Question

Consider below code:

template<typename T>
void f(T a[])
{

    if(sizeof(T) > 1)
        for(...)a[i] = j
    else
        memset(a, j, ...
}

I think compiler should remove one of the if-branches in compile-time.
Is it true?

Answer 1

Since the compiler can decide if (sizeof(T) > 1) will return true or not, at compile time itself, the compiler can emit machine code without any branch if compiled with optimization flag on. So the resultant code will have either for loop (or an equivalent code generated out of it), or memset. In other words, the resultant code will not have if-else block (provided you’re using a smart compiler).