Add more missing libc/libc++ functions

- Add sched_rr_get_interval()
- Add `unbuffer` command example
- Add more locale function stubs
- Vendor most of remaining libcxx content

third_party/libcxx/memory.cc

@@ -0,0 +1,239 @@
+// clang-format off
+//===------------------------ memory.cpp ----------------------------------===//
+//
+// 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/memory"
+#ifndef _LIBCPP_HAS_NO_THREADS
+#include "third_party/libcxx/mutex"
+#include "third_party/libcxx/thread"
+#if defined(__unix__) && !defined(__ANDROID__) && defined(__ELF__) && defined(_LIBCPP_HAS_COMMENT_LIB_PRAGMA)
+#pragma comment(lib, "pthread")
+#endif
+#endif
+#include "third_party/libcxx/include/atomic_support.hh"
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+// TODO(jart): why does this need to be commented?
+// const allocator_arg_t allocator_arg = allocator_arg_t();
+
+bad_weak_ptr::~bad_weak_ptr() _NOEXCEPT {}
+
+const char*
+bad_weak_ptr::what() const _NOEXCEPT
+{
+    return "bad_weak_ptr";
+}
+
+__shared_count::~__shared_count()
+{
+}
+
+__shared_weak_count::~__shared_weak_count()
+{
+}
+
+#if defined(_LIBCPP_DEPRECATED_ABI_LEGACY_LIBRARY_DEFINITIONS_FOR_INLINE_FUNCTIONS)
+void
+__shared_count::__add_shared() _NOEXCEPT
+{
+    __libcpp_atomic_refcount_increment(__shared_owners_);
+}
+
+bool
+__shared_count::__release_shared() _NOEXCEPT
+{
+    if (__libcpp_atomic_refcount_decrement(__shared_owners_) == -1)
+    {
+        __on_zero_shared();
+        return true;
+    }
+    return false;
+}
+
+void
+__shared_weak_count::__add_shared() _NOEXCEPT
+{
+    __shared_count::__add_shared();
+}
+
+void
+__shared_weak_count::__add_weak() _NOEXCEPT
+{
+    __libcpp_atomic_refcount_increment(__shared_weak_owners_);
+}
+
+void
+__shared_weak_count::__release_shared() _NOEXCEPT
+{
+    if (__shared_count::__release_shared())
+        __release_weak();
+}
+
+#endif // _LIBCPP_DEPRECATED_ABI_LEGACY_LIBRARY_DEFINITIONS_FOR_INLINE_FUNCTIONS
+
+void
+__shared_weak_count::__release_weak() _NOEXCEPT
+{
+    // NOTE: The acquire load here is an optimization of the very
+    // common case where a shared pointer is being destructed while
+    // having no other contended references.
+    //
+    // BENEFIT: We avoid expensive atomic stores like XADD and STREX
+    // in a common case.  Those instructions are slow and do nasty
+    // things to caches.
+    //
+    // IS THIS SAFE?  Yes.  During weak destruction, if we see that we
+    // are the last reference, we know that no-one else is accessing
+    // us. If someone were accessing us, then they would be doing so
+    // while the last shared / weak_ptr was being destructed, and
+    // that's undefined anyway.
+    //
+    // If we see anything other than a 0, then we have possible
+    // contention, and need to use an atomicrmw primitive.
+    // The same arguments don't apply for increment, where it is legal
+    // (though inadvisable) to share shared_ptr references between
+    // threads, and have them all get copied at once.  The argument
+    // also doesn't apply for __release_shared, because an outstanding
+    // weak_ptr::lock() could read / modify the shared count.
+    if (__libcpp_atomic_load(&__shared_weak_owners_, _AO_Acquire) == 0)
+    {
+        // no need to do this store, because we are about
+        // to destroy everything.
+        //__libcpp_atomic_store(&__shared_weak_owners_, -1, _AO_Release);
+        __on_zero_shared_weak();
+    }
+    else if (__libcpp_atomic_refcount_decrement(__shared_weak_owners_) == -1)
+        __on_zero_shared_weak();
+}
+
+__shared_weak_count*
+__shared_weak_count::lock() _NOEXCEPT
+{
+    long object_owners = __libcpp_atomic_load(&__shared_owners_);
+    while (object_owners != -1)
+    {
+        if (__libcpp_atomic_compare_exchange(&__shared_owners_,
+                                             &object_owners,
+                                             object_owners+1))
+            return this;
+    }
+    return nullptr;
+}
+
+#if !defined(_LIBCPP_NO_RTTI) || !defined(_LIBCPP_BUILD_STATIC)
+
+const void*
+__shared_weak_count::__get_deleter(const type_info&) const _NOEXCEPT
+{
+    return nullptr;
+}
+
+#endif  // _LIBCPP_NO_RTTI
+
+#if !defined(_LIBCPP_HAS_NO_ATOMIC_HEADER)
+
+_LIBCPP_SAFE_STATIC static const std::size_t __sp_mut_count = 16;
+_LIBCPP_SAFE_STATIC static __libcpp_mutex_t mut_back[__sp_mut_count] =
+{
+    _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER,
+    _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER,
+    _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER,
+    _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER
+};
+
+_LIBCPP_CONSTEXPR __sp_mut::__sp_mut(void* p) _NOEXCEPT
+   : __lx(p)
+{
+}
+
+void
+__sp_mut::lock() _NOEXCEPT
+{
+    auto m = static_cast<__libcpp_mutex_t*>(__lx);
+    unsigned count = 0;
+    while (!__libcpp_mutex_trylock(m))
+    {
+        if (++count > 16)
+        {
+            __libcpp_mutex_lock(m);
+            break;
+        }
+        this_thread::yield();
+    }
+}
+
+void
+__sp_mut::unlock() _NOEXCEPT
+{
+    __libcpp_mutex_unlock(static_cast<__libcpp_mutex_t*>(__lx));
+}
+
+__sp_mut&
+__get_sp_mut(const void* p)
+{
+    static __sp_mut muts[__sp_mut_count]
+    {
+        &mut_back[ 0], &mut_back[ 1], &mut_back[ 2], &mut_back[ 3],
+        &mut_back[ 4], &mut_back[ 5], &mut_back[ 6], &mut_back[ 7],
+        &mut_back[ 8], &mut_back[ 9], &mut_back[10], &mut_back[11],
+        &mut_back[12], &mut_back[13], &mut_back[14], &mut_back[15]
+    };
+    return muts[hash<const void*>()(p) & (__sp_mut_count-1)];
+}
+
+#endif // !defined(_LIBCPP_HAS_NO_ATOMIC_HEADER)
+
+void
+declare_reachable(void*)
+{
+}
+
+void
+declare_no_pointers(char*, size_t)
+{
+}
+
+void
+undeclare_no_pointers(char*, size_t)
+{
+}
+
+#if !defined(_LIBCPP_ABI_POINTER_SAFETY_ENUM_TYPE)
+pointer_safety get_pointer_safety() _NOEXCEPT
+{
+    return pointer_safety::relaxed;
+}
+#endif
+
+void*
+__undeclare_reachable(void* p)
+{
+    return p;
+}
+
+void*
+align(size_t alignment, size_t size, void*& ptr, size_t& space)
+{
+    void* r = nullptr;
+    if (size <= space)
+    {
+        char* p1 = static_cast<char*>(ptr);
+        char* p2 = reinterpret_cast<char*>(reinterpret_cast<size_t>(p1 + (alignment - 1)) & -alignment);
+        size_t d = static_cast<size_t>(p2 - p1);
+        if (d <= space - size)
+        {
+            r = p2;
+            ptr = r;
+            space -= d;
+        }
+    }
+    return r;
+}
+
+_LIBCPP_END_NAMESPACE_STD