Date: Wed, 23 Jul 2003 18:48:46 -0400 From: Barney Wolff <barney@databus.com> To: Darryl Okahata <darrylo@soco.agilent.com> Cc: Gabor <gabor@vmunix.com> Subject: Re: malloc does not return null when out of memory Message-ID: <20030723224846.GB26555@pit.databus.com> In-Reply-To: <200307232222.PAA26360@mina.soco.agilent.com> References: <20030723221336.GA26555@pit.databus.com> <200307232222.PAA26360@mina.soco.agilent.com>
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On Wed, Jul 23, 2003 at 03:22:30PM -0700, Darryl Okahata wrote:
> Barney Wolff <barney@databus.com> wrote:
>
> > Shouldn't malloc return 0 when out of memory rather than returning
> > an address that won't work? I believe that was the complaint. Presumably
> > having NO_SWAPPING has something to do with it, but filling the swap
> > might well do the same thing.
>
> Well, it goes against the man page, but FreeBSD typically never
> returns NULL [*] when you run out of VM. It's been this way for YEARS.
>
> [*] -- Yes, it's annoying as h*ll, but that's the way it works. I
> thought that there was a FAQ or handbook entry on this, but I
> couldn't find any.
This test prog appears to work correctly:
#include <stdio.h>
main() {
char *p;
int i=0;
while (p=(char*)malloc(102400)) {
*p = i;
fprintf(stderr,"Ok after %d mallocs\n",++i);
}
fprintf(stderr,"Malloc returned 0 after %d calls\n",i);
exit(0);
}
FreeBSD pit.databus.com 4.8-STABLE FreeBSD 4.8-STABLE #0: Tue Jul 8 23:22:41 EDT 2003 toor@pit.databus.com:/usr/obj/usr/src/sys/PIT i386
ulimit -a says my data limit is 524288 KB, and the test says:
Malloc returned 0 after 5242 calls
When I ulimit -v 20000, malloc returns 0 after 191 calls.
So I believe things work correctly on my host, which does have swap although
the test does not use it.
--
Barney Wolff http://www.databus.com/bwresume.pdf
I'm available by contract or FT, in the NYC metro area or via the 'Net.
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