April 2019 | The Old New Thing

Async-Async: Reducing the chattiness of cross-thread asynchronous operations

Raymond Chen April 30, 2019 Apr 30, 2019 04/30/19

Setting up fakes on both sides.

Spotting problems with destructors for C++ temporaries

Raymond Chen April 29, 2019 Apr 29, 2019 04/29/19

Consider the unique_handle. It specializes std::unique_ptr to support Windows kernel handles. It lets you get all the niceties of std::unique_ptr with just a handful of lines of code. But then you have the problem of interoperating with the rest of the system. For example, how would you use a unique_handle to receive the result of a ...

How many ways are there to sort GUIDs? How much time do you have?

Raymond Chen April 26, 2019 Apr 26, 2019 04/26/19

Suppose you want to sort GUIDs, say because they are a key in an ordered map. How many ways are there to order them? Before we can even talk about how to order GUIDs, we need to figure out how we're going to represent them. You can take the view that a GUID is just an array of 16 bytes.¹ But the GUID structure itself groups them into four...

How can I launch an unelevated process from my elevated process, redux

Raymond Chen April 25, 2019 Apr 25, 2019 04/25/19

Some time ago, I showed how you can launch an unelevated process from an elevated process by asking Explorer to launch the program on your behalf. There's another way which is a bit more direct, but it assumes that the thing you want to do can be done with a direct CreateProcess call. In other words, if you need the system to look up the...

The administrative assistant who lasted only one day: A legendary prank from days of yore

Raymond Chen April 24, 2019 Apr 24, 2019 04/24/19

Today is Administrative Professionals Day, according to somebody who decided to declare today to be Administrative Professionals Day. Administrative assistants are perhaps one of the most important members of a team. They work almost invisibly behind the scenes to keep everything running smoothly. They make sure everybody has what they need, ...

Why was Texas Hold ‘Em Poker a Windows Ultimate Extra instead of a built-in game?

Raymond Chen April 23, 2019 Apr 23, 2019 04/23/19

Windows Vista came with a variety of in-box games. Old stand-bys like Freecell were given a facelift, and some new games were been added, like Purble Place. Other games were available as a separate download as part of the (disastrous) Windows Ultimate Extras. In particular, one of the games was Texas Hold 'Em Poker. Why was this game made a ...

A little program to look for files with inconsistent line endings

Raymond Chen April 22, 2019 Apr 22, 2019 04/22/19

I wrote this little program to look for files with inconsistent line endings. Maybe you'll find it useful. Probably not, but I'm posting it anyway. The EnumerateFiles method recursively enumerates the contents of the directory, but skips over hidden files, hidden directories, and directories with specific names. The main program takes ...

On resolving the type vs member conflict in C++: The Color Color problem

Raymond Chen April 19, 2019 Apr 19, 2019 04/19/19

In C++, there are ambiguities when a member function has the same name as a type. Consider: Your project has a custom element, say like this: And now you are implementing the OnThemeChanged method. This code doesn't compile. The word Style can mean multiple things: C++ unqualified name lookup in member functions searches the ...

How arbitrary is the ArbitraryUserPointer in the TEB?

Raymond Chen April 18, 2019 Apr 18, 2019 04/18/19

There's a member of the NT_TIB structure called ArbitraryUserPointer. How arbitrary is this value? Can I use it for anything I want? This is another case of looking at the world through kernel-colored glasses. The ArbitraryUserPointer is arbitrary from the kernel's point of view, but that doesn't mean that it's available ...

What does this strange value for “Percent CPU” mean in Performance Monitor?

Raymond Chen April 17, 2019 Apr 17, 2019 04/17/19

A customer was monitoring the CPU usage of one of their processes in the Performance Monitor tool, and they got a pretty graph and this summary: What did the process consume 271828 of? What does this number mean in the context of percent processor time? FIrst thing to notice is that the comma is a decimal separator, not a thousands ...

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