From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gdb-return-44321-listarch-gdb=sources.redhat.com@sourceware.org>
Received: (qmail 99152 invoked by alias); 10 Apr 2015 12:31:52 -0000
Mailing-List: contact gdb-help@sourceware.org; run by ezmlm
Precedence: bulk
List-Id: <gdb.sourceware.org>
List-Subscribe: <mailto:gdb-subscribe@sourceware.org>
List-Archive: <http://sourceware.org/ml/gdb/>
List-Post: <mailto:gdb@sourceware.org>
List-Help: <mailto:gdb-help@sourceware.org>, <http://sourceware.org/ml/#faqs>
Sender: gdb-owner@sourceware.org
Received: (qmail 99128 invoked by uid 89); 10 Apr 2015 12:31:52 -0000
Authentication-Results: sourceware.org; auth=none
X-Virus-Found: No
X-Spam-SWARE-Status: No, score=-3.5 required=5.0 tests=AWL,BAYES_00,KAM_ASCII_DIVIDERS,SPF_HELO_PASS,SPF_PASS,T_RP_MATCHES_RCVD autolearn=no 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; Fri, 10 Apr 2015 12:31:51 +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 F03F18E707;	Fri, 10 Apr 2015 12:31:49 +0000 (UTC)
Received: from host1.jankratochvil.net (ovpn-116-27.ams2.redhat.com [10.36.116.27])	by int-mx09.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id t3ACVjkT009274	(version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO);	Fri, 10 Apr 2015 08:31:48 -0400
Date: Fri, 10 Apr 2015 12:31:00 -0000
From: Jan Kratochvil <jan.kratochvil@redhat.com>
To: gcc@gcc.gnu.org
Cc: Phil Muldoon <pmuldoon@redhat.com>, Tom Tromey <tom@tromey.com>,        gdb@sourceware.org
Subject: [gcc libcc1] build_qualified_type for self-referencing/incomplete types
Message-ID: <20150410123145.GA18073@host1.jankratochvil.net>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
User-Agent: Mutt/1.5.23 (2014-03-12)
X-IsSubscribed: yes
X-SW-Source: 2015-04/txt/msg00023.txt.bz2

Hi,

[compile] cv-qualified self-references crash
https://sourceware.org/bugzilla/show_bug.cgi?id=18202
------------------------------------------------------------------------------
cat >1.c <<EOH
// b tree.c:build_qualified_type
// p TYPE_SIZE (type)
volatile struct sv { volatile struct sv *p; } sv; // CRASH: compile code sv.p
= &sv;
volatile struct s { int i; } s, *sp; // OK: compile code sp = &s;
int main(void) { return 0; }
EOH
gcc -o 1 1.c -Wall -g; gdb ./1 -ex start -ex 'compile code sv.p = &sv'
------------------------------------------------------------------------------
gdb command line:1:1: internal compiler error: Segmentation fault
0xd901f4 crash_signal
	../../gccgitatsign/gcc/toplev.c:383
0x714941 c_incomplete_type_error(tree_node const*, tree_node const*)
	../../gccgitatsign/gcc/c/c-typeck.c:282
0x71d4ff build_component_ref(unsigned int, tree_node*, tree_node*)
	../../gccgitatsign/gcc/c/c-typeck.c:2304
[...]
------------------------------------------------------------------------------

The problem is GDB calls build_qualified_type() for that 'volatile' when
constructing the 'p' field while 'struct sv' is still incomplete that time.
That is at build_qualified_type() there is COMPLETE_TYPE_P(type)==false.
But build_qualified_type() create a copy of (not reference to) the type so
after 'struct sv' gets finished its 'p' still points to an incomplete type.

What is the recommended fix?  I expect pointer to a declaration / opaque type
which gets completed only when one references the 'p' field later?

GDB currently does not fill in TYPE_NAME as it references all the types by
their addresses.  So I guess GDB needs to start filling in TYPE_NAME at least
for RECORD_TYPEs and probably UNION_TYPEs.


Thanks,
Jan