extern storage class & multiple declaration

extern storage class & multiple declaration

[Alina Valea]

Hello everybody,

Suppose we have:

---------------------------------------- file.h

extern int i; ----------------------------------------

and ---------------------------------------- file.c

#include "file.h"

int i; ...

/* No actual use of i here */
------------------------------------------

----------------------------------------- another_file.c

#include "file.h"

void func() {

i=3; }

-----------------------------------------

I know this is entirely correct, but is it an acceptable
programming habit?

Thank you, Alina


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Re: extern storage class & multiple declaration

[Jan-Benedict Glaw]

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On Thu, 2002-08-22 07:52:34 -0000, Alina Valea <avalea@home.ro>
wrote in message <20020822075234.20104.qmail@relay1.home.ro>:
> Hello everybody,
> 
> Suppose we have:

[
	file.h declares a variable,
	file.c defines it, but doesn't use it and
	some_file.c includes file.h and uses mentioned variable
]

> I know this is entirely correct, but is it an acceptable
> programming habit?

This is not only correct but also done very often. Sometimes, you can't
go around global variables. In such a case, it's better to have a
"globals.h" (declaring *all* global variables) and a matchins globals.c
file (defining them all, possibly initializing them to useful default
values).

This is a _lot_ better than spreading all those global variables over a
zillion .c files, and locally declaring them in any .c file which uses
(but doesn't define) it. That's quite error-prone (eg. small things like
signed <-> unsigned conflicts *will* come up at some time, and you'll
spend a day or two for searching the difference).

Having all global variables (if any exist) iat one place (in conjunction
with a matching header file) is a good thing helping to not do stupid
mistakes...

MfG, JBG

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