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

Arrgh, it will, even under ideal circumstances, dammit!

As of today (January 2018), and gcc 7.3 and clang 5.0, if you compile:

#include 

void bar(char c);

void foo(const char* __restrict__ ss) 
{
    for (int i = 0; i < strlen(ss); ++i) 
    {
        bar(*ss);
    }
}    

So, we have:

• ss is a constant pointer.
• ss is marked __restrict__
• The loop body cannot in any way touch the memory pointed to by ss (well, unless it violates the __restrict__).

and still, both compilers execute strlen() every single iteration of that loop. Amazing.

This also means the allusions/wishful thinking of @Praetorian and @JaredPar doesn't pan out.