Question

I am trying to create a thread using pthread. So far I have this:

sample.h:

void* ReceiveLoop(void*);
pthread_t mythread;

sample.cpp:

void* ReceiveLoop(void*) {
  cout<<"whatever";
}

void sample::read() {
  pthread_create(&mythread, NULL, ReceiveLoop, NULL);
}

Which I think is ok having read some posts about this. I have also tried with

pthread_create(&mythread, NULL, &ReceiveLoop, NULL);

But I get this:

.cpp:532: error: no matches converting function 'ReceiveLoop' to type 'void* (*)(void*)'
.cpp:234: error:                 void* sample::ReceiveLoop(void*)

Anyone can help me? Thanks.

Answer 1

I recall a few idiosyncrasies between older versions of gcc/g++ with regards to errors like this. You didn’t indicate the compiler you were using.

Go ahead and give the void* parameter passed to ReceiveLoop a name:

 void ReceiveLoop(void* threadarg);

 void* ReceiveLoop(void* threadarg){ cout<<"whatever"; }

For some reason, I seem to recall that’s the only way I could get a particular piece of code to compile on some random compiler even though the parameter passed in wasn’t actually used.

Also, if ReceiveLoop is a member function of a class, it needs to be declared static.

class sample
{
 public:

    void ReceiveLoopImpl()
    {
        cout<<"whatever";
    }

    static void* ReceiveLoop(void* threadargs)
    {
        return ((sample*)threadargs)->RecieveLoopImpl();
    }

    void read()
    {
         pthread_create(&mythread, NULL, sample::ReceiveLoop, this);
    }

};