Critical section - to be or not to be?

Question

I`m writing a chat using WinSock2 and WinAPI functions. And I have a little trouble.
I store the std::vector of client connections on server. When new client connects, new thread starts and all work with the client is done in this new thread. I do not use classes (I know it is not very good) so this list of connections is just defined as global variable.
It seems to me that it can be a situation when several threads try to access this list simultaneously. Though I have not noticed that there are any problems with that, do I need to do something like this:

template 
class SharedVector {
    std::vector vect;
    CRITICAL_SECTION cs;
    SharedVector(const SharedVector& rhs) {}
public:
    SharedVector();
    explicit SharedVector(const CRITICAL_SECTION& CS);
    void PushBack(const T& value);
    void PopBack();
    unsigned int size();
    T& operator[](int index);
    virtual ~SharedVector();
};

template
SharedVector::SharedVector() {
    InitializeCriticalSection(&cs);
}

template
SharedVector::SharedVector(const CRITICAL_SECTION& r): cs(r) {
    InitializeCriticalSection(&cs);
}

template
void SharedVector::PushBack(const T& value) {
    EnterCriticalSection(&cs);
    vect.push_back(value);
    LeaveCriticalSection(&cs);
}

template
void SharedVector::PopBack() {
    EnterCriticalSection(&cs);
    vect.pop_back();
    LeaveCriticalSection(&cs);
}

So, does my situation require using CRITICAL_SECTION and am I just the lucky guy who did not find a mistake?

Answer 1

Yes, you are just lucky never to experience any problems. This is the problem with synchronization issues and race conditions, that the code will work in 99.9% of all cases, and when disaster strikes you won't know why.

I would take away the constructor taking a CRITICAL_SECTION as a parameter since it is not clear without looking at (presumably non-existing) documentation to realize that the constructor will initialize it.