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.
30 inline _LIBCPP_HIDE_FROM_ABI
31 void* __libcpp_aligned_alloc(std::size_t __alignment, std::size_t __size) {
32 #  if defined(_LIBCPP_MSVCRT_LIKE)
33     return ::_aligned_malloc(__size, __alignment);
34 #  elif _LIBCPP_STD_VER >= 17 && !defined(_LIBCPP_HAS_NO_C11_ALIGNED_ALLOC)
35     // aligned_alloc() requires that __size is a multiple of __alignment,
36     // but for C++ [new.delete.general], only states "if the value of an
37     // alignment argument passed to any of these functions is not a valid
38     // alignment value, the behavior is undefined".
39     // To handle calls such as ::operator new(1, std::align_val_t(128)), we
40     // round __size up to the next multiple of __alignment.
41     size_t __rounded_size = (__size + __alignment - 1) & ~(__alignment - 1);
42     // Rounding up could have wrapped around to zero, so we have to add another
43     // max() ternary to the actual call site to avoid succeeded in that case.
44     return ::aligned_alloc(__alignment, __size > __rounded_size ? __size : __rounded_size);
45 #  else
46     void* __result = nullptr;
47     (void)::posix_memalign(&__result, __alignment, __size);
48     // If posix_memalign fails, __result is unmodified so we still return `nullptr`.
49     return __result;
50 #  endif
51 }
52 
53 inline _LIBCPP_HIDE_FROM_ABI
54 void __libcpp_aligned_free(void* __ptr) {
55 #if defined(_LIBCPP_MSVCRT_LIKE)
56   ::_aligned_free(__ptr);
57 #else
58   ::free(__ptr);
59 #endif
60 }
61 
62 #endif // !_LIBCPP_HAS_NO_LIBRARY_ALIGNED_ALLOCATION
63 
64 _LIBCPP_END_NAMESPACE_STD
65 
66 #endif // _LIBCPP___MEMORY_ALIGNED_ALLOC_H
67