Pointer gets lost when allocated struct with pointer on allocated string gets passed as argument for pthread

Question

I'm writing a server who starts a thread for each incomming request. I want to pass the arugments of the request and some other things to the thread. To do so Iam using a struct, which is allocated and contains a pointer which points onto an allocated string. I do so to keep the struct alive for the thread even when the main-thread enters its next loop. When I pass the pointer to this struct to my thread, the pointer in the struct which should point onto the string, "lost" its information. Well I get a EXC_BAD_ACCESS and I have no Idea why.

Any help is welcome :-)

typedef struct _thdata
{
    int socket;
    int thread_no;
    char *parameter;
}thdata;

void *thread_function(thdata *data)
{
    printf("Thread %i: got:%s\n",
            data->thread_no, data->parameter);<-EXC_BAD_ACCESS
    ...
    free data->parameter;
    free data;
    pthread_exit((void *)0);
}

int main(...)
{   ...
    while(1){
    ...
       thdata *data;
       data = (thdata*)malloc(sizeof(data));
       data->socket=connSocket;
       data->thread_no=i;
       data->parameter=(char*)malloc(strlen(param)+1);
       strcpy(data->parameter, param);
    ...
       pthread_create( &p_thread, NULL, (void *(*)(void *))thread_function, 
                    (void*) &data);
    ...
    }
}

Answer 1

You're passing the address of a pointer , ie a pointer to a pointer , to pthread_create , but what you want to pass is the address of your _thdata object. You need to pass the pointer to the object itself, like:

pthread_create(&p_thread, NULL, thread_function, data);

Also, there's no need to cast to void* here.