Re: [Dev-C++] what is a resource? how do I create my own headers?

[Luc M. <lu...@ho...>]

----- Original Message -----
From: "Ioannis Vranos" <no...@ya...>
To: <dev...@li...>
Sent: Thursday, January 04, 2001 6:52 PM
Subject: RE: [Dev-C++] what is a resource? how do I create my own headers?

> > The #ifdef/#endif only works for the current compile. So, if you include
> > a header file that contains a definition in more than one translation
unit
> > (.cpp file), you will get multiple definitions of the function, which is
> > gonna
> > be flagged as an error by the linker.
>
> I agree with you, but why create many definitions in many cpp files?
Except
> of that, you can use #ifndef at definitions too (it is called "conditional
> compilation").
>  Anyway, if i remember well we were talking about definitions included in
> the header file, not external source code files (where as i said we can
use
> conditional compilation too).


I don't see where I might have hinted at having "many
definition in many .cpp files".

In C/C++ (I don't know for other languages), you can't
have more than one definition for a symbol, be it a variable,
a function or a class. This is called, IIRC, the "One Definition
Rule".

If you start putting definitions in header files, as projects grow
bigger, those header files risk being included in more than
one .cpp file, leading to multiple definitions of the functions
in the header files.

Now, I've seen tricks posted here to work around this, but
why use tricks when all you have to do is _declare_ your
functions (or classes) in a header file, and _define_ said
functions (or classes) in only one .cpp file. Then, wherever
you need that function, all you need to do is #include your
header file.

Let the linker do its job :-)

Regards,

Luc Morin