Will this be a tail call or not?

Question

Is the recursive call in my code a tail call or is it just ordinary recursion?

void sum(const int values[], size_t count,int* result){
  if(count <= 0) return;
  *result += values[0];
  sum(values + 1,count - 1,result);
}

Because as far as I know, a tail call is recursion that occurs as the last call in a function.

Answer 1

If no code follows a call, it's a tail call.

In C, this would like one of these:

void g( … );

void f( … ) {
   …
   g( … );  // Tail call.
}

void g( … );

void f( … ) {
   …
   g( … );  // Tail call.
   return;
   …
}

T g( … );

T f( … ) {
   …
   return g( … );  // Tail call.
   …
}

It has nothing to do with recursion, but it does include recursive calls.

Tail calls are interesting since they can be eliminated. C neither mandates nor forbids tail-call elimination. That's up to the compiler.