Yet another task macro

task.c

// CFLAGS="-Wall -Wextra"
#include <assert.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>

typedef struct task {
    void (*func)(void *);
    void *args;
    struct task *next;
} Task;

static Task *task_alloc(void (*func)(void *), void *args)
{
    Task *task = (Task *)malloc(sizeof(Task));
    if (!task) {
        fprintf(stderr, "Warning: task_alloc failed\n");
        return NULL;
    }

    task->func = func;
    task->args = args;
    task->next = NULL;
    return task;
}

// Constructor for tasks
#define TASK(func, ...) \
({ \
    struct func##_args *args = malloc(sizeof(struct func##_args)); \
    if (!args) { \
        fprintf(stderr, "Warning: TASK failed\n"); \
        assert(false); \
    } \
    *args = (struct func##_args){ __VA_ARGS__ }; \
    task_alloc(func, args); \
})

struct task_func_args {
    int *answer;
};

void task_func(void *args)
{
    assert(args != NULL);

    int *answer = ((struct task_func_args *)args)->answer;
    *answer = 42;
}

int main(void)
{
    int answer;

    Task *t = TASK(task_func, &answer);

    // ...

    t->func(t->args);
    free(t->args);
    free(t);

    assert(answer == 42);

    return 0;
}

See also https://github.com/aprell/compiler-potpourri/blob/master/openmp/task.h