🚀 go-pugleaf

"Mike Collins" <its@TheBottomOfThePost> wrote in message 
news:478a96e3@newsgroups.borland.com...

> Hay all, just a quicky, just wondering if anyone had any
> thoughts on using try... __finally to ensure that a critical section
> is always released?

That wll work fine, as long as you do not have any 'return' statements 
inside the 'try' section, as 'return' is an immediate exit that does not 
allow '__finally' to run correctly.

A better approach is to use an RAII object instead, where the constructor 
enters the critical section and the destructor leaves it.  That way, the CS 
is always guaranteed to be unlocked when the object goes out of scope, and 
you don't need to use a try...__finally block at all.

> I have a thread with a getter and setter to provide access to a private 
> variable.  I use a CRITICAL_SECTION to ensure thead-safety but i
> wasn't sure about whether or not to use a try.. __finally to ensure that
> the CS always gets released...

Either approach will work fine in that situation, ie:

    --- try..finally ---

    int MyThread::GetSomething()
    {
        int tmp;
        EnterCriticalSection(&fMyCS);
        try
        {
            tmp = fSomething;
        }
        __finally
        {
            LeaveCriticalSection(&fMyCS);
        }
        return tmp;
    }

    void MyThread::SetSomething(int Value)
    {
        EnterCriticalSection(&fMyCS);
        try
        {
            // assign Something...
        }
        __finally
        {
            LeaveCriticalSection(&fMyCS);
        }
    }


    --- RAII ---

    class TCSGuard
    {
    private:
        LPCRITICAL_SECTION fCS;
    public:
        TCSGuard(LPCRITICAL_SECTION aCS)
            : fCS(aCS)
        {
            if( fCS ) EnterCriticalSection(fCS);
        }

        ~TCSGuard()
        {
            if( fCS ) LeaveCriticalSection(fCS);
        }
    };


    int MyThread::GetSomething()
    {
        TCSGuard g(&fMyCS);
        return Something;
    }

    void MyThread::SetSomething(int Value)
    {
        TCSGuard g(&fMyCS);
        // assign Something...
    }


Gambit