Friday, May 12, 2006

It Had To Be That Way

I just found an extremely rare bug in X-Plane caused by an uninitialized variable in a constructor; this code functioned in such a way that a compiler cannot do the code anlaysis to find the bug, and unfortunately it happens rarely enough that it’s probably in the shipping sim.

To paraphrase the philosophy of C++:

  • A C++ programmer can do anything, no matter how stupid. After all, 0.001% of the time it might be necessary.
  • The fastest performance path must be accessable via C++.
  • Reducing development time by catching dumb mistakes isn’t even remotely a language goal.

Given this, it’s understandable what happened; the language has to allow me to leave junk in my data because it’s faster not to initialize it and sometimes I want to be lazy for speed. Unfortunately it means that catching errors is up to me, and I am human and fallable, especially when I’ve been drinking beer all night.

It got me thinking about whether there could be a language that provides the performance options of C++ but without the “dangerous environment” of C++. Java and C# are managed; I am definitely among the snotty bitflingers who think that for my app garbage collection and managed memory mean unacceptable performance loss. This probably isn’t true 99% of the time, but in the case of X-Plane, we’ve got a number of specialized allocators (hrm — future blog?) that give us better memory performance than we could get by just newing and deleting objects. (This is indeed the 0.001% that C++ cators to.)

As a straw-man, I’m imagining a language where you have to declare your intention to sin. Basically the rules of the language are restricted until you apply some kind of attribute, similar to static. So most classes would work the slow way, e.g. automatic initialization, perhaps managemed memory, who knows, but then when you tag a class as low-level, you assume responsibility for all aspects of the environment.

My guess is that we’d have to apply such a tag to a very small number of classes in X-Plane, and thus we’d get better compiler support for most of our code.

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