NetBSD Problem Report #51893

From www@NetBSD.org  Sun Jan 15 21:29:47 2017
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Date: Sun, 15 Jan 2017 21:29:41 +0000 (UTC)
From: yaneurabeya@gmail.com
Reply-To: yaneurabeya@gmail.com
To: gnats-bugs@NetBSD.org
Subject: [PATCH] tests/lib/libc/ssp/h_memset: prevent toolchain from optimizing out memset call
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>Number:         51893
>Category:       bin
>Synopsis:       [PATCH] tests/lib/libc/ssp/h_memset: prevent toolchain from optimizing out memset call
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    bin-bug-people
>State:          closed
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Jan 15 21:30:01 +0000 2017
>Closed-Date:    Mon Jan 16 18:45:08 +0000 2017
>Last-Modified:  Mon Jan 16 18:45:08 +0000 2017
>Originator:     Ngie Cooper
>Release:        7.0.2
>Organization:
>Environment:
n/a
>Description:
Peter Holm (pholm@FreeBSD.org) discovered that h_memset's memset call was being compiled out by an earlier version of clang (3.3.x/3.4.x) -- this change uses the result of the memset (b[0]) to ensure that the call to memset isn't over ambitiously optimized out by the toolchain.

Submitted by: Peter Holm <pholm@FreeBSD.org>
>How-To-Repeat:

>Fix:

>Release-Note:

>Audit-Trail:
From: "Ngie Cooper (yaneurabeya)" <yaneurabeya@gmail.com>
To: gnats-bugs@NetBSD.org
Cc: 
Subject: Re: bin/51893: [PATCH] tests/lib/libc/ssp/h_memset: prevent toolchain
 from optimizing out memset call
Date: Sun, 15 Jan 2017 13:34:53 -0800

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 	charset=us-ascii

 Patch attached.
 -Ngie

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 	filename=h_memset-return-b_0-to-prevent-memset-optimization.patch
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 Index: lib/libc/ssp/h_memset.c
 ===================================================================
 RCS file: /cvsroot/src/tests/lib/libc/ssp/h_memset.c,v
 retrieving revision 1.1
 diff -u -r1.1 h_memset.c
 --- lib/libc/ssp/h_memset.c	27 Dec 2010 02:04:19 -0000	1.1
 +++ lib/libc/ssp/h_memset.c	15 Jan 2017 21:27:18 -0000
 @@ -41,5 +41,5 @@
  	char b[10];
  	size_t len =  atoi(argv[1]);
  	(void)memset(b, 0, len);
 -	return 0;
 +	return b[0]; /* keeps optimizer from zapping the call to memset() */
  }

 --Apple-Mail=_4FC2B394-64E4-4066-A7B5-FBCDED173B3C--

From: "Christos Zoulas" <christos@netbsd.org>
To: gnats-bugs@gnats.NetBSD.org
Cc: 
Subject: PR/51893 CVS commit: src/tests/lib/libc/ssp
Date: Mon, 16 Jan 2017 11:34:24 -0500

 Module Name:	src
 Committed By:	christos
 Date:		Mon Jan 16 16:34:24 UTC 2017

 Modified Files:
 	src/tests/lib/libc/ssp: h_memset.c

 Log Message:
 PR/51893: Ngie Cooper: prevent toolchain from optimizing out memset call


 To generate a diff of this commit:
 cvs rdiff -u -r1.1 -r1.2 src/tests/lib/libc/ssp/h_memset.c

 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.

State-Changed-From-To: open->closed
State-Changed-By: snj@NetBSD.org
State-Changed-When: Mon, 16 Jan 2017 18:45:08 +0000
State-Changed-Why:
christos committed it. thanks!


>Unformatted:

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