From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 67805 invoked by alias); 30 Sep 2015 12:21:39 -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 67782 invoked by uid 89); 30 Sep 2015 12:21:38 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-1.9 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 12:21:37 +0000 Received: from int-mx14.intmail.prod.int.phx2.redhat.com (int-mx14.intmail.prod.int.phx2.redhat.com [10.5.11.27]) by mx1.redhat.com (Postfix) with ESMTPS id A60FEC15CA85 for ; Wed, 30 Sep 2015 12:21:36 +0000 (UTC) Received: from [127.0.0.1] (ovpn01.gateway.prod.ext.ams2.redhat.com [10.39.146.11]) by int-mx14.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id t8UCLZJ9029846; Wed, 30 Sep 2015 08:21:35 -0400 Message-ID: <560BD3CE.1040107@redhat.com> Date: Wed, 30 Sep 2015 12:21:00 -0000 From: Pedro Alves User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 MIME-Version: 1.0 To: Kevin Buettner CC: gdb-patches@sourceware.org Subject: Re: [PATCH] infcmd.c: Don't attempt to record a NULL value after a finish command References: <20150929214350.44b076c7@pinnacle.lan> <560BB90D.70905@redhat.com> <20150930051736.457e072c@pinnacle.lan> In-Reply-To: <20150930051736.457e072c@pinnacle.lan> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-SW-Source: 2015-09/txt/msg00653.txt.bz2 On 09/30/2015 01:17 PM, Kevin Buettner wrote: > 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. I don't have a patch -- I wrote that hunk by hand in the mail client. :-) Please fix up yours and push it. Thanks, Pedro Alves