Date: Wed, 07 Apr 2004 14:39:53 +0200 From: Georges-Andre Silber <silber@cri.ensmp.fr> To: freebsd-amd64@freebsd.org Subject: malloc: bug or feature ? Message-ID: <4073F699.6010402@cri.ensmp.fr>
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Hello,
On my bi/opteron HDAMA workstation running FreeBSD 5.2-CURRENT AMD64
with 8GB RAM + 16GB Swap, I have a strange result for a test program I
wrote in C:
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#define ITEM 100000000L
int
main (int ac, char* av[])
{
unsigned long int memsize;
void *mem;
memsize = 0UL;
while (1) {
mem = malloc (ITEM);
assert (mem != NULL);
memsize += ITEM;
}
}
As you can see, I just call malloc() until it returns NULL. The problem
is that when total memory allocated reaches a value close to MAXDSIZE,
it leads to a 'segmentation fault'.
I ran the program through gdb:
-bash-2.05b$ gcc -g taille.c
-bash-2.05b$ ls
a.out taille.c
-bash-2.05b$ gdb a.out
GNU gdb 20040323 [FreeBSD]
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain
conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB. Type "show warranty" for details.
This GDB was configured as "x86_64-portbld-freebsd5.2"...
(gdb) run
Starting program: /home/silber/a.out
Program received signal SIGSEGV, Segmentation fault.
0x0000000200eec000 in ?? ()
(gdb) up
#1 0x0000000200681d79 in ldexp () from /lib/libc.so.5
(gdb) up
#2 0x00000002006821fd in ldexp () from /lib/libc.so.5
(gdb) up
#3 0x00000002006823e1 in ldexp () from /lib/libc.so.5
(gdb) up
#4 0x0000000200682789 in ldexp () from /lib/libc.so.5
(gdb) up
#5 0x0000000200682840 in malloc () from /lib/libc.so.5
(gdb) up
#6 0x00000000004006a9 in main (ac=1, av=0x7fffffffec38) at taille.c:12
12 mem = malloc (ITEM);
(gdb)
--------------------------------------------------------------------
tcsh> limit
cputime unlimited
filesize unlimited
datasize 8388608 kbytes
stacksize 524288 kbytes
coredumpsize unlimited
memoryuse unlimited
vmemoryuse unlimited
descriptors 11095
memorylocked unlimited
maxproc 5547
sbsize unlimited
tcsh> uname -a
FreeBSD surville.cri.ensmp.fr 5.2-CURRENT FreeBSD 5.2-CURRENT #2: Wed
Apr 7 13:20:40 CEST 2004
root@surville.cri.ensmp.fr:/usr/src/sys/amd64/compile/SURVILLE amd64
Is it a 'normal' behaviour of malloc()? Shouldn't malloc() return NULL?
Georges Silber.
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