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From: "law at redhat dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug other/17437] [4.0 Regression] obscure GC problem Date: Tue, 14 Sep 2004 19:19:00 -0000 [thread overview] Message-ID: <20040914191906.8187.qmail@sourceware.org> (raw) In-Reply-To: <20040912151302.17437.steven@gcc.gnu.org> ------- Additional Comments From law at redhat dot com 2004-09-14 19:19 ------- Subject: Re: [4.0 Regression] obscure GC problem On Tue, 2004-09-14 at 13:07, Diego Novillo wrote: > On Tue, 2004-09-14 at 11:31, Jeffrey A Law wrote: > > > What doesn't make sense to me is that the dataflow information isn't > > attached to SSA_NAMEs, it's attached to statement nodes and PHIs. > > So at least that part of my analysis is faulty. > > > Because SSA_NAMEs store their defining statement in tree.common.chain > and gt_ggc_mx_lang_tree_node jumps from the SSA_NAME into its defining > statement. From there, we start traversing the statement's DU chains > and end up in a statement whose basic block has been ggc_free'd already > by cfg.c:expunge_block. Which is part of the reason why I think sprinkling ggc_free calls around is generally a bad idea. While we may think we know the lifetime of some object, it's bloody easy to miss some pointer pointing into the object keeping it live. > > This allows me to go past this failure and go into stage3, but I think > the real issue may be that somebody is holding on to DU chains too long. Agreed. > I don't know what the right approach would be here. Force people to > always flush out DU chains? Maybe. But then, why put these things on > GC memory to begin with? Well, IMHO the ggc_free is bogus and we need to fix whatever code forgot to call free_df. jeff -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17437
next prev parent reply other threads:[~2004-09-14 19:19 UTC|newest] Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top 2004-09-12 15:13 [Bug other/17437] New: " steven at gcc dot gnu dot org 2004-09-12 15:14 ` [Bug other/17437] " steven at gcc dot gnu dot org 2004-09-12 17:30 ` graham dot stott at btinternet dot com 2004-09-12 17:30 ` [Bug other/17437] New: " Graham Stott 2004-09-12 17:35 ` [Bug other/17437] " pinskia at gcc dot gnu dot org 2004-09-14 3:12 ` [Bug other/17437] [4.0 Regression] " pinskia at gcc dot gnu dot org 2004-09-14 5:36 ` pinskia at gcc dot gnu dot org 2004-09-14 6:23 ` steven at gcc dot gnu dot org 2004-09-14 6:25 ` stevenb at suse dot de 2004-09-14 15:31 ` law at redhat dot com 2004-09-14 19:07 ` dnovillo at redhat dot com 2004-09-14 19:19 ` law at redhat dot com [this message] 2004-09-14 19:48 ` law at redhat dot com 2004-09-15 4:31 ` pinskia at gcc dot gnu dot org 2004-10-12 13:03 ` pinskia at gcc dot gnu dot org 2004-10-14 16:10 ` stevenb at novell dot com 2004-10-14 16:30 ` pinskia at gcc dot gnu dot org
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