Why is (int) pow ( variable1, variable2 ) cast different from (int) pow ( constant1, constant2 )?

Question

C++ / C#

#include <stdio.h>
#include <math.h>
int main() {
  int base = 10;
  int k = 2;
  printf("%d\n", (int) pow(base, k) );//99
  printf("%d\n", (int) pow(base, 2) );//99
  printf("%d\n", (int) pow(10, k) );//99
  printf("%d\n", (int) pow(10, 2) );//100
  return 0;
}

gcc (MinGW.org GCC-6.3.0-1) 6.3.0

Answer 1

In the latter case, apparently, some kind of compiler optimization played and there was no real call to pow.
In general, 99 is obtained as a result of converting a floating point to an int.

Answer 2

Your code is basically incorrect. The function powis not declared. The C language does not allow calls to undeclared functions. Even if your compiler manages to compile it somehow, the behavior is still undefined.