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