Re: malloc peut retourner un pointeur nul

Oui il fait chaud, mais soyons joueur :

#include <stdlib.h>
#include <stdio.h>
int main()
{
 size_t L = (size_t)20*1024;
 char *str = malloc(L);
 printf("str=%p\n", str);
}

$ gcc maloq.c
$ size ./a.out 
 text data bss dec hex filename
 1617 608 8 2233 8b9 ./a.out
$ ulimit -a
core file size (blocks, -c) 0
data seg size (kbytes, -d) unlimited
scheduling priority (-e) 0
file size (blocks, -f) unlimited
pending signals (-i) 63452
max locked memory (kbytes, -l) 16384
max memory size (kbytes, -m) unlimited
open files (-n) 1024
pipe size (512 bytes, -p) 8
POSIX message queues (bytes, -q) 819200
real-time priority (-r) 0
stack size (kbytes, -s) 8192
cpu time (seconds, -t) unlimited
max user processes (-u) 63452
virtual memory (kbytes, -v) unlimited
file locks (-x) unlimited
$ ./a.out 
str=0x5577f3ab2260
# virtual memory
$ sh -c 'ulimit -v 1000 ; ./a.out'
Segmentation fault
(...)
$ sh -c 'ulimit -v 2359 ; ./a.out'
Segmentation fault
$ sh -c 'ulimit -v 2360 ; ./a.out'
./a.out: error while loading shared libraries: libc.so.6: failed to map segment from shared object
(...)
$ sh -c 'ulimit -v 4491 ; ./a.out'
./a.out: error while loading shared libraries: libc.so.6: failed to map segment from shared object
$ sh -c 'ulimit -v 4492 ; ./a.out'
str=(nil)
(...)
$ sh -c 'ulimit -v 4507 ; ./a.out'
str=(nil)
$ sh -c 'ulimit -v 4508 ; ./a.out'
str=0x560591527260
# stack size
$ sh -c 'ulimit -s 11 ; ./a.out'
Segmentation fault (core dumped)
$ sh -c 'ulimit -s 12 ; ./a.out'
str=0x55f97206f260
# data seg size
$ sh -c 'ulimit -d 19 ; ./a.out'
Segmentation fault
$ sh -c 'ulimit -d 20 ; ./a.out'
./a.out: error while loading shared libraries: libc.so.6: cannot create shared object descriptor: Cannot allocate memory
(..)
$ sh -c 'ulimit -d 27 ; ./a.out'
./a.out: error while loading shared libraries: libc.so.6: cannot create shared object descriptor: Cannot allocate memory
$ sh -c 'ulimit -d 28 ; ./a.out'
./a.out: error while loading shared libraries: libc.so.6: cannot map zero-fill pages
(...)
$ sh -c 'ulimit -d 51 ; ./a.out'
./a.out: error while loading shared libraries: libc.so.6: cannot map zero-fill pages
$ sh -c 'ulimit -d 52 ; ./a.out'
str=(nil)
(...)
$ sh -c 'ulimit -d 175 ; ./a.out'
str=(nil)
$ sh -c 'ulimit -d 176 ; ./a.out'
str=0x55b201c5a260