Thread: help me with this guys.what will happen if i put "return(0)" outside main? why?

why don't you try it and find out for yourself?

It will not be an error if you include the following before your main function

Code:

#define return(...)

Originally Posted by c99tutorial

It will not be an error if you include the following before your main function

Code:

#define return(...)

It might be. The result of #define'ing language keywords is undefined behaviour.

Originally Posted by grumpy

The result of #define'ing language keywords is undefined behaviour.

Isn't a macro with parameters technically distinct from the keyword. For example, the following program clearly returns 1.

Code:

#define return(...)

int main()
{
    return 1;
}

return(0);

Originally Posted by c99tutorial

Isn't a macro with parameters technically distinct from the keyword. For example, the following program clearly returns 1.

Code:

#define return(...)

int main()
{
    return 1;
}

return(0);

what happens then, if you #define sizeof(...)? The syntax for using the macro or the keyword would be identical. Sounds like a recipe for disaster if you ask me.

I believe it is legal:

Originally Posted by C99 Clause 6.4.1 Paragraph 2

The above tokens (case sensitive) are reserved (in translation phases 7 and 8) for use as keywords, and shall not be used otherwise.

The preprocessor does its work in translation phase 4.

Hmmm ... that's interesting. I could have sworn I remember reading it was undefined behaviour.

I just looked up in the 1999 C standard (only one handy on my current machine) and the only reference I can find which is relevant is Section J.2, where it says that the behaviour is undefined if any standard header is #include'd while a macro is #define'd as a keyword.