function ptrs to member functions and pthreads with member functions.

noWorks.cpp

#include <unistd.h>
#include <iostream>
#include <map>
#include <set>
#include <vector>
#include <pthread.h>

class Base{
public:
    int x;
    Base(int x_): x(x_){}
    virtual ~Base(){}
    
    void *myFunc( void * ) 
    {   
        int N = 10000000;
        for ( int i = 0; i < N; ++i )
        {
            ++x;
        }
    }   
};

int main(int argc, char** argv){
    Base b(0);
    void *(Base::*fp)() = &Base::myFunc;
    pthread_t t;
    pthread_create( &t, NULL, b.*fp, NULL);
    pthread_detach( t );
    b.myFunc();
    sleep(2);
    std::cout << b.x << std::endl;

}

works.cpp

#include <iostream>
#include <map>
#include <set>
#include <vector>
#include <thread>

class Base{
public:
    int x;
    Base(int x_): x(x_){}
    virtual ~Base(){}
    int f() 
    {   
        int (Base::*fp)() = &Base::myFunc;
        int x = (this->*fp)();
        return x;    
    }   
     
    int myFunc()
    {   
        return 1;
    }   
};

int main(int argc, char** argv){
    Base b( 1 );
    std::cout << b.f() << std::endl;
    
    int (Base::*fp)() = &Base::myFunc;
    std::cout << (b.*fp)() << std::endl;
}