December 2015 | The Old New Thing

2015 year-end link clearance

Raymond ChenDecember 31, 2015Dec 31, 201512/31/15

The year-end link clearance is here! You may have noticed that the link clearances are getting shorter and shorter. I may have to cut back to only one link clearance per year. Not Even Close: The State of Computer Security. James Mickens once again dazzles the audience with his brilliance. It Was Never Going to Work, So Le

Why is my call to ChangeTimerQueueTimer having no effect? (And another case of looking past the question to solve the problem.)

Raymond ChenDecember 30, 2015Dec 30, 201512/30/15

A customer had a question about the ChangeTimerQueueTimer function, and they shared a sample program that demonstrated the issue. (Hooray for reduction.) The customer asked, "Why aren't we getting the ticks after calling ChangeTimerQueueTimer?" This is explained down in the documentation for the ChangeTimer

Why are Windows setup logs stored in a Panther directory? Does it have anything to do with the abandoned Panther project from the precursor to Windows 95?

Raymond ChenDecember 29, 2015Dec 29, 201512/29/15

Some time ago, I discussed the fates of the various cat projects that led to Windows 95, which was in turn a follow-up to a list of cat-related code names from projects that led to Windows 95. In summary: There were a bunch of projects with cat-related code names. Only one of the projects survived to Windows 95 in its originally-envisioned fo

Determining how each Explorer window is sorted

Raymond ChenDecember 28, 2015Dec 28, 201512/28/15

Today's Little Program lists all the open Explorer windows and their current sort criteria. (I will refrain from mentioning how auto-sort makes this meaningful.) Remember that Little Programs do little to no error checking. To process a window, we first ask for the top-level browser, and from that we ask for the active shell view, then conver

When is the correct time to call FreeLibraryWhenCallbackReturns?

Raymond ChenDecember 25, 2015Dec 25, 201512/25/15

When is the correct time to call FreeLibraryWhenCallbackReturns, or any of the other ...WhenCallbackReturns functions? In practice, many people call the function immediately before returning from the callback. Is this a requirement? No. You can call the ...WhenCallbackReturns function at any time during

Why does my in-place tooltip dismiss itself as soon as it appears?

Raymond ChenDecember 24, 2015Dec 24, 201512/24/15

One subtlety in the use of in-place tooltips is that you should create the tooltip with the WS_EX_TRANSPARENT extended style. This style makes the window invisible to hit-testing, which is a good thing here. The code that decides when to show and hide an in-place tooltip goes like this: If the mouse enters the thing that needs a tooltip, the

Confusing gotcha: PSECURITY_DESCRIPTOR is not a pointer to a SECURITY_DESCRIPTOR

Raymond ChenDecember 23, 2015Dec 23, 201512/23/15

There is a structure called a SECURITY_DESCRIPTOR. It describes the layout of an absolute security descriptor. There is also a structure called a SECURITY_DESCRIPTOR_RELATIVE. It describes the layout of a relative security descriptor. And then there is a type called PSECURITY_DESCRIPTOR. You might think based on its name that it is a pointer

Unhandled Exception: Cannot print exception string because Exception.ToString() failed.

Raymond ChenDecember 22, 2015Dec 22, 201512/22/15

I ran an internal tool, and it communicated with a back-end service, and then displayed the error Unhandled Exception: Cannot print exception string because Exception.ToString() failed. I can't figure out what that even means. I waited a little while, then tried again, It worked the second time. Didn't even need to turn it off and back on

Allocating page file space without allocating RAM

Raymond ChenDecember 21, 2015Dec 21, 201512/21/15

The Windows Server 2003 Resource Kit comes with a tool called consume.exe, and one of the things you can ask it to do is to suck up space in your swap file. If you run the program in that mode, you see that it manages to do its job without consuming physical memory. (The amount of Free Pages in Task Manager remains constant.) How is that poss

Are views of memory-mapped files coherent within a single process? (And how this was the wrong question.)

Raymond ChenDecember 18, 2015Dec 18, 201512/18/15

A customer wanted some clarification. An MSDN article says This means that changes made to a page in the memory-mapped file via one process's view are automatically reflected in a common view of the memory-mapped file in another process. "The above paragraph says that the views are coherent across processes, but what about within a single pr

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