Many of the normal interlocked operations come with variants called InterlockedXxxAcquire and InterlockedXxxRelease. What do the terms Acquire and Release mean here? They have to do with the memory model and how aggressively the CPU can reorder operations around it. An operation with acquire semantics is one which does not permit subsequent ...

Each component that uses ACLs to control access has its own idea of what GENERIC_READ, GENERIC_WRITE, and GENERIC_EXECUTE mean. It's not like there's a master list that somebody can make that lists them all, because I can make up a new one right here. Watch me: #define GIZMO_QUERY_STATUS 0x0001 #define GIZMO_QUERY_MEMBERS 0x0002 #define ...

The command interpreter cmd.exe has a concept known as the error level, which is the exit code of the program most recently run. You can test the error level with the IF ERRORLEVEL command: IF ERRORLEVEL 1 ECHO error level is 1 or more <sidebar> The IF ERRORLEVEL n test succeeds if the error level is n or more. This was presumably ...

Now, it may very well be true that many people who use GetForegroundWindow() as the owner for a dialog box because they don't know any better, but I'm not convinced that everyone who does so did it out of ignorance; I'm sure there's some malice in there, too. Here's how it may have gone down: Bug: I start the product setup, and then I go ...

Last time, we looked at a customer who wanted to know how to tell whether a given folder was a Recycle Bin folder or not. We answered the question as stated, but made the mistake of not looking at the problem the customer was trying to solve. I need to know which folders are Recycle Bin folders so I can skip over them when searching the drive ...

Here's a question inspired by an actual customer question: I need a function that, given a path, tells me whether it is a Recycle Bin folder. I tried using functions like SHGetSpecialFolderPath with CSIDL_BITBUCKET, but that doesn't work because the Recycle Bin is a virtual folder that is the union of the Recycle Bins of all drives. The ...

The WM_SETFONT message tells a control which font you would like the control to use for its text. This message is a convention, not a rule. For example, our scratch program doesn't pay attention to the WM_SETFONT message. If somebody sends it a WM_SETFONT, nothing happens. The scratch program just ignores the caller and uses whatever font it ...

For the same reason that not all error codes are defined in winerror.h, not all error strings are defined in the system message table. If you've ever played with the message compiler, you'd quickly have recognized the winerror.h file as the header file associated with a message resource. In other words, there's a .mc file that gets processed by ...

Last time, we saw how those extra bits can be used to multiplex HANDLE with other values. That was a specific case of a more general scenario: Expanding the handle namespace to include things that aren't handles. (You can also view today's example as a generalization of the sentinel value problem, where we need to generate an arbitrary number ...

Last time, we saw how those extra bits can be used to develop safe sentinel values. That is a special case of a more general problem: How do you pack 33 bits of information into a 32-bit value? Whereas last time, we weren't forced into the use of a sentinel value because we could develop a (cumbersome) helper class and switch people over to ...