C++ passing member function as argument of another member function

Question

I have problem using Borland C++ compiler in Eclipse, I want to pass address of one member function to constructor of another class which is friend of first class

PCB::PCB(Thread *t, long stack, int time, void (*method)())

I'm using method to find FP_SEG and FP_OFF, but it's giving me errors when I write

Thread::Thread (StackSize stackSize, Time timeSlice){
    myPCB = new PCB(this, stackSize, timeSlice, run);
}

This is error I'm getting all the time:

Could not find a match for 'PCB::PCB(Thread * const,unsigned long,unsigned int,void)' in function Thread::Thread(unsigned long,unsigned int)

But when I add (Thread::*method) FP_OFF(method) doesn't work anymore — Brana, May 15 '16 at 22:31
I suggest reading this answer http://stackoverflow.com/a/7218633/5404527 — o9000, May 15 '16 at 22:33

score 4 · Answer 1 · answered May 15 '16 at 22:31

Although member function invocation looks like a regular function invocation, the two are not the same, because there is compiler trickery involved in passing the this pointer to the function being called. When you call a member-function from another member function, C++ fills in the this pointer for you. That is why member functions are incompatible with regular functions, only static functions are.

If you need to pass a function to an API that you did not write, you need to pass a regular function. Otherwise, consider changing the code to take std::function instead, because it is compatible with member functions.

Sometimes third-party C-style APIs support passing an extra parameter for the "context" of the call. If your API supports a void* as well, you could write a regular function that casts a void pointer coming back to an instance of your class, and call a member function on that instance.

C++ passing member function as argument of another member function

1 Answers1