using extern with different type but same name variable in C

Question

I have int a[] in one C file. Now in another .c file I have extern int *a .

I need to know what will be the behavior if I try to access variable a in second file and why? What all problems would occur?

Sorry that was a typo.actually both have same name 'a' – vaibhav shukla Jun 01 '13 at 15:20 — vaibhav shukla, Jun 01 '13 at 15:20

score 2 · Answer 1 · answered Jun 01 '13 at 11:25

2

Undefined behaviour. So anything might happen.

answered Jun 01 '13 at 11:25

could you please elaborate a bit as to why undefined behavior? – vaibhav shukla Jun 01 '13 at 11:31
@vaibhavshukla: Because the standard says it is. (See section 6.2.7 of C99.) On a more practical level, see some of the answers here: http://stackoverflow.com/questions/6385850/pointer-array-extern-question. – Oliver Charlesworth Jun 01 '13 at 11:34
What if I include first file in second? What will be outcome? Linking error or compiler error? – vaibhav shukla Jun 01 '13 at 13:11
@vaibhavshukla: You could try it... ;) – Oliver Charlesworth Jun 01 '13 at 13:12
:) I definitely will. But still want to be shown some more light to the concept before coming to conclusion. – vaibhav shukla Jun 01 '13 at 13:18

Dineshkumar · Answer 2 · 2013-06-01T14:06:40.327

0

If you include the file(declaration) twice or declared variable named a, then there may be error redefinition of a;

when i tried the above compiler shows error :

conflicting types for a;
//previous definition in other file...

edited Jun 01 '13 at 14:06

answered Jun 01 '13 at 11:27

Dineshkumar

@dinesh: I dnt think so bcoz extern keyword says that its a declaration not definition or say when we say extern, it means somewhere in other file variable has been define, so how come redefinition error? – vaibhav shukla Jun 01 '13 at 13:54

2 Answers2