Re: union type is evil, redux

Dmitry> Compiler bugs should be proven. The presence of crash is Dmitry> obviously not enough. Everything should be proven. There should be no crashes. Good luck. The question is, is it worth proving some particular thing? If you ask me, the compiler (and library) authors should be more interested in getting code that works under the broadest possible set of circumstances rather than defending whatever tricky thing they currently do, relying on the ability to excuse silly behavior with "the standard doesn't guarantee sane behavior in this case." While I strongly dislike faking a union with casts, I sympathize with Ben having recently had a similar experience with malloc. I don't think that having a standard is meaningful unless (a) it's obvious by Patent Office standards or (b) the people who are excusing surprising behavior with "the standard says it's OK" are willing to explain how to go about writing compliant code. Neither (a) nor (b) is satisfied in the "union builds crash when they shouldn't" case. Basically what it comes down to is the compiler writers are saying "we don't support union type when you use it to make obscure things clear, only when you use it to make trivial things verbose." Why bother? Ben's reaction, though a little violent, is perfectly plausible: OK, we'll deprecate union type since in practice we can't rely on reasonable behavior. -- Institute of Policy and Planning Sciences http://turnbull.sk.tsukuba.ac.jp University of Tsukuba Tennodai 1-1-1 Tsukuba 305-8573 JAPAN Ask not how you can "do" free software business; ask what your business can "do for" free software.