May 2017 | The Old New Thing

Extending our critical section based on WaitOnAddress to support timeouts

Raymond Chen May 31, 2017 May 31, 2017 05/31/17

Let's take the critical section we constructed in terms of WaitOnAddress and add two new functions: The first function is a simplification of the existing EnterAltCs function. It simply gives up if the critical section is not available. The second function is a modification of the existing EnterAltCs function...

Why isn’t the original window order always preserved when you undo an Aero Shake?

Raymond Chen May 30, 2017 May 30, 2017 05/30/17

A customer reported that when they used Aero Shake to minimize all the windows on their desktop, and then used it again to restore all the windows, the restored windows didn't always have exactly the same z-order as they did originally. The customer wanted to know whether this was expected. It's not expected, but it's not unexpected either. ...

Does DebugBreak work to launch the debugger, or doesn’t it?

Raymond Chen May 29, 2017 May 29, 2017 05/29/17

Jorge asked why the DebugBreak function stopped working. Specifically, why it doesn't launch the Visual Studio debugger. Okay, first of all, the primary purpose of the DebugBreak function is not to launch the debugger. The primary purpose of the DebugBreak function is to trigger a break into any attached debugger. That still works the ...

Why are hidden files with a leading tilde treated as super-hidden?

Raymond Chen May 26, 2017 May 26, 2017 05/26/17

Open a command prompt and perform the following operations: This creates a hidden file called ~test.txt on the desktop. Configure Explorer to show hidden files. Observe that the ~test.txt file does not appear. But wait, there's more, if you're running Windows 7 (but not Windows 8 or higher): Configure Explorer to show both hidden ...

Diagnosing why you cannot create a stable subkey under a volatile parent key

Raymond Chen May 25, 2017 May 25, 2017 05/25/17

A customer encountered crashes in their program's initialization code. They weren't able to reproduce the problem in-house, but their failure logs suggested it was coming from here: The call was failing with System.IO.IOException: Cannot create a stable subkey under a volatile parent key. The corresponding Win32 error code is ...

Some questions about unflushed data and calling FlushFileBuffers on a new handle to a file

Raymond Chen May 24, 2017 May 24, 2017 05/24/17

Consider the following sequence of events: First question: Under these conditions, will the data written in step 2 be lazy-written to disk? Or is it at risk of being lost forever because the handle wasn't closed? Let's look at the last part first. Whether the process closed the handle before crashing doesn't affect the story, ...

What do these hard drive icons mean?

Raymond Chen May 23, 2017 May 23, 2017 05/23/17

Here are the different icon adornments for hard drives that may appear in My Computer This PC. (Sorry for the broken images earlier. The blog system corrupts the data URIs on upload, and I have to remember to manually fix them...

Why doesn’t searching my Start menu with Cortana find Internet shortcuts in my All Programs list?

Raymond Chen May 22, 2017 May 22, 2017 05/22/17

A customer had a program that installed a number of shortcuts to the Start menu. Among them were some Internet shortcut files, like "View Contoso User Guide" and "Get Online Support from Contoso". In Windows 7 and 8, if the user searched the Start menu for "Contoso", these shortcuts would appear in the search results. But in Windows 10, they ...

Debugging a GDI resource leak: Case study

Raymond Chen May 19, 2017 May 19, 2017 05/19/17

I was asked to help debug a problem. A program was leaking GDI bitmaps like crazy, and after a while, the GDI resource handle count reached 9,999, at which point GDI said, "That's it, I'm cutting you off." The problem isn't discovered until after the limit has been reached. To debug this, I'm gong to use different poor man's way of ...

Why is the !locks command called !locks even though it debugs only critical sections?

Raymond Chen May 18, 2017 May 18, 2017 05/18/17

Commenter DWalker07 notes that the !locks command is called !locks even though it doesn't actually debug all types of locks, only critical sections. Why the bad name? Because at the time it was written, critical sections were the only types of user-mode locks. In the original incarnation of Win32, there were semaphores and mutexes and other ...

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