Generalizing C++11 Threads class to work with lambda - c++

Question

I have a simple Threads class based on pthreads which works fine with a standard static callback function.
Is it possible to generalize Threads to work with lambdas, too?
problems:
sandbox.cpp:27:26: error: invalid cast from type ‘main(int, char*)::’ to type ‘void’
thread_cb() needs to deal with generically casting void* back into something callable
I suspect the second problem may be solved with template methods or maybe std::function, but not sure how.
#include <vector>
#include <iostream>
#include <pthread.h>
class Threads
{
public:
Threads() { }
~Threads() { }
private:
static void *thread_cb( void *v )
{
// following will also need to change
void (*my_fptr)() =
reinterpret_cast<void(*)()>(reinterpret_cast<long long>(v));
my_fptr();
return nullptr;
}
public:
template<typename CALLBACK>
void spawn( CALLBACK cb )
{
pthread_t t;
void *p = (void*)( cb ); // problem here
pthread_create( &t, nullptr, thread_cb, p );
m_threads.push_back( t );
}
void join_all()
{
for ( auto& p : m_threads )
pthread_join( p, nullptr );
}
private:
std::vector< pthread_t > m_threads;
};
static void my_cb()
{
std::cerr << "bar" << std::endl;
}
int main(int argc, char** argv)
{
Threads t;
t.spawn( my_cb ); // ok
t.spawn( []() { std::cerr << "foo" << std::endl; } ); // not ok
t.join_all();
return 0;
}

Answer 1

You can use "lambda to function pointer" conversion. ...be that as it may, I strongly recommend std::thread.
template<typename CALLBACK>
void spawn( CALLBACK cb )
{
pthread_t t;
// void *p = (void*)( cb );
// pthread_create( &t, nullptr, thread_cb, p );
void (*pfn)() = cb; // function pointer to `void()`
pthread_create( &t, nullptr, thread_cb, reinterpret_cast<void*>(pfn) );
m_threads.push_back( t );
}