The Old New Thing

Why are DLLs unloaded in the "wrong" order?

May 23, 2005 May 23, 2005 05/23/05
Raymond Chen
When a program starts or when a DLL is loaded, the loader builds a dependency tree of all the DLLs referenced by that program/DLL, that DLL's dependents, and so on. It then determines the correct order in which to initialize those DLLs so that no DLL is initialized until after all the DLLs upon which it is dependent have been initialized. (Of...

I'd like to register my stolen car, please

May 20, 2005 May 20, 2005 05/20/05
Raymond Chen
On NPR's All Things Considered Robert Siegel reported on the curious status of legally stolen cars in Gaza. Gaza license plates can be red for official, green for taxis, and white for private vehicles. The lower the number on the red plates, the higher the position of the official. The number 30 designates a truck. All this is pretty ...

When is a window visible yet not visible?

May 20, 2005 May 20, 2005 05/20/05
Raymond Chen
Today, a quick puzzler. Consider the following code fragment: We just showed the window, certainly it is visible, right? Yet the assertion can fire (even in the absence of multi-threading). Why? Answer below - stop reading if you want to try to solve it yourself. Take a look at the function. If the specified ...

Loading the dictionary, part 5: Avoiding string copying

May 18, 2005 May 18, 2005 05/18/05
Raymond Chen
Looking at the profile for our program so far, 35% of the CPU time is spent copying strings around. Let's see if we can improve that. The best way to speed up copying strings is not to copy them in the first place. Using a in our structure forces the class to copy the string data, when all we really need to copy is the pointer and size ...

You can't escape those AOL CDs

May 17, 2005 May 17, 2005 05/17/05
Raymond Chen
One of my colleagues was unpacking one of those $30,000 quad-processor more-memory-than-you-know-what-to-do-with super-server computers. The kind that require their own electrical substation. And it came with an AOL CD. It's like buying a Lexus and finding a 35-cents-off coupon in the glove compartment. Apparently, one of the questions AOL ...

Loading the dictionary, part 4: Character conversion redux

May 16, 2005 May 16, 2005 05/16/05
Raymond Chen
Getting rid of was a big help, but 480ms is still not quite peppy enough. You need to respond to user actions within a tenth of a second for thing to seem responsive. Profiling the latest endeavor reveals that 40% of our CPU time is spent in . Some debugging reveals that ultimately calls but uses it to convert only one or two ...

Loading the dictionary, part 3: Breaking the text into lines

May 13, 2005 May 13, 2005 05/13/05
Raymond Chen
Even after moving the character conversion out of the function, profiling reveals that is still taking nearly 50% of our CPU. The fastest code is code that isn't there, so let's get rid of altogether. Oh wait, we still need to break the file into lines. But maybe we can break the file into lines faster than did. This very simple class...

The Microsoft corporate network: 1.7 times worse than hell

May 12, 2005 May 12, 2005 05/12/05
Raymond Chen
Today I'm going to tell a story from 1996. Why? Because I can. One of the tests performed by Windows Hardware Quality Labs (WHQL) was the NCT packet stress test which had the nickname "Hell". The purpose of the test was to flood a network card with an insane number of packets, in order to see how it handled extreme conditions. It uncovered ...

Loading the dictionary, part 2: Character conversion

May 11, 2005 May 11, 2005 05/11/05
Raymond Chen
When you want to optimize a program, you first need to know where the time is being spent. There's no point optimizing a function that isn't actually responsible for your poor performance. For example, if a particular function is responsible for 2% of your CPU time, then even if you optimized it down to infinite speed, your program would...