When are global objects constructed and destructed by Visual C++?, redux

Raymond Chen September 30, 2016 Sep 30, 2016 09/30/16

Today we're going to make some clarifications to this table, which came from an earlier article: It turns out that the upper right corner of the diagram actually splits into two cases. The table lists what happens if the process terminates by calling Exit­Process. The thing that makes termination with Exit­Process interesting is that...

The lackey catastrophe

Raymond Chen September 29, 2016 Sep 29, 2016 09/29/16

We encountered a real problem with global object destruction in Explorer. The object in question was an RAII container for a graphics object, so its destructor destroyed the graphics object. But the call to destroy the object was crashing. What's going on? The call to Delete­Object was occurring after GDI32 had already run its ...

When can you free the memory backing the HSTRING you created with WindowsCreateStringReference?

Raymond Chen September 28, 2016 Sep 28, 2016 09/28/16

A little while back, I posted my complete guide to HSTRING semantics (a rip-off of Eric's complete guide to BSTR semantics). A discussion of security descriptor lifetime somehow triggered the question "When can you free the memory backing the HSTRING you created with Windows­Create­String­Reference?" You can free the memory ...

It says that I should use USB usage page 1 and usage 6 to get raw keyboard data, but what if I have a PS/2 keyboard?

Raymond Chen September 26, 2016 Sep 26, 2016 09/26/16

Some time ago, I wrote about raw input and noted that if you want to receive raw keyboard input, you set the usage page to 1 and the usage to 6, noting that these numbers come from the USB HID specification. Commenter onodera asks, "Does this work for PS/2 input devices as well?" Let's try it. I happen to have a laptop within easy reach, so I...

The case of the system() call that returned before finishing

Raymond Chen September 21, 2016 Sep 21, 2016 09/21/16

A customer was having trouble with some code that copies a bunch of files and then processes the copy. Here's the code they shared (suitably redacted): The customer reported that "It appears that Find­First­FileA does not wait for system() to finish copying the files. Here's a sample log file: "Observe that Find­First­FileA ...

It’s an unfortunate choice of data type for the file system redirection cookie

Raymond Chen September 19, 2016 Sep 19, 2016 09/19/16

If you want to disable 64-bit file system redirection, you call the Wow64­Disable­Wow64­Fs­Redirection function. This function gives you a cookie. When you are finished, you call Wow64­Revert­Wow64­Fs­Redirection, passing the cookie you received from the previous call. Like this: The unfortunate thing is that ...