Will strlen be calculated multiple times if used in a loop condition?

Question

I\'m not sure if the following code can cause redundant calculations, or is it compiler-specific?

for (int i = 0; i < strlen(ss); ++i)
{
    // blabla
}
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Answer 1

A good compiler may not calculate it every time, but I don't think you can be sure, that every compiler does it.

In addition to that, the compiler has to know, that strlen(ss) does not change. This is only true if ss is not changed in for loop.

For example, if you use a read-only function on ss in for loop but don't declare the ss-parameter as const, the compiler cannot even know that ss is not changed in the loop and has to calculate strlen(ss) in every iteration.