/*
 * Problem with stack limit per process. 
 * 	Bypass process stack limit quota from threads :) NICE! :-P
 *
 * Tested on FreeBSD 8.x/9.x
 *
 * Author: Michael Pounov <misho@elwix.org>
 *
 * cc -o pt -O2 -g -Wall pt.c -lpthread
 *
 * Test: ./pt [KBytes]
 * Example: ./pt 10000  # test with 10MB stack size per thread * 10 = 100MB total size
 * 				you may add and 100MB stack size per thread :):):)
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <pthread.h>
#include <sys/types.h>
#include <sys/resource.h>

void *
meow(void *slen)
{
	char *buf = (char*) &buf;

	buf = alloca(((size_t) slen) - sizeof(char*));
	printf("buf[%u]->%p\n", ((size_t) slen) - sizeof(char*), buf);
	fflush(stdout);
	if (!buf)
		printf("allocation with size %u failed #%d - %s\n", 
				(size_t) slen, errno, strerror(errno));
	else {
		memset(buf, '*', ((size_t) slen) - sizeof(char*));
		buf[((size_t) slen) - sizeof(char*) - 1] = 0;
		printf("successful allocated memory with %u bytes :) test print=%s\n", 
				(size_t) slen, buf + (((size_t) slen) - sizeof(char*) - 8));
	}

	sleep(10);
	printf("done.\n");
	return NULL;
}

int
main(int argc, char **argv)
{
#define TIDZ 10
	pthread_attr_t attr;
	pthread_t tid[TIDZ];
	size_t stacklen;
	register int i;
	struct rlimit rl;
	int kblen;

	kblen = argc > 1 ? strtol(argv[1], NULL, 0) : 1;

	getrlimit(RLIMIT_STACK, &rl);
	printf("stack limit: current=%llu KB max=%llu KB\n", 
			rl.rlim_cur / ((rlim_t) 1024), rl.rlim_max / ((rlim_t) 1024));
	printf("we try to get %d * %u KB = %u KB\n", TIDZ, kblen, kblen * TIDZ);
	if (((rlim_t) kblen * TIDZ) < (rl.rlim_max / ((rlim_t) 1024))) {
		printf("Error:: new stack size %u KB is under process stack limit %llu KB\n", 
				kblen * TIDZ, rl.rlim_max / ((rlim_t) 1024));
		return 1;
	}

	pthread_attr_init(&attr);
	pthread_attr_getstacksize(&attr, &stacklen);
	printf("default stacklen=%u\n", stacklen);
	pthread_attr_setstacksize(&attr, kblen * 1024);
	pthread_attr_getstacksize(&attr, &stacklen);
	printf("new stacklen=%u\n", stacklen);

	for (i = 0; i < TIDZ; i++)
		pthread_create(&tid[i], &attr, meow, (void*) stacklen);

	for (i = 0; i < TIDZ; i++)
		pthread_join(tid[i], NULL);

	pthread_attr_destroy(&attr);

	return 0;
}