False positive stlIfStrFind

[scpeters]

The following code gets flagged with a stlIfStrFind error "Inefficient usage of string::find() in condition; string::compare() would be faster."

std::string line = getLine();
if (line.find(" GL_EXTENSIONS =") < 12)
  continue;

The full context of the error message is in checkstl.cpp, which notes that one should use compare if comparing to 0 or compare to std::string::npos if looking for no matches.

In the above example, a string is checked for existence of a substring in an unknown but bounded location (starts within the first 12 characters), so I think it's a valid use of the API. I'm planning to suppress this warning but wanted to report it as a false positive.

[CHR]

v2.3 reports

0c113d65.cpp:5:5: performance: Inefficient usage of string::find() in condition; string::starts_with() could be faster. [stlIfStrFind]
if (line.find(" GL_EXTENSIONS =") < 12)

on this completed snippet:

int main() {
int c{};
while (c < 5) {
std::string line = getLine();
if (line.find(" GL_EXTENSIONS =") < 12)
  continue;
++c;
}
return c;
}

Since starts_with() can't be used in this situation, I think it's a FP.

[CHR]

Ticket is here: https://trac.cppcheck.net/ticket/10153