On 11/7/06, Mike Stump <[EMAIL PROTECTED]> wrote:
Anyway, in C++, the entire template mechanism was rife with building up duplicates. I'd propose that this problem can (and should be addressed) and that we can do it incrementally. Start with a hello world, then in comptypes, check to see when it says yes, they are the same, but the address equality checker says they might not be the same, print a warning. Fix the dup builders until no warnings. Then rebuild the world and repeat. :-) Work can be checked in, as dups are eliminated.
It's a good plan. Now, how much do we worry about the fact that we won't be printing typedef names when we combine duplicate nodes? If we don't care, our job is much easier. If we do care, then we need to introduce a system for equivalence classes to keep those typedef names, which will complicate matters a bit.
I did an extensive investigation in this area years ago, templates were the worse offender at that time. <int,int,char> != <int,int,char> type stuff.
Templates also have the opposite problem, because they do some strange sharing, e.g., X<T1> == X<T2> (where T1 and T2 are template type parameters from different templates). It makes for some strange diagnostics in ConceptGCC, but without concepts it doesn't seem harmful. Since we know that type canonicalization is incremental, could we work toward type canonicalization in the GCC 4.3 time frame? Cheers, Doug
