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Make std::get_temporary_buffer respect overaligned types when possible 

Patch by Chris Kennelly!

Differential Revision: https://reviews.llvm.org/D41746

llvm-svn: 324020
This commit is contained in:
Richard Smith 2018-02-01 22:24:45 +00:00
parent e885768640
commit 4e3195c9b3
2 changed files with 81 additions and 1 deletions
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49
libcxx/include/memory
View File

@ -2004,7 +2004,38 @@ get_temporary_buffer(ptrdiff_t __n) _NOEXCEPT
__n = __m;
while (__n > 0)
{
#if !defined(_LIBCPP_HAS_NO_ALIGNED_ALLOCATION)
#if defined(__STDCPP_DEFAULT_NEW_ALIGNMENT__)
if (std::alignment_of<_Tp>::value > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
#else
if (std::alignment_of<_Tp>::value >
std::alignment_of<std::max_align_t>::value)
#endif
{
std::align_val_t __al =
std::align_val_t(std::alignment_of<_Tp>::value);
__r.first = static_cast<_Tp*>(::operator new(
__n * sizeof(_Tp), __al, nothrow));
} else {
__r.first = static_cast<_Tp*>(::operator new(
__n * sizeof(_Tp), nothrow));
}
#else
#if defined(__STDCPP_DEFAULT_NEW_ALIGNMENT__)
if (std::alignment_of<_Tp>::value > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
#else
if (std::alignment_of<_Tp>::value >
std::alignment_of<std::max_align_t>::value)
#endif
{
// Since aligned operator new is unavailable, return an empty
// buffer rather than one with invalid alignment.
return __r;
}
__r.first = static_cast<_Tp*>(::operator new(__n * sizeof(_Tp), nothrow));
#endif
if (__r.first)
{
__r.second = __n;
@ -2017,7 +2048,23 @@ get_temporary_buffer(ptrdiff_t __n) _NOEXCEPT
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
void return_temporary_buffer(_Tp* __p) _NOEXCEPT {::operator delete(__p);}
void return_temporary_buffer(_Tp* __p) _NOEXCEPT
{
#if !defined(_LIBCPP_HAS_NO_ALIGNED_ALLOCATION)
#if defined(__STDCPP_DEFAULT_NEW_ALIGNMENT__)
if (std::alignment_of<_Tp>::value > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
#else
if (std::alignment_of<_Tp>::value >
std::alignment_of<std::max_align_t>::value)
#endif
{
std::align_val_t __al = std::align_val_t(std::alignment_of<_Tp>::value);
::operator delete(__p, __al);
return;
}
#endif
::operator delete(__p);
}
#if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_AUTO_PTR)
template <class _Tp>

33
libcxx/test/std/utilities/memory/temporary.buffer/overaligned.pass.cpp Normal file
View File

@ -0,0 +1,33 @@
//===----------------------------------------------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
// <memory>
// template <class T>
// pair<T*, ptrdiff_t>
// get_temporary_buffer(ptrdiff_t n);
//
// template <class T>
// void
// return_temporary_buffer(T* p);
#include <memory>
#include <cassert>
struct alignas(32) A {
int field;
};
int main()
{
std::pair<A*, std::ptrdiff_t> ip = std::get_temporary_buffer<A>(5);
assert(!(ip.first == nullptr) ^ (ip.second == 0));
assert(reinterpret_cast<uintptr_t>(ip.first) % alignof(A) == 0);
std::return_temporary_buffer(ip.first);
}