The Old New Thing

The case of the file that won't copy because of an Invalid Handle error message

October 31, 2014 Oct 31, 2014 10/31/14

Raymond Chen

A customer reported that they had a file that was "haunted" on their machine: Explorer was unable to copy the file. If you did a copy/paste, the copy dialog displayed an error. Okay, time to roll up your sleeves and get to work. This investigation took several hours, but you'll be able to read it in ten minutes because I'm deleting ...

The contents of the Start page are not programmatically accessible

October 29, 2014 Oct 29, 2014 10/29/14

Raymond Chen

A customer wanted to know if is possible for an application to edit the user's Start page. No, there is no interface for editing the user's Start page or even knowing what is on it. The Start page is the user's personal space and applications should not be messing with it. Imagine if it were possible. Every application would edit the Start ...

A question about preventing the system from going to the idle state turns out to be misguided

October 28, 2014 Oct 28, 2014 10/28/14

Raymond Chen

A customer asked how they could have their program prevent the system from going to the idle state. Specifically, when the system goes idle, the application gets into a weird state where it starts leaking memory like crazy. The program normally uses around 100MB of memory, but when the system goes idle, something funky happens and the program'...

Enumerating the ways of distributing n balls into k boxes

October 27, 2014 Oct 27, 2014 10/27/14

Raymond Chen

Suppose you had n indistinguishable balls and k distinguishable boxes. Enumerate the ways of distributing the balls into boxes. Some boxes may be empty. We can represent each distribution in the form of n stars and k − 1 vertical lines. The stars represent balls, and the vertical lines divide the balls into boxes. For example, here ...

Debugging a hang: Chasing the wait chain inside a process

October 24, 2014 Oct 24, 2014 10/24/14

Raymond Chen

Today we're going to debug a hang. Here are some of the (redacted) stacks of the process. I left some red herrings and other frustrations. Since debugging is an exercise in optimism, let's ignore the stacks that didn't come out properly. If we can't make any headway, we can try to fix them, but let's be hopeful that the stacks that are ...

How can I detect programmatically whether the /3GB switch is enabled?

October 23, 2014 Oct 23, 2014 10/23/14

Raymond Chen

A customer was doing some diagnostic work and wanted a way to detect whether the /3GB switch was enabled. (Remember that the /3GB switch is meaningful only for 32-bit versions of Windows.) The way to detect the setting is to call Get­System­Info and look at the lp­Maximum­Application­Address. Compile this as a 32-bit ...

How do I disable Windows 8 touch contact visualizations for my application?

October 22, 2014 Oct 22, 2014 10/22/14

Raymond Chen

You might have an application (like a game) where the default touch contact visualizations are a distraction. In WinRT, you can disable the contact visualizations by simply saying In Win32, you use the Set­Window­Feedback­Setting function. To demonstrate that, let's take our scratch program and make this simple change: The ...

The great thing about regular expression languages is that there are so many to choose from!

October 21, 2014 Oct 21, 2014 10/21/14

Raymond Chen

Before you ask a question about regular expressions, you should make sure you and your audience agree on which regular expression language you are talking about. Here is a handy table of which features are supported by which regular expression language. You can use that table to solve this customer's problem: I have a regular ...

Scripting an Internet Explorer window

October 20, 2014 Oct 20, 2014 10/20/14

Raymond Chen

Today's Little Program takes a random walk through MSDN by starting at the Create­Process page and randomly clicking links. The exercise is not as important as the technique it demonstrates. (I'm assuming the reader can figure out what language this script is written in. If you have to ask, then you probably won't understand this ...