Re: [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*);
      }