Extra Clang Tools 3.9 documentation

clang-tidy - misc-suspicious-string-compare

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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.

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