Hi all, this will be my first post but hopefully if someone can help me out I'd more than happy to help someone else out. I'm currently working on a project by myself that involves making a Winsock based server in C++. I chose to use IOCP since I will have a high volume of users accessing the server but the documentation/tutorials I've found online are either extremely over-complicated or they just don't tell me what I want to know. Right now my code is full of memory leaks so lately I've taken a break from expanding the code and have just focused on fixing the leaks before I move on. The issue comes in at....
I have my worker thread code below:
The code may be kind of hard to figure out since there is a ton of more code to explain what's going on. The way I figured I'm probably doing this incorrectly to start with and there is probably a much easier way to go about this. But anyway, my issue occurs when I log in around 100 users and try to log them out simultaneously, I get a seg fault, which this issue only occurs if I attempt to delete the user, if I leave the deletion code out everything runs 100% okay but of course I have massive memory leaks from not deleting the users. Below is the code I'm currently using to delete the user:Code:void workerthread::run(){ vector<string>pbuffer; while (WAIT_OBJECT_0 != WaitForSingleObject(s->g_hShutdownEvent, 0)) { top: BOOL bReturn = GetQueuedCompletionStatus( s->g_hIOCompletionPort, &dwBytesTransfered, (LPDWORD)&lpContext, &pOverlapped, INFINITE); if (NULL == lpContext) { //cleanup() cout<<"NULL, Serious error has occurred"; break; } u=(user *)lpContext; if ((FALSE == bReturn) || ((TRUE == bReturn) && (0 == dwBytesTransfered))) { cout<<"Socket Error, user("<<u->username<<") disconnected: 0 bytes transferred"<<endl; u->logout(); cout<<"User: "<<u->username<<" deleted.\n"; // //had "delete u" code here but caused a memory fault<<<<<<<<<<<<< goto top; } //If type of IO is send if(pOverlapped==u->s_pol) { //Will check to make sure all data was sent after memory leak fixing. cout<<dwBytesTransfered<<" bytes sent to user-> "<<u->username<<endl; goto top; } //Else type of IO is recv else { cout<<dwBytesTransfered<<" bytes received from user-> "<<u->username<<endl; //Output packet data in a form of <integers> if not visible using cout. cout<<"Data : "<<getreadable(u->recvwbuf->buf)<<endl; temp=u->recvwbuf->buf; ZeroMemory(u->recvwbuf->buf, MAX_BUFFER); int i=0; pbuffer.clear(); while(i<temp.length()) { //Found end of a packet, throw it in the vector. if(temp[i]=='\3') { pbuffer.push_back(u->parsing_buff); u->parsing_buff=""; } else //Not at the end of a packet, continue to concat. { u->parsing_buff+=temp[i]; } ++i; } //FOR each packet received, check it out. for(int i=0;i<pbuffer.size() ;++i) { packet=""; tempstr=""; for(int j=0;j<pbuffer.at(i).length();++j) { //base64_decode each entry in the vector line by line. if(pbuffer.at(i)[j]=='\n') { packet+=base64_decode(tempstr); tempstr=""; } else { tempstr+=pbuffer.at(i)[j]; } } //Get what's left over and throw it in packet. if(!tempstr.empty()) packet+=base64_decode(tempstr); //Initial handshake, perform if it hasn't been already. if(u->hs==false) { if(base64_decode(pbuffer.at(i)).compare(u->keystr)==0) { cout<<"Handshake() accepted\n"; u->hs=true; } else { data.clear(); data.push_back("Error: Handshake() failed."); try{ u->sendmsg(u->constructpacket(101,data));} catch(Error e) { //cleanup cout<<"User disconnected"<<endl; /*delete u;*/closesocket(u->socket); goto top; } /*delete u;*/closesocket(u->socket); goto top; } } else { try{u->parsedata(packet,data);} catch(Error e) { data.clear(); data.push_back(e.msg); u->sendmsg(u->constructpacket(101,data)); u->logout(); /*delete u;*/closesocket(u->socket); goto top; } //Depending on what type of packet, perform an action. int type=data.at(0)[0]; switch(type) { case 0: cout<<"Login packet received.\n"; if(u->loggedin==false && data.size()==4) { try { u->login(data.at(1),data.at(2),data.at(3)); continue; } catch(Error e) { data.clear(); data.push_back(e.msg); u->sendmsg(u->constructpacket(101,data)); u->logout(); /*delete u;*/closesocket(u->socket); goto top; } } else { data.clear(); data.push_back("Error, you are already logged in or malformed login packet received."); u->sendmsg(u->constructpacket(101,data)); u->logout(); /*delete u;*/closesocket(u->socket); goto top; } break; case 3: if(u->loggedin==true && data.size()==2) { try { time_t curr=time(NULL); if(curr-u->msgtime>u->mysite->time) { u->msgtime=time(NULL); u->msgcount=0; }else { u->msgcount+=1; if(u->msgcount>u->mysite->msgs_per_time) { data.clear(); data.push_back("You have been kicked for flooding."); u->sendmsg(u->constructpacket(101,data)); u->logout(); /*delete u;*/closesocket(u->socket); goto top; } } u->roommsg(data.at(1)); } catch(Error e) { data.clear(); data.push_back(e.msg); u->sendmsg(u->constructpacket(101,data)); u->logout(); /*delete u;*/closesocket(u->socket); goto top; } } else { data.clear(); data.push_back("Error, attempt to send message without being logged in, logged."); u->sendmsg(u->constructpacket(101,data)); u->logout(); /*delete u;*/closesocket(u->socket); goto top; } break; default: data.clear(); data.push_back("Error, invalid packet type received."); u->sendmsg(u->constructpacket(101,data)); u->logout(); /*delete u;*/closesocket(u->socket); goto top; } } } nBytesRecv=WSARecv(u->socket,u->recvwbuf, 1,&u->dwBytes, &u->dwFlags, u->r_pol, NULL); if ((SOCKET_ERROR == nBytesRecv) && (WSA_IO_PENDING != WSAGetLastError())) { //cleanup() cout<<"Socket Error, user disconnected: Recv()"<<endl; u->logout(); /*delete u;*/closesocket(u->socket); goto top; } } } return; }
NOTE: The exact moment the segmentation fault is occurring is when the console is at this point in code:
cout<<dwBytesTransfered<<" bytes received from user-> "<<!!!!!!!!!HERE>>!!!!!!!!!!u->username<<endl;
I know that most likely the reason its happening is because it's trying to print a string that doesn't exist anymore but I don't see how this is even occurring!!!?????
Which sometimes that loop in the destructor actually goes into an infinite loop and never releases(I understand a deadlock condition can occur because all of the thread pool could attempt to go into that loop at once, I fixed that by spawning a new thread everytime). Below is my code for when a user logs out which is what is called when a user logs out or performs an illegal action:Code:user::~user() { //while there are any receive or send operations left for this user... while (!HasOverlappedIoCompleted(r_pol) || !HasOverlappedIoCompleted(s_pol)) { cout<<"LOOPING"<<endl; Sleep(100); } closesocket(socket); cout<<"All IO complete, deleting..."<<endl; delete r_pol; delete s_pol; delete recvwbuf; delete sendwbuf; delete [] recv_szBuffer; delete [] sendbuf; }
Any help at all is extremely appreciated. Thanks!Code:void user::logout() { vector<string>data; if(loggedin) { //MUTEX object for user list WaitForSingleObject(mysite->UserMutex,INFINITE); //Tell everyone but myself that I am logging out! for(int i=0;i<mysite->users.size();++i) { data.clear(); data.push_back(username); if(lower(mysite->users.at(i)->username)!=lower(username)) { try{ mysite->users.at(i)->sendmsg(constructpacket(2,data)); } catch(Error e) { continue; } } } //Erase me from the user list if(loggedin) { for(int i=0;i<mysite->users.size();++i) { if(lower(mysite->users.at(i)->username)==lower(username)) mysite->users.erase(mysite->users.begin()+i); } } //Release the mutex to the user list. ReleaseMutex(mysite->UserMutex); } }
