Re: [Dev-C++] Where to include files

[Paul I. <pi...@ot...>]

Matthews <dem...@uw...> wrote:

> Guard statements are lines like these in your header files:
>=20
> #ifndef FOOHEADER_H
> #define FOOHEADER_H
>=20
> int foo;
> char *foostring;
> //...
>=20
> #endif
>=20
> Then if two files include foo.h, it won't be recompiled because FOOHEAD=
ER_H
> has already been defined.

I think this answer is confusing to all the newbees out there...

First point:
Of course the header file will be compiled-in with each .cpp/.c that incl=
udes=20
it. If you check the makefile, each .cpp is compiled by it self and there=
 is=20
no way for the compiler to know if the header has already been included a=
nd=20
thus compiled...

Second point:
The guard statements mentioned prevent the same header from being include=
d=20
more than once during the compilation of _one_ .cpp=B4. Consider the foll=
owing:

file1.h

#include "file2.h"

....

file2.h

#include "file1.h"

...


Without the guard stetements file1.h would include file2.h whitch include=
s=20
file1.h...=20

Third point:
The example .h-file above contains definitions of variables. If you inclu=
de=20
this file the variables foo and foostring would be instanciated as local =
(file-
scope) in each .cpp where the .h is included. Not very useful?! To make g=
lobal=20
variables declare as _external_ in header fil and move the instansiation =
to=20
the .cpp file.

Regards, Paul.