# Extra Clang Tools 4 documentation

## clang-tidy - misc-suspicious-string-compare

# misc-suspicious-string-compare

Find suspicious usage of runtime string comparison functions. This check is valid in C and C++.

Checks for calls with implicit comparator and proposed to explicitly add it.

    if (strcmp(...))       // Implicitly compare to zero
    if (!strcmp(...))      // Won't warn
    if (strcmp(...) != 0)  // Won't warn

Checks that compare function results (i,e, `strcmp`) are compared to valid constant. The resulting value is

    <  0    when lower than,
    >  0    when greater than,
    == 0    when equals.

A common mistake is to compare the result to 1 or -1.

    if (strcmp(...) == -1)  // Incorrect usage of the returned value.

Additionally, the check warns if the results value is implicitly cast to a suspicious non-integer type. It’s happening when the returned value is used in a wrong context.

    if (strcmp(...) < 0.)  // Incorrect usage of the returned value.

## Options

`WarnOnImplicitComparison```

  When non-zero, the check will warn on implicit comparison. 1 by default.

`WarnOnLogicalNotComparison```

  When non-zero, the check will warn on logical not comparison. 0 by default.

`StringCompareLikeFunctions```

  A string specifying the comma-separated names of the extra string comparison functions. Default is an empty string. The check will detect the following string comparison functions: __builtin_memcmp, __builtin_strcasecmp, __builtin_strcmp, __builtin_strncasecmp, __builtin_strncmp, _mbscmp, _mbscmp_l, _mbsicmp, _mbsicmp_l, _mbsnbcmp, _mbsnbcmp_l, _mbsnbicmp, _mbsnbicmp_l, _mbsncmp, _mbsncmp_l, _mbsnicmp, _mbsnicmp_l, _memicmp, _memicmp_l, _stricmp, _stricmp_l, _strnicmp, _strnicmp_l, _wcsicmp, _wcsicmp_l, _wcsnicmp, _wcsnicmp_l, lstrcmp, lstrcmpi, memcmp, memicmp, strcasecmp, strcmp, strcmpi, stricmp, strncasecmp, strncmp, strnicmp, wcscasecmp, wcscmp, wcsicmp, wcsncmp, wcsnicmp, wmemcmp.