From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 44248 invoked by alias); 16 Dec 2016 13:07:13 -0000 Mailing-List: contact gdb-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-owner@sourceware.org Received: (qmail 44087 invoked by uid 89); 16 Dec 2016 13:07:11 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-5.0 required=5.0 tests=BAYES_00,RP_MATCHES_RCVD,SPF_HELO_PASS autolearn=ham version=3.3.2 spammy=bbc, UD:c.d, Hx-languages-length:1858, Oops 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 ESMTP; Fri, 16 Dec 2016 13:07:01 +0000 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 263C23F3C0; Fri, 16 Dec 2016 13:07:00 +0000 (UTC) Received: from host1.jankratochvil.net (ovpn-204-40.brq.redhat.com [10.40.204.40]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id uBGD6jH6028881 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Fri, 16 Dec 2016 08:06:58 -0500 Date: Fri, 16 Dec 2016 13:07:00 -0000 From: Jan Kratochvil To: Jonathan Wakely Cc: libstdc++@gcc.gnu.org, gcc-patches@gcc.gnu.org, Keith Seitz , Pedro Alves , gdb@sourceware.org Subject: Re: [PATCH] PR59170 make pretty printers check for singular iterators Message-ID: <20161216130645.GA27556@host1.jankratochvil.net> References: <20161215141817.GA22699@redhat.com> <20161215211903.GA22897@host1.jankratochvil.net> <20161216010707.GF22266@redhat.com> <20161216075136.GA21305@host1.jankratochvil.net> <20161216123352.GB895@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161216123352.GB895@redhat.com> User-Agent: Mutt/1.7.1 (2016-10-04) X-IsSubscribed: yes X-SW-Source: 2016-12/txt/msg00025.txt.bz2 On Fri, 16 Dec 2016 13:33:52 +0100, Jonathan Wakely wrote: > We don't do auto-deref for std::shared_ptr or std::unique_ptr, even > though we know the object they point to definitely is live and safe to > access, and that's because those types have pointer semantics not > reference semantics. This is wrong std::shared_ptr or std::unique_ptr is not auto-dereferenced for GDB printing. But it may be more a GDB problem, not libstdc++ pretty printers problem. For example glib pretty printers already auto-dereference data structures: 5 GList* list = NULL; (gdb) p/r list $1 = (GList *) 0x607a00 (gdb) p list $2 = 0x607a00 = {0x400810} /usr/share/glib-2.0/gdb/glib.py if type.code == gdb.TYPE_CODE_PTR: type = type.target().unqualified() t = str(type) if t == "GList": return GListPrinter(val, "GList") But that is more a GDB bug that should be solved even for generic pointers. Currently while traversing through data structures one has to randomly add or remove '*' from the beginning of the GDB print expression: 1 class E { int a[1000]; int i=42; } ee; 2 class D { E *e=ⅇ } dd; 3 class C { D &d=dd; } cc; 4 class B { C *c=&cc; } bb; 5 int main() {} (gdb) p bb $1 = {c = 0x601030 } (gdb) p bb.c $2 = (C *) 0x601030 Oops, I need to add a dereference: (gdb) p *bb.c $3 = {d = @0x601028} (gdb) p *bb.c.d No symbol "operator*" in current context. Oops, I need to remove a dereference: (gdb) p bb.c.d $4 = (D &) @0x601028: {e = 0x601060 } (gdb) p bb.c.d.e $5 = (E *) 0x601060 Oops, I need to add a dereference: (gdb) p *bb.c.d.e $6 = {a = {0 }, i = 42} (gdb) p *bb.c.d.e.i Cannot access memory at address 0x2a Oops, I need to remove a dereference: (gdb) p bb.c.d.e.i $7 = 42 This is probably solved in some clickable front-end interfaces. Jan