(NameWithTemplateArgs)
+NODE(GlobalQualifiedName)
+NODE(ExpandedSpecialSubstitution)
+NODE(SpecialSubstitution)
+NODE(CtorDtorName)
+NODE(DtorName)
+NODE(UnnamedTypeName)
+NODE(ClosureTypeName)
+NODE(StructuredBindingName)
+NODE(BinaryExpr)
+NODE(ArraySubscriptExpr)
+NODE(PostfixExpr)
+NODE(ConditionalExpr)
+NODE(MemberExpr)
+NODE(SubobjectExpr)
+NODE(EnclosingExpr)
+NODE(CastExpr)
+NODE(SizeofParamPackExpr)
+NODE(CallExpr)
+NODE(NewExpr)
+NODE(DeleteExpr)
+NODE(PrefixExpr)
+NODE(FunctionParam)
+NODE(ConversionExpr)
+NODE(PointerToMemberConversionExpr)
+NODE(InitListExpr)
+NODE(FoldExpr)
+NODE(ThrowExpr)
+NODE(BoolExpr)
+NODE(StringLiteral)
+NODE(LambdaExpr)
+NODE(EnumLiteral)
+NODE(IntegerLiteral)
+NODE(FloatLiteral)
+NODE(DoubleLiteral)
+NODE(LongDoubleLiteral)
+NODE(BracedExpr)
+NODE(BracedRangeExpr)
+
+#undef NODE

third_party/libcxxabi/demangle/StringViewExtras.h

@@ -0,0 +1,38 @@
+//===--- StringViewExtras.h -------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// There are two copies of this file in the source tree.  The one under
+// libcxxabi is the original and the one under llvm is the copy.  Use
+// cp-to-llvm.sh to update the copy.  See README.txt for more details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef DEMANGLE_STRINGVIEW_H
+#define DEMANGLE_STRINGVIEW_H
+
+#include "third_party/libcxxabi/demangle/DemangleConfig.h"
+
+#include "third_party/libcxx/string_view"
+
+DEMANGLE_NAMESPACE_BEGIN
+
+inline bool starts_with(std::string_view self, char C) noexcept {
+  return !self.empty() && *self.begin() == C;
+}
+
+inline bool starts_with(std::string_view haystack,
+                        std::string_view needle) noexcept {
+  if (needle.size() > haystack.size())
+    return false;
+  haystack.remove_suffix(haystack.size() - needle.size());
+  return haystack == needle;
+}
+
+DEMANGLE_NAMESPACE_END
+
+#endif

third_party/libcxxabi/demangle/Utility.h

@@ -0,0 +1,205 @@
+//===--- Utility.h ----------------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Provide some utility classes for use in the demangler.
+// There are two copies of this file in the source tree.  The one in libcxxabi
+// is the original and the one in llvm is the copy.  Use cp-to-llvm.sh to update
+// the copy.  See README.txt for more details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef DEMANGLE_UTILITY_H
+#define DEMANGLE_UTILITY_H
+
+#include "third_party/libcxxabi/demangle/DemangleConfig.h"
+
+#include "third_party/libcxx/array"
+#include "third_party/libcxx/cassert"
+#include "third_party/libcxx/cstdint"
+#include "third_party/libcxx/cstdlib"
+#include "third_party/libcxx/cstring"
+#include "third_party/libcxx/exception"
+#include "third_party/libcxx/limits"
+#include "third_party/libcxx/string_view"
+
+DEMANGLE_NAMESPACE_BEGIN
+
+// Stream that AST nodes write their string representation into after the AST
+// has been parsed.
+class OutputBuffer {
+  char *Buffer = nullptr;
+  size_t CurrentPosition = 0;
+  size_t BufferCapacity = 0;
+
+  // Ensure there are at least N more positions in the buffer.
+  void grow(size_t N) {
+    size_t Need = N + CurrentPosition;
+    if (Need > BufferCapacity) {
+      // Reduce the number of reallocations, with a bit of hysteresis. The
+      // number here is chosen so the first allocation will more-than-likely not
+      // allocate more than 1K.
+      Need += 1024 - 32;
+      BufferCapacity *= 2;
+      if (BufferCapacity < Need)
+        BufferCapacity = Need;
+      Buffer = static_cast<char *>(std::realloc(Buffer, BufferCapacity));
+      if (Buffer == nullptr)
+        std::terminate();
+    }
+  }
+
+  OutputBuffer &writeUnsigned(uint64_t N, bool isNeg = false) {
+    std::array<char, 21> Temp;
+    char *TempPtr = Temp.data() + Temp.size();
+
+    // Output at least one character.
+    do {
+      *--TempPtr = char('0' + N % 10);
+      N /= 10;
+    } while (N);
+
+    // Add negative sign.
+    if (isNeg)
+      *--TempPtr = '-';
+
+    return operator+=(
+        std::string_view(TempPtr, Temp.data() + Temp.size() - TempPtr));
+  }
+
+public:
+  OutputBuffer(char *StartBuf, size_t Size)
+      : Buffer(StartBuf), BufferCapacity(Size) {}
+  OutputBuffer(char *StartBuf, size_t *SizePtr)
+      : OutputBuffer(StartBuf, StartBuf ? *SizePtr : 0) {}
+  OutputBuffer() = default;
+  // Non-copyable
+  OutputBuffer(const OutputBuffer &) = delete;
+  OutputBuffer &operator=(const OutputBuffer &) = delete;
+
+  operator std::string_view() const {
+    return std::string_view(Buffer, CurrentPosition);
+  }
+
+  /// If a ParameterPackExpansion (or similar type) is encountered, the offset
+  /// into the pack that we're currently printing.
+  unsigned CurrentPackIndex = std::numeric_limits<unsigned>::max();
+  unsigned CurrentPackMax = std::numeric_limits<unsigned>::max();
+
+  /// When zero, we're printing template args and '>' needs to be parenthesized.
+  /// Use a counter so we can simply increment inside parentheses.
+  unsigned GtIsGt = 1;
+
+  bool isGtInsideTemplateArgs() const { return GtIsGt == 0; }
+
+  void printOpen(char Open = '(') {
+    GtIsGt++;
+    *this += Open;
+  }
+  void printClose(char Close = ')') {
+    GtIsGt--;
+    *this += Close;
+  }
+
+  OutputBuffer &operator+=(std::string_view R) {
+    if (size_t Size = R.size()) {
+      grow(Size);
+      std::memcpy(Buffer + CurrentPosition, &*R.begin(), Size);
+      CurrentPosition += Size;
+    }
+    return *this;
+  }
+
+  OutputBuffer &operator+=(char C) {
+    grow(1);
+    Buffer[CurrentPosition++] = C;
+    return *this;
+  }
+
+  OutputBuffer &prepend(std::string_view R) {
+    size_t Size = R.size();
+
+    grow(Size);
+    std::memmove(Buffer + Size, Buffer, CurrentPosition);
+    std::memcpy(Buffer, &*R.begin(), Size);
+    CurrentPosition += Size;
+
+    return *this;
+  }
+
+  OutputBuffer &operator<<(std::string_view R) { return (*this += R); }
+
+  OutputBuffer &operator<<(char C) { return (*this += C); }
+
+  OutputBuffer &operator<<(long long N) {
+    return writeUnsigned(static_cast<unsigned long long>(std::abs(N)), N < 0);
+  }
+
+  OutputBuffer &operator<<(unsigned long long N) {
+    return writeUnsigned(N, false);
+  }
+
+  OutputBuffer &operator<<(long N) {
+    return this->operator<<(static_cast<long long>(N));
+  }
+
+  OutputBuffer &operator<<(unsigned long N) {
+    return this->operator<<(static_cast<unsigned long long>(N));
+  }
+
+  OutputBuffer &operator<<(int N) {
+    return this->operator<<(static_cast<long long>(N));
+  }
+
+  OutputBuffer &operator<<(unsigned int N) {
+    return this->operator<<(static_cast<unsigned long long>(N));
+  }
+
+  void insert(size_t Pos, const char *S, size_t N) {
+    assert(Pos <= CurrentPosition);
+    if (N == 0)
+      return;
+    grow(N);
+    std::memmove(Buffer + Pos + N, Buffer + Pos, CurrentPosition - Pos);
+    std::memcpy(Buffer + Pos, S, N);
+    CurrentPosition += N;
+  }
+
+  size_t getCurrentPosition() const { return CurrentPosition; }
+  void setCurrentPosition(size_t NewPos) { CurrentPosition = NewPos; }
+
+  char back() const {
+    assert(CurrentPosition);
+    return Buffer[CurrentPosition - 1];
+  }
+
+  bool empty() const { return CurrentPosition == 0; }
+
+  char *getBuffer() { return Buffer; }
+  char *getBufferEnd() { return Buffer + CurrentPosition - 1; }
+  size_t getBufferCapacity() const { return BufferCapacity; }
+};
+
+template <class T> class ScopedOverride {
+  T &Loc;
+  T Original;
+
+public:
+  ScopedOverride(T &Loc_) : ScopedOverride(Loc_, Loc_) {}
+
+  ScopedOverride(T &Loc_, T NewVal) : Loc(Loc_), Original(Loc_) {
+    Loc_ = std::move(NewVal);
+  }
+  ~ScopedOverride() { Loc = std::move(Original); }
+
+  ScopedOverride(const ScopedOverride &) = delete;
+  ScopedOverride &operator=(const ScopedOverride &) = delete;
+};
+
+DEMANGLE_NAMESPACE_END
+
+#endif

third_party/libcxxabi/fallback_malloc.cc

@@ -0,0 +1,303 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "third_party/libcxxabi/fallback_malloc.h"
+
+#include "third_party/libcxx/__threading_support"
+#ifndef _LIBCXXABI_HAS_NO_THREADS
+#if defined(__ELF__) && defined(_LIBCXXABI_LINK_PTHREAD_LIB)
+#pragma comment(lib, "pthread")
+#endif
+#endif
+
+#include "third_party/libcxxabi/libcxx/include/__memory/aligned_alloc.h"
+#include "libc/isystem/assert.h"
+#include "libc/isystem/stdlib.h" // for malloc, calloc, free
+#include "libc/isystem/string.h" // for memset
+
+//  A small, simple heap manager based (loosely) on
+//  the startup heap manager from FreeBSD, optimized for space.
+//
+//  Manages a fixed-size memory pool, supports malloc and free only.
+//  No support for realloc.
+//
+//  Allocates chunks in multiples of four bytes, with a four byte header
+//  for each chunk. The overhead of each chunk is kept low by keeping pointers
+//  as two byte offsets within the heap, rather than (4 or 8 byte) pointers.
+
+namespace {
+
+// When POSIX threads are not available, make the mutex operations a nop
+#ifndef _LIBCXXABI_HAS_NO_THREADS
+static _LIBCPP_CONSTINIT std::__libcpp_mutex_t heap_mutex = _LIBCPP_MUTEX_INITIALIZER;
+#else
+static _LIBCPP_CONSTINIT void* heap_mutex = 0;
+#endif
+
+class mutexor {
+public:
+#ifndef _LIBCXXABI_HAS_NO_THREADS
+  mutexor(std::__libcpp_mutex_t* m) : mtx_(m) {
+    std::__libcpp_mutex_lock(mtx_);
+  }
+  ~mutexor() { std::__libcpp_mutex_unlock(mtx_); }
+#else
+  mutexor(void*) {}
+  ~mutexor() {}
+#endif
+private:
+  mutexor(const mutexor& rhs);
+  mutexor& operator=(const mutexor& rhs);
+#ifndef _LIBCXXABI_HAS_NO_THREADS
+  std::__libcpp_mutex_t* mtx_;
+#endif
+};
+
+static const size_t HEAP_SIZE = 512;
+char heap[HEAP_SIZE] __attribute__((aligned));
+
+typedef unsigned short heap_offset;
+typedef unsigned short heap_size;
+
+// On both 64 and 32 bit targets heap_node should have the following properties
+// Size: 4
+// Alignment: 2
+struct heap_node {
+  heap_offset next_node; // offset into heap
+  heap_size len;         // size in units of "sizeof(heap_node)"
+};
+
+// All pointers returned by fallback_malloc must be at least aligned
+// as RequiredAligned. Note that RequiredAlignment can be greater than
+// alignof(std::max_align_t) on 64 bit systems compiling 32 bit code.
+struct FallbackMaxAlignType {
+} __attribute__((aligned));
+const size_t RequiredAlignment = alignof(FallbackMaxAlignType);
+
+static_assert(alignof(FallbackMaxAlignType) % sizeof(heap_node) == 0,
+              "The required alignment must be evenly divisible by the sizeof(heap_node)");
+
+// The number of heap_node's that can fit in a chunk of memory with the size
+// of the RequiredAlignment. On 64 bit targets NodesPerAlignment should be 4.
+const size_t NodesPerAlignment = alignof(FallbackMaxAlignType) / sizeof(heap_node);
+
+static const heap_node* list_end =
+    (heap_node*)(&heap[HEAP_SIZE]); // one past the end of the heap
+static heap_node* freelist = NULL;
+
+heap_node* node_from_offset(const heap_offset offset) {
+  return (heap_node*)(heap + (offset * sizeof(heap_node)));
+}
+
+heap_offset offset_from_node(const heap_node* ptr) {
+  return static_cast<heap_offset>(
+      static_cast<size_t>(reinterpret_cast<const char*>(ptr) - heap) /
+      sizeof(heap_node));
+}
+
+// Return a pointer to the first address, 'A', in `heap` that can actually be
+// used to represent a heap_node. 'A' must be aligned so that
+// '(A + sizeof(heap_node)) % RequiredAlignment == 0'. On 64 bit systems this
+// address should be 12 bytes after the first 16 byte boundary.
+heap_node* getFirstAlignedNodeInHeap() {
+  heap_node* node = (heap_node*)heap;
+  const size_t alignNBytesAfterBoundary = RequiredAlignment - sizeof(heap_node);
+  size_t boundaryOffset = reinterpret_cast<size_t>(node) % RequiredAlignment;
+  size_t requiredOffset = alignNBytesAfterBoundary - boundaryOffset;
+  size_t NElemOffset = requiredOffset / sizeof(heap_node);
+  return node + NElemOffset;
+}
+
+void init_heap() {
+  freelist = getFirstAlignedNodeInHeap();
+  freelist->next_node = offset_from_node(list_end);
+  freelist->len = static_cast<heap_size>(list_end - freelist);
+}
+
+//  How big a chunk we allocate
+size_t alloc_size(size_t len) {
+  return (len + sizeof(heap_node) - 1) / sizeof(heap_node) + 1;
+}
+
+bool is_fallback_ptr(void* ptr) {
+  return ptr >= heap && ptr < (heap + HEAP_SIZE);
+}
+
+void* fallback_malloc(size_t len) {
+  heap_node *p, *prev;
+  const size_t nelems = alloc_size(len);
+  mutexor mtx(&heap_mutex);
+
+  if (NULL == freelist)
+    init_heap();
+
+  //  Walk the free list, looking for a "big enough" chunk
+  for (p = freelist, prev = 0; p && p != list_end;
+       prev = p, p = node_from_offset(p->next_node)) {
+
+    // Check the invariant that all heap_nodes pointers 'p' are aligned
+    // so that 'p + 1' has an alignment of at least RequiredAlignment
+    assert(reinterpret_cast<size_t>(p + 1) % RequiredAlignment == 0);
+
+    // Calculate the number of extra padding elements needed in order
+    // to split 'p' and create a properly aligned heap_node from the tail
+    // of 'p'. We calculate aligned_nelems such that 'p->len - aligned_nelems'
+    // will be a multiple of NodesPerAlignment.
+    size_t aligned_nelems = nelems;
+    if (p->len > nelems) {
+      heap_size remaining_len = static_cast<heap_size>(p->len - nelems);
+      aligned_nelems += remaining_len % NodesPerAlignment;
+    }
+
+    // chunk is larger and we can create a properly aligned heap_node
+    // from the tail. In this case we shorten 'p' and return the tail.
+    if (p->len > aligned_nelems) {
+      heap_node* q;
+      p->len = static_cast<heap_size>(p->len - aligned_nelems);
+      q = p + p->len;
+      q->next_node = 0;
+      q->len = static_cast<heap_size>(aligned_nelems);
+      void* ptr = q + 1;
+      assert(reinterpret_cast<size_t>(ptr) % RequiredAlignment == 0);
+      return ptr;
+    }
+
+    // The chunk is the exact size or the chunk is larger but not large
+    // enough to split due to alignment constraints.
+    if (p->len >= nelems) {
+      if (prev == 0)
+        freelist = node_from_offset(p->next_node);
+      else
+        prev->next_node = p->next_node;
+      p->next_node = 0;
+      void* ptr = p + 1;
+      assert(reinterpret_cast<size_t>(ptr) % RequiredAlignment == 0);
+      return ptr;
+    }
+  }
+  return NULL; // couldn't find a spot big enough
+}
+
+//  Return the start of the next block
+heap_node* after(struct heap_node* p) { return p + p->len; }
+
+void fallback_free(void* ptr) {
+  struct heap_node* cp = ((struct heap_node*)ptr) - 1; // retrieve the chunk
+  struct heap_node *p, *prev;
+
+  mutexor mtx(&heap_mutex);
+
+#ifdef DEBUG_FALLBACK_MALLOC
+  std::printf("Freeing item at %d of size %d\n", offset_from_node(cp), cp->len);
+#endif
+
+  for (p = freelist, prev = 0; p && p != list_end;
+       prev = p, p = node_from_offset(p->next_node)) {
+#ifdef DEBUG_FALLBACK_MALLOC
+    std::printf("  p=%d, cp=%d, after(p)=%d, after(cp)=%d\n",
+      offset_from_node(p), offset_from_node(cp),
+      offset_from_node(after(p)), offset_from_node(after(cp)));
+#endif
+    if (after(p) == cp) {
+#ifdef DEBUG_FALLBACK_MALLOC
+      std::printf("  Appending onto chunk at %d\n", offset_from_node(p));
+#endif
+      p->len = static_cast<heap_size>(
+          p->len + cp->len); // make the free heap_node larger
+      return;
+    } else if (after(cp) == p) { // there's a free heap_node right after
+#ifdef DEBUG_FALLBACK_MALLOC
+      std::printf("  Appending free chunk at %d\n", offset_from_node(p));
+#endif
+      cp->len = static_cast<heap_size>(cp->len + p->len);
+      if (prev == 0) {
+        freelist = cp;
+        cp->next_node = p->next_node;
+      } else
+        prev->next_node = offset_from_node(cp);
+      return;
+    }
+  }
+//  Nothing to merge with, add it to the start of the free list
+#ifdef DEBUG_FALLBACK_MALLOC
+  std::printf("  Making new free list entry %d\n", offset_from_node(cp));
+#endif
+  cp->next_node = offset_from_node(freelist);
+  freelist = cp;
+}
+
+#ifdef INSTRUMENT_FALLBACK_MALLOC
+size_t print_free_list() {
+  struct heap_node *p, *prev;
+  heap_size total_free = 0;
+  if (NULL == freelist)
+    init_heap();
+
+  for (p = freelist, prev = 0; p && p != list_end;
+       prev = p, p = node_from_offset(p->next_node)) {
+    std::printf("%sOffset: %d\tsize: %d Next: %d\n",
+      (prev == 0 ? "" : "  "), offset_from_node(p), p->len, p->next_node);
+    total_free += p->len;
+  }
+  std::printf("Total Free space: %d\n", total_free);
+  return total_free;
+}
+#endif
+} // end unnamed namespace
+
+namespace __cxxabiv1 {
+
+struct __attribute__((aligned)) __aligned_type {};
+
+void* __aligned_malloc_with_fallback(size_t size) {
+#if defined(_WIN32)
+  if (void* dest = std::__libcpp_aligned_alloc(alignof(__aligned_type), size))
+    return dest;
+#elif defined(_LIBCPP_HAS_NO_LIBRARY_ALIGNED_ALLOCATION)
+  if (void* dest = ::malloc(size))
+    return dest;
+#else
+  if (size == 0)
+    size = 1;
+  if (void* dest = std::__libcpp_aligned_alloc(__alignof(__aligned_type), size))
+    return dest;
+#endif
+  return fallback_malloc(size);
+}
+
+void* __calloc_with_fallback(size_t count, size_t size) {
+  void* ptr = ::calloc(count, size);
+  if (NULL != ptr)
+    return ptr;
+  // if calloc fails, fall back to emergency stash
+  ptr = fallback_malloc(size * count);
+  if (NULL != ptr)
+    ::memset(ptr, 0, size * count);
+  return ptr;
+}
+
+void __aligned_free_with_fallback(void* ptr) {
+  if (is_fallback_ptr(ptr))
+    fallback_free(ptr);
+  else {
+#if defined(_LIBCPP_HAS_NO_LIBRARY_ALIGNED_ALLOCATION)
+    ::free(ptr);
+#else
+    std::__libcpp_aligned_free(ptr);
+#endif
+  }
+}
+
+void __free_with_fallback(void* ptr) {
+  if (is_fallback_ptr(ptr))
+    fallback_free(ptr);
+  else
+    ::free(ptr);
+}
+
+} // namespace __cxxabiv1

third_party/libcxxabi/fallback_malloc.h

@@ -0,0 +1,28 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _FALLBACK_MALLOC_H
+#define _FALLBACK_MALLOC_H
+
+#include "third_party/libcxxabi/include/__cxxabi_config.h"
+#include "libc/isystem/stddef.h" // for size_t
+
+namespace __cxxabiv1 {
+
+// Allocate some memory from _somewhere_
+_LIBCXXABI_HIDDEN void * __aligned_malloc_with_fallback(size_t size);
+
+// Allocate and zero-initialize memory from _somewhere_
+_LIBCXXABI_HIDDEN void * __calloc_with_fallback(size_t count, size_t size);
+
+_LIBCXXABI_HIDDEN void __aligned_free_with_fallback(void *ptr);
+_LIBCXXABI_HIDDEN void __free_with_fallback(void *ptr);
+
+} // namespace __cxxabiv1
+
+#endif

third_party/libcxxabi/include/__cxxabi_config.h

@@ -0,0 +1,106 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef ____CXXABI_CONFIG_H
+#define ____CXXABI_CONFIG_H
+
+#if defined(__arm__) && !defined(__USING_SJLJ_EXCEPTIONS__) &&                 \
+    !defined(__ARM_DWARF_EH__) && !defined(__SEH__)
+#define _LIBCXXABI_ARM_EHABI
+#endif
+
+#if !defined(__has_attribute)
+#define __has_attribute(_attribute_) 0
+#endif
+
+#if defined(__clang__)
+#  define _LIBCXXABI_COMPILER_CLANG
+#  ifndef __apple_build_version__
+#    define _LIBCXXABI_CLANG_VER (__clang_major__ * 100 + __clang_minor__)
+#  endif
+#elif defined(__GNUC__)
+#  define _LIBCXXABI_COMPILER_GCC
+#elif defined(_MSC_VER)
+#  define _LIBCXXABI_COMPILER_MSVC
+#elif defined(__IBMCPP__)
+#  define _LIBCXXABI_COMPILER_IBM
+#endif
+
+#if defined(_WIN32)
+ #if defined(_LIBCXXABI_DISABLE_VISIBILITY_ANNOTATIONS) || (defined(__MINGW32__) && !defined(_LIBCXXABI_BUILDING_LIBRARY))
+  #define _LIBCXXABI_HIDDEN
+  #define _LIBCXXABI_DATA_VIS
+  #define _LIBCXXABI_FUNC_VIS
+  #define _LIBCXXABI_TYPE_VIS
+ #elif defined(_LIBCXXABI_BUILDING_LIBRARY)
+  #define _LIBCXXABI_HIDDEN
+  #define _LIBCXXABI_DATA_VIS __declspec(dllexport)
+  #define _LIBCXXABI_FUNC_VIS __declspec(dllexport)
+  #define _LIBCXXABI_TYPE_VIS __declspec(dllexport)
+ #else
+  #define _LIBCXXABI_HIDDEN
+  #define _LIBCXXABI_DATA_VIS __declspec(dllimport)
+  #define _LIBCXXABI_FUNC_VIS __declspec(dllimport)
+  #define _LIBCXXABI_TYPE_VIS __declspec(dllimport)
+ #endif
+#else
+ #if !defined(_LIBCXXABI_DISABLE_VISIBILITY_ANNOTATIONS)
+  #define _LIBCXXABI_HIDDEN __attribute__((__visibility__("hidden")))
+  #define _LIBCXXABI_DATA_VIS __attribute__((__visibility__("default")))
+  #define _LIBCXXABI_FUNC_VIS __attribute__((__visibility__("default")))
+  #if __has_attribute(__type_visibility__)
+   #define _LIBCXXABI_TYPE_VIS __attribute__((__type_visibility__("default")))
+  #else
+   #define _LIBCXXABI_TYPE_VIS __attribute__((__visibility__("default")))
+  #endif
+ #else
+  #define _LIBCXXABI_HIDDEN
+  #define _LIBCXXABI_DATA_VIS
+  #define _LIBCXXABI_FUNC_VIS
+  #define _LIBCXXABI_TYPE_VIS
+ #endif
+#endif
+
+#if defined(_LIBCXXABI_COMPILER_MSVC)
+#define _LIBCXXABI_WEAK
+#else
+#define _LIBCXXABI_WEAK __attribute__((__weak__))
+#endif
+
+#if defined(__clang__)
+#define _LIBCXXABI_COMPILER_CLANG
+#elif defined(__GNUC__)
+#define _LIBCXXABI_COMPILER_GCC
+#endif
+
+#if __has_attribute(__no_sanitize__) && defined(_LIBCXXABI_COMPILER_CLANG)
+#define _LIBCXXABI_NO_CFI __attribute__((__no_sanitize__("cfi")))
+#else
+#define _LIBCXXABI_NO_CFI
+#endif
+
+// wasm32 follows the arm32 ABI convention of using 32-bit guard.
+#if defined(__arm__) || defined(__wasm32__) || defined(__ARM64_ARCH_8_32__)
+#  define _LIBCXXABI_GUARD_ABI_ARM
+#endif
+
+#if defined(_LIBCXXABI_COMPILER_CLANG)
+#  if !__has_feature(cxx_exceptions)
+#    define _LIBCXXABI_NO_EXCEPTIONS
+#  endif
+#elif defined(_LIBCXXABI_COMPILER_GCC) && !defined(__EXCEPTIONS)
+#  define _LIBCXXABI_NO_EXCEPTIONS
+#endif
+
+#if defined(_WIN32)
+#define _LIBCXXABI_DTOR_FUNC __thiscall
+#else
+#define _LIBCXXABI_DTOR_FUNC
+#endif
+
+#endif // ____CXXABI_CONFIG_H

third_party/libcxxabi/include/cxxabi.h

@@ -0,0 +1,177 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef __CXXABI_H
+#define __CXXABI_H
+
+/*
+ * This header provides the interface to the C++ ABI as defined at:
+ *       https://itanium-cxx-abi.github.io/cxx-abi/
+ */
+
+#include "libc/isystem/stddef.h"
+#include "libc/isystem/stdint.h"
+
+#include "third_party/libcxxabi/include/__cxxabi_config.h"
+
+#define _LIBCPPABI_VERSION 15000
+#define _LIBCXXABI_NORETURN  __attribute__((noreturn))
+#define _LIBCXXABI_ALWAYS_COLD __attribute__((cold))
+
+#ifdef __cplusplus
+
+namespace std {
+#if defined(_WIN32)
+class _LIBCXXABI_TYPE_VIS type_info; // forward declaration
+#else
+class type_info; // forward declaration
+#endif
+}
+
+
+// runtime routines use C calling conventions, but are in __cxxabiv1 namespace
+namespace __cxxabiv1 {
+extern "C"  {
+
+// 2.4.2 Allocating the Exception Object
+extern _LIBCXXABI_FUNC_VIS void *
+__cxa_allocate_exception(size_t thrown_size) throw();
+extern _LIBCXXABI_FUNC_VIS void
+__cxa_free_exception(void *thrown_exception) throw();
+
+// 2.4.3 Throwing the Exception Object
+extern _LIBCXXABI_FUNC_VIS _LIBCXXABI_NORETURN void
+__cxa_throw(void *thrown_exception, std::type_info *tinfo,
+            void (_LIBCXXABI_DTOR_FUNC *dest)(void *));
+
+// 2.5.3 Exception Handlers
+extern _LIBCXXABI_FUNC_VIS void *
+__cxa_get_exception_ptr(void *exceptionObject) throw();
+extern _LIBCXXABI_FUNC_VIS void *
+__cxa_begin_catch(void *exceptionObject) throw();
+extern _LIBCXXABI_FUNC_VIS void __cxa_end_catch();
+#if defined(_LIBCXXABI_ARM_EHABI)
+extern _LIBCXXABI_FUNC_VIS bool
+__cxa_begin_cleanup(void *exceptionObject) throw();
+extern _LIBCXXABI_FUNC_VIS void __cxa_end_cleanup();
+#endif
+extern _LIBCXXABI_FUNC_VIS std::type_info *__cxa_current_exception_type();
+
+// 2.5.4 Rethrowing Exceptions
+extern _LIBCXXABI_FUNC_VIS _LIBCXXABI_NORETURN void __cxa_rethrow();
+
+// 2.6 Auxiliary Runtime APIs
+extern _LIBCXXABI_FUNC_VIS _LIBCXXABI_NORETURN void __cxa_bad_cast(void);
+extern _LIBCXXABI_FUNC_VIS _LIBCXXABI_NORETURN void __cxa_bad_typeid(void);
+extern _LIBCXXABI_FUNC_VIS _LIBCXXABI_NORETURN void
+__cxa_throw_bad_array_new_length(void);
+
+// 3.2.6 Pure Virtual Function API
+extern _LIBCXXABI_FUNC_VIS _LIBCXXABI_NORETURN void __cxa_pure_virtual(void);
+
+// 3.2.7 Deleted Virtual Function API
+extern _LIBCXXABI_FUNC_VIS _LIBCXXABI_NORETURN void __cxa_deleted_virtual(void);
+
+// 3.3.2 One-time Construction API
+#if defined(_LIBCXXABI_GUARD_ABI_ARM)
+extern _LIBCXXABI_FUNC_VIS _LIBCXXABI_ALWAYS_COLD int __cxa_guard_acquire(uint32_t *);
+extern _LIBCXXABI_FUNC_VIS _LIBCXXABI_ALWAYS_COLD void __cxa_guard_release(uint32_t *);
+extern _LIBCXXABI_FUNC_VIS _LIBCXXABI_ALWAYS_COLD void __cxa_guard_abort(uint32_t *);
+#else
+extern _LIBCXXABI_FUNC_VIS _LIBCXXABI_ALWAYS_COLD int __cxa_guard_acquire(uint64_t *);
+extern _LIBCXXABI_FUNC_VIS _LIBCXXABI_ALWAYS_COLD void __cxa_guard_release(uint64_t *);
+extern _LIBCXXABI_FUNC_VIS _LIBCXXABI_ALWAYS_COLD void __cxa_guard_abort(uint64_t *);
+#endif
+
+// 3.3.3 Array Construction and Destruction API
+extern _LIBCXXABI_FUNC_VIS void *
+__cxa_vec_new(size_t element_count, size_t element_size, size_t padding_size,
+              void (*constructor)(void *), void (*destructor)(void *));
+
+extern _LIBCXXABI_FUNC_VIS void *
+__cxa_vec_new2(size_t element_count, size_t element_size, size_t padding_size,
+               void (*constructor)(void *), void (*destructor)(void *),
+               void *(*alloc)(size_t), void (*dealloc)(void *));
+
+extern _LIBCXXABI_FUNC_VIS void *
+__cxa_vec_new3(size_t element_count, size_t element_size, size_t padding_size,
+               void (*constructor)(void *), void (*destructor)(void *),
+               void *(*alloc)(size_t), void (*dealloc)(void *, size_t));
+
+extern _LIBCXXABI_FUNC_VIS void
+__cxa_vec_ctor(void *array_address, size_t element_count, size_t element_size,
+               void (*constructor)(void *), void (*destructor)(void *));
+
+extern _LIBCXXABI_FUNC_VIS void __cxa_vec_dtor(void *array_address,
+                                               size_t element_count,
+                                               size_t element_size,
+                                               void (*destructor)(void *));
+
+extern _LIBCXXABI_FUNC_VIS void __cxa_vec_cleanup(void *array_address,
+                                                  size_t element_count,
+                                                  size_t element_size,
+                                                  void (*destructor)(void *));
+
+extern _LIBCXXABI_FUNC_VIS void __cxa_vec_delete(void *array_address,
+                                                 size_t element_size,
+                                                 size_t padding_size,
+                                                 void (*destructor)(void *));
+
+extern _LIBCXXABI_FUNC_VIS void
+__cxa_vec_delete2(void *array_address, size_t element_size, size_t padding_size,
+                  void (*destructor)(void *), void (*dealloc)(void *));
+
+extern _LIBCXXABI_FUNC_VIS void
+__cxa_vec_delete3(void *__array_address, size_t element_size,
+                  size_t padding_size, void (*destructor)(void *),
+                  void (*dealloc)(void *, size_t));
+
+extern _LIBCXXABI_FUNC_VIS void
+__cxa_vec_cctor(void *dest_array, void *src_array, size_t element_count,
+                size_t element_size, void (*constructor)(void *, void *),
+                void (*destructor)(void *));
+
+// 3.3.5.3 Runtime API
+// These functions are part of the C++ ABI, but they are not defined in libc++abi:
+//    int __cxa_atexit(void (*)(void *), void *, void *);
+//    void __cxa_finalize(void *);
+
+// 3.4 Demangler API
+extern _LIBCXXABI_FUNC_VIS char *__cxa_demangle(const char *mangled_name,
+                                                char *output_buffer,
+                                                size_t *length, int *status);
+
+// Apple additions to support C++ 0x exception_ptr class
+// These are primitives to wrap a smart pointer around an exception object
+extern _LIBCXXABI_FUNC_VIS void *__cxa_current_primary_exception() throw();
+extern _LIBCXXABI_FUNC_VIS void
+__cxa_rethrow_primary_exception(void *primary_exception);
+extern _LIBCXXABI_FUNC_VIS void
+__cxa_increment_exception_refcount(void *primary_exception) throw();
+extern _LIBCXXABI_FUNC_VIS void
+__cxa_decrement_exception_refcount(void *primary_exception) throw();
+
+// Apple extension to support std::uncaught_exception()
+extern _LIBCXXABI_FUNC_VIS bool __cxa_uncaught_exception() throw();
+extern _LIBCXXABI_FUNC_VIS unsigned int __cxa_uncaught_exceptions() throw();
+
+#if defined(__linux__) || defined(__Fuchsia__) || defined(__COSMOPOLITAN__)
+// Linux and Fuchsia TLS support. Not yet an official part of the Itanium ABI.
+// https://sourceware.org/glibc/wiki/Destructor%20support%20for%20thread_local%20variables
+extern _LIBCXXABI_FUNC_VIS int __cxa_thread_atexit(void (*)(void *), void *,
+                                                   void *) throw();
+#endif
+
+} // extern "C"
+} // namespace __cxxabiv1
+
+namespace abi = __cxxabiv1;
+
+#endif // __cplusplus
+
+#endif // __CXXABI_H

third_party/libcxxabi/libcxx/include/__memory/aligned_alloc.h

@@ -0,0 +1,66 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___MEMORY_ALIGNED_ALLOC_H
+#define _LIBCPP___MEMORY_ALIGNED_ALLOC_H
+
+#include "third_party/libcxx/__config"
+#include "third_party/libcxx/cstddef"
+#include "third_party/libcxx/cstdlib"
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#ifndef _LIBCPP_HAS_NO_LIBRARY_ALIGNED_ALLOCATION
+
+// Low-level helpers to call the aligned allocation and deallocation functions
+// on the target platform. This is used to implement libc++'s own memory
+// allocation routines -- if you need to allocate memory inside the library,
+// chances are that you want to use `__libcpp_allocate` instead.
+//
+// Returns the allocated memory, or `nullptr` on failure.
+inline _LIBCPP_HIDE_FROM_ABI
+void* __libcpp_aligned_alloc(std::size_t __alignment, std::size_t __size) {
+#  if defined(_LIBCPP_MSVCRT_LIKE)
+    return ::_aligned_malloc(__size, __alignment);
+#  elif _LIBCPP_STD_VER >= 17 && !defined(_LIBCPP_HAS_NO_C11_ALIGNED_ALLOC)
+    // aligned_alloc() requires that __size is a multiple of __alignment,
+    // but for C++ [new.delete.general], only states "if the value of an
+    // alignment argument passed to any of these functions is not a valid
+    // alignment value, the behavior is undefined".
+    // To handle calls such as ::operator new(1, std::align_val_t(128)), we
+    // round __size up to the next multiple of __alignment.
+    size_t __rounded_size = (__size + __alignment - 1) & ~(__alignment - 1);
+    // Rounding up could have wrapped around to zero, so we have to add another
+    // max() ternary to the actual call site to avoid succeeded in that case.
+    return ::aligned_alloc(__alignment, __size > __rounded_size ? __size : __rounded_size);
+#  else
+    void* __result = nullptr;
+    (void)::posix_memalign(&__result, __alignment, __size);
+    // If posix_memalign fails, __result is unmodified so we still return `nullptr`.
+    return __result;
+#  endif
+}
+
+inline _LIBCPP_HIDE_FROM_ABI
+void __libcpp_aligned_free(void* __ptr) {
+#if defined(_LIBCPP_MSVCRT_LIKE)
+  ::_aligned_free(__ptr);
+#else
+  ::free(__ptr);
+#endif
+}
+
+#endif // !_LIBCPP_HAS_NO_LIBRARY_ALIGNED_ALLOCATION
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___MEMORY_ALIGNED_ALLOC_H

third_party/libcxxabi/private_typeinfo.h

@@ -0,0 +1,251 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef __PRIVATE_TYPEINFO_H_
+#define __PRIVATE_TYPEINFO_H_
+
+#include "third_party/libcxxabi/include/__cxxabi_config.h"
+
+#include "third_party/libcxx/typeinfo"
+#include "libc/isystem/stddef.h"
+
+namespace __cxxabiv1 {
+
+class _LIBCXXABI_TYPE_VIS __shim_type_info : public std::type_info {
+public:
+  _LIBCXXABI_HIDDEN virtual ~__shim_type_info();
+
+  _LIBCXXABI_HIDDEN virtual void noop1() const;
+  _LIBCXXABI_HIDDEN virtual void noop2() const;
+  _LIBCXXABI_HIDDEN virtual bool can_catch(const __shim_type_info *thrown_type,
+                                           void *&adjustedPtr) const = 0;
+};
+
+class _LIBCXXABI_TYPE_VIS __fundamental_type_info : public __shim_type_info {
+public:
+  _LIBCXXABI_HIDDEN virtual ~__fundamental_type_info();
+  _LIBCXXABI_HIDDEN virtual bool can_catch(const __shim_type_info *,
+                                           void *&) const;
+};
+
+class _LIBCXXABI_TYPE_VIS __array_type_info : public __shim_type_info {
+public:
+  _LIBCXXABI_HIDDEN virtual ~__array_type_info();
+  _LIBCXXABI_HIDDEN virtual bool can_catch(const __shim_type_info *,
+                                           void *&) const;
+};
+
+class _LIBCXXABI_TYPE_VIS __function_type_info : public __shim_type_info {
+public:
+  _LIBCXXABI_HIDDEN virtual ~__function_type_info();
+  _LIBCXXABI_HIDDEN virtual bool can_catch(const __shim_type_info *,
+                                           void *&) const;
+};
+
+class _LIBCXXABI_TYPE_VIS __enum_type_info : public __shim_type_info {
+public:
+  _LIBCXXABI_HIDDEN virtual ~__enum_type_info();
+  _LIBCXXABI_HIDDEN virtual bool can_catch(const __shim_type_info *,
+                                           void *&) const;
+};
+
+enum
+{
+    unknown = 0,
+    public_path,
+    not_public_path,
+    yes,
+    no
+};
+
+class _LIBCXXABI_TYPE_VIS __class_type_info;
+
+struct _LIBCXXABI_HIDDEN __dynamic_cast_info
+{
+// const data supplied to the search:
+
+    const __class_type_info* dst_type;
+    const void* static_ptr;
+    const __class_type_info* static_type;
+    ptrdiff_t src2dst_offset;
+
+// Data that represents the answer:
+
+    // pointer to a dst_type which has (static_ptr, static_type) above it
+    const void* dst_ptr_leading_to_static_ptr;
+    // pointer to a dst_type which does not have (static_ptr, static_type) above it
+    const void* dst_ptr_not_leading_to_static_ptr;
+
+    // The following three paths are either unknown, public_path or not_public_path.
+    // access of path from dst_ptr_leading_to_static_ptr to (static_ptr, static_type)
+    int path_dst_ptr_to_static_ptr;
+    // access of path from (dynamic_ptr, dynamic_type) to (static_ptr, static_type)
+    //    when there is no dst_type along the path
+    int path_dynamic_ptr_to_static_ptr;
+    // access of path from (dynamic_ptr, dynamic_type) to dst_type
+    //    (not used if there is a (static_ptr, static_type) above a dst_type).
+    int path_dynamic_ptr_to_dst_ptr;
+
+    // Number of dst_types below (static_ptr, static_type)
+    int number_to_static_ptr;
+    // Number of dst_types not below (static_ptr, static_type)
+    int number_to_dst_ptr;
+
+// Data that helps stop the search before the entire tree is searched:
+
+    // is_dst_type_derived_from_static_type is either unknown, yes or no.
+    int is_dst_type_derived_from_static_type;
+    // Number of dst_type in tree.  If 0, then that means unknown.
+    int number_of_dst_type;
+    // communicates to a dst_type node that (static_ptr, static_type) was found
+    //    above it.
+    bool found_our_static_ptr;
+    // communicates to a dst_type node that a static_type was found
+    //    above it, but it wasn't (static_ptr, static_type)
+    bool found_any_static_type;
+    // Set whenever a search can be stopped
+    bool search_done;
+};
+
+// Has no base class
+class _LIBCXXABI_TYPE_VIS __class_type_info : public __shim_type_info {
+public:
+  _LIBCXXABI_HIDDEN virtual ~__class_type_info();
+
+  _LIBCXXABI_HIDDEN void process_static_type_above_dst(__dynamic_cast_info *,
+                                                       const void *,
+                                                       const void *, int) const;
+  _LIBCXXABI_HIDDEN void process_static_type_below_dst(__dynamic_cast_info *,
+                                                       const void *, int) const;
+  _LIBCXXABI_HIDDEN void process_found_base_class(__dynamic_cast_info *, void *,
+                                                  int) const;
+  _LIBCXXABI_HIDDEN virtual void search_above_dst(__dynamic_cast_info *,
+                                                  const void *, const void *,
+                                                  int, bool) const;
+  _LIBCXXABI_HIDDEN virtual void
+  search_below_dst(__dynamic_cast_info *, const void *, int, bool) const;
+  _LIBCXXABI_HIDDEN virtual bool can_catch(const __shim_type_info *,
+                                           void *&) const;
+  _LIBCXXABI_HIDDEN virtual void
+  has_unambiguous_public_base(__dynamic_cast_info *, void *, int) const;
+};
+
+// Has one non-virtual public base class at offset zero
+class _LIBCXXABI_TYPE_VIS __si_class_type_info : public __class_type_info {
+public:
+  const __class_type_info *__base_type;
+
+  _LIBCXXABI_HIDDEN virtual ~__si_class_type_info();
+
+  _LIBCXXABI_HIDDEN virtual void search_above_dst(__dynamic_cast_info *,
+                                                  const void *, const void *,
+                                                  int, bool) const;
+  _LIBCXXABI_HIDDEN virtual void
+  search_below_dst(__dynamic_cast_info *, const void *, int, bool) const;
+  _LIBCXXABI_HIDDEN virtual void
+  has_unambiguous_public_base(__dynamic_cast_info *, void *, int) const;
+};
+
+struct _LIBCXXABI_HIDDEN __base_class_type_info
+{
+public:
+    const __class_type_info* __base_type;
+    long __offset_flags;
+
+    enum __offset_flags_masks
+    {
+        __virtual_mask = 0x1,
+        __public_mask  = 0x2, // base is public
+        __offset_shift = 8
+    };
+
+    void search_above_dst(__dynamic_cast_info*, const void*, const void*, int, bool) const;
+    void search_below_dst(__dynamic_cast_info*, const void*, int, bool) const;
+    void has_unambiguous_public_base(__dynamic_cast_info*, void*, int) const;
+};
+
+// Has one or more base classes
+class _LIBCXXABI_TYPE_VIS __vmi_class_type_info : public __class_type_info {
+public:
+  unsigned int __flags;
+  unsigned int __base_count;
+  __base_class_type_info __base_info[1];
+
+  enum __flags_masks {
+    __non_diamond_repeat_mask = 0x1, // has two or more distinct base class
+                                     //    objects of the same type
+    __diamond_shaped_mask = 0x2      // has base class object with two or
+                                     //    more derived objects
+  };
+
+  _LIBCXXABI_HIDDEN virtual ~__vmi_class_type_info();
+
+  _LIBCXXABI_HIDDEN virtual void search_above_dst(__dynamic_cast_info *,
+                                                  const void *, const void *,
+                                                  int, bool) const;
+  _LIBCXXABI_HIDDEN virtual void
+  search_below_dst(__dynamic_cast_info *, const void *, int, bool) const;
+  _LIBCXXABI_HIDDEN virtual void
+  has_unambiguous_public_base(__dynamic_cast_info *, void *, int) const;
+};
+
+class _LIBCXXABI_TYPE_VIS __pbase_type_info : public __shim_type_info {
+public:
+  unsigned int __flags;
+  const __shim_type_info *__pointee;
+
+  enum __masks {
+    __const_mask = 0x1,
+    __volatile_mask = 0x2,
+    __restrict_mask = 0x4,
+    __incomplete_mask = 0x8,
+    __incomplete_class_mask = 0x10,
+    __transaction_safe_mask = 0x20,
+    // This implements the following proposal from cxx-abi-dev (not yet part of
+    // the ABI document):
+    //
+    //   http://sourcerytools.com/pipermail/cxx-abi-dev/2016-October/002986.html
+    //
+    // This is necessary for support of http://wg21.link/p0012, which permits
+    // throwing noexcept function and member function pointers and catching
+    // them as non-noexcept pointers.
+    __noexcept_mask = 0x40,
+
+    // Flags that cannot be removed by a standard conversion.
+    __no_remove_flags_mask = __const_mask | __volatile_mask | __restrict_mask,
+    // Flags that cannot be added by a standard conversion.
+    __no_add_flags_mask = __transaction_safe_mask | __noexcept_mask
+  };
+
+  _LIBCXXABI_HIDDEN virtual ~__pbase_type_info();
+  _LIBCXXABI_HIDDEN virtual bool can_catch(const __shim_type_info *,
+                                           void *&) const;
+};
+
+class _LIBCXXABI_TYPE_VIS __pointer_type_info : public __pbase_type_info {
+public:
+  _LIBCXXABI_HIDDEN virtual ~__pointer_type_info();
+  _LIBCXXABI_HIDDEN virtual bool can_catch(const __shim_type_info *,
+                                           void *&) const;
+  _LIBCXXABI_HIDDEN bool can_catch_nested(const __shim_type_info *) const;
+};
+
+class _LIBCXXABI_TYPE_VIS __pointer_to_member_type_info
+    : public __pbase_type_info {
+public:
+  const __class_type_info *__context;
+
+  _LIBCXXABI_HIDDEN virtual ~__pointer_to_member_type_info();
+  _LIBCXXABI_HIDDEN virtual bool can_catch(const __shim_type_info *,
+                                           void *&) const;
+  _LIBCXXABI_HIDDEN bool can_catch_nested(const __shim_type_info *) const;
+};
+
+}  // __cxxabiv1
+
+#endif // __PRIVATE_TYPEINFO_H_

third_party/libcxxabi/stdlib_exception.cc

@@ -0,0 +1,70 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "third_party/libcxx/new"
+#include "third_party/libcxx/exception"
+
+namespace std
+{
+
+// exception
+
+exception::~exception() noexcept
+{
+}
+
+const char* exception::what() const noexcept
+{
+  return "std::exception";
+}
+
+// bad_exception
+
+bad_exception::~bad_exception() noexcept
+{
+}
+
+const char* bad_exception::what() const noexcept
+{
+  return "std::bad_exception";
+}
+
+
+//  bad_alloc
+
+bad_alloc::bad_alloc() noexcept
+{
+}
+
+bad_alloc::~bad_alloc() noexcept
+{
+}
+
+const char*
+bad_alloc::what() const noexcept
+{
+    return "std::bad_alloc";
+}
+
+// bad_array_new_length
+
+bad_array_new_length::bad_array_new_length() noexcept
+{
+}
+
+bad_array_new_length::~bad_array_new_length() noexcept
+{
+}
+
+const char*
+bad_array_new_length::what() const noexcept
+{
+    return "bad_array_new_length";
+}
+
+}  // std

third_party/libcxxabi/stdlib_new_delete.cc

@@ -0,0 +1,266 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "third_party/libcxxabi/include/__cxxabi_config.h"
+#include "third_party/libcxxabi/libcxx/include/__memory/aligned_alloc.h"
+#include "third_party/libcxx/cstdlib"
+#include "third_party/libcxx/new"
+
+// Perform a few sanity checks on libc++ and libc++abi macros to ensure that
+// the code below can be an exact copy of the code in libcxx/src/new.cpp.
+#if !defined(_THROW_BAD_ALLOC)
+#  error The _THROW_BAD_ALLOC macro should be already defined by libc++
+#endif
+
+#ifndef _LIBCPP_WEAK
+#  error The _LIBCPP_WEAK macro should be already defined by libc++
+#endif
+
+#if defined(_LIBCXXABI_NO_EXCEPTIONS) != defined(_LIBCPP_HAS_NO_EXCEPTIONS)
+#  error libc++ and libc++abi seem to disagree on whether exceptions are enabled
+#endif
+
+// ------------------ BEGIN COPY ------------------
+// Implement all new and delete operators as weak definitions
+// in this shared library, so that they can be overridden by programs
+// that define non-weak copies of the functions.
+
+_LIBCPP_WEAK
+void *
+operator new(std::size_t size) _THROW_BAD_ALLOC
+{
+    if (size == 0)
+        size = 1;
+    void* p;
+    while ((p = std::malloc(size)) == nullptr)
+    {
+        // If malloc fails and there is a new_handler,
+        // call it to try free up memory.
+        std::new_handler nh = std::get_new_handler();
+        if (nh)
+            nh();
+        else
+#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
+            throw std::bad_alloc();
+#else
+            break;
+#endif
+    }
+    return p;
+}
+
+_LIBCPP_WEAK
+void*
+operator new(size_t size, const std::nothrow_t&) noexcept
+{
+    void* p = nullptr;
+#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
+    try
+    {
+#endif // _LIBCPP_HAS_NO_EXCEPTIONS
+        p = ::operator new(size);
+#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
+    }
+    catch (...)
+    {
+    }
+#endif // _LIBCPP_HAS_NO_EXCEPTIONS
+    return p;
+}
+
+_LIBCPP_WEAK
+void*
+operator new[](size_t size) _THROW_BAD_ALLOC
+{
+    return ::operator new(size);
+}
+
+_LIBCPP_WEAK
+void*
+operator new[](size_t size, const std::nothrow_t&) noexcept
+{
+    void* p = nullptr;
+#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
+    try
+    {
+#endif // _LIBCPP_HAS_NO_EXCEPTIONS
+        p = ::operator new[](size);
+#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
+    }
+    catch (...)
+    {
+    }
+#endif // _LIBCPP_HAS_NO_EXCEPTIONS
+    return p;
+}
+
+_LIBCPP_WEAK
+void
+operator delete(void* ptr) noexcept
+{
+    std::free(ptr);
+}
+
+_LIBCPP_WEAK
+void
+operator delete(void* ptr, const std::nothrow_t&) noexcept
+{
+    ::operator delete(ptr);
+}
+
+_LIBCPP_WEAK
+void
+operator delete(void* ptr, size_t) noexcept
+{
+    ::operator delete(ptr);
+}
+
+_LIBCPP_WEAK
+void
+operator delete[] (void* ptr) noexcept
+{
+    ::operator delete(ptr);
+}
+
+_LIBCPP_WEAK
+void
+operator delete[] (void* ptr, const std::nothrow_t&) noexcept
+{
+    ::operator delete[](ptr);
+}
+
+_LIBCPP_WEAK
+void
+operator delete[] (void* ptr, size_t) noexcept
+{
+    ::operator delete[](ptr);
+}
+
+#if !defined(_LIBCPP_HAS_NO_LIBRARY_ALIGNED_ALLOCATION)
+
+_LIBCPP_WEAK
+void *
+operator new(std::size_t size, std::align_val_t alignment) _THROW_BAD_ALLOC
+{
+    if (size == 0)
+        size = 1;
+    if (static_cast<size_t>(alignment) < sizeof(void*))
+      alignment = std::align_val_t(sizeof(void*));
+
+    // Try allocating memory. If allocation fails and there is a new_handler,
+    // call it to try free up memory, and try again until it succeeds, or until
+    // the new_handler decides to terminate.
+    //
+    // If allocation fails and there is no new_handler, we throw bad_alloc
+    // (or return nullptr if exceptions are disabled).
+    void* p;
+    while ((p = std::__libcpp_aligned_alloc(static_cast<std::size_t>(alignment), size)) == nullptr)
+    {
+        std::new_handler nh = std::get_new_handler();
+        if (nh)
+            nh();
+        else {
+#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
+            throw std::bad_alloc();
+#else
+            break;
+#endif
+        }
+    }
+    return p;
+}
+
+_LIBCPP_WEAK
+void*
+operator new(size_t size, std::align_val_t alignment, const std::nothrow_t&) noexcept
+{
+    void* p = nullptr;
+#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
+    try
+    {
+#endif // _LIBCPP_HAS_NO_EXCEPTIONS
+        p = ::operator new(size, alignment);
+#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
+    }
+    catch (...)
+    {
+    }
+#endif // _LIBCPP_HAS_NO_EXCEPTIONS
+    return p;
+}
+
+_LIBCPP_WEAK
+void*
+operator new[](size_t size, std::align_val_t alignment) _THROW_BAD_ALLOC
+{
+    return ::operator new(size, alignment);
+}
+
+_LIBCPP_WEAK
+void*
+operator new[](size_t size, std::align_val_t alignment, const std::nothrow_t&) noexcept
+{
+    void* p = nullptr;
+#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
+    try
+    {
+#endif // _LIBCPP_HAS_NO_EXCEPTIONS
+        p = ::operator new[](size, alignment);
+#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
+    }
+    catch (...)
+    {
+    }
+#endif // _LIBCPP_HAS_NO_EXCEPTIONS
+    return p;
+}
+
+_LIBCPP_WEAK
+void
+operator delete(void* ptr, std::align_val_t) noexcept
+{
+    std::__libcpp_aligned_free(ptr);
+}
+
+_LIBCPP_WEAK
+void
+operator delete(void* ptr, std::align_val_t alignment, const std::nothrow_t&) noexcept
+{
+    ::operator delete(ptr, alignment);
+}
+
+_LIBCPP_WEAK
+void
+operator delete(void* ptr, size_t, std::align_val_t alignment) noexcept
+{
+    ::operator delete(ptr, alignment);
+}
+
+_LIBCPP_WEAK
+void
+operator delete[] (void* ptr, std::align_val_t alignment) noexcept
+{
+    ::operator delete(ptr, alignment);
+}
+
+_LIBCPP_WEAK
+void
+operator delete[] (void* ptr, std::align_val_t alignment, const std::nothrow_t&) noexcept
+{
+    ::operator delete[](ptr, alignment);
+}
+
+_LIBCPP_WEAK
+void
+operator delete[] (void* ptr, size_t, std::align_val_t alignment) noexcept
+{
+    ::operator delete[](ptr, alignment);
+}
+
+#endif // !_LIBCPP_HAS_NO_LIBRARY_ALIGNED_ALLOCATION
+// ------------------ END COPY ------------------

third_party/libcxxabi/stdlib_stdexcept.cc

@@ -0,0 +1,47 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "third_party/libcxx/stdexcept"
+#include "third_party/libcxx/new"
+#include "third_party/libcxx/cstdlib"
+#include "third_party/libcxx/cstring"
+#include "third_party/libcxx/cstdint"
+#include "third_party/libcxx/cstddef"
+#include "third_party/libcxx/refstring.hh" // from libc++
+
+static_assert(sizeof(std::__libcpp_refstring) == sizeof(const char *), "");
+
+namespace std  // purposefully not using versioning namespace
+{
+
+logic_error::~logic_error() noexcept {}
+
+const char*
+logic_error::what() const noexcept
+{
+    return __imp_.c_str();
+}
+
+runtime_error::~runtime_error() noexcept {}
+
+const char*
+runtime_error::what() const noexcept
+{
+    return __imp_.c_str();
+}
+
+domain_error::~domain_error() noexcept {}
+invalid_argument::~invalid_argument() noexcept {}
+length_error::~length_error() noexcept {}
+out_of_range::~out_of_range() noexcept {}
+
+range_error::~range_error() noexcept {}
+overflow_error::~overflow_error() noexcept {}
+underflow_error::~underflow_error() noexcept {}
+
+}  // std

third_party/libcxxabi/stdlib_typeinfo.cc

@@ -0,0 +1,52 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "third_party/libcxx/typeinfo"
+
+namespace std
+{
+
+// type_info
+
+type_info::~type_info()
+{
+}
+
+// bad_cast
+
+bad_cast::bad_cast() noexcept
+{
+}
+
+bad_cast::~bad_cast() noexcept
+{
+}
+
+const char*
+bad_cast::what() const noexcept
+{
+  return "std::bad_cast";
+}
+
+// bad_typeid
+
+bad_typeid::bad_typeid() noexcept
+{
+}
+
+bad_typeid::~bad_typeid() noexcept
+{
+}
+
+const char*
+bad_typeid::what() const noexcept
+{
+  return "std::bad_typeid";
+}
+
+}  // std

third_party/libunwind/BUILD.mk

@@ -54,8 +54,7 @@ THIRD_PARTY_LIBUNWIND_A_CHECKS =					\
 THIRD_PARTY_LIBUNWIND_A_DIRECTDEPS =					\
 	LIBC_CALLS							\
 	LIBC_INTRIN							\
-	LIBC_STDIO							\
+	LIBC_STDIO
-	THIRD_PARTY_LIBCXX
 
 THIRD_PARTY_LIBUNWIND_A_DEPS :=						\
 	$(call uniq,$(foreach x,$(THIRD_PARTY_LIBUNWIND_A_DIRECTDEPS),$($(x))))