Date: Mon, 6 Apr 2015 21:40:07 +0200 From: Olivier Houchard <mlfbsd@ci0.org> To: Rui Paulo <rpaulo@me.com> Cc: freebsd-arm@freebsd.org Subject: Re: remove broken lib/libc/arm/string/memcpy_xscale.S Message-ID: <20150406194007.GA64433@ci0.org> In-Reply-To: <3427080.JV46itjP9L@akita> References: <20150405015245.GO51048@funkthat.com> <20150406171248.GV51048@funkthat.com> <20150406174130.GA63423@ci0.org> <3427080.JV46itjP9L@akita>
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On Mon, Apr 06, 2015 at 11:32:25AM -0700, Rui Paulo wrote: > On Monday 06 April 2015 19:41:30 Olivier Houchard wrote: > > On Mon, Apr 06, 2015 at 10:12:48AM -0700, John-Mark Gurney wrote: > > > Warner Losh wrote this message on Mon, Apr 06, 2015 at 09:58 -0600: > > > > > On Apr 4, 2015, at 7:52 PM, John-Mark Gurney <jmg@funkthat.com> wrote: > > > > > > > > > > I would like to remove this file as it does not implement our defined > > > > > memcpy. Per POSIX, overlapping regions passed to memcpy is undefined > > > > > behavior. We have defined it to have the same symatics as memmove. > > > > > > > > > > Sample test program: > > > > > #include <stdio.h> > > > > > #include <string.h> > > > > > > > > > > char bufa[512] = "this is a test buffer that should be copied fine."; > > > > > int > > > > > main() > > > > > { > > > > > > > > > > memcpy(&bufa[10], &bufa[0], strlen(&bufa[10])); > > > > > printf("%s\n", bufa); > > > > > > > > > > return 0; > > > > > > > > > > } > > > > > > > > > > Output on amd64 HEAD: > > > > > this is a this is a test buffer that should be co > > > > > > > > > > Output on old armv4 from 9.x: > > > > > this is a this is a thst buffethst bufhould beufh > > > > > > > > > > If you just look at the file, it is clear that the implementation does > > > > > not adjust the copy direction based upon pointers. We imported the > > > > > code from NetBSD, and NetBSD does apparently require memcpy's > > > > > arguments > > > > > to be non-overlapping. > > > > > > > > > > I'll remove the file shortly unless someone can prove to me that all > > > > > uses of memcpy in our tree do not depend upon our defined behavior > > > > > per memcpy(3)'s man page. > > > > > > > > Any chance you can fix this implementation instead? > > > > > > I don't know arm assembly well enough, nor do I have the time to fix > > > it.. I am willing to test any implementations as I have access to > > > hardware... > > > > > > I guess I should add a test to verify that memcpy behavese like memmove > > > to our test suite... > > > > I think the bug is in the manpage, not the code, and we should fix it the > > way NetBSD did. > > Our implementation of memcpy() allows strings to overlap, so we really > shouldn't be special-casing armv4. > Any use of memcpy() with overlapping strings is a bug, I fail to see why we should make any effort to make it work. Olivier
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