Re: #ifndef main

[Bernd Strieder]

Hello,

awhan.iitk@gmail.com wrote:

> I have two files and the contents are as follows :
> 
> file :: main.h
> -------------------------------------

> #define main

> --------------------------------------
> file :: main.cpp
> -------------------------------------
> #include "main.h"
> 
> int main(void)


> May somebody please shed some light on this ?

Everything with those # at the beginning of the line is handled by the
preprocessor before the actual compiler gets its input. That
preprocessor is basically able to replace identifiers by arbitrary
strings. So

#define main

will send every identifier "main" to the empty string. A macro named
main with empty value has been defined.

You can see the result with

g++ -E main.cc

and then you will understand the compiler error message.

Try the following: #define main foobar
or even: #define main(x) main(int argc)

I think the textbooks on C++ explain the preprocessor as far as
necessary, because there is no way around in any real-world project.


Bernd Strieder