Is it okay to call TryAcquireSRWLock from a thread that has already acquired the lock?

Raymond Chen August 19, 2016 Aug 19, 2016 08/19/16

A customer found the MSDN documentation ambiguous. Wouldn't be the first time. In the description of Slim Reader/Writer Locks: An SRW lock is the size of a pointer. The advantage is that it is fast to update the lock state. The disadvantage is that very little state information can be stored, so SRW locks cannot be acquired recursively. In ...

If I have a modeless dialog box with custom accelerators, which should I call first: IsDialogMessage or TranslateAccelerator

Raymond Chen August 18, 2016 Aug 18, 2016 08/18/16

A customer had a modeless dialog box with custom accelerators. If their window had been a modeless dialog box without custom accelerators, then their message dispatch would be On the other hand, if their window with accelerators had been a plain window rather than a dialog box, then their message dispatch would be But since they have both, ...

On installing a custom unhandled exception filter and intentionally raising an exception to get its attention

Raymond Chen August 17, 2016 Aug 17, 2016 08/17/16

A customer reported that they were seeing inconsistent behavior when they intentionally raised a Win32 exception and tried to catch it in a custom unhandled exception filter. The customer observed a few things. First, if the Test function was called from inside a window procedure, then the behavior changed depending on the execution ...

How can I debug a function that has been subjected to COMDAT folding?

Raymond Chen August 15, 2016 Aug 15, 2016 08/15/16

Suppose you want to set a breakpoint on a function, but you find that the function has been subjected to COMDAT folding, so your attempt to set a breakpoint on the function ends up setting a breakpoint on some other function, and your breakpoint ends up firing when either your desired function or the other identical function gets called. How ...

On the importance of making sure WaitForInputIdle doesn’t think you’re idle, episode 2

Raymond Chen August 12, 2016 Aug 12, 2016 08/12/16

Continuing our DDE micro-series, we'll look at another customer who was having trouble getting the shell to recognize their DDE server. We have a program that supports DDE for legacy reasons. More specifically, we have two versions of that program, and we support the user installing both of them side by side. To mediate this uneasy ...

On the importance of making sure WaitForInputIdle doesn’t think you’re idle, episode 1

Raymond Chen August 11, 2016 Aug 11, 2016 08/11/16

A customer had a program that was originally designed back when DDE ruled the land, and it continues to support DDE for (yup) backward compatibility. Today and tomorrow are going to deal with DDE issues, but not because DDE is actually anything recommended. Quite the contrary: Please feel free to stop using DDE. DDE is so obsolete that when ...

How to create a file mapping that allows others to open the file in exclusive mode?

Raymond Chen August 10, 2016 Aug 10, 2016 08/10/16

A customer had a tool that opens files like DLLs and TLBs in order to extract information from them. We currently use Create­File, Create­File­Mapping, and Map­View­Of­File to access the file. The problem is that the Create­File­Mapping prevents the file from being renamed or deleted, even if the Create­...