#undef main gives no result

Question

I'm working with MVisualC++ 2010 and when I try to undefine the "main", there's no result and the console launches as usual. I was expecting some missing entry point error or something. Why is that?

#undef main
int main()
{
}

Answer 1

main isn't a #define in the first place. Your #undef changes nothing at all.

#define foo bar tells the preprocessor "replace all occurences of foo with bar". #undef foo tells the preprocessor "foo has no special meaning anymore, leave it as is"

If you want a linker error, rename main to e.g. main2, or do e.g. this:

void foo();
int main() {
  foo();
}

This tells the compiler that a foo function exists (but not what it is). main tries to use it, so the linker will give an error when it can't find it.