Do I need to #undef a local #define? Is there such a thing as a local define?

Question

Sometimes to make things easier to write and read, I write some local #define macros within functions (for example, #define O_REAL Ogre::Real).

Answer 1

there is no such thing as a local define. Defines are always tentative evil ;-)

For your example I would recommend typedef to make alias for variable names

However, sometimes local defines are a nice thing for the programmer (but the are never for the maintainer). To make things a bit easier and a bit safer I always undef these things and I even guard their entry:

#if defined(LOCAL_CROWBAR)
#error Hurgh!
#endif /* LOCAL_CROWBAR */
#define LOCAL_CROWBAR

... use LOCAL_CROWBAR ...

#undef LOCAL_CROWBAR

Nevertheless, avoid those whenever possible!