Is u_char a standard?

Question

Just curious if u_char is a standard. I\'ve always used it assuming it was defined along with uintX_t types and so on. But am seeing some of our code base transition from

Answer 1

It's not present in any older header files (except certain specific areas, like Kerberos and networking headers), and not a built-in type in any compiler I know of.

Answer 2

The string u_char does not appear in this draft of the C standard:

http://www.open-std.org/jtc1/sc22/WG14/www/docs/n1256.pdf

It's not required by POSIX either, as far as I know.

I think it's in BSD (sys/types.h), and Windows (winsock.h). I would not consider either one to be "a standard" - they aren't formal standards, and they certainly aren't part of standard C, but they are clearly defined and documented.

Answer 3

No, u_char is non-standard. If you need to use a standard type that's equivalent to u_char, you can use uint8_t which is part of the C99 standard library (check your specific platforms/compilers for C99-compliance). stdint.h defines this type (along with many other specific integral types). This Wikipedia article contains more information about stdint.h.