The Old New Thing

March 2013 - The Old New Thing

The C language specification describes an abstract computer, not a real one

March 28, 2013 Mar 28, 2013 03/28/13
Raymond Chen
If a null pointer is zero, how do you access the memory whose address is zero? And if C allows you to take the address one past the end of an array, how do you make an array that ends at 0xFFFFFFFF, since adding one to that value would wrap around? First of all, who says that there is a byte zero? Or a byte 0xFFFFFFFF? The C language does...

“Adjust visual effects for best performance” should really be called “Adjust visual effects for crappiest appearance”

March 27, 2013 Mar 27, 2013 03/27/13
Raymond Chen
In the Performance Options control panel, on the tab labeled Visual Effects, there is a radio button called Adjust for best performance. If you select it, then all the visual effects are disabled. But the name of that radio button has been wrong for a long time. It doesn't actually adjust your visual effects for best performance. It just ...

There’s no law that says two people can’t have the same thing to eat

March 26, 2013 Mar 26, 2013 03/26/13
Raymond Chen
Some time ago, my group went out for a team lunch. It was to a restaurant we were not familiar with, so there was quite a bit of time studying the menu. As everybody looked over the menu, discussion naturally turned to "So what are you going to have?" "I think I'll have the salmon sandwich." One of my colleagues replied, "Oh, rats. I was ...

Using accessibility to monitor windows as they come and go

March 25, 2013 Mar 25, 2013 03/25/13
Raymond Chen
Today's Little Program monitors windows as they come and go. When people contemplate doing this, they come up with ideas like installing a WH_CBT hook or a WH_SHELL hook, but one of the major problems with those types of hooks is that they are injected hooks. Injection is bad for a number of reasons. It forces the hook to be in a DLL so it ...
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When will GetMessage return -1?

March 22, 2013 Mar 22, 2013 03/22/13
Raymond Chen
A source of great consternation is the mysterious -1 return value from Get­Message: If there is an error, the return value is −1. For example, the function fails if hWnd is an invalid window handle or lpMsg is an invalid pointer. That paragraph has caused all sorts of havoc, because it throws into disarray the standard message pump: ...
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Does this operation work when file system redirection is disabled? The default answer is NO

March 21, 2013 Mar 21, 2013 03/21/13
Raymond Chen
A customer reported that when their program called SH­Get­File­Info to get the icon for a folder, the call failed. "It works on some machines but not others. We don't know what the difference is between the working and non-working machines." They included the offending function from their program, but everything in the function ...
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The x86 architecture is the weirdo: Structured exception handling

March 20, 2013 Mar 20, 2013 03/20/13
Raymond Chen
If your reference architecture is x86, then you will think that everything it does is normal and the rest of the world is weird. Except it's the other way around: The x86 architecture is the weirdo. I was reminded of this when commenter 640k complained, on the subject of what I think is table-based structured exception handling, "It would ...