[Bug other/55981] New: std::atomic store is split in two smaller stores

[eugeni.stepanov at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55981



             Bug #: 55981

           Summary: std::atomic store is split in two smaller stores

    Classification: Unclassified

           Product: gcc

           Version: 4.7.2

            Status: UNCONFIRMED

          Severity: normal

          Priority: P3

         Component: other

        AssignedTo: unassig...@gcc.gnu.org

        ReportedBy: eugeni.stepa...@gmail.com





Created attachment 29166

  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=29166

miscompiled program



Hi,



in the attached program, std::atomic<unsigned long> store is compiled as two

4-byte stores, becoming not atomic at all. This happens at -O2 and higher.



To reproduce,

# g++ -std=c++11 -O3 1.cc  -lpthread -o 1

# ./1

100000004



^ this can also be 300000002, both outcomes are invalid.