From owner-freebsd-current  Wed Nov 25 12:38:22 1998
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
Received: (from majordom@localhost)
          by hub.freebsd.org (8.8.8/8.8.8) id MAA08333
          for freebsd-current-outgoing; Wed, 25 Nov 1998 12:38:22 -0800 (PST)
          (envelope-from owner-freebsd-current@FreeBSD.ORG)
Received: from ns.mt.sri.com (sri-gw.MT.net [206.127.105.141])
          by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id MAA08157
          for <current@FreeBSD.org>; Wed, 25 Nov 1998 12:38:19 -0800 (PST)
          (envelope-from nate@mt.sri.com)
Received: from mt.sri.com (rocky.mt.sri.com [206.127.76.100])
	by ns.mt.sri.com (8.8.8/8.8.8) with SMTP id NAA09604
	for <current@FreeBSD.org>; Wed, 25 Nov 1998 13:38:11 -0700 (MST)
	(envelope-from nate@rocky.mt.sri.com)
Received: by mt.sri.com (SMI-8.6/SMI-SVR4)
	id NAA10234; Wed, 25 Nov 1998 13:38:11 -0700
Date: Wed, 25 Nov 1998 13:38:11 -0700
Message-Id: <199811252038.NAA10234@mt.sri.com>
From: Nate Williams <nate@mt.sri.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
To: current@FreeBSD.ORG
Subject: FWD: src/lib/libc/quad/moddi3.c broken!
X-Mailer: VM 6.34 under 19.16 "Lille" XEmacs Lucid
Sender: owner-freebsd-current@FreeBSD.ORG
Precedence: bulk
X-Loop: FreeBSD.ORG

Keith White just fixed a bug in the JDK that turned out to be a bug in
the libc source code.  It's not normally seen because the version in
libgcc.a works, and is used before the libc version.
------- start of forwarded message -------
From: Keith White <Keith.White@site.uottawa.ca>
Date: Wed, 25 Nov 1998 15:05:50 -0500 (EST)

> You're a God!  How did you figure this out?  I kept writing trivial
> programs and couldn't figure out what was going on, since all of my
> trivial programs behaved correctly.

For the curious:

I first did 'nm -op /usr/lib/*.a | egrep moddi3'.  This gave
libc.a and libgcc.a.  I then compared the source for the two
versions.  The version in /usr/src/lib/libc/quad/moddi3.c looked a
little suspicious. To verify the problem, I built the following test
program:

---
main() {
        long long a, b, c, d;
        a = -12L; b = -5L;
        c = a % b;
        d = a - (a / b) * b;

        printf("long long '%%' %s\n", (c == d) ? "passed" : "failed");
}
---
like this:
	cc -o remtest remtest.c
	./remtest
	long long '%' passed

	cc -c remtest.c
	ld -r -o x.o remtest.o -lc
	cc -o remtest x.o
	./remtest
	long long '%' failed

Then I was convinced there was a problem with libc.  Then a
	find javasrc/build -name '*.o' | xargs nm -op | egrep moddi3
gave me the likely candidates in the jdk build tree.  The most
critical one being in java/java.  Quick check of the GNUmakefile
showed '-lc'...

I suppose this might actually be a true bug with libc.

...keith
-- 
Keith White, EITI/SITE, University of Ottawa
kwhite@site.uottawa.ca [+1 613 562 5800 x6681] FAX [+1 613 562 5187]


------- end of forwarded message -------

To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-current" in the body of the message