C++ – Simple pthread! C++

c++pthreads

I have no idea why this doesn't work

#include <iostream>
#include <pthread.h>
using namespace std;

void *print_message(){

    cout << "Threading\n";
}



int main() {

    pthread_t t1;

    pthread_create(&t1, NULL, &print_message, NULL);
    cout << "Hello";

    return 0;
}

The error:

[Description, Resource, Path, Location, Type] initializing argument 3
of 'int pthread_create(pthread_t*, const pthread_attr_t*, void*
(*)(void*), void*)' threading.cpp threading/src line 24 C/C++
Problem

Best Solution

You should declare the thread main as:

void* print_message(void*) // takes one parameter, unnamed if you aren't using it

Related Solutions

C++ – pthread function from a class

You can't do it the way you've written it because C++ class member functions have a hidden this parameter passed in. pthread_create() has no idea what value of this to use, so if you try to get around the compiler by casting the method to a function pointer of the appropriate type, you'll get a segmetnation fault. You have to use a static class method (which has no this parameter), or a plain ordinary function to bootstrap the class:

class C
{
public:
    void *hello(void)
    {
        std::cout << "Hello, world!" << std::endl;
        return 0;
    }

    static void *hello_helper(void *context)
    {
        return ((C *)context)->hello();
    }
};
...
C c;
pthread_t t;
pthread_create(&t, NULL, &C::hello_helper, &c);

C++ – pthread_create from non-static member function

You are casting the third argument to a void* ((void*), and then getting an error, as void* cannot be cast to a function pointer.

I believe it should compile if you just use &LaunchMemberFunction instead.

Best Solution

Related Solutions

C++ – pthread function from a class

C++ – pthread_create from non-static member function

Related Question