Showing tag results for Code

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 synchronization ob...

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: "This alg...

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 with a u...

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 signal it,...

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 to s...

The function has been the subject of much rumor and innuendo. In response to all the confusion, the kernel folks put together a page which tries to settle the controversy once and for all. It discusses the history of QPC over the ages, the problems it had on earlier versions of Windows or older firmware (which is probably where a lot of the myth...

A customer discovered strange behavior in the function and wondered whether it was expected. We use the function to obtain a thread handle with , passing in a valid thread ID. We later pass this handle to to get the thread exit code. We have found that the function succeeds if the thread in question belongs to another process, provided the thre...

In the same week, the shell team was asked to investigate two failures. The first one was a deadlock in Explorer. The participating threads look like this: The shell extension caused this problem because it ignored the rule against calling shell and COM functions from the entry point, as specifically called out in the documentation as example...

Today's Little Program is an exercise that solves the following problem: Given a JavaScript array and an unsorted array (possibly containing duplicates), calculate the result of deleting all of the elements from the original array as specified by the indices. For example, suppose and . The indices specify that elements 2 (charles), 4 (eve...

C# has operators and to control the behavior of the language in the face of integer overflow. There are also and statements which apply the behavior to blocks of statements rather than single expressions. Why, then, doesn't this code below raise an overflow exception? (Mini-exercise: Why couldn't I have just written ?) The answer is th...