C : Is the scope of #undef important?

[bartoli]

Hi and happy new year,
I'm having a doubt about a simple thing : i know that macros are evaluated at compile time, but does their position have an importance? Let me explain.
if i have for example

#define SOMEMACRO//line that can be present or not depending on my code generator
doStuff();
if(condition()){
 #ifdef SOMEMACRO
  doSpecificStuff();
 #undef SOMEMACRO
 #endif
}

Will SOMEMACRO be undefined even if condition() is false? Sorry for the stupid question :P

[Disch]

yes.

All preprocessor commands (anything that starts with a #) ignore all scope and language rules (one of the many reasons you generally want to avoid them when possible).

They're sort of like a separate language that is run through and compiled before the actual C++ code is even started to be compiled.