typedef

[Stefano Chiappa]

Hi all,
I'd like to know if there is a way to know if a type already exist in C.
Suppose I have

typedef unsigned char uchar;

and, due to a messy-include dependency, I'd like to know if the type 
uchar already exists.
I checked that:

#if defined(uchar)

... something to do if uchar has not already defined ...

#endif

I think that this does not work while typedef is a C keyword and not a 
pre-processor command as #if defined( is.
I'm using gcc4.1.1
Thank you.
Stefano