Xref: utzoo comp.lang.c:25862 comp.std.c:2452
Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!umich!samsung!usc!apple!snorkelwacker!spdcc!ima!haddock!karl
From: karl@haddock.ima.isc.com (Karl Heuer)
Newsgroups: comp.lang.c,comp.std.c
Subject: Re: extern int f();     VS     int f();
Keywords: Storage Classes, External References
Message-ID: <15929@haddock.ima.isc.com>
Date: 12 Feb 90 20:53:40 GMT
References: <2912@hcx1.SSD.CSD.HARRIS.COM>
Reply-To: karl@haddock.ima.isc.com (Karl Heuer)
Organization: Interactive Systems, Cambridge, MA 02138-5302
Lines: 30

Doug already posted the details, but it might not be clear what the answer is
to the original question.

In article <2912@hcx1.SSD.CSD.HARRIS.COM> brad@SSD.CSD.HARRIS.COM (Brad Appleton) writes:
>Are the following function declarations equivalent?
>(1)	extern int foo();
>(2)	int foo();

Yes.  They are completely identical in any sane compiler.

>I was just asked this question and I thought I knew a precise answer but
>I find that I am a little fuzzy on this one! I thought (2) is like a
>"forward" declaration in Pascal and that the only difference between these
>two is that If I use (2) then I may define the function "foo" (give it
>a body) later on in the same file. Is this right?

With either spelling, the actual definition for the function can appear in
either the same file or in a different file.  (Some people prefer to use
"extern" for functions defined in separate files and omit "extern" for forward
declarations; this is a matter of taste.)  But it must be a global function.
To forward-declare a static function%, you should use "static int foo();".

When dealing with objects rather than functions, the situation gets worse.

Karl W. Z. Heuer (karl@ima.ima.isc.com or harvard!ima!karl), The Walking Lint
________
% There may be some compilers that won't let you forward-declare a static
  function.  If you have to deal with such a beast, it's probably best to sort
  the function definitions (if they aren't mutually recursive) or promote one
  of them from static to global so you can forward-declare it.