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From: "vries at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/61964] [4.8/4.9/4.10 regression] krb5 database propagation enters infinite loop; reduced test case Date: Thu, 31 Jul 2014 12:20:00 -0000 [thread overview] Message-ID: <bug-61964-4-HA9awTueay@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-61964-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61964 vries at gcc dot gnu.org changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |vries at gcc dot gnu.org --- Comment #8 from vries at gcc dot gnu.org --- Using this patch on the example from the description field, I can modify the example on the command line: ... $ diff -u bug-orig.c bug-mod.c --- bug-orig.c 2014-07-31 14:00:50.663275717 +0200 +++ bug-mod.c 2014-07-31 14:01:49.403276412 +0200 @@ -11,7 +11,7 @@ struct node *n = head->first; struct head *h = &heads[k]; - if (n->prev == (void *)h) + if (FORCE n->prev == (void *)h) h->first = n->next; else n->prev->next = n->next; ... 1. -DFORCE="" gives the original 2. -DFORCE="1 ||" forces the condition to true 3. -DFORCE="0 &&" forces the confition to false In this experiment, we don't use tree-tail-merge: ... $ gcc -DFORCE="1 ||" bug-mod.c -O2 -fno-strict-aliasing -fno-tree-tail-merge && ./a.out ; echo $? 0 $ gcc -DFORCE="1 ||" bug-mod.c -O2 -fstrict-aliasing -fno-tree-tail-merge && ./a.out ; echo $? 0 $ gcc -DFORCE="0 &&" bug-mod.c -O2 -fno-strict-aliasing -fno-tree-tail-merge && ./a.out ; echo $? 0 $ gcc -DFORCE="0 &&" bug-mod.c -O2 -fstrict-aliasing -fno-tree-tail-merge && ./a.out ; echo $? 1 ... The last result seems to suggest that the example is not type-safe. My understanding is that the problem is in the line: n->prev->next = n->next; where we effectively do: /* ((struct node*)&heads[2])->next = node.next */ which is type-unsafe.
next prev parent reply other threads:[~2014-07-31 12:20 UTC|newest] Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top 2014-07-30 13:21 [Bug tree-optimization/61964] New: [4.8 " andersk at mit dot edu 2014-07-30 14:31 ` [Bug tree-optimization/61964] " ghudson at mit dot edu 2014-07-30 20:21 ` andersk at mit dot edu 2014-07-31 4:20 ` andersk at mit dot edu 2014-07-31 9:29 ` mikpelinux at gmail dot com 2014-07-31 9:48 ` schwab@linux-m68k.org 2014-07-31 10:05 ` [Bug tree-optimization/61964] [4.8/4.9/4.10 " rguenth at gcc dot gnu.org 2014-07-31 12:20 ` vries at gcc dot gnu.org [this message] 2014-07-31 12:24 ` rguenther at suse dot de 2014-07-31 14:07 ` rguenth at gcc dot gnu.org 2014-07-31 14:10 ` [Bug tree-optimization/61964] [4.8/4.9 " rguenth at gcc dot gnu.org 2014-07-31 17:09 ` vries at gcc dot gnu.org 2014-08-01 7:32 ` rguenth at gcc dot gnu.org 2014-08-01 7:36 ` rguenth at gcc dot gnu.org 2014-08-01 7:40 ` rguenth at gcc dot gnu.org 2014-08-01 8:17 ` rguenth at gcc dot gnu.org 2014-08-01 8:18 ` andersk at mit dot edu 2014-08-04 0:25 ` vries at gcc dot gnu.org 2014-08-18 8:38 ` vries at gcc dot gnu.org
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