What will the actual source code this template creates look like?

Question

template <int N>
struct Factorial {
    enum { value = N * Factorial<N - 1>::value };
};

template <>
struct Factorial<0> {
    enum { value = 1 };
};


const int x = Factorial<4>::value; // == 24
const int y = Factorial<0>::value; // == 1

After pre-compilation, if we could magically see what the compiler produced, would we actually see:

const int x = 24;
const int y = 1;

And would we see actual definitions for the struct Factorial, multiple of these? If so how would they look? I'm trying wrap my head around this part of the metaprogramming process.

Answer 1

Using g++ -fdump-tree-original on this code, I see the following result, which for this case seems to confirm your suspicion:

;; Function int main() (null)
;; enabled by -tree-original



{
  const int x = 24;
  const int y = 1;

  <<cleanup_point   const int x = 24;>>;
  <<cleanup_point   const int y = 1;>>;
}
return <retval> = 0;