SIGSEGV，分段错误。 仅在Linux上，它可在Windows上使用

Question

I have been stuck on this for hours, for some reason I am getting a Segmentation fault error only on Linux. It only happens with packets of length 17 or more characters. I am using Enet library to send the packets. Anyone can help me out, I don't know what I am missing here ...

Here is a screenshot of gdb output Here is the server side sample:

void GameServer::start()
{
if (!m_isRunning)
    m_isRunning = true;

ENetEvent  event;
//ENetPacket *packet;

while (m_isRunning)
{
    while (enet_host_service(server, &event, 1000) > 0)
    {
        switch (event.type)
        {
        case ENET_EVENT_TYPE_CONNECT:
            std::cout << "A new client connected from ";
            std::cout << event.peer->address.host << " ";
            std::cout << event.peer->address.port << std::endl;

            break;
        case ENET_EVENT_TYPE_DISCONNECT:
            printf("%s disconnected.\n", event.peer->data);
            delete (char*)event.peer->data;
            break;
        case ENET_EVENT_TYPE_RECEIVE:
        {
            std::cout << "A packet of length ";
            std::cout << event.packet->dataLength;
            std::cout << " containing ";
            std::cout << event.packet->data;
            std::cout << " was received from ";
            printf("%s", event.peer->data);
            std::cout << " on channel ";
            std::cout << event.channelID << std::endl;

            // Split the packet data, ex:   packettype:data:data
            std::vector<std::string> tokens;
            std::string data;
            std::istringstream split((const char *)event.packet->data);

            // Process the packet data
            while (std::getline(split, data, ':')) Line 89: Crash here
                tokens.push_back(data);

            if (tokens.size() > 1)
            {

                //pc = player connected so we will broadcast the name to all peers
                if (tokens[0] == "pc")
                {
                    if (tokens.size() == 2)
                    {
                        char* data = new char[tokens[1].length() + 1];
                        strcpy(data, tokens[1].c_str());
                        event.peer->data = (void*)data;
                        for (size_t i = 0; i < server->connectedPeers; i++)
                        {
                            enet_host_broadcast(server, 0, event.packet);
                        }
                    }
                }

                //ma = message all so we are going to broadcast the message to all peers
                else if (tokens[0] == "ma") 
                {
                    if (tokens.size() == 2)
                    {
                        enet_host_broadcast(server, 0, event.packet);
                    }
                }


                /* One could just use enet_host_service() instead. */
                enet_host_flush(server);
            }
            /* Clean up the packet now that we're done using it. */
            enet_packet_destroy(event.packet);
            break;
        }
        case ENET_EVENT_TYPE_NONE:
            break;
        default:
            break;
        }

    }
}

}

Here is how the packet is created by the client and then sent to the server.

if (connected) {
        std::cout << "Input: ";
        std::string str = "";
        std::getline(std::cin, str);

        if (str.length() == 0) { continue; }

        packet = enet_packet_create(str.c_str(), str.length() + 1, ENET_PACKET_FLAG_RELIABLE);
        enet_peer_send(peer, 0, packet);

    }

If code sample if not enough I can provide more.

Answer 1

A crash in malloc() usually means that someone wrote over the end of an allocated buffer some time earlier . That buffer overrun corrupted the pointers that get stored in free memory to link free blocks together. It didn't cause a problem until malloc() tried to use those pointers. Then BOOM!

Post the declaration of the event.packet type. Are you sure data[] is big enough for the data you put in it?