1//===----------------------------------------------------------------------===//
 2//
 3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 4// See https://llvm.org/LICENSE.txt for license information.
 5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 6//
 7//===----------------------------------------------------------------------===//
 8
 9#ifndef _LIBCPP___MEMORY_ALIGNED_ALLOC_H
10#define _LIBCPP___MEMORY_ALIGNED_ALLOC_H
11
12#include <__config>
13#include <cstdlib>
14
15#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
16#  pragma GCC system_header
17#endif
18
19_LIBCPP_BEGIN_NAMESPACE_STD
20
21#if _LIBCPP_HAS_LIBRARY_ALIGNED_ALLOCATION
22
23// Low-level helpers to call the aligned allocation and deallocation functions
24// on the target platform. This is used to implement libc++'s own memory
25// allocation routines -- if you need to allocate memory inside the library,
26// chances are that you want to use `__libcpp_allocate` instead.
27//
28// Returns the allocated memory, or `nullptr` on failure.
29inline _LIBCPP_HIDE_FROM_ABI void* __libcpp_aligned_alloc(std::size_t __alignment, std::size_t __size) {
30#  if defined(_LIBCPP_MSVCRT_LIKE)
31  return ::_aligned_malloc(__size, __alignment);
32#  elif _LIBCPP_STD_VER >= 17 && _LIBCPP_HAS_C11_ALIGNED_ALLOC
33  // aligned_alloc() requires that __size is a multiple of __alignment,
34  // but for C++ [new.delete.general], only states "if the value of an
35  // alignment argument passed to any of these functions is not a valid
36  // alignment value, the behavior is undefined".
37  // To handle calls such as ::operator new(1, std::align_val_t(128)), we
38  // round __size up to the next multiple of __alignment.
39  size_t __rounded_size = (__size + __alignment - 1) & ~(__alignment - 1);
40  // Rounding up could have wrapped around to zero, so we have to add another
41  // max() ternary to the actual call site to avoid succeeded in that case.
42  return ::aligned_alloc(__alignment, __size > __rounded_size ? __size : __rounded_size);
43#  else
44  void* __result = nullptr;
45  (void)::posix_memalign(&__result, __alignment, __size);
46  // If posix_memalign fails, __result is unmodified so we still return `nullptr`.
47  return __result;
48#  endif
49}
50
51inline _LIBCPP_HIDE_FROM_ABI void __libcpp_aligned_free(void* __ptr) {
52#  if defined(_LIBCPP_MSVCRT_LIKE)
53  ::_aligned_free(__ptr);
54#  else
55  ::free(__ptr);
56#  endif
57}
58
59#endif // _LIBCPP_HAS_LIBRARY_ALIGNED_ALLOCATION
60
61_LIBCPP_END_NAMESPACE_STD
62
63#endif // _LIBCPP___MEMORY_ALIGNED_ALLOC_H