Re: union type is EVIL EVIL EVIL

Ville> On Tue, 2002-12-17 at 04:20, Ben Wing wrote: Ville> [...] Ville> Uh, --use-union-type has been many times suggested on Ville> xemacs-beta as a way to prevent crashes in something Ville> related to aggressive compiler Ville> What's correct? To some extent, both. Sometimes you lose, and other times you lose big. There's nothing we can do about compiler bugs except write them up in PROBLEMS and code defensively. There are any number of temporaries in XEmacs notated with "Compiler XYZ chokes without this." This is more of the same. :-( To me it's a pragmatic issue (if anything, union type is more "righteous" than the int Lisp_Object type). GCC (and now VC++) has historically had problems with unions.[1] OTOH unions have historically been good at smoking out "if (lisp_object) ..." constructs and the like, and to some extent aliasing issues. I think if you look, you'll find that (a) it's often been me recommending union type[2] and (b) --use-union-type typically doesn't solve any problems. If better diagnosis tools are now available, then there may be reason to avoid union type. Footnotes: [1] They've also had problems with std C++ ... but I doubt Ben would argue that is EVIL EVIL EVIL ;-) [2] Ie, you're really only citing one opinion. -- 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.