Memory Card Bugs (and a note about static analysis)

I was watching John Carmack’s QuakeCon 2011 keynote, and he mentioned that Rage was currently in the stage where they are creating cert builds, and just fixing bugs like (paraphrased) “getting a multiplayer invite and pulling your memory card out.” Memory card bugs are one of those things that tend to be a big annoyance for game programmers, because of the number of asynchronous use cases that need to be handled and the need to tie what are essentially supposed to be serial operations to a game that may be doing many other things in parallel. (Memory card support was optional on the original Xbox, due to the guaranteed presence of the internal hard drive. Accordingly, hardly any games actually support managing memory cards directly in-game.)

Carmack’s mention of memory card bugs reminded me of a funny story from Obsidian. For the Onyx Engine, one of my coworkers was working on writing the save/load code and then fixing bugs in the system, including memory card bugs on Xbox 360. Many of these bugs were timing-specific, so he would remove and reinsert his test memory card to try and reproduce the bug. Eventually, though, the first memory card slot on his development kit broke from the repeated (and potentially forceful, because of the need to try and reproduce specific timings) insertions and removals of the memory card. He had to switch over to the second slot on the kit — which, thankfully, survived until the project was over.

Another thing that came up in Carmack’s keynote is the use of static code analysis. He mentioned that id have drunk the proverbial Kool-Aid as far as static code analysis goes, and mentioned that turning on the “/analyze” switch for Xbox 360 builds (a flag that the XDK compiler supports — normally I think you need the Ultimate version of Visual Studio) brought to light many issues with their codebase. I can also vouch for this — I used to do this semi-regularly at Obsidian, and every time I ran it there were several subtle bugs that were sniffed out. It’s really worth using if you have it available.

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