astutils.cpp: fixed suboptimal string comparisons / small cleanup

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[chrchr-github]

What is the performance gain here? Why would strcmp be faster than ==?

[firewave]

What is the performance gain here?

Less than a percent in the example I tested but as usual that depends how hot the path is.

Why would strcmp be faster than ==?

It gets rid of the strlen() to determine the length of of the const char* to compare with.

[chrchr-github]

Why would strcmp be faster than ==?

It gets rid of the strlen() to determine the length of of the const char* to compare with.

Seems like all three compilers do strlen + memcmp in operator== as well as std::string::compare(). Maybe it depends on the use case which one is faster? We probably only check very short strings.

[firewave]

We probably only check very short strings.

I think it is always a single character. I would have just changed it to char but there is one instance where a pointer is passed through. Maybe that can be fixated.

[danmar]

when I benchmarked in quick bench I did not see a difference in performance but perhaps my benchmark was not well written.

[danmar]

when I benchmarked in quick bench I did not see a difference in performance but perhaps my benchmark was not well written.

in benchmark I wrote and executed locally it seems the strcmp is considerably faster.

int direct(const std::string& s, const char* op) {
    return s == op;
}

int use_strcmp(const std::string& s, const char* op) {
    return std::strcmp(s.c_str(), op);
}

👍

[firewave]

There's also benchmark in these tickets:
https://trac.cppcheck.net/ticket/11253
https://trac.cppcheck.net/ticket/11252