[LLVMbugs] [Bug 9510] New: Warning for ctype.h misuse

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Fri Mar 18 17:48:26 PDT 2011


           Summary: Warning for ctype.h misuse
           Product: clang
           Version: trunk
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Static Analyzer
        AssignedTo: kremenek at apple.com
        ReportedBy: joerg at NetBSD.org
                CC: llvmbugs at cs.uiuc.edu

One of the most often misused APIs in C is ctype.h. A lot of programmers don't
understand the value range of the functions and the following code fragments
are seen over and over again:

char c;

isalpha((int)c); // Attempt to pacify the compiler warning on some systems

Correct usage is:
isalpha((unsigned char)c)
if EOF can be ruled out. Above is valid only if a check for ASCII was done
before (e.g. with isascii).

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