Passing Parameters to pthread_create [closed]

Question

I have a structure named graph.

graph *G;

Now I create memory of size of structure using malloc and the start pointer is stored in pointer G.

G = (graph*)malloc(sizeof(graph));

My question is how do I pass this as a argument to pthread_create?

pthread_create(&th,NULL,function_call, ? );

Answer 1

the prototype of pthread_create is

 int pthread_create(pthread_t *thread, const pthread_attr_t *attr,
                          void *(*start_routine) (void *), void *arg);

As the arg parameter is a void* you can simply write

pthread_create(&th,NULL,function_call, G);

However, it the function_call(), you will need to cast you arg parameter to the real type. either:

function_call(void *arg)
{
    graph *tmp_G;

    tmp_G = arg;
    //  then I use tmp_G as G
}

or

((graph *)arg)->the_field_of_G;

Then you will be able to use you parameter as you need.

If you want to give more then one parameter to you function, you simply have to create a new structure that will contain all your parameters, then cast it as above to use them in your function_call().

here is an example :

typedef struct s_my_function_call_arg
{
    graph *G;
    int   arg2;
    char  *arg3;
}              t_my_function_call_arg;