August 2018 | The Old New Thing

Removing the <CODE>TerminateThread</CODE> from code that waits for a job object to empty

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

Raymond Chen August 31, 2018 Aug 31, 2018 08/31/18

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 Chen August 30, 2018 Aug 30, 2018 08/30/18

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 Chen August 29, 2018 Aug 29, 2018 08/29/18

Old Windows 8 terminology.

The evolution of Windows 8 charms

Raymond Chen August 28, 2018 Aug 28, 2018 08/28/18

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 Chen August 27, 2018 Aug 27, 2018 08/27/18

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 Chen August 24, 2018 Aug 24, 2018 08/24/18

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 Chen August 23, 2018 Aug 23, 2018 08/23/18

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 Chen August 22, 2018 Aug 22, 2018 08/22/18

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 Chen August 21, 2018 Aug 21, 2018 08/21/18

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 Chen August 20, 2018 Aug 20, 2018 08/20/18

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...

The Old New Thing