[MadeMan]

It doesn't matter what code you have between lines with #.

When compiling, your code actually looks like this:

pawn Код:

#if !defined SOMETHING
            #define SOMETHING
        #endif

        #if defined SOMETHING
            #undef SOMETHING
        #endif

    #if defined SOMETHING
    print("Defined :D");
    #else
    print("Not defined :D");
    #endif

So it will #undef SOMETHING anyway, because it comes after #define.