No Magic Numbers

Action Solitaire 1.31 is now available for download.

After the last posting, we discovered a rather significant bug in Action Solitaire. It was fortunate that it was discovered in house, but unfortunate that it was not found during beta testing and, hence, required a public update. The problem caused two of the 65 games to behave incorrectly (or even crash) when large or huge card sizes were selected, either explicitly or implicitly through automatic sizing.

The problem turned out to be magic numbers in the code. We released the first version of Action Solitaire back in 2003, which was six years of coding experience ago and at a time when I felt under some (self-imposed) pressure to get the product finished. Unlike some of the other projects, the source code for this game has not been refactored, except to the extent necessary to make updates for Vista and add new games, so I never revisited these (working) games to see the problem.

For those who do not know, a magic number is an explicit and undocumented constant in the source code for a program, so named because the value works like magic, without any proper explanation. In this particular case, the width and height of an image buffer were set to constant values, calculated (manually) to accommodate an area based on the largest card sizes supported by the game at that time. Rather than actually letting the computer determine the necessary buffer size, based on named constant values (e.g., MaxCardWidth and MaxCardHeight), the code just used constant numbers directly. When the maximum card size increased, the buffer was too small and problems ensued. Such are the dangers of magic numbers.

It did not take long to find and fix the problem, but it should not have been necessary in the first place, especially since we had standards, even back then, that discouraged the use of magic numbers. I made an exception and got burned. Ouch.

Anyway, Action Solitaire can be downloaded here, and I guarantee ample opportunity to find other bugs in this product, but the game is fun (and addictive) as well.

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