🚀 go-pugleaf

In article <4hdqjq$8pr@solutions.solon.com> fred@genesis.demon.co.uk (Lawrence Kirby) writes:


> I mentioned object declarations above. Consider the following (assume
> everything from here on is declared outside of any function):
> 
>     int i = 1;
> 
> The simplest case - this is a declaration that reserves space and hence
> is also a definition. It has file scope i.e. is visible up until the end
[...]
>
>     extern int i = 1;
> 
> This means exactly the same thing as int i = 1; The initialisation 'forces'
> the definition (allocation of space).

I've got a question here : what if the same above declaration is made
in two (or more) files, compiled seperately then linked together ?

ie, in file a.c :

extern int i = 1;

...

and in file b.c :

extern int i = 2;

If I understand correctly what you've said, both of these declarations
will reserve space, and give i a value. My question is, what decides
which value will actually be "used", and what happens to the "duplicate"
space ?

>From what I've tried, the final effective value of i depends on the
order of linking of the objects :

cc a.o b.o -o foo  ---> i=1
cc b.o a.o -o foo  ---> i=2

But I'm still wondering about the "duplicate" space...

> I'm curious - do people find this enlightening (you learnt something),

Yes, I do.
-- 
--
					Guillaume