[LLVMbugs] [Bug 13005] New: Report FP based in impossible condition

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=13005

             Bug #: 13005
           Summary: Report FP based in impossible condition
           Product: clang
           Version: 3.0
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Static Analyzer
        AssignedTo: kremenek at apple.com
        ReportedBy: zdenek.kabelac at gmail.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified


It's not uncommon that analyzer makes this construct:

{
  int var2;

  if (p->var1 == NULL) {
     var2 = set;

  }

  if (p->var1 == NULL) {
     use(var2);
  }
}


Here the 'var2' is reported as uninitialized usage - and the construct is based
on the assumption that first path goes via 'false branch', and on the test
'true branch' is taken - obviously this combination doesn't make sense, since
nothing is changing content of 'p->var1' between those calls - but generates a
lot of FP in case the first if(){} sets vars to some state and second if(){}
uses them.

Several such constructs could be found in:
git://anongit.freedesktop.org/git/xorg/driver/xf86-video-intel

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