pthread_Create with g++ compiler error

[Emma Smith]

Hi i was wondering if someone could help me as i'm trying to do some multithreading in c++ using g++ compiler and i am getting the following error.

I'm basically trying to pass the value of i1 to printmessage where i want to change its value and return this to main.


thread.cpp: In function 'int main()':
thread.cpp:17: error: invalid conversion from 'void* (*)(int*)' to 'void* (*)(void
*)'
thread.cpp:17: error: initializing argument 3 of 'int pthread_create(pthread_t*,
void* const*, void* (*)(void*), void*)'

#include <iostream>
#include <pthread.h>
using namespace std;
 
void *print_message(int *i1)
{
    cout << "Threading\n";
}
 
int main()
{
    int i1;
    pthread_t t1;
 
    i1 = 10;
    pthread_create(&t1, NULL, print_message, &i1);
 
    return 0;
}
 

[newb16]

You have it declared

void *print_message(int *i1)

and compiler expects it
'void* (*)(int*)' to 'void* (*)(void
*)'
to take an argument of void*

[Banfa]

That isn't to say that you can't pass an int into the thread via a pointer only that you will have to convert (cast) to from a void*.