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In article <4hmslm$b3l@solutions.solon.com>
Guillaume Laurent <glaurent@nissart.lagaude.ibm.com> writes:

GL: In article <4hdqjq$8pr@solutions.solon.com>
fred@genesis.demon.co.uk (Lawrence Kirby) writes: 
<snip>
GL: I've got a question here : what if the same above declaration is made
GL: in two (or more) files, compiled seperately then linked together ?
GL: 
GL: ie, in file a.c :
GL: 
GL: extern int i = 1;
GL: 
GL: ...
GL: 
GL: and in file b.c :
GL: 
GL: extern int i = 2;
GL: 
GL: If I understand correctly what you've said, both of these declarations
GL: will reserve space, and give i a value. My question is, what decides
GL: which value will actually be "used", and what happens to the "duplicate"
GL: space ?

It leads to undefined behaviour: the compiler/linker can do anything
it pleases. There must be exactly one definition for every object. 

GL: 
GL: >From what I've tried, the final effective value of i depends on the
GL: order of linking of the objects :
GL: 
GL: cc a.o b.o -o foo  ---> i=1
GL: cc b.o a.o -o foo  ---> i=2
GL: 
GL: But I'm still wondering about the "duplicate" space...

This is a `peculiarity' of your linker. There are linkers which will
complain about `duplicate symbols'

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