如何将结构数组传递给pthread_create？ C

Question

Help!!!! How can I cast args.tab1 to (void *) and pass it as an argument of pthread ? Thanks

//struct

typedef struct args args; 
struct args {
    int *tab1;
    int *tab2;
    int *tab3;
    int *tab4;
};

//pthread

args args; //define struct
pthread_t tid;
pthread_create(&tid, NULL, function1, (void *)args.tab1);
pthread_join(tid, NULL);

//function1

void *function1(void *input)
{
    int *arr = (int*)input;
    function2(arr);
}

//function2
void function2(int *arr) 
{
...
}

Answer 1

There is no need to cast. The compiler will not complain when casting any pointer to void * . Just do

    args a;
    pthread_create(&tid, NULL, function1, a.tab1);

Answer 2

A demo on how to pass a struct

#include <pthread.h>
#include <stdio.h>

struct args {
    int *tab1;
    int *tab2;
    int *tab3;
    int *tab4;
};

void *f(void *arg)
{
    struct args *o = (struct args *)arg;
    printf("%d\n", *(o->tab1));
    printf("%d\n", *(o->tab2));
    printf("%d\n", *(o->tab3));
    printf("%d\n", *(o->tab4));
}

int main()
{
    pthread_t thread1;
    int n = 100;
    struct args o = {
        .tab1 = &n,
        .tab2 = &n,
        .tab3 = &n,
        .tab4 = &n
    };

    pthread_create(&thread1, NULL, f, &o);
    pthread_join(thread1, NULL);
}

Alternatively, you could

    pthread_create(&thread1, NULL, f, o);

If o wasn't on stack (ie you allocated memory for it and it's the pointer to that memory).

Output:

100
100
100
100

---

And if you only wish to pass a single pointer from struct args then

void *f(void *arg)
{
        int* tab1 = (int *)arg;
        printf("%d\n", *tab1);
}

int main()
{
   ...
    pthread_create(&thread1, NULL, f, o.tab1);
   ...
}