multiple inclusions of a header file

[vexstorm]

I have read about how to avoid multiple inclusions of header files.But what problem does including multiple inclusions of the same header actually cause? Im still new to this and just trying to learn ^_^ I understand that you get an error if you try to double include a header file (from what i've read online) but does this cause your program to basically generate 2 of everything? Or is it simply a warning that it could mess with your program? I don't really understand what exactly is being done when you include multiple header files of the same name... >.>

-vexstorm

[Bazzy]

You can try it out, your compiler should stop compiling when it finds a double declaration for the same symbol

[helios]

The compiler will probably (it depends on the actual contents of the header) generate the same error than with this:

int a;
int a;

[Zaita]

Actually, with proper include guards, including the same header file twice has no effect. It just takes a little bit longer to compile the code.

Without a header guard, you'd end up with multiple-definition errors on anything declared in the header.