libowfat/mult/imult16.c

#if defined(__GNUC__) && (__GNUC__ >= 5)

#include "uint16.h"

int imult16( int16 a, int16 b, int16* c) { return !__builtin_mul_overflow(a,b,c); }

#else

#include "safemult.h"

int imult16(int16 a,int16 b,int16* c) {
  int32 x=(int32)a*b;
  if ((int16)x != x) return 0;
  *c=x;
  return 1;
}

#endif

#ifdef UNITTEST
#include <assert.h>

int main() {
  int16 a;
  assert(imult16(4,10000,&a)==0);
  assert(imult16(-4,10000,&a)==0);
  assert(imult16(5,10,&a)==1 && a==50);
  assert(imult16(-3,10000,&a)==1 && a==-30000);
  return 0;
}
#endif