[LLVMbugs] [Bug 6912] New: Spurious null pointer dereference warning

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Fri Apr 23 18:23:21 PDT 2010


           Summary: Spurious null pointer dereference warning
           Product: clang
           Version: trunk
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Static Analyzer
        AssignedTo: kremenek at apple.com
        ReportedBy: evan at chromium.org
                CC: llvmbugs at cs.uiuc.edu

I just tried out scan-build on a large project and reduced many of the spurious
warnings to the attached simple test case.

The pattern is that there's a global variable along with a function that may
initialize it, and anyone who uses it tests either that the variable has been
initialized or that the initialization function succeeds.  So we always either
return or have the variable end up initialized.

This code is kind of crazy, I agree, but it's a real open source library (NSS,
from http://www.mozilla.org/projects/security/pki/nss/) that does this.

The error message is as follows:
crazy.c:19:18: warning: Dereference of null pointer (loaded from variable
  printf("%d\n", *global_p);

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