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

Unfortunately, #defines do not respect scoping rules. #defines that are not #undef'd will affect all code after them. Additionally, if code before you defines the same macro name, you'll have problems. In C++ you can usually avoid needing to use such local macros with local typedefs and references. For example, you could do:

void foo() {
    typedef Ogre::Real O_REAL;
    // ... 
}

This will respect scoping rules. For variables you can use references:

void foo() {
    int &BAR = Foo::quux::baz::static_bar;
    // ...
}