From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 4319 invoked by alias); 12 Jan 2010 12:23:49 -0000 Received: (qmail 4303 invoked by uid 22791); 12 Jan 2010 12:23:48 -0000 X-SWARE-Spam-Status: No, hits=-2.5 required=5.0 tests=AWL,BAYES_00,SPF_PASS X-Spam-Check-By: sourceware.org Received: from mail.codesourcery.com (HELO mail.codesourcery.com) (38.113.113.100) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Tue, 12 Jan 2010 12:23:41 +0000 Received: (qmail 28680 invoked from network); 12 Jan 2010 12:23:39 -0000 Received: from unknown (HELO orlando) (pedro@127.0.0.2) by mail.codesourcery.com with ESMTPA; 12 Jan 2010 12:23:39 -0000 From: Pedro Alves To: gdb-patches@sourceware.org Subject: Re: [commit] Fix -Wunused warning in dec-thread.c. Date: Tue, 12 Jan 2010 12:23:00 -0000 User-Agent: KMail/1.9.10 Cc: Joel Brobecker References: <1263282971-16934-1-git-send-email-brobecker@adacore.com> In-Reply-To: <1263282971-16934-1-git-send-email-brobecker@adacore.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <201001121223.39632.pedro@codesourcery.com> X-IsSubscribed: yes Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org X-SW-Source: 2010-01/txt/msg00299.txt.bz2 On Tuesday 12 January 2010 07:56:11, Joel Brobecker wrote: > From: brobecke > > Hello, > > The compiler complains that the result of a couple of *PTR++ is never > used. This is because the compiler is tricked by the way the pointer > was defined. For instance: > > | dec_thread_count_gdb_threads (struct thread_info *ignored, void *context) > | { > | int *count = (int *) context; > > The compiler complains that the result is never used for the following > line: > > | *count++; > > The result is stored for the caller to use, so it is in fact potentially > used, but elsewhere... > > gdb/ChangeLog: > > * dec-thread.c (dec_thread_count_gdb_threads) > (dec_thread_add_gdb_thread): Prevent -Wunused warning. > > Checked in. > > --- > gdb/dec-thread.c | 4 ++-- > 1 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/gdb/dec-thread.c b/gdb/dec-thread.c > index 5083221..be6db4c 100644 > --- a/gdb/dec-thread.c > +++ b/gdb/dec-thread.c > @@ -352,7 +352,7 @@ dec_thread_count_gdb_threads (struct thread_info *ignored, void *context) > { > int *count = (int *) context; > > - *count++; > + (void) *count++; /* The cast to void is to prevent a -Wunused warning. */ > return 0; > } > Does the resulting gdb actually count threads correctly? '++' has higher precedence than '*', so '*count++' is incrementing the count pointer, not what it points to. The correct fix is either: - *count++; + (*count)++; or - *count++; + ++*count; Grepping for `grep iterate_over * | grep count' shows that the `(*count)++' form is used at least in two places, giter_count and count_events_callback: aix-thread.c:/* iterate_over_threads() callback for counting GDB threads. aix-thread.c: iterate_over_threads (giter_count, &gcount); dec-thread.c: iterate_over_threads (dec_thread_count_gdb_threads, linux-nat.c: iterate_over_lwps (filter, count_events_callback, &num_events); -- Pedro Alves