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

The scope of a macro is part of compilation unit that comes after #define, up until the end of the unit (which is to say, until the end of .cpp file). However Visual C++ has a pair of #pragma push_macro/pop_macro that can be used in a case where macro definitions overlap. You can push previous definition, define your own, use it, and when you decide just pop previous definition.