[LLVMbugs] [Bug 12335] New: Optimization bug when testing for integer overflows

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=12335

             Bug #: 12335
           Summary: Optimization bug when testing for integer overflows
           Product: clang
           Version: unspecified
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: Static Analyzer
        AssignedTo: kremenek at apple.com
        ReportedBy: wellnhofer at aevum.de
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified


Created attachment 8257
  --> http://llvm.org/bugs/attachment.cgi?id=8257
Reduced test case

The Apache Lucy developers discovered what we think is an optimization bug in
clang. See the following bug report:

https://issues.apache.org/jira/browse/LUCY-216

And the following mailing list thread with some analysis:

http://mail-archives.apache.org/mod_mbox/incubator-lucy-dev/201203.mbox/%3CCAHkJ3Cup-Nqd2BHKfaNXF80D5m0_eC8s%2BA1EBszeJ5hZohfrGg%40mail.gmail.com%3E

Attached is a reduced test case. The program is expected to report an integer
overflow. As soon as it is compiled with optimizations, the overflow is not
detected. We could reproduce this with clang 2.9 on 32-but Linux and clang 3.1
on 64-bit OS X.

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