Does a function that returns a constant work slower than a void function? [closed]

Question

Simplest example to highlight the difference:

int foo()
{
   doSomething();
   return 0;
}

void bar()
{
   doSomething();
   return;
}

int main()
{
   foo();
   bar();
}

Is bar faster than foo, and why?

Answer 1

This is such a micro optimization that you should never have to even consider it. Yet the usual caveats when talking about performance:

• measure
• measure again
• change something
• measure
• make sure that you understand what you are measuring and why the change had an effect
• change it again a bit more with the new understanding and check whether the premise holds

As of the particular case of returning a small object (something that fits in a register), the cost is going to be negligible, basically a load into a register in most architectures.