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libstdc++: Do not use C++11 alignof in C++98 mode [PR104395]

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When -faligned-new (or Clang's -faligned-allocation) is used our
allocators try to support extended alignments, gated on the
__cpp_aligned_new macro. However, because they use alignof(_Tp) which is
not a keyword in C++98 mode, using -std=c++98 -faligned-new results in
errors from <memory> and other headers.

We could change them to use __alignof__ instead of alignof, but that
would potentially alter the result of the conditions, because e.g.
alignof(long long) != __alignof__(long long) on some targets. That's
probably not an issue for any types with extended alignment, so maybe it
would be a safe change.

For now, it seems acceptable to just disable the extended alignment
support in C++98 mode, so that -faligned-new enables std::align_val_t
and the corresponding operator new overloads, but doesn't affect
std::allocator, __gnu_cxx::__bitmap_allocator etc.

libstdc++-v3/ChangeLog:

	PR libstdc++/104395
	* include/bits/new_allocator.h: Disable extended alignment
	support in C++98 mode.
	* include/bits/stl_tempbuf.h: Likewise.
	* include/ext/bitmap_allocator.h: Likewise.
	* include/ext/malloc_allocator.h: Likewise.
	* include/ext/mt_allocator.h: Likewise.
	* include/ext/pool_allocator.h: Likewise.
	* testsuite/ext/104395.cc: New test.
This commit is contained in:
Jonathan Wakely
2024-06-26 14:09:07 +01:00
committed by Jonathan Wakely
parent ac8c61b62e
commit 03d3aeb0e0
7 changed files with 20 additions and 12 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
libstdc++-v3/include/bits/new_allocator.h
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@@ -140,7 +140,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
std::__throw_bad_alloc();
}
#if __cpp_aligned_new
#if __cpp_aligned_new && __cplusplus >= 201103L
if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
{
std::align_val_t __al = std::align_val_t(alignof(_Tp));
@@ -161,7 +161,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
# define _GLIBCXX_SIZED_DEALLOC(p, n) (p)
#endif
#if __cpp_aligned_new
#if __cpp_aligned_new && __cplusplus >= 201103L
if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
{
_GLIBCXX_OPERATOR_DELETE(_GLIBCXX_SIZED_DEALLOC(__p, __n),

6
libstdc++-v3/include/bits/stl_tempbuf.h
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@@ -85,7 +85,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
if (__builtin_expect(size_t(__len) > (size_t(-1) / sizeof(_Tp)), 0))
return 0;
#if __cpp_aligned_new
#if __cpp_aligned_new && __cplusplus >= 201103L
if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
return (_Tp*) _GLIBCXX_OPERATOR_NEW(__len * sizeof(_Tp),
align_val_t(alignof(_Tp)),
@@ -107,7 +107,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
# define _GLIBCXX_SIZED_DEALLOC(T, p, n) (p)
#endif
#if __cpp_aligned_new
#if __cpp_aligned_new && __cplusplus >= 201103L
if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
{
_GLIBCXX_OPERATOR_DELETE(_GLIBCXX_SIZED_DEALLOC(_Tp, __p, __len),
@@ -168,7 +168,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
inline void
return_temporary_buffer(_Tp* __p)
{
#if __cpp_aligned_new
#if __cpp_aligned_new && __cplusplus >= 201103L
if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
_GLIBCXX_OPERATOR_DELETE(__p, align_val_t(alignof(_Tp)));
else

4
libstdc++-v3/include/ext/bitmap_allocator.h
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@@ -1017,7 +1017,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
if (__n > this->max_size())
std::__throw_bad_alloc();
#if __cpp_aligned_new
#if __cpp_aligned_new && __cplusplus >= 201103L
if (alignof(value_type) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
{
const size_type __b = __n * sizeof(value_type);
@@ -1044,7 +1044,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{
if (__builtin_expect(__p != 0, true))
{
#if __cpp_aligned_new
#if __cpp_aligned_new && __cplusplus >= 201103L
// Types with extended alignment are handled by operator delete.
if (alignof(value_type) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
{

2
libstdc++-v3/include/ext/malloc_allocator.h
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@@ -120,7 +120,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
}
_Tp* __ret = 0;
#if __cpp_aligned_new
#if __cpp_aligned_new && __cplusplus >= 201103L
#if __cplusplus > 201402L && _GLIBCXX_HAVE_ALIGNED_ALLOC
if (alignof(_Tp) > alignof(std::max_align_t))
{

4
libstdc++-v3/include/ext/mt_allocator.h
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@@ -693,7 +693,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
if (__n > this->max_size())
std::__throw_bad_alloc();
#if __cpp_aligned_new
#if __cpp_aligned_new && __cplusplus >= 201103L
// Types with extended alignment are handled by operator new/delete.
if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
{
@@ -748,7 +748,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{
if (__builtin_expect(__p != 0, true))
{
#if __cpp_aligned_new
#if __cpp_aligned_new && __cplusplus >= 201103L
// Types with extended alignment are handled by operator new/delete.
if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
{

4
libstdc++-v3/include/ext/pool_allocator.h
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@@ -224,7 +224,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
const size_t __bytes = __n * sizeof(_Tp);
#if __cpp_aligned_new
#if __cpp_aligned_new && __cplusplus >= 201103L
if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
{
std::align_val_t __al = std::align_val_t(alignof(_Tp));
@@ -272,7 +272,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
using std::size_t;
if (__builtin_expect(__n != 0 && __p != 0, true))
{
#if __cpp_aligned_new
#if __cpp_aligned_new && __cplusplus >= 201103L
if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
{
::operator delete(__p, std::align_val_t(alignof(_Tp)));

8
libstdc++-v3/testsuite/ext/104395.cc Normal file
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@@ -0,0 +1,8 @@
// { dg-options "-std=gnu++98 -faligned-new" }
// { dg-do compile }
#include <ext/memory>
#include <ext/bitmap_allocator.h>
#include <ext/mt_allocator.h>
#include <ext/malloc_allocator.h>
#include <ext/new_allocator.h>
#include <ext/pool_allocator.h>