The Old New Thing

November 2014 - The Old New Thing

A user's SID can change, so make sure to check the SID history

November 28, 2014 Nov 28, 2014 11/28/14
Raymond Chen
It doesn't happen often, but a user's SID can change. For example, when I started at Microsoft, my account was in the SYS-WIN4 domain, which is where all the people on the Windows 95 team were placed. At some point, that domain was retired, and my account moved to the REDMOND domain. We saw some time ago that the format of a user SID is...

Some light reading on lock-free programming

November 27, 2014 Nov 27, 2014 11/27/14
Raymond Chen
Today is a holiday in the United States, so I'm going to celebrate by referring you to other things to read. I'm going to start with a presentation by Bruce Dawson at GDC 2009, which is basically multiple instances of the question "Is this code correct?", and the answer is always "No!" Although the title of the talk is Lockless Programming in...

The crazy world of stripping diacritics

November 24, 2014 Nov 24, 2014 11/24/14
Raymond Chen
Today's Little Program strips diacritics from a Unicode string. Why? Hey, I said that Little Programs require little to no motivation. It might come in handy in a spam filter, since it was popular, at least for a time, to put random accent marks on spam subject lines in order to sneak past keyword filters. (It doesn't seem to be popular any ...

Is it wrong to call SHFileOperation from a service? Revised

November 21, 2014 Nov 21, 2014 11/21/14
Raymond Chen
My initial reaction to this question was to say, "I don't know if I'd call it wrong, but I'd call it highly inadvisable." I'd like to revise my guidance. It's flat-out wrong, at least in the case where you call it while impersonating. The registry key is bound to the current user at the time the key is first accessed by a process: The ...

A library loaded via LOAD_LIBRARY_AS_DATAFILE (or similar flags) doesn't get to play in any reindeer module games

November 20, 2014 Nov 20, 2014 11/20/14
Raymond Chen
If you load a library with the flag, then it isn't really loaded in any normal sense. In fact, it's kept completely off the books. If you load a library with the , , or flag (or any similar flag added in the future), then the library gets mapped into the process address space, but it is not a true module. Functions like , , and will not ...

Distinguishing between normative and positive statements to help people answer your question

November 19, 2014 Nov 19, 2014 11/19/14
Raymond Chen
Often, we get questions from a customer that use the word should in an ambiguous way: Our program creates a widget whose flux capacitor should have reverse polarity. Attached is a sample program that shows how we create the widget with . However, the resulting widget still has a flux capacitor with standard polarity. Can you help us? The ...

How do I enumerate drives the same way that the NET USE command does?

November 17, 2014 Nov 17, 2014 11/17/14
Raymond Chen
If you use the Remote Desktop Connection client to connect to another computer, you have the option of making your local drives available to the remote computer. A customer wanted to know how to enumerate all the drives on the local machine. The were able to get the volumes mapped to drive letters, but they also wanted to get the ...