The Old New Thing

You can use a file as a synchronization object, too

A customer was looking for a synchronization object that had the following properties: Can be placed in a memory-mapped file. Can be used by multiple processes simultaneously. Bonus if it can even be used by different machines simultaneously. Does not leak resources if the file is deleted. It turns out there is already a ...

Aha, I have found a flaw in the logic to detect whether my program is running on 64-bit Windows

Some time ago, I described how to detect programmatically whether you are running on 64-bit Windows, and one of the steps of the algorithm was "If you are a 64-bit program, then you are running on 64-bit Windows, because 32-bit Windows cannot run 64-bit programs." Every so often, somebody will claim that they found a flaw in this logic: "...

Why does the timestamp of a file increase by up to 2 seconds when I copy it to a USB thumb drive?

We saw some time ago that the FAT file system records timestamps in local time to only two-second resolution. This means that copying a file to a FAT-formatted device (typically a floppy drive or a USB thumb drive) can increase the timestamp by up two seconds. And even after the file is copied, the timestamp is not stable. The timestamp ...

How can I detect that a user's SID has changed and recover their old data?

A customer maintained a database which recorded information per user. The information in the database is keyed by the user's SID. This works out great most of the time, but there are cases in which a user's SID can change. "Wait, I thought SIDs don't change." While it's true that SIDs don't change, it is also true that the SID associated ...

Taking advantage of the fact that the handle returned when you create a kernel synchronization object has full access regardless of the actual ACL

A customer wanted some help deciding what security attributes to place on an event object intended to be used by multiple security contexts. We have two processes, call them A and B, running in different security contexts. I have an event that process A creates and shares with process B. The only thing process A does with the event is ...

It's time we face reality, my friends: We're not rocket scientists

During the development of Windows 95, it was common for team members to pay visits to other teams to touch base and let them know what's been happening on the Windows 95 side of the project. It was during one of these informal visits that the one of my colleagues reported that he saw that one of the members of the partner team had...

How do I read the "Double-click to open an item (single-click to select)" setting in Folder Options?

Today's Little Program reports whether the Double-click to open an item (single-click to select) option is selected in the Folder Options dialog. A customer wanted to know how to do this, presumably so that their program would respect the setting and adjust its user interface to match. The flag and member name is kind of weird. The ability...