On Sun, Apr 11, 2010 at 03:49:26AM -0700, James Hartley wrote:
> On Sat, Apr 10, 2010 at 9:14 PM, Jesus Sanchez <zexe...@gmail.com> wrote:
>
> > This is not really OpenBSD related but since it's a UNIX-like OS and
> > here are really experienced people coding in C I thought this was a good
> > place to ask.
> >
>
> Actually, not. Your questions are general C programming questions. A
> number of sites exist which thrive on questions like this. Sometimes, they
> actually give the right answers.
>
>
> > Back to a.c later than the 0x2211
> > assignement I printed the variable and showed 0x11 (at that point i
> > realized the mistake). But I was just wondering where the h*ll went the
> > 0x22 bits on the memory??
>
>
> Truncated.
>
>
> > I know the rigth thing is to declare the variable 'foo' on a header
> > file and include it in all my code...
>
>
> No, this is incorrect. It is a poor idea to declare variables within header
> files. This bad practice will lead to linker errors due to duplicate
> definitions.
>
> One solution is to define all global variables in a single *.c file & place
> extern statements to each of these global variables in a header file which
> can then be included as many times in as many places as you choose. Here,
> all global variables are defined only once which is required.
You are mixing up the terms definition and declaration.
In C, a declaration introduces a name and some or all properties of
that name.
A definition does the same, but also reserves memory for the object.
In global scape "int a" is a definition, while "extern int a" is a declaration.
So a declaration of a variable in a header file is pefectly ok. A
definition, hoewever, is frowned upon. There exist some rules to allow
old code (where this idom is pretty comon) to compile and link, but
you'd better no introduce so called "commons" in new code.
-Otto
