Date: Wed, 3 Apr 1996 11:34:51 +0200 (MET DST) From: Luigi Rizzo <luigi@labinfo.iet.unipi.it> To: cracauer@wavehh.hanse.de Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: phkmalloc and buggy sw... Message-ID: <199604030934.LAA01484@labinfo.iet.unipi.it> In-Reply-To: <9604030928.AA14346@wavehh.hanse.de> from "Martin Cracauer" at Apr 3, 96 11:28:07 am
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> >It happened to me twice now... I have some software which intermixes
> >printf() and putchar(), and since the switch to phkmalloc it coredumps
> >at times on the putchar() call.
>
> >Just for the records... I can't tell if there is something terribly
> >wrong in my program or it is putchar which must be fixed. I solve the
> >problem by replacing putchar('\n') with printf("\n"), and it doesn't
> >coredump anymore.
>
> I'm running a NetBSD-1.1B/i386 with phkmalloc and would really
> appreciate it when you could send me a test program that fails on your
> machine. Looks like a bug in libc for me, not in phkmalloc. I would be
I am afraid I have not saved the buggy program (it was the driver
for a PIC programmer, I needed it working and was in a hurry), and
I am unable to reproduce the problem now. The coredump was down in
__vprintf... or something like this, from memory.
Poul also suggests that it is a bug in libc, I tend to agree with this.
I'll try to do my best to reproduce the bug, I believe it was related
to the use of printf/putchar/puts.
> interested to see how the normal malloc could get around without
> dumping core.
It's probably because the normal malloc locates the memory block
descriptors farther away from the data block. Thus, small overflows
(say a few bytes beyond the allocated area) are not noticed, as
opposed to the case of phkmalloc which probably does more strict
consistency checks.
Hope this helps
Luigi
====================================================================
Luigi Rizzo Dip. di Ingegneria dell'Informazione
email: luigi@iet.unipi.it Universita' di Pisa
tel: +39-50-568533 via Diotisalvi 2, 56126 PISA (Italy)
fax: +39-50-568522 http://www.iet.unipi.it/~luigi/
====================================================================
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