Tuesday, December 11, 2007

What's wrong with Monitor::Enter()

Suppose we have the following variable we'd like to set as a state and we'd like to make it thread safe (at most one thread is allowed to access the variable):

bool workQueued;

Now if we write something like this, it's not gonna work:

Monitor::Enter(__box(workQueued));
try
{
workQueued = true;
}
__finally
{
Monitor::Exit(__box(workQueued));
}

Why it will not work? The problem is, after workQueued is boxed, the value is not store anywhere. So the second thread reaches here will execute Enter statement with another object value.

To make it work as desired, we need to create a object whose only purpose is to act like a lock:

Object* lock;

Then, we feed this object to Enter and Exit method:

Monitor::Enter(lock);
try
{
workQueued = true;
}
__finally
{
Monitor::Exit(lock);
}

Wednesday, December 5, 2007

LINK : warning LNK4075: ignoring '/EDITANDCONTINUE' due to '/INCREMENTAL:NO' specification

What the heck?! If you've spent more than ten minutes just trying to find where to set EDITANDCONTINUE property in VC++ project property page, you are not alone. It can be set through: (Under Project Property Pages) Configuration Properties -> C/C++ -> General -> Debug Information Format.

OK. Now I've set it NOT to be /ZI and disabled incremental link, why the darn VS still complain the same warning. Remember that no matter how bizarre a problem seems to be, computer always works as expected. Why don't you check the project properties of other projects that this project depends on?

Monday, December 3, 2007

Visual Studio got stuck when opening sln file

Sometimes VS may get stuck when we double-click a .sln file. We can see the file name on which it got stuck. But even if we try to rename that file or replace with another one with the same name, it may still not work. In this case, try to delete the corresponding .suo file.