The Old New Thing
Practical development throughout the evolution of Windows.
Latest posts
Debugging a hang: Chasing the wait chain inside a process
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 good will provide enough information. Generally speaking, the deeper the stack, the more interesting it is, because uninteresting threads tend to be hanging out in their message loop or event loop, whereas interesting threads are busy doing something and have a complex stack ...
How can I detect programmatically whether the /3GB switch is enabled?
A customer was doing some diagnostic work and wanted a way to detect whether the switch was enabled. (Remember that the switch is meaningful only for 32-bit versions of Windows.) The way to detect the setting is to call and look at the . Compile this as a 32-bit program and run it. On 32-bit systems, this reports the system-wide setting that specifies the maximum user-mode address space, regardless of how your application is marked. Note, however, that your application must be marked in order to take advantage of the space above 2GB. On the other hand, when you run a 32-bit application on 64-bit Wi...
How do I disable Windows 8 touch contact visualizations for my application?
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 function. To demonstrate that, let's take our scratch program and make this simple change: The touch visualizations are white and the default window color is white, so the visualizations are hard to see in the scratch program. Let's change the color to something that the visualizations will be more visible against. Run the program, and you'll see that if you touch the window and drag your finger around,...
The great thing about regular expression languages is that there are so many to choose from!
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 expression that works just fine when I test it in ⟨insert regular expression testing tool, like RegExr or RegexPlanet⟩, but I can't get it to work in real life. My goal is to find all lines that contain an not followed anywhere by a .
Scripting an Internet Explorer window
Today's Little Program takes a random walk through MSDN by starting at the 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 article at all. I am also not concerned with random number bias because Little Program.) To talk a random walk through MSDN, we ask for all the links in the element. Note that I'm taking an undocumented dependency on the structure of MSDN pages. This structure has changed in the past, so be awa...
When are global objects constructed and destructed by Visual C++?
Today we're going to fill in the following chart: The C++ language specification provides some leeway to implementations on when global static objects are constructed. It can construct the object before begins, or it construct the object on demand according to complicated rules. You can read [basic.start.init] for the gory details. Let's assume for the sake of discussion that global static objects are constructed before begins. For global objects in the EXE, constructing them is no big deal because the C runtime startup code linked into the EXE does a bunch of preparation before calling the formal entry...
If only DLLs can get DllMain notifications, how can an EXE receive a notification when a thread is created (for example)?
When a DLL is loaded, it receives a notification, and when it is unloaded (or when the process terminates), it gets a notification. DLLs also receive notifications when a thread is created and notifications when a thread exits. But what if you are an EXE? EXEs don't have a , so there is no way to receive these notifications. The trick here is to hire a lackey. Create a helper DLL, called, say, . Your EXE links to the lackey, and the lackey's job is to forward all notifications back to your EXE. The DLL would naturally have to have a way for your EXE to provide the callback address, so you might have a f...
The GetCurrentThread function is like a check payable to Bearer: What it means depends on who's holding it
The function returns a pseudo-handle to the current thread. The documentation goes into significant detail on what this means, but I fear that it may have fallen into the trap of providing so much documentation that people decide to skip it. Okay, so first of all, what is a pseudo-handle? a pseudo-handle is a sentinel value for that is not really a handle, but it can act like one. The pseudo-handle returned by means, "The thread that this code is running on." Note that this is a context-sensitive proposition. All the text in MSDN is explaining the consequences of that sentence. In a sense, the functi...
Is there a way to disable a specific balloon notification without disabling all of them?
There is a group policy called Turn off all balloon notifications, but what if you want to turn off only one specific notification? The taskbar does not offer fine-grained policy control over balloon notifications. All you have is the giant sledgehammer that turns off all of them. If there is a specific balloon you want to disable, you have to check with the specific program that is raising them, or the specific product feature, to see if it offers a way to turn the balloon off. For example, there is a setting to disable the low disk space checks and another one to disable notifications that tell you when you...