pthread c ++从void *（*）到void *（*）（void *）的无效对话

Question

I'm new in C++ and trying to create multiple threads with pthread .

typedef struct thread_args{
    int &sockfd;
    struct sockaddr_in &serv_addr;
    int size_serv_addr;
    socklen_t &clilen;
    int &newsockfd;
};

void create_server(int &sockfd, struct sockaddr_in &serv_addr, int size_serv_addr, socklen_t &clilen, int &newsockfd){
}

int main(int argc, char *argv[])
{
     int sockfd, newsockfd;
     socklen_t clilen;

     pthread_t t1;
     struct sockaddr_in serv_addr, cli_addr;
     struct thread_args *args;
     args->clilen = clilen;
     args->newsockfd = newsockfd;
     args->serv_addr = serv_addr;
     args->size_serv_addr = sizeof(serv_addr);
     args->sockfd = sockfd;


     pthread_create(&t1, NULL, create_server, &args);
     printf("hello abc");
     return 0; 
}

When I run this code, it has a message:

error:/bin/sh -c 'make -j 4 -e -f   error: invalid conversion from 'void* (*)(int&, sockaddr_in&, int, socklen_t&, int&) {aka void* (*)(int&, sockaddr_in&, int, unsigned int&, int&)}' to 'void* (*)(void*)' [-fpermissive]
      pthread_create(&t1, NULL, create_server, &args);

How can I fix this?

Answer 1

Signature for your thread function should be:

void *(*start_routine) (void *)

but you provide:

void create_server(int &sockfd, struct sockaddr_in &serv_addr, int size_serv_addr, socklen_t &clilen, int &newsockfd)

you should create a function like:

void* myThread(void *arg);

then args argument in pthread_create call will be passed as arg parameter to myThread , you can use its fields to call create_server

Answer 2

Your function definition does not match the type pthread_create wants to have. It requires only 1 arguments and that is a void* (so a function void function(void* args) ).

you need to change create_server to

void create_server(void* voidArgs) {
    thread_args* args = static_cast<thread_args*>(voidArgs);
    //...
}

You will not have those issues though if you use the c++11 std::thread object. There you can directly use the argument type and with any number of arguments you like. So you don't have to define the thread_args struct.