Release Cosmopolitan v3.6.0

This release is an atomic upgrade to GCC 14.1.0 with C23 and C++23

third_party/libcxx/__utility/small_buffer.h

@@ -0,0 +1,99 @@
+//===----------------------------------------------------------------------===//
+//
+// 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___UTILITY_SMALL_BUFFER_H
+#define _LIBCPP___UTILITY_SMALL_BUFFER_H
+
+#include <__config>
+#include <__memory/construct_at.h>
+#include <__type_traits/decay.h>
+#include <__type_traits/is_trivially_constructible.h>
+#include <__type_traits/is_trivially_destructible.h>
+#include <__utility/exception_guard.h>
+#include <__utility/forward.h>
+#include <cstddef>
+#include <new>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+#if _LIBCPP_STD_VER >= 23
+
+// __small_buffer is a helper class to perform the well known SBO (small buffer optimization). It is mainly useful to
+// allow type-erasing classes like move_only_function to store small objects in a local buffer without requiring an
+// allocation.
+//
+// This small buffer class only allows storing trivially relocatable objects inside the local storage to allow
+// __small_buffer to be trivially relocatable itself. Since the buffer doesn't know what's stored inside it, the user
+// has to manage the object's lifetime, in particular the destruction of the object.
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <size_t _BufferSize, size_t _BufferAlignment>
+  requires(_BufferSize > 0 && _BufferAlignment > 0)
+class __small_buffer {
+public:
+  template <class _Tp, class _Decayed = decay_t<_Tp>>
+  static constexpr bool __fits_in_buffer =
+      is_trivially_move_constructible_v<_Decayed> && is_trivially_destructible_v<_Decayed> &&
+      sizeof(_Decayed) <= _BufferSize && alignof(_Decayed) <= _BufferAlignment;
+
+  _LIBCPP_HIDE_FROM_ABI __small_buffer()           = default;
+  __small_buffer(const __small_buffer&)            = delete;
+  __small_buffer& operator=(const __small_buffer&) = delete;
+  _LIBCPP_HIDE_FROM_ABI ~__small_buffer()          = default;
+
+  // Relocates the buffer - __delete() should never be called on a moved-from __small_buffer
+  _LIBCPP_HIDE_FROM_ABI __small_buffer(__small_buffer&&)            = default;
+  _LIBCPP_HIDE_FROM_ABI __small_buffer& operator=(__small_buffer&&) = default;
+
+  template <class _Stored>
+  _LIBCPP_HIDE_FROM_ABI _Stored* __get() {
+    if constexpr (__fits_in_buffer<_Stored>)
+      return std::launder(reinterpret_cast<_Stored*>(__buffer_));
+    else
+      return *std::launder(reinterpret_cast<_Stored**>(__buffer_));
+  }
+
+  template <class _Stored>
+  _LIBCPP_HIDE_FROM_ABI _Stored* __alloc() {
+    if constexpr (__fits_in_buffer<_Stored>) {
+      return std::launder(reinterpret_cast<_Stored*>(__buffer_));
+    } else {
+      byte* __allocation = static_cast<byte*>(::operator new[](sizeof(_Stored), align_val_t{alignof(_Stored)}));
+      std::construct_at(reinterpret_cast<byte**>(__buffer_), __allocation);
+      return std::launder(reinterpret_cast<_Stored*>(__allocation));
+    }
+  }
+
+  template <class _Stored>
+  _LIBCPP_HIDE_FROM_ABI void __dealloc() noexcept {
+    if constexpr (!__fits_in_buffer<_Stored>)
+      ::operator delete[](*reinterpret_cast<void**>(__buffer_), sizeof(_Stored), align_val_t{alignof(_Stored)});
+  }
+
+  template <class _Stored, class... _Args>
+  _LIBCPP_HIDE_FROM_ABI void __construct(_Args&&... __args) {
+    _Stored* __buffer = __alloc<_Stored>();
+    auto __guard      = std::__make_exception_guard([&] { __dealloc<_Stored>(); });
+    std::construct_at(__buffer, std::forward<_Args>(__args)...);
+    __guard.__complete();
+  }
+
+private:
+  alignas(_BufferAlignment) byte __buffer_[_BufferSize];
+};
+
+#  undef _LIBCPP_SMALL_BUFFER_TRIVIAL_ABI
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STD_VER >= 23
+
+#endif // _LIBCPP___UTILITY_SMALL_BUFFER_H