[LLVMbugs] [Bug 14461] New: false positive: uninitialised/garbage values

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Thu Nov 29 20:53:12 PST 2012


             Bug #: 14461
           Summary: false positive: uninitialised/garbage values
           Product: clang
           Version: unspecified
          Platform: Macintosh
        OS/Version: MacOS X
            Status: NEW
          Severity: normal
          Priority: P
         Component: Static Analyzer
        AssignedTo: kremenek at apple.com
        ReportedBy: marka at isc.org
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Created attachment 9612
  --> http://llvm.org/bugs/attachment.cgi?id=9612
pre-processed code.

Multiple versions of clang.

Apple clang version 4.1 (tags/Apple/clang-421.11.66) (based on LLVM 3.1svn)
Target: x86_64-apple-darwin12.2.0
Thread model: posix

clang version 3.1 (branches/release_31)
Target: i386-portbld-freebsd8.3
Thread model: posix

The static analyser fails to remember that it set response to 0 for the
analysis then proceeds to complain about code that will not be reached when
response is 0.

clang --analyze tsig.preprocessed.c
In file included from tsig.c:1:
tsig.c:1337:4: warning: Function call argument is an uninitialized value
   isc__buffer_putuint16(&databuf, querytsig.siglen);
   ^                               ~~~~~~~~~~~~~~~~
tsig.c:1075:26: warning: The right operand of '<' is a garbage value
   if (response && bytes < querytsig.siglen)
                         ^ ~~~~~~~~~~~~~~~~
tsig.c:1024:20: warning: Assigned value is garbage or undefined
   tsig.timesigned = querytsig.timesigned;
                   ^ ~~~~~~~~~~~~~~~~~~~~

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