August 2018 | The Old New Thing

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Removing the `TerminateThread` from code that waits for a job object to empty

Raymond ChenAugust 31, 2018Aug 31, 201808/31/18

Some time ago I showed how to wait until all processes in a job have exited. Consider the following code which wants to create a job, put a single process in it, and then return a handle that will become signaled when that process and all its child processes have exited. This exercise is inspired by actual production code, so we're solving a ...

The early history of Windows file attributes, and why there is a gap between System and Directory

Raymond ChenAugust 30, 2018Aug 30, 201808/30/18

Let's look at the values for the basic Windows file attributes. There's a gap where 8 should be. Rewind to CP/M. CP/M supported eleven attributes: The operating system imposed no semantics for user-defined attributes. You can use them for whatever you want. The meanings of the interface-defined attributes were defined by each operating ...

Obsolete Microspeak: TDBN and the six-pack

Raymond ChenAugust 29, 2018Aug 29, 201808/29/18

Windows 8 introduced its own code names. Last time we learned about charms, a term which started out as an internal code name but wound up as the public name for the feature. When you called up the charms bar, a little information box also appeared in the lower left corner of the screen. This showed the time, date, battery status, and ...

The evolution of Windows 8 charms

Raymond ChenAugust 28, 2018Aug 28, 201808/28/18

It's unclear what inspired the name for charms. It may have come from the item of jewelry, or perhaps from wine glass charms which are used at cocktail parties in certain social circles to identify which wine glass is yours. Whatever the origin, the charms feature quickly gained the internal nickname Lucky Charms from the breakfast cereal. I...

How do I force the Task Manager window closed whenever it opens?

Raymond ChenAugust 27, 2018Aug 27, 201808/27/18

A customer wanted to close (or at least hide) the Task Manager window whenever it opens. They did so by setting a timer and periodically running this code: This code worked on Windows 7, but stopped working on Windows 8. Well, yeah, because you're searching for a window by name. The name of the Task Manager window in Windows 7 was Windows ...

The Windows 95 team were proud slackers

Raymond ChenAugust 24, 2018Aug 24, 201808/24/18

During one of the many (many) team meetings during the course of Windows 95, there was a slide that showed something-or-other broken down by job discipline. There was a column for developers, another for quality assurance, and a third column labeled Slackers. The presenter was one of the lead program managers and explained that the Slackers ...

The PowerPC 600 series, part 14: Code walkthrough

Raymond ChenAugust 23, 2018Aug 23, 201808/23/18

Today we're going to take a relatively small function and watch what the compiler did with it. The function is this guy from the C runtime library, although I've simplified it a bit to avoid some distractions. Here's the corresponding disassembly: On entry, the parameters to a function are passed in r3 through r10. This function has only one...

The PowerPC 600 series, part 13: Common patterns

Raymond ChenAugust 22, 2018Aug 22, 201808/22/18

Now that we understand function calls and the table of contents, we can demonstrate some common calling sequences. If you are debugging through PowerPC code, you'll need to be able to recognize these different types of calling sequences in order to keep your bearings. Non-virtual calls generally look like this: The final nop may be omitted if...

The PowerPC 600 series, part 12: Leaf functions

Raymond ChenAugust 21, 2018Aug 21, 201808/21/18

On Windows NT for the PowerPC, there is a leaf function optimization available provided your function meets these criteria: If all of these conditions are met, then the function does not need to declare any function unwind codes, and it does not need to set up a stack frame. It can reuse the stack frame of its caller. In order for the ...

The PowerPC 600 series, part 11: Glue routines

Raymond ChenAugust 20, 2018Aug 20, 201808/20/18

The PowerPC has a concept of a "glue routine". This is a little block of code to assist with control transfer, most of the time to allow a caller in one module to call a function in another module. There are two things that make glue routines tricky: Jumping to the final target and juggling two tables of contents (the caller's and the callee's...

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