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 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 52 inline _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