Byte precision pointer arithmetic in C when sizeof(char) != 1

Question

How can one portably perform pointer arithmetic with single byte precision?

Keep in mind that:

• char is not 1 byte on all platforms

Answer 1

sizeof(char) is guaranteed to be 1 by the C standard. Even if char uses 9 bits or more.

So you can do:

type *pt;
unsigned char *pc = (unsigned char *)pt;

And use pc for arithmetic. Assigning pc to pt by using the cast above is undefined behavior by the C standard though.

If char is more than 8-bits wide, you can't do byte-precision pointer arithmetic in portable (ANSI/ISO) C. Here, by byte, I mean 8 bits. This is because the fundamental type itself is bigger than 8 bits.