The Old New Thing

What does 1#J mean? A strange corner case of the printing of special values

February 28, 2013 Feb 28, 2013 02/28/13

Raymond Chen

As a puzzle, commenter nobugz asks, "What kind of infinity is 1.#J?" double z = 0; printf("%.2f", 1/z); Now, the division by zero results in IEEE positive infinity, would would normally be printed as 1#INF. But the catch here is that the print format says "Display at most two places after the decimal point." But where is the decimal point...

Is there a way to specify an icon to appear next to a menu item via the resource template?

February 28, 2013 Feb 28, 2013 02/28/13

Raymond Chen

The MENU­ITEM­INFO structure lets you specify a bitmap to appear next to the menu item. Is there a way to do this from a menu resource template? No. If you look at the format of menu templates, you'll see that there is nowhere to specify a bitmap. Which kind of makes sense, because it is the responsibility of the application ...

Display a custom thumbnail for your application (and while you’re at it, a custom live preview)

February 25, 2013 Feb 25, 2013 02/25/13

Raymond Chen

By default, when the taskbar or any other application wants to display a thumbnail for a window, the result is a copy of the window contents shrunk down to the requested size. Today we're going to override that behavior and display a custom thumbnail. Take the program from last week and make these changes: #include <dwmapi.h> BOOL...

Now that version 4 of the .NET Framework supports in-process side-by-side runtimes, is it now okay to write shell extensions in managed code?

February 22, 2013 Feb 22, 2013 02/22/13

Raymond Chen

Many years ago, I wrote, "Do not write in-process shell extensions in managed code." Since I originally wrote that article, version 4 of the .NET Framework was released, and one of the features of that version is that it supports in-process side-by-side runtimes. Does that mean that it's now okay to write shell extensions in managed code? ...

Isn’t the CompletionKey parameter to CreateIoCompletionPort superfluous?

February 22, 2013 Feb 22, 2013 02/22/13

Raymond Chen

When you associate a file handle with an I/O completion port with the Create­Io­Completion­Port function, you can pass an arbitrary pointer-sized integer called the Completion­Key which will be returned by the Get­Queued­Completion­Status function for every I/O that completes against that file handle. But isn't ...

What does -1.#IND mean?: A survey of how the Visual C runtime library prints special floating point values

February 21, 2013 Feb 21, 2013 02/21/13

Raymond Chen

As every computer scientist knows, the IEEE floating point format reserves a number of representations for infinity and non-numeric values (collectively known as NaN, short for not a number). If you try to print one of these special values with the Visual C runtime library, you will get a corresponding special result: Positive and ...

You can ask the compiler to answer your calling convention questions

February 20, 2013 Feb 20, 2013 02/20/13

Raymond Chen

If you want to figure out some quirks of a calling convention, you can always ask the compiler to do it for you, on the not unreasonable assumption that the compiler understands calling conventions. "When a __stdcall function returns a large structure by value, there is a hidden first parameter that specifies the address the return value ...