The Old New Thing

C++ scoped static initialization is not thread-safe, on purpose!

March 8, 2004 Mar 8, 2004 03/8/04

Raymond Chen

How the design of the C++ language subverts thread safety.

The correct order for disabling and enabling windows

February 27, 2004 Feb 27, 2004 02/27/04

Raymond Chen

If you want to display modal UI, you need to disable the owner and enable the modal child, and then reverse the procedure when the modal child is finished. And if you do it wrong, focus will get all messed up. If you are finished with a modal dialog, your temptation would be to clean up in the following order: But if you do that, ...

What's so special about the desktop window?

February 24, 2004 Feb 24, 2004 02/24/04

Raymond Chen

The window returned by GetDesktopWindow() is very special, and I see people abusing it all over the place. For example, many functions in the shell accept a window handle parameter to be used in case UI is needed. IShellFolder::EnumObjects, for example. What happens if you pass GetDesktopWindow()? If UI does indeed need to be ...

Invalid thread and process IDs

February 23, 2004 Feb 23, 2004 02/23/04

Raymond Chen

Perhaps you want a value to use as a sentinel, which you want to be guaranteed is never a valid thread ID or process ID. What values can you use? Nothing is explicitly written about this topic, but you can put on your logic cap and figure it out. If you need an invalid thread ID, you can use zero. How do you know that zero is an ...

Why do I get a QueryInterface(IID_IMarshal) and then nothing?

February 20, 2004 Feb 20, 2004 02/20/04

Raymond Chen

A common problem when trying to get your new COM object off the ground is that you can't seem to be able to get it created. The object comes out of the class factory, and it gets a QueryInterface for IMarshal, and then nothing. What's going on? This is a sure sign that you didn't register your CLSID properly; most likely you forgot to ...

GetDialogBaseUnits is a crock

February 17, 2004 Feb 17, 2004 02/17/04

Raymond Chen

Each dialog can have different base units, so it's meaningless to have a global converter.

TEXT vs. _TEXT vs. _T, and UNICODE vs. _UNICODE

February 12, 2004 Feb 12, 2004 02/12/04

Raymond Chen

Different settings for different components.

Answer to exercise: Pointer to member function cast

February 10, 2004 Feb 10, 2004 02/10/04

Raymond Chen

Yesterday's exercise asked you to predict and explain the codegen for the following fragment: Well, the codegen might go something like this: Let's use one of our fancy pictures: Just for fun, I swapped the order of Base1 and Base2. There is no requirement in the standard about the order in which storage is allocated for base classes...

Pointers to member functions are very strange animals

February 9, 2004 Feb 9, 2004 02/9/04

Raymond Chen

Pointers to member functions are very strange animals. Warning: The discussion that follows is specific to the way pointers to member functions are implemented by the Microsoft Visual C++ compiler. Other compilers may do things differently. Well, okay, if you only use single inheritance, then pointers to member functions are just a ...

Answers to exercises – mismatching new/delete

February 4, 2004 Feb 4, 2004 02/4/04

Raymond Chen

Answers to yesterday's exercises: What happens if you allocate with scalar "new" and free with vector "delete[]"? The scalar "new" will allocate a single object with no hidden counter. The vector "delete[]" will look for the hidden counter, which isn't there, so it will either crash (accessing nonexistent memory) or grab a random number ...