From: Jakub Jelinek <jakub@redhat.com>
To: Richard Biener <rguenther@suse.de>
Cc: "Martin Liška" <mliska@suse.cz>, gcc-patches@gcc.gnu.org
Subject: Re: [RFC PATCH] Fix pointer diff (was: -fsanitize=pointer-overflow support (PR sanitizer/80998))
Date: Wed, 21 Jun 2017 15:17:00 -0000 [thread overview]
Message-ID: <20170621151722.GS2123@tucnak> (raw)
In-Reply-To: <20170621144001.GR2123@tucnak>
On Wed, Jun 21, 2017 at 04:40:01PM +0200, Jakub Jelinek wrote:
> So, I wrote following patch to do the subtraction in unsigned
> type. It passes bootstrap, but on both x86_64-linux and i686-linux
> regresses:
> +FAIL: gcc.dg/torture/pr66178.c -O* (test for excess errors)
> +FAIL: gcc.dg/tree-ssa/cmpexactdiv-2.c scan-tree-dump-not optimized "minus_expr"
> +FAIL: g++.dg/tree-ssa/pr21082.C -std=gnu++* (test for excess errors)
Another option is to do what the patch does only when sanitizing and accept
in that case less efficient code and rejection of weird corner case
testcases like the first one. We risk miscompilation of the pointer
differences, but I haven't managed to come up with a testcase where it would
show (I guess more likely is when we propagate constants into the pointers).
Jakub
next prev parent reply other threads:[~2017-06-21 15:17 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-19 18:25 [RFC PATCH] -fsanitize=pointer-overflow support (PR sanitizer/80998) Jakub Jelinek
2017-06-20 7:41 ` Richard Biener
2017-06-20 8:14 ` Jakub Jelinek
2017-06-20 8:18 ` Richard Biener
2017-06-21 7:58 ` Jakub Jelinek
2017-06-21 8:04 ` Richard Biener
2017-06-21 14:40 ` [RFC PATCH] Fix pointer diff (was: -fsanitize=pointer-overflow support (PR sanitizer/80998)) Jakub Jelinek
2017-06-21 15:17 ` Jakub Jelinek [this message]
2017-06-21 16:27 ` Marc Glisse
2017-06-22 8:31 ` Richard Biener
2017-06-22 9:29 ` Marc Glisse
2017-06-22 9:46 ` Richard Biener
2017-07-01 16:41 ` Marc Glisse
2017-07-03 12:37 ` Richard Biener
2017-10-09 11:01 ` Marc Glisse
2017-10-19 15:11 ` Richard Biener
2017-10-28 13:04 ` Marc Glisse
2017-10-28 17:13 ` Richard Biener
2017-07-04 8:53 ` [RFC PATCH] -fsanitize=pointer-overflow support (PR sanitizer/80998) Jakub Jelinek
2017-06-21 8:00 ` Jakub Jelinek
2017-06-21 8:05 ` Richard Biener
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