test_malloc_fork.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

static void usage(char **argv)  {
	fprintf(stderr, "usage: %s size\n", argv[0]);
	exit(1);
}

volatile char c;

int main(int argc, char **argv) {
	if (argc != 2)
		usage(argv);
	size_t size = atol(argv[1]);
	char *data = malloc(size);
	if (!data) {
		perror("malloc");
		exit(1);
	}
	for (long unsigned i=0;i<size;i++) {
		volatile char *p = &data[i];
		*p = 1;
		c = *p;
	}

	pid_t pid = fork();
	if (pid == 0) {
		sleep(120);
		exit(0);
	}
	if (pid == -1) {
		perror("fork");
		exit(1);
	}
	sleep(120);
}