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.

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