From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 24736 invoked by alias); 30 Sep 2015 12:17:41 -0000 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 Received: (qmail 24724 invoked by uid 89); 30 Sep 2015 12:17:40 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-3.7 required=5.0 tests=AWL,BAYES_00,SPF_HELO_PASS,T_RP_MATCHES_RCVD autolearn=ham version=3.3.2 X-HELO: mx1.redhat.com Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES256-GCM-SHA384 encrypted) ESMTPS; Wed, 30 Sep 2015 12:17:40 +0000 Received: from int-mx09.intmail.prod.int.phx2.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.22]) by mx1.redhat.com (Postfix) with ESMTPS id E0947C0B64DC for ; Wed, 30 Sep 2015 12:17:38 +0000 (UTC) Received: from pinnacle.lan ([10.3.113.5]) by int-mx09.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id t8UCHckn026036 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA256 bits=256 verify=NO); Wed, 30 Sep 2015 08:17:38 -0400 Date: Wed, 30 Sep 2015 12:17:00 -0000 From: Kevin Buettner To: Pedro Alves Cc: gdb-patches@sourceware.org Subject: Re: [PATCH] infcmd.c: Don't attempt to record a NULL value after a finish command Message-ID: <20150930051736.457e072c@pinnacle.lan> In-Reply-To: <560BB90D.70905@redhat.com> References: <20150929214350.44b076c7@pinnacle.lan> <560BB90D.70905@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-IsSubscribed: yes X-SW-Source: 2015-09/txt/msg00652.txt.bz2 On Wed, 30 Sep 2015 11:27:25 +0100 Pedro Alves wrote: > On 09/30/2015 05:43 AM, Kevin Buettner wrote: > > Architectures which use RETURN_VALUE_STRUCT_CONVENTION will have a > > NULL return value after executing a finish command. See get_return_value() > > in infcmd.c. > > > > This patch avoids an eventual SIGSEV (caused by attempting to > > derefrence a NULL pointer) by adding a suitable test to > > finish_command_fsm_should_stop(). > > > > I encountered this problem while testing msp430: > > > > (gdb) PASS: gdb.base/structs.exp: zed L for finish; return 1 structs-tc > > finish > > Run till exit from #0 fun1 () at /ironwood1/sourceware-git/msp430-elf/../binutils-gdb/gdb/testsuite/gdb.base/structs.c:125 > > ERROR: Process no longer exists > > > > gdb/ChangeLog: > > * infcmd.c (finish_command_fsm_should_stop): Don't attempt to > > record a NULL value. > > --- > > gdb/infcmd.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/gdb/infcmd.c b/gdb/infcmd.c > > index c4d7d8b..6be95e4 100644 > > --- a/gdb/infcmd.c > > +++ b/gdb/infcmd.c > > @@ -1788,7 +1788,7 @@ finish_command_fsm_should_stop (struct thread_fsm *self) > > internal_error (__FILE__, __LINE__, > > _("finish_command: function has no target type")); > > > > - if (TYPE_CODE (rv->type) != TYPE_CODE_VOID) > > + if (rv->value != NULL && TYPE_CODE (rv->type) != TYPE_CODE_VOID) > > { > > struct value *func; > > It's this else block that below sets rv->value in the first place: > > if (TYPE_CODE (rv->type) != TYPE_CODE_VOID) > { > struct value *func; > > func = read_var_value (f->function, NULL, get_current_frame ()); > rv->value = get_return_value (func, rv->type); > rv->value_history_index = record_latest_value (rv->value); > } > > So seems like that patch would break !RETURN_VALUE_STRUCT_CONVENTION > targets? > > I assume that it's record_latest_value that crashes? Isn't the right > fix instead: > > rv->value = get_return_value (func, rv->type); > - rv->value_history_index = record_latest_value (rv->value); > + if (rv->value != NULL) > + rv->value_history_index = record_latest_value (rv->value); > You're right. (I honestly don't know what I was thinking.) Please commit your patch instead. Thanks, Kevin