Why does C print my hex values incorrectly?

Question

So I\'m a bit of a newbie to C and I am curious to figure out why I am getting this unusual behavior.

I am reading a file 16 bits at a time and just printing them ou

Answer 1

This is due to integer type-promotion.

Your shorts are being implicitly promoted to int. (which is 32-bits here) So these are sign-extension promotions in this case.

Therefore, your printf() is printing out the hexadecimal digits of the full 32-bit int.

When your short value is negative, the sign-extension will fill the top 16 bits with ones, thus you get ffffcade rather than cade.

---

The reason why this line:

printf("\n%x", endian(hex));

seems to work is because your macro is implicitly getting rid of the upper 16-bits.