The Old New Thing

Ow, I'm too safe!

August 18, 2011 Aug 18, 2011 08/18/11

Raymond Chen

One of my friends is a geek, and, naturally, fully researches everything he does, from cement pouring to bicycle parts, perhaps a bit obsessively. He made sure to get five-point restraints for his children's car seats, for example. And he naturally tightens the belts snugly when putting his children in the car. At one point, as he was ...

Why does IFileOperation skip junctions even though I passed FOFX_NOSKIPJUNCTIONS?

August 18, 2011 Aug 18, 2011 08/18/11

Raymond Chen

The method accepts a number of flags to modify the file operation, among them today's subject . A customer reported that they couldn't get this flag to work: Whether they set it or not, the skipped over file system junctions. The term junction evolved two independent different meanings. The shell team invented the term shell namespace ...

Starting up inside the box

August 17, 2011 Aug 17, 2011 08/17/11

Raymond Chen

the shell team received two customer questions about a month apart which seemed unrelated but had the same root cause. I found that in Windows Vista, the command is ten times slower than it was in Windows XP. What is the source of this slowdown, and how can I fix it? We have an application which takes a very long time to start up on ...

Why does creating a shortcut to a file change its last-modified time… sometimes?

August 16, 2011 Aug 16, 2011 08/16/11

Raymond Chen

A customer observed that sometimes, the last-modified timestamp on a file would change even though nobody modified the file, or at least consciously took any steps to modify the file. In particular, they found that simply double-clicking the file in Explorer was enough to trigger the file modification. It took a while to puzzle out, but here'...

Why does the runas command require its command line to be quoted?

August 15, 2011 Aug 15, 2011 08/15/11

Raymond Chen

Commenter teo complained that the command requires its command line to be quoted. Well, if you think about it, why single out ? Pretty much all programs require their command line to be quoted if they contain special characters (like spaces that you want to be interpreted as part of a file name instead of as an argument separator). The ...

ReadDirectoryChangesW reads directory changes, but what if the directory doesn't change?

August 12, 2011 Aug 12, 2011 08/12/11

Raymond Chen

The function reads changes to a directory. But not all changes that happen to files in a directory result in changes to the directory. Now, it so happens that nearly all changes to a file in a directory really do result in something happening to the file's directory entry. If you write to a file, the last-write time in the directory entry ...

The ways people mess up IUnknown::QueryInterface, episode 4

August 11, 2011 Aug 11, 2011 08/11/11

Raymond Chen

One of the rules for is so obvious that nobody even bothers to state it explicitly as a rule: "If somebody asks you for an interface, and you return , then the pointer you return must point to the interface the caller requested." (This feels like the software version of dumb warning labels.) During compatibility testing for Windows ...

Slim reader/writer locks don't remember who the owners are, so you'll have to find them some other way

August 10, 2011 Aug 10, 2011 08/10/11

Raymond Chen

The slim reader/writer lock is a very convenient synchronization facility, but one of the downsides is that it doesn't keep track of who the current owners are. When your thread is stuck waiting to acquire a slim reader/writer lock, a natural thing to want to know is which threads own the resource your stuck thread waiting for. Since there...

Why does the Shift+F10 menu differ from the right-click menu?

August 9, 2011 Aug 9, 2011 08/9/11

Raymond Chen

The Shift+F10 key is a keyboard shortcut for calling up the context menu on the selected item. but if you look closely, you might discover that the right-click menu and the Shift+F10 menu differ in subtle ways. Shouldn't they be the same? After all, that's the point of being a keyboard shortcut, right? Let's set aside the possibility that a ...

What does the CreateProcess function do if there is no space between the program name and the arguments?

August 8, 2011 Aug 8, 2011 08/8/11

Raymond Chen

In an old discussion of why the function modifies its command line, commenter Random832 asked, "What if there is no space between the program name and arguments - like "cmd/?" - where does it put the null then?" The function requires a space between the program name and arguments. If you leave out the space, then the arguments are ...

The Old New Thing

August 2011 - Page 2 of 3 - The Old New Thing