In C/C++, is there a directive similar to #ifndef for typedefs?

Question

If I want to define a value only if it is not defined, I do something like this :

#ifndef THING
#define THING OTHER_THING
#endif

What if

Answer 1

No there is nothing like what you wanted. I have had your same problem with libraries that include their owntypedefs for things like bool. It gets to be a problem when they just don't care about what you use for bool or if any other libs might be doing the same thing!!

So here's what I do. I edit the header file for the libs that do such things and find the typedef bool and add some code like this:

#ifdef USE_LIBNAME_BOOL
typedef unsigned char bool; // This is the lib's bool implementation
#else
#include 
#endif

Notice that I included if I didn't want to use the libs' own bool typdef. This means that you need C99 support or later.