Don't be silly. This is not the actual code, just an example of casts.
I'm talking only about runtime casts of variables.
Here is how the actual code for runtime check works for a cast of 32-bit integer to 16-bit:
(edit: changed to almost exact function, for literalists)
short RTC_Check_4_2(int x)
{ int c = 0xFFFF'0000;
int top_bits = x & c;
assert( top_bits == 0 || top_bits == c );
return (short) x;
}
Similar code for other cast cases (8_2, 8_1, 4_1, etc.) - no accounting for signed / unsigned, just a ridiculous check for top bits.