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PR libstdc++/77691 increase allocation size to at least alignment 

It's not safe to assume that malloc(n) returns memory aligned to more
than n, so when relying on the guaranteed alignment of malloc ensure
that the number of bytes allocated is at least as large as the
alignment.

	PR libstdc++/77691
	* include/experimental/memory_resource (__resource_adaptor_imp): Do
	not allocate sizes smaller than alignment when relying on guaranteed
	alignment.
	* testsuite/experimental/memory_resource/new_delete_resource.cc:
	Adjust expected number of bytes allocated for alignof(max_align_t).

From-SVN: r265068
This commit is contained in:
Jonathan Wakely 2018-10-12 00:21:11 +01:00 committed by Jonathan Wakely
parent 47d31f1aa4
commit 49cb790a4c
3 changed files with 23 additions and 5 deletions
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9
libstdc++-v3/ChangeLog
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@ -1,3 +1,12 @@
2018-10-12 Jonathan Wakely <jwakely@redhat.com>
PR libstdc++/77691
* include/experimental/memory_resource (__resource_adaptor_imp): Do
not allocate sizes smaller than alignment when relying on guaranteed
alignment.
* testsuite/experimental/memory_resource/new_delete_resource.cc:
Adjust expected number of bytes allocated for alignof(max_align_t).
2018-10-11 François Dumont <fdumont@gcc.gnu.org>
* include/debug/forward_list

9
libstdc++-v3/include/experimental/memory_resource
View File

@ -421,7 +421,12 @@ namespace pmr {
do_allocate(size_t __bytes, size_t __alignment) override
{
if (__alignment <= __guaranteed_alignment<_Alloc>::value)
return _M_alloc.allocate(__bytes);
{
if (__bytes < __alignment)
__bytes = __alignment;
return _M_alloc.allocate(__bytes);
}
const _AlignMgr __mgr(__bytes, __alignment);
// Assume _M_alloc returns 1-byte aligned memory, so allocate enough
@ -437,6 +442,8 @@ namespace pmr {
auto __ptr = static_cast<char*>(__p);
if (__alignment <= __guaranteed_alignment<_Alloc>::value)
{
if (__bytes < __alignment)
__bytes = __alignment;
_M_alloc.deallocate(__ptr, __bytes);
return;
}

10
libstdc++-v3/testsuite/experimental/memory_resource/new_delete_resource.cc
View File

@ -109,11 +109,13 @@ test03()
using std::size_t;
void* p = nullptr;
auto max = [](int n, int a) { return n > a ? n : a; };
bytes_allocated = 0;
memory_resource* r1 = new_delete_resource();
p = r1->allocate(1);
VERIFY( bytes_allocated == 1 );
p = r1->allocate(1); // uses alignment = alignof(max_align_t)
VERIFY( bytes_allocated <= alignof(max_align_t) );
VERIFY( aligned<max_align_t>(p) );
r1->deallocate(p, 1);
VERIFY( bytes_allocated == 0 );
@ -125,13 +127,13 @@ test03()
VERIFY( bytes_allocated == 0 );
p = r1->allocate(3, alignof(short));
VERIFY( bytes_allocated == 3 );
VERIFY( bytes_allocated == max(3, alignof(short)) );
VERIFY( aligned<short>(p) );
r1->deallocate(p, 3, alignof(short));
VERIFY( bytes_allocated == 0 );
p = r1->allocate(4, alignof(long));
VERIFY( bytes_allocated == 4 );
VERIFY( bytes_allocated == max(4, alignof(long)) );
VERIFY( aligned<long>(p) );
r1->deallocate(p, 4, alignof(long));
VERIFY( bytes_allocated == 0 );