Question

There is code:

#include <iostream>
int main(){
  unsigned char a = 4, b = 255;
  int g = (unsigned char)a + (unsigned char)b;
  std::cout << g << std::endl;
  return 0;
}

Result:

259

Why the result is 259, not 3? If there are added two unsigned char variables, there should be overflow, result should be 3 and then it should convert from unsigned char 3 to int 3.

Answer 1

The addition operation will first promote its operands to int, before doing the addition. This is how C works. If you want to truncate, you need to assign it back into a narrower type, such as unsigned char.