On Fri, Aug 17, 2012 at 1:03 PM, Mike Stump <mikest...@comcast.net> wrote: > On Aug 17, 2012, at 6:58 AM, Paolo Carlini wrote: >> On 08/17/2012 01:26 PM, Richard Guenther wrote: >>> This gets rid of this field, pushing it into a short int in tree_base >>> (hopefully 2^16 non-defaulted template args are enough ...). >> Honestly, I don't think it's a trivial issue. > > Love to hear from Jason, but, my take would be 2^16 should be enough for > anyone. I think long before people hit that limit, they would merely > aggregate arguments into classes and structures. I think in another 20-80 > years, we might want to bump it back up to 32 bits, but... I think we can > safely wait until we get a compelling bug report for it.
C++11 says that an implementation should be able to handle at least 2^10 template parameters, 2^12 members declared in a single class. I believe that even for automatically generated programs, 2^16 is a good limit. I suspect that by the time that limit is a hindrance, C++ would have gone through several iterations and more importantly 128-bit integers would be common place, so by that time we would have plenty of spare bits -- if we haven't already restructured the tree data structures to use idiomatic C++ constructs that are both more space and time efficient. This is a very long of saying "I am comfortable with the 2^16 restriction on the number of template parameters. The patch needs to document that in the usual .texi file." -- Gaby
