In message DCEAAC0833DD314AB0B58112AD99B93B06DA9D@ismail.innsys.innovsys.com you wrote:
This usually works even on cranky compilers:
unsigned char x = 0xC2; printf("this is the problem %02X\n", (unsigned int)x);
But we agree that the conversion "unsigned char" ==> "unsigned int" must result in exactly the same result, no matter if done implicitely or by explicit cast?
If this doesn't work it means that the toolchain is broken and/or misconfigured. Maybe there is no valid prototype for printf() active, etc., but this should be visible when compiling with warnings turned on.
I agree, unsigned char should be promoted to unsigned int.
However, char can be unsigned or signed depending on the platform. On a platform where char is signed by default and having a value of 0x80 or more, compiler can simply sign extend the value to promote to an integer before passing it to printf. So, a value like 0xC2 (-62 as 8-bit value) will be promoted to 0xffffffc2 (-62 as 32-bit value) on a 32-bit computer with twos complement arithmetic. %02X can only suppress leaving zeros so additional f's will be printed.
Best regards, Tolunay Orkun