Jacques Caron wrote:
> Hi,
>
> At 14:40 12/06/2008, Cyril SCETBON wrote:
>> I've tested it on the host and did not get any error with a negative 
>> value or a big value :
>>
>> cat test_malloc.c
>>
>> #include <stdlib.h>
>> #include <stdio.h>
>>
>> int main()
>> {
>>        printf("malloc(-4096)\n");
>>        malloc(-4096);
>>        printf("malloc(18446744073709547520)\n");
>>        malloc(18446744073709547520);
>>        return 0;
>> }
>>
>> cc -g -w test_malloc.c -o test_malloc
>>
>> ./test_malloc
>> malloc(-4096)
>> malloc(18446744073709547520)
>>
>> no segmentation fault
>
> Quite normal, the malloc itself won't cause a segfault, it's the fact 
> that something later uses space requested via malloc that couldn't be 
> allocated (malloc then returned 0). What's the return value of the 
> malloc calls?
malloc returns NULL in the both cases
>
>> , and the strace command shows :
>>
>> write(1, "malloc(-4096)\n", 14malloc(-4096)
>> )         = 14
>> brk(0)                                  = 0x501000
>> brk(0x521000)                           = 0x521000
>> mmap(NULL, 2097152, PROT_NONE, 
>> MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0) = 0x2b78f91d1000
>> munmap(0x2b78f91d1000, 192512)          = 0
>> munmap(0x2b78f9300000, 856064)          = 0
>> mprotect(0x2b78f9200000, 131072, PROT_READ|PROT_WRITE) = 0
>> mmap(NULL, 2097152, PROT_NONE, 
>> MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0) = 0x2b78f9300000
>> munmap(0x2b78f9400000, 1048576)         = 0
>> mprotect(0x2b78f9300000, 131072, PROT_READ|PROT_WRITE) = 0
>> munmap(0x2b78f9300000, 1048576)         = 0
>> write(1, "malloc(18446744073709547520)\n", 
>> 29malloc(18446744073709547520)
>> ) = 29
>> mmap(NULL, 2097152, PROT_NONE, 
>> MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0) = 0x2b78f9300000
>> munmap(0x2b78f9400000, 1048576)         = 0
>> mprotect(0x2b78f9300000, 131072, PROT_READ|PROT_WRITE) = 0
>> munmap(0x2b78f9300000, 1048576)         = 0
>> munmap(0x2b78f8e94000, 4096)            = 0
>> exit_group(0)                           = ?
>> Process 15518 detached
>
> - you'll notice that the mmap calls are the same for both calls (don't 
> quite know what malloc is really doing here, it seems to be allocating 
> more space then freeing up bits, probably trying to align on some 
> large size), though neither size matches the actual request (?)
ok
>
> - the malloc-induced mmap is quite different from the one in your 
> original strace (see the flags). Is that the same box? 
It's the same host
> You must have some special compile flags or libraries in your slonik 
> compile that change malloc's behaviour. Was your slony-1 install 
> locally compiled or installed from binaries?
packaged (debian) from sources :

cc -g -Wall -O2 -Wall -Wmissing-prototypes -Wmissing-declarations 
-I../.. -DPGSHARE="\"/usr/share/slony1\""  -I/usr/incl
ude/postgresql/8.2/server/ -I/usr/include/postgresql/  -c -o slonik.o 
slonik.c
cc -g -Wall -O2 -Wall -Wmissing-prototypes -Wmissing-declarations 
-I../.. -DPGSHARE="\"/usr/share/slony1\""  -I/usr/incl
ude/postgresql/8.2/server/ -I/usr/include/postgresql/  -c -o dbutil.o 
dbutil.c
cc -g -Wall -O2 -Wall -Wmissing-prototypes -Wmissing-declarations 
-I../.. -DPGSHARE="\"/usr/share/slony1\""  -I/usr/incl
ude/postgresql/8.2/server/ -I/usr/include/postgresql/  -c -o parser.o 
parser.c
> If the latter you might want to try a good old wget/tar/configure/make 
> to see if the result is the same...
>
> Jacques.
>

-- 
Cyril SCETBON - Ingénieur bases de données
AUSY pour France Télécom - OPF/PORTAILS/DOP/HEBEX

Tél : +33 (0)4 97 12 87 60
Jabber : cscetbon at jabber.org
France Telecom - Orange
790 Avenue du Docteur Maurice Donat 
Bâtiment Marco Polo C2 - Bureau 202
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France

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