From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Eli Zaretskii Newsgroups: gmane.emacs.devel Subject: Re: gdb doesn't print Lisp backtrace in some circumstances. Date: Fri, 12 Apr 2024 14:11:04 +0300 Message-ID: <86pluusunr.fsf@gnu.org> References: Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="36025"; mail-complaints-to="usenet@ciao.gmane.io" Cc: emacs-devel@gnu.org To: Alan Mackenzie Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Fri Apr 12 13:12:15 2024 Return-path: Envelope-to: ged-emacs-devel@m.gmane-mx.org Original-Received: from lists.gnu.org ([209.51.188.17]) by ciao.gmane.io with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1rvEpK-0009C0-Ii for ged-emacs-devel@m.gmane-mx.org; Fri, 12 Apr 2024 13:12:14 +0200 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rvEoI-0001Sg-SP; Fri, 12 Apr 2024 07:11:10 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rvEoG-0001SJ-Lw for emacs-devel@gnu.org; Fri, 12 Apr 2024 07:11:08 -0400 Original-Received: from fencepost.gnu.org ([2001:470:142:3::e]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rvEoF-0006GM-Pm; Fri, 12 Apr 2024 07:11:07 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=gnu.org; s=fencepost-gnu-org; h=References:Subject:In-Reply-To:To:From:Date: mime-version; bh=CV88SEgNJlJLZBYrEKu35OH16JYSSm5IOMimrTwajuw=; b=YvU0ZNxIxtoa 3Es4fI01HLmqNpr1sgdnNuBe4WaT1jZdVcbbOCokgtRvi7ekTSVV18PGkEeKEjzeV7SQcSCnj2/5f /kARAljVre4pYtNeYDmxl9B4bvmwEbJWrRuGF0LHzYrscjOAFo5W8DX6/4yOvBSdbpTMggVnWG2p0 0knQtPeXN6NPhKFr3qYY8L7+CMwT8aYpb4U8lNQKv4GN/7ScmJXmNZBhP/xghRFXc5WIejks4OPNg vsVC4aSpkAPaqGXSFdfuo+L1kQ7lIP5e2tWrwFVlFe2X/9cQpqVkitRkreezCgRLKeCcIB5E1AERu aXKvnNK64jfCXs7WJKyoiQ==; In-Reply-To: (message from Alan Mackenzie on Fri, 12 Apr 2024 10:31:53 +0000) X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Original-Sender: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Xref: news.gmane.io gmane.emacs.devel:317689 Archived-At: > Date: Fri, 12 Apr 2024 10:31:53 +0000 > From: Alan Mackenzie > > Yesterday I got a core dump from a segmentation fault in Emacs (my > development version, not master). I loaded this into gdb inside Emacs > to have a look at it. > > The backtrace command output the C data as it should, but on coming to > the Lisp backtrace gave an error message about there needing to be a > process running to "do this". (I don't have the exact message any > more.) It would seem these fancy Lisp facilities only work when the > process that produced them is still running. Yes, because they call functions inside Emacs to format Lisp objects. > All the information required to produce this Lisp backtrace is present > in the core dump. Would it be possible, perhaps, to modify our .gdbinit > to use the running Emacs to process the core dump, or something like > that? I don't think so, no. But you can reproduce the Lisp backtrace manually (albeit tediously, by going over all the calls to Ffuncall, eval_sub and suchlikes, and displaying their arg[0]. If it's a symbol, typing xsymbol should show you the Lisp function being called. If it is not a symbol, you could use xcar/xcdr etc., but that is much more tedious, and I usually give up on those frames in the stack.