If I request __stackavail() [1] it returns something slightly above 500K (I have qnx 6.3.2)

but ulimit says that stack is unlimited [2]

How can I increase stack size available for alloca?

Thanks a lot!

[1]
#include <alloca.h> 
main() {
int n = __stackavail();
printf("avail: %d\n", n);
}

[2]
bash-2.05a$ ulimit -a
core file size        (blocks, -c) unlimited
data seg size         (kbytes, -d) unlimited
file size             (blocks, -f) unlimited
max locked memory     (kbytes, -l) unlimited
max memory size       (kbytes, -m) unlimited
open files                    (-n) 1000
pipe size          (512 bytes, -p) 10
stack size            (kbytes, -s) unlimited
cpu time             (seconds, -t) unlimited
max user processes            (-u) unlimited
virtual memory        (kbytes, -v) unlimited