pointers - Convert (void **) to object in C++ -

i trying convert (void**) object queue in c++.

in 1 file hashtablevoid.cc use method find to:

bool hashtablevoid::find( const char * key, void ** data) {   // add implementation here   int = hash(key);   hashtablevoidentry * node = _buckets[i];  while(node){   if(strcmp(node->_key,key) == 0)   {     *data = node->_data;     return true;   }   node = node->_next; } return false; } 

and in ircserver.cc used

void ircserver::sendmessage(int fd, const char * user, const char * password, const char * args) { //get user's room  //write room messages char * temp; temp = strdup(args); void ** q; queue<char*> data; const char * room = //found room; communication.find(room, q); data =  (queue<char*>) ((char *)q); data.push(temp); //make sure 100 elements or less in list while(data.size() > 100)     data.pop(); } 

i creating void ** q pass parameter communication. variable communication hashtable key room name , value unique queue of messages. having trouble converting void object queue. can't change find method.

two problems can see directly:

first call find without initializing q, doesn't point anywhere. in find function when dereference *data dereference unknown pointer leading undefined behavior. think you're supposed declare q single pointer, , pass address of find function (emulating pass reference). like

void *q; ... communication.find(room, &q); 

however, since you're programming in c++ don't see reasong use double-pointer emulate pass reference, since c++ have built-in:

bool hashtablevoid::find( const char * key, void *& data); 

the above declares argument data reference pointer.

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the second problem assignment pointer q variable data:

data =  (queue<char*>) ((char *)q); 

what have (without changes above), q pointer pointer, , try use single pointer, try cast value. pointer not value, , can never be.

maybe mean

data = *reinterpret_cast<std::queue<char*>*>(q);  // after change detailed above