Question

class classe (){
public: 
    int key;

    static void *funct(void *context){
        printf("Output: %d, ", key);
    }

    void Go(){
        classe c = static_cast<this>(context); //<- This doesn't work, Context of this-> goes here
        pthread_create(&t, NULL, &classe::funct, c);
    }
};

int main(){

    classe c;
    c.key = 15;
    c.Go();

    c.key = 18;
    c.Go();
}

The output should be Output: 15, Output: 18,, the thing is to get context of this throws error.

Someone know how to fix this?

Answer 1

I can see a few problems with your code:

First, static_cast<> requires a type in the <>, and this acts like a variable (so not a type). The type of this is classe* (pointer to classe object) within classe.

Second, there is no context available in classe:Go(). There is a parameter for classe::fuct() by that name, but that is not available where you want to use it.

Third, pthread_create() assumes a free function (or a static member function) and you provide a class member function (classe::funct). Class memeber functions require an object to work on (sort of like an implicit parameter == this). You also don’t have a t defined in classe::Go() that you could pass to pthread_create()

You could try:

static void *funct(void *key){ // funct is now a free function, all data is provided to it
    printf("Output: %d, ", *static_cast<int*>(key)); 
} 

class classe ()
{ 
public:  
  int key; 

  void Go(){
    pthread t; 
    pthread_create(&t, NULL, funct, &key); // pass (address of) key to funct
  } 
}; 

int main(){ 

  classe c; 
  c.key = 15; 
  c.Go(); 

  c.key = 18; 
  c.Go(); 
}