Doesn't seem so fine to me..

  /*compare.c*/
  #include <stdio.h>
  
  int compare( int x, int y )
  {
      return x - y;
  }
  
  void testCompare( int x, int y )
  {
      if ( compare( x, y ) < 0 )
      {
          printf( "%d is less than %d\n", x, y );
      }
      else
      {
          printf( "%d is greater than or equal to %d\n", x, y );
      }
  }
  
  int main()
  {
      testCompare( 5, 10 );
      testCompare( 10, 5 );
      testCompare( 1987654321, -1987654321 );
      return 0;
  }

$ clang -o compare compare.c

$ ./compare

5 is less than 10

10 is greater than or equal to 5

1987654321 is less than -1987654321