[PATCH] PR libstdc++/70940 make pmr::resource_adaptor return aligned memory

[Jonathan Wakely]

On 22/06/18 14:34 +0200, Rainer Orth wrote:
>Hi Jonathan,
>
>> 	PR libstdc++/70940
>> 	* include/experimental/memory_resource (__resource_adaptor_common):
>> 	New base class.
>> 	(__resource_adaptor_common::_AlignMgr): Helper for obtaining aligned
>> 	pointer from unaligned, and vice versa.
>> 	(__resource_adaptor_imp::do_allocate): Use _AlignMgr to adjust
>> 	allocated pointer to meet alignment request.
>> 	(__resource_adaptor_imp::do_deallocate): Use _AlignMgr to retrieve
>> 	original pointer for deallocation.
>> 	(__resource_adaptor_imp::do_is_equal): Reformat.
>> 	(__resource_adaptor_imp::_S_aligned_size): Remove.
>> 	(__resource_adaptor_imp::_S_supported): Remove.
>> 	(new_delete_resource): Use __gnu_cxx::new_allocator.
>> 	* testsuite/experimental/memory_resource/resource_adaptor.cc: Test
>> 	extended alignments and use debug_allocator to check for matching
>> 	allocate/deallocate pairs.
>>
>> Tested x86_64-linux, committed to trunk. This is more experimental TS
>> material, so I'll probably backport it.
>
>this patch has cause a couple of FAILures on 32-bit targets/multilibs.
>I'm seeing it on i386-pc-solaris2.11 and sparc-sun-solaris2.11, with
>gcc-testresults postings to the same effect for
>i586-unknown-freebsd10.4, i686-pc-linux-gnu, s390x-ibm-linux-gnu,
>x86_64-pc-linux-gnu:
>
>+FAIL: experimental/memory_resource/1.cc (test for excess errors)
>+FAIL: experimental/memory_resource/70966.cc (test for excess errors)
>+FAIL: experimental/memory_resource/null_memory_resource.cc (test for excess errors)
>+FAIL: experimental/memory_resource/resource_adaptor.cc (test for excess errors)
>+XPASS: experimental/memory_resource/resource_adaptor.cc execution test
>+FAIL: experimental/type_erased_allocator/2.cc (test for excess errors)
>
>FAIL: experimental/type_erased_allocator/2.cc (test for excess errors)
>Excess errors:
>/var/gcc/regression/trunk/11.4-gcc/build/i386-pc-solaris2.11/libstdc++-v3/include/experimental/memory_resource:329: warning: left shift count >= width of type [-Wshift-count-overflow]

David just created https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86280

This should fix it. I'll commit it later, or if you want to test and
commit it please go ahead.

--- a/libstdc++-v3/include/experimental/memory_resource
+++ b/libstdc++-v3/include/experimental/memory_resource
@@ -326,7 +326,7 @@ namespace pmr {
          return 1;
        if (_M_align <= (1ul << (sizeof(short) * __CHAR_BIT__)))
          return sizeof(short);
-       if (_M_align <= (1ul << (sizeof(int) * __CHAR_BIT__)))
+       if (_M_align <= (1ull << (sizeof(int) * __CHAR_BIT__)))
          return sizeof(int);
        return sizeof(char*);
       }