Passing a pointer as argument to a function!!

[vador]

I want to pass a pointer to a function and when the function returns, the pointer must maintain the state! EXAMPLE:

int main(){
byte *myPtr = NULL;
int status;

status = game(myPtr);

cout << myPtr[0] << endl;
}

int game(byte *ptr){
ptr = (byte *) malloc(sizeof(byte) * 10);
ptr[0] = 1;
return 20;
}

The problem is that the pointer when Return from the function game, loose the reference to the allocated space!!

Anyone can help me?

Thanks!!

[horace1]

the function call

  status = game(myPtr);
 

passes a copy of the value of ptr into function game() so any information stored in it is lost on function return.
what you need to do is to pass the address of ptr so that the address of the storage allocated by malloc() can be assigned to ptr

// ptr is a pointer to a pointer to byte
int game(byte **ptr){
*ptr = (byte *) malloc(sizeof(byte) * 10);
(*ptr)[0] = 1;     // assign some values
(*ptr)[1] = 2;
return 20;
}
 
int main(){
byte *myPtr = NULL;
int status;
status = game(&myPtr);  // pass address of ptr
cout << (int) myPtr[0] << endl;  // see if values are OK
cout << (int) myPtr[1] << endl;
}
 
 
 

the parameter ptr to function game() is now byte** a pointer to pointer to byte and you have dereference it for malloc() etc