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[Bug middle-end/38937] New: [4.4 regression] dereferencing pointer '<anonymous>' does break strict-aliasing


On s390x, there are some libstdc++ failures that are not present on other
platforms. 

Here is a representative test run:
http://gcc.gnu.org/ml/gcc-testresults/2009-01/msg02102.html

And here is the failure analysis:
http://gcc.gnu.org/ml/libstdc++/2009-01/msg00109.html

The following fails appear to be spurious and only occur on s390x. At first I
thought this might be because of the extra flags "-fstack-protector
--param=ssp-buffer-size=4" but compiling the problem testcases on x86_64/linux
with the same flag doesn't show an error. So, I don't know what's up.

The same testcases (when present) pass without error on 4.3.2.

FAIL: 21_strings/basic_string/element_access/wchar_t/empty.cc
FAIL: 23_containers/list/modifiers/1.cc
FAIL: 23_containers/list/modifiers/3.cc
FAIL: 23_containers/list/modifiers/insert/25288.cc

The usual error looks like:

warning: dereferencing pointer '<anonymous>' does break strict-aliasing
rules

which is incomprehensible.


-- 
           Summary: [4.4 regression] dereferencing pointer '<anonymous>'
                    does break  strict-aliasing
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Keywords: diagnostic
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: bkoz at gcc dot gnu dot org
  GCC host triplet: s390x-redhat-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38937


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