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

As mentioned before this is not included in the C++ standard, but you might be able to use autotools to get the same functionality.

You could use the ac_cxx_bool macro to make sure bool is defined (or different routines for different datatypes).