From owner-freebsd-questions@FreeBSD.ORG  Tue Nov 29 13:33:28 2005
Return-Path: <owner-freebsd-questions@FreeBSD.ORG>
X-Original-To: freebsd-questions@freebsd.org
Delivered-To: freebsd-questions@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id E646616A41F
	for <freebsd-questions@freebsd.org>;
	Tue, 29 Nov 2005 13:33:28 +0000 (GMT)
	(envelope-from freebsd-questions-local@be-well.ilk.org)
Received: from mail25.sea5.speakeasy.net (mail25.sea5.speakeasy.net
	[69.17.117.27]) by mx1.FreeBSD.org (Postfix) with ESMTP id C8A0843D55
	for <freebsd-questions@freebsd.org>;
	Tue, 29 Nov 2005 13:33:27 +0000 (GMT)
	(envelope-from freebsd-questions-local@be-well.ilk.org)
Received: (qmail 4936 invoked from network); 29 Nov 2005 13:33:27 -0000
Received: from dsl092-078-145.bos1.dsl.speakeasy.net (HELO be-well.ilk.org)
	([66.92.78.145])
	(envelope-sender <freebsd-questions-local@be-well.ilk.org>)
	by mail25.sea5.speakeasy.net (qmail-ldap-1.03) with SMTP
	for <freebsd-questions@freebsd.org>; 29 Nov 2005 13:33:27 -0000
Received: by be-well.ilk.org (Postfix, from userid 1147)
	id 2F68E28424; Tue, 29 Nov 2005 08:33:26 -0500 (EST)
Sender: lowell@be-well.ilk.org
To: Mamta BANSAL <mamta.bansal@st.com>
References: <438AAD0F.90205@st.com>
From: Lowell Gilbert <freebsd-questions-local@be-well.ilk.org>
Date: 29 Nov 2005 08:33:25 -0500
In-Reply-To: <438AAD0F.90205@st.com>
Message-ID: <441x0zlgt6.fsf@be-well.ilk.org>
Lines: 32
User-Agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.3
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Cc: freebsd-questions@freebsd.org
Subject: Re: questions about gcc options
X-BeenThere: freebsd-questions@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
Reply-To: freebsd-questions@freebsd.org
List-Id: User questions <freebsd-questions.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-questions>, 
	<mailto:freebsd-questions-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-questions>
List-Post: <mailto:freebsd-questions@freebsd.org>
List-Help: <mailto:freebsd-questions-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-questions>, 
	<mailto:freebsd-questions-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Tue, 29 Nov 2005 13:33:29 -0000

Mamta BANSAL <mamta.bansal@st.com> writes:

> Hello
>          for a c code i am using gcc compiler.
> i have doubt using -c option.
> for a c code the code compiles (without error ) with -c option even if
> i don't provide prior declaration of function.
> i mean i have try.c
> //*******************
> 
> void my_func( ){
> call_to_undeclared_func( );
> }
> //********************
> i do : gcc -c try.c , it works.
> is it the correct behaviour , i mean should it not ask for atleast
> declearation of call_to_undeclared_func( );
> 
> like if my make the same as try.cpp then usen use the same command it
> gives the foll. error.:
> 
> try.cpp: In function `void my_func()':
> try.cpp:2: implicit declaration of function `int
> call_to_undeclared_func(...)'
> which i feel is expected behaviour.

That doesn't require a diagnostic in C, but it does in C++.

If you want the diagnostics anyway, use the
-Wimplicit-function-declaration flag to the compiler.  Or -Wall, which
adds a pretty extensive set of non-required warnings.  See the gcc
manual if you want more information.