WaitForSingleObeject runtime error

Discussion in 'C++' started by Larry, Jan 27, 2010.

  1. Larry

    Larry Guest

    Hi,

    I am getting this close to finish my tiny streaming server...having said
    that I have a problem with the following code. It basically fires a runtime
    error when I disconect from the sever! (closing the telnet window)

    I wound up finding out that the error may be fired because of this line:

    WaitForSingleObject(eventi[threadid], INFINITE);

    If I replaceit with: Sleep(1000) everything goes ok....


    /*
    *
    * Streaming Server v1.0 by THEARTOFWEB Software
    *
    */

    #include <iostream>
    #include <string>
    #include <map>
    #include <algorithm>
    #include <process.h>
    #include <cstdlib>
    #include <ctime>
    #include "socket.h"
    #include <boost/circular_buffer.hpp>
    using namespace std;
    using namespace boost;

    const string CRLF = "\r\n";
    const int numbuff = 3;

    unsigned int __stdcall Consumer(void* sock);
    unsigned int __stdcall Producer(void*);

    void getDateTime(char * szTime);

    enum buffer_status
    {
    BUFF_DONE = 1,
    BUFF_EMPTY = 0
    };

    struct buffer
    {
    unsigned char data[1024];
    int bytesRecorded;
    int flag;
    buffer(const unsigned char * data_, const int bytesRecorded_, const int
    flag_) :
    bytesRecorded(bytesRecorded_), flag(flag_)
    {
    copy(data_, data_ + bytesRecorded_, data);
    }
    };

    struct circular
    {
    circular_buffer<buffer> cb;
    };

    map<int, circular> users;
    map<int, circular>::iterator uit;
    map<int, HANDLE> eventi;

    int main()
    {
    // Launch Producer
    unsigned int prodRet;
    _beginthreadex(0,0,Producer,NULL,0,&prodRet);
    if(prodRet)
    cout << "Launched Producer Thread!" << endl;

    // Set up server (port: 8000, maxconn: 10)
    SocketServer sockIn(8000, 10);

    while(1)
    {
    // ...wait for incoming connections...
    Socket* s = sockIn.Accept();
    unsigned int sockRet;
    _beginthreadex(0,0,Consumer,s,0,&sockRet);
    if(sockRet)
    cout << "Spawned a new thread!" << endl;
    }

    sockIn.Close();

    return EXIT_SUCCESS;
    }

    // Consumer
    unsigned int __stdcall Consumer(void* sock)
    {
    Socket* s = (Socket*) sock;

    s->SendBytes("Hello World!" + CRLF);

    int threadid = (int)GetCurrentThreadId();

    // Create Event & push it in the event map
    HANDLE hevent = CreateEvent(NULL,FALSE,FALSE,NULL);
    eventi.insert(make_pair(threadid,hevent));

    // Prepare & add circular buffer to the map
    circular c;
    c.cb.set_capacity(numbuff);

    for(int i = 0; i<numbuff; i++)
    {
    c.cb.push_back(buffer(NULL,0,BUFF_EMPTY));
    }

    users.insert(make_pair(threadid, c));

    //
    // TODO:
    // Read data from the buffer
    // and send it to the client
    //
    // When using push_back the oldest
    // element in the circular buffer
    // will be in the index 0
    //

    Sleep(500);

    while(1)
    {
    // CALLBACK EVENT
    WaitForSingleObject(eventi[threadid], INFINITE);
    if(users[threadid].cb.at(0).flag == BUFF_DONE)
    {
    string line = (char*)users[threadid].cb.at(0).data;
    int ret = s->SendBytes(line + CRLF);
    if(SOCKET_ERROR == ret)
    break;
    }
    }

    // Close & remove event from event map
    CloseHandle(eventi[threadid]);
    eventi.erase(threadid);

    // Remove buffer from the map
    users.erase(threadid);

    // Say bye to the client
    s->SendBytes("Bye bye!" + CRLF);

    // Disconnect client
    cout << "Closing thread..." << endl;
    s->Close();
    delete s;
    return 0;
    }

    // Producer
    unsigned int __stdcall Producer(void*)
    {
    while(1)
    {
    Sleep(1000);
    char szTime[30]; getDateTime(szTime);
    for(uit=users.begin(); uit!=users.end(); ++uit)
    {
    users[uit->first].cb.push_back(buffer((unsigned char*)szTime,
    30, BUFF_DONE));
    SetEvent(eventi[uit->first]);
    cout << "Producer is writing to: " << uit->first << endl;
    }
    }
    return 0;
    }

    void getDateTime(char * szTime)
    {
    time_t rawtime = time(NULL);
    struct tm timeinfo;
    gmtime_s(&timeinfo, &rawtime);
    strftime(szTime, 30, "%a, %d %b %Y %X GMT", &timeinfo);
    }

    // thanks
    Larry, Jan 27, 2010
    #1
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  2. Larry wrote:
    > Hi,
    >
    > I am getting this close to finish my tiny streaming server...having
    > said that I have a problem with the following code. It basically fires a
    > runtime error


    ...with which we really can't help you - that's OS-specific..

    > when I disconect from the sever! (closing the telnet window)
    >
    > I wound up finding out that the error may be fired because of this line:


    "May be"? So, it's possible that it's not the call to
    WaitForSingleObject but something else that screws up the memory
    occupied by the actual 'eventi' map...

    >
    > WaitForSingleObject(eventi[threadid], INFINITE);
    >
    > If I replaceit with: Sleep(1000) everything goes ok....


    Does the 'eventi' map actually contain a valid value with the key
    'threadid' for passing it to 'WaitForSingleObject'? Those things need
    to be checked, you know.

    If access to 'data' in your 'buffer' is somehow incorrect (you need to
    check), and you write beyond the boundary of 1024 elements, it's very
    likely that you stomp all over the dynamically allocated memory used to
    keep your 'eventi' map elements. Then attempt to access them can cause
    undefined behaviour, which in your case ends up being a run-time error
    reported by the OS.

    > [..]
    >
    > struct buffer
    > {
    > unsigned char data[1024];
    > int bytesRecorded;
    > int flag;
    > buffer(const unsigned char * data_, const int bytesRecorded_, const
    > int flag_) :
    > bytesRecorded(bytesRecorded_), flag(flag_)
    > {
    > copy(data_, data_ + bytesRecorded_, data);
    > }
    > };
    >
    > struct circular
    > {
    > circular_buffer<buffer> cb;
    > };
    >
    > map<int, circular> users;
    > map<int, circular>::iterator uit;
    > map<int, HANDLE> eventi;
    >
    > int main()
    > {
    > [..]
    > // thanks


    V
    --
    Please remove capital 'A's when replying by e-mail
    I do not respond to top-posted replies, please don't ask
    Victor Bazarov, Jan 27, 2010
    #2
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