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 <cstddef>
14#include <cstdlib>
15
16#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
17#  pragma GCC system_header
18#endif
19
20_LIBCPP_BEGIN_NAMESPACE_STD
21
22#ifndef _LIBCPP_HAS_NO_LIBRARY_ALIGNED_ALLOCATION
23
24// Low-level helpers to call the aligned allocation and deallocation functions
25// on the target platform. This is used to implement libc++'s own memory
26// allocation routines -- if you need to allocate memory inside the library,
27// chances are that you want to use `__libcpp_allocate` instead.
28//
29// Returns the allocated memory, or `nullptr` on failure.
30inline _LIBCPP_HIDE_FROM_ABI void* __libcpp_aligned_alloc(std::size_t __alignment, std::size_t __size) {
31#  if defined(_LIBCPP_MSVCRT_LIKE)
32  return ::_aligned_malloc(__size, __alignment);
33#  elif _LIBCPP_STD_VER >= 17 && !defined(_LIBCPP_HAS_NO_C11_ALIGNED_ALLOC)
34  // aligned_alloc() requires that __size is a multiple of __alignment,
35  // but for C++ [new.delete.general], only states "if the value of an
36  // alignment argument passed to any of these functions is not a valid
37  // alignment value, the behavior is undefined".
38  // To handle calls such as ::operator new(1, std::align_val_t(128)), we
39  // round __size up to the next multiple of __alignment.
40  size_t __rounded_size = (__size + __alignment - 1) & ~(__alignment - 1);
41  // Rounding up could have wrapped around to zero, so we have to add another
42  // max() ternary to the actual call site to avoid succeeded in that case.
43  return ::aligned_alloc(__alignment, __size > __rounded_size ? __size : __rounded_size);
44#  else
45  void* __result = nullptr;
46  (void)::posix_memalign(&__result, __alignment, __size);
47  // If posix_memalign fails, __result is unmodified so we still return `nullptr`.
48  return __result;
49#  endif
50}
51
52inline _LIBCPP_HIDE_FROM_ABI void __libcpp_aligned_free(void* __ptr) {
53#  if defined(_LIBCPP_MSVCRT_LIKE)
54  ::_aligned_free(__ptr);
55#  else
56  ::free(__ptr);
57#  endif
58}
59
60#endif // !_LIBCPP_HAS_NO_LIBRARY_ALIGNED_ALLOCATION
61
62_LIBCPP_END_NAMESPACE_STD
63
64#endif // _LIBCPP___MEMORY_ALIGNED_ALLOC_H
65