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Date: Thu, 19 Jun 1997 20:53:46 -0500 (EST)
From: John Fieber <jfieber@indiana.edu>
Reply-To: John Fieber <jfieber@indiana.edu>
To: brian@awfulhak.org, brian@utell.co.uk
cc: jmz@FreeBSD.ORG, freebsd-hackers@FreeBSD.ORG
Subject: realloc() quirk (was: Re: xperfmon++ problem (again))
In-Reply-To: <199706191725.SAA00390@utell.co.uk>
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On Thu, 19 Jun 1997, Brian Somers wrote:

[Way to many quotes to get straight, so I won't even try.]

> >>>> > Sorry. I was doing this from memory. The message was
> >>>> >
> >>>> >       Error: Cannot perform realloc
> >>>> 
> >>>> Well, i was checking all ``Cannot'' messages in the source, and none
> >>>> didn't come close to what you've mentioned.

[snip]

> >>> [pozzo:/usr/home/mefoster] strings /usr/X11R6/lib/libXt.so.6.0 | grep
> >>> perform
> >>> Cannot perform %s

[snip]

> >> Ouch.  I just built XFree86-3.3, and I'm now getting this from knews.
> >> I rebuilt knews too - no change.
> >> 
> >> It happens just after I press the post key !!!!!!

[snip]

> > Well, xc/lib/Xt/Alloc.c does the realloc (in function XtRealloc).
> > I changed the diagnostic so that it says how much we're allocating,
> > and it comes out as zero !  Ah ha !

[snip]

> > Now this is *really* bad news AFAIK.  X provides the following in
> > FreeBSD.cf:
> > #define Malloc0ReturnsNull      NO

[snip]

> FWIW, this is the patch - it solves my knews problem, but isn't
> *really* the right answer :|  Copy it to
> /usr/ports/x11/XFree86/patches/patch-af, and just "make".

The problem is that malloc(0) and realloc(ptr, 0) behave
differently but X assumes they behave the same.  This was fixed
recently in -current but phk has not (that I noticed) committed
it to RELENG_2_2.  However, I grabbed malloc.c from -current and
re-built my 2.2.1 libc and both knews and xperfmon++ work fine.

I think this is a pretty important thing to get fixed in
RELENG_2_2.  It might even be worthwhile to make updated copies
of libc available to people who can't easily upgrade or rebuild
their libc.

-john