Is char signed or unsigned by default?

Question

In the book \"Complete Reference of C\" it is mentioned that char is by default unsigned.

But I am trying to verify this with GCC as well as Visual Stud

Answer 1

Now, we known the standard leaves that up to the implementation.

But how to check a type is signed or unsigned, such as char?

I wrote a macro to do this:

#define IS_UNSIGNED(t) ((t)~1 > 0)

and test it with gcc, clang, and cl. But I do not sure it's always safe for other cases.