Re: incompatible function declaration

["Michael" <gonwg at hotmail dot com>]

----- Original Message ----- 
From: "Matthew Woehlke" <mw_triad@users.sourceforge.net>
To: <gcc-help@gcc.gnu.org>
Sent: Thursday, April 12, 2007 12:31 PM
Subject: Re: incompatible function declaration


> Michael wrote:
> > gcc behaves differently for following program:
> >
> > void foo2();
> > int main() {
> >    extern void foo(void);
> >    foo();
> >    foo2();
> >    return 0;
> > }
> >
> > void foo2() {
> >    foo();
> > }
> >
> >
> > compilation command:  gcc -c t1.c
> >
> > result:
> > 1. gcc 3.2.2 compiles successfully.
> >
> > 2. gcc 4.0.3 gives following message:
> >
> > t1.c: In function 'foo2':
> > t1.c:10: error: incompatible implicit declaration of function 'foo'
> > t1.c:3: error: previous implicit declaration of 'foo' was here
> >
> >
> > question:
> >    which one is more correct ? Is the error message too severe ?
>
> I would say 4.0.3 is right... you made the declaration in a local 
> scope so it does not apply to foo2(). When foo2() tries to call foo(), 
> the default implicit prototype is 'int foo()', which is incompatible 
> with the previous declaration as the error states.

I am fine with both behaviors. The more important issue is that the 
change in 4.0.3 might break existing code because of the error message.

Anyway, just let you guys know about it.


Mike


> --
> Matthew
> GDRLaH - Grin, Duck, and Run Like a Hippo! :-)