chromium/third_party/libc++/src/include/__memory/allocation_guard.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
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP___MEMORY_ALLOCATION_GUARD_H
#define _LIBCPP___MEMORY_ALLOCATION_GUARD_H

#include <__config>
#include <__memory/addressof.h>
#include <__memory/allocator_traits.h>
#include <__utility/move.h>
#include <cstddef>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#  pragma GCC system_header
#endif

_LIBCPP_PUSH_MACROS
#include <__undef_macros>

_LIBCPP_BEGIN_NAMESPACE_STD

// Helper class to allocate memory using an Allocator in an exception safe
// manner.
//
// The intended usage of this class is as follows:
//
// 0
// 1     __allocation_guard<SomeAllocator> guard(alloc, 10);
// 2     do_some_initialization_that_may_throw(guard.__get());
// 3     save_allocated_pointer_in_a_noexcept_operation(guard.__release_ptr());
// 4
//
// If line (2) throws an exception during initialization of the memory, the
// guard's destructor will be called, and the memory will be released using
// Allocator deallocation. Otherwise, we release the memory from the guard on
// line (3) in an operation that can't throw -- after that, the guard is not
// responsible for the memory anymore.
//
// This is similar to a unique_ptr, except it's easier to use with a
// custom allocator.
template <class _Alloc>
struct __allocation_guard { … };

_LIBCPP_END_NAMESPACE_STD

_LIBCPP_POP_MACROS

#endif // _LIBCPP___MEMORY_ALLOCATION_GUARD_H