Switching between coroutines/tasks: GNU Pth (separate stacks)

pth.c

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <assert.h>
#include <unistd.h>
#include <time.h>
#include <pth.h>
#include "list.h"

struct task {
	pth_t tid;
	struct list_head list;
};

static LIST_HEAD(tasklist);
static void (*tasks[2])(void *);
static int ntasks;

static void task_create(struct list_head *tasklist, void *(*fn)(void *), void *args)
{
	struct task *t = malloc(sizeof(*t));
	list_add(&t->list, tasklist);
	t->tid = pth_spawn(PTH_ATTR_DEFAULT, fn, args);
	pth_yield(t->tid);
}

static void task_join(struct list_head *tasklist)
{
	while (!list_empty(tasklist)) {
		struct task *t = list_first_entry(tasklist, struct task, list);
		list_del(&t->list);
		pth_join(t->tid, NULL);
		free(t);
	}
}

void schedule(void)
{
	int i;

	srand(time(NULL));

	for (i = 0; i < ntasks; i++) {
		int n = rand() % 5;
		task_create(&tasklist, (void *(*)(void *))tasks[i], &n);
	}

	task_join(&tasklist);
}

// A task yields control n times

void task0(void *arg)
{
	int n = *(int *)arg, i;

	printf("Task 0: n = %d\n", n);

	for (i = 0; i < n; i++) {
		// Assume we block and yield control
		pth_yield(NULL);
		printf("Task 0: resume\n");
	}

	printf("Task 0: complete\n");
}

void task1(void *arg)
{
	int n = *(int *)arg, i;
	
	printf("Task 1: n = %d\n", n);
	
	for (i = 0; i < n; i++) {
		// Assume we block and yield control
		pth_yield(NULL);
		printf("Task 1: resume\n");
	}

	printf("Task 1: complete\n");
}

int main(void)
{
	pth_init();

	tasks[0] = task0;
	tasks[1] = task1;
	ntasks = 2;
	schedule();
	
	pth_kill();

	return 0;
}