May 2017 | The Old New Thing

Extending our critical section based on WaitOnAddress to support timeouts

Raymond ChenMay 31, 2017May 31, 201705/31/17

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 ChenMay 30, 2017May 30, 201705/30/17

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 ChenMay 29, 2017May 29, 201705/29/17

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 ChenMay 26, 2017May 26, 201705/26/17

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 f

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

Raymond ChenMay 25, 2017May 25, 201705/25/17

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 ERROR_CHILD

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

Raymond ChenMay 24, 2017May 24, 201705/24/17

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, becaus

What do these hard drive icons mean?

Raymond ChenMay 23, 2017May 23, 201705/23/17

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 ChenMay 22, 2017May 22, 201705/22/17

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 d

Debugging a GDI resource leak: Case study

Raymond ChenMay 19, 2017May 19, 201705/19/17

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 identifyi

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

Raymond ChenMay 18, 2017May 18, 201705/18/17

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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