How can static_cast can cast an int to char but not reinterpret_cast?

Question

I'm not sure if it has been asked earlier, but must have been I believe. Consider the simple line for start of question :

int a ;
char b = reinterpret_cast<char> (a);

I understand reinterpret_cast interpret the bits pattern of type x as type y, ofcouse it shouldn't work due to size mismatch and indeed it doesn't.

Now consider this another code:

int a ;
char b = static_cast<char> (a);

This works! . Now my question is how it can work ? I mean does the compiler chops off the bits? . I am certain sizeof(char) < sizeof(int) . If that, reinterpret_cast should also work by same technique ?

Answer 1

There is a well-defined conversion from int to char; that's what static_cast does. In fact, you don't need the cast; you can just use an assignment here. On the other hand, reinterpret_cast says to pretend that the bits in an object of one type represent an object of another type; for some types that's okay (more or less), but there's no sensible way to pretend that the bits in an int can be used as the bits in a char without applying a conversion, and reinterpret_cast doesn't do that.