[LLVMbugs] [Bug 9423] New: False positive with *++p = value

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Mon Mar 7 20:03:39 PST 2011


           Summary: False positive with  *++p = value
           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

Created an attachment (id=6290)
 --> (http://llvm.org/bugs/attachment.cgi?id=6290)
False positive example

Using prefix increment causes false positive.  If "*++p = value;" is replaced
with "p++; *p = value;"
no fault is reported.  The two constructs should be identical.

This was with checker-255.

scan-build -V make junk
/Users/marka/Downloads/checker-255/libexec/ccc-analyzer -g -O2
-I/usr/include/libxml2    junk.c   -o junk
ANALYZE: junk.c foo
junk.c:7:3: warning: Assigned value is garbage or undefined
                int new = *p;
                ^         ~~
ANALYZE: junk.c main
1 warning generated.
scan-build: 1 bugs found.
scan-build: Run 'scan-view
/var/folders/dB/dBXhI1vFESG2tu8vPjUq7U+++TI/-Tmp-/scan-build-2011-03-08-19' to
examine bug reports.
scan-build: Analysis run complete.
scan-build: Viewing analysis results in
using scan-view.

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