Why is there a performance warning on cast pointer to bool?

Question

Extends.

I thought I was being cool when I did something like:

bool hasParent()
{
  return this->parentNode ;
}

Even with a (bool) cast, the

Answer 1

The compiler needs to generate additional code for converting a pointer to bool. It is basically a comparision against zero and setting the result to one if not zero.

00000000004005e0 <_Z4testPv>:
bool test(void* adr) {
  4005e0:       48 85 ff                test   %rdi,%rdi
  4005e3:       0f 95 c0                setne  %al
    return adr;
}
  4005f8:       c3                      retq

This isn't directly visible from the source, so the compiler thinks this is something the user should be warned about.