http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51653
--- Comment #2 from Marc Glisse <marc.glisse at normalesup dot org> 2011-12-24 22:25:51 UTC --- (In reply to comment #1) > I'm not yet convinced we want to apply it, Hi, just so I know, what part are you not convinced about? 1) that we want a library solution? it is just a proof of concept, I would be happy with a compiler solution (although it might still require a library rewrite so it can be applied). 2) that we want a more compact tuple? sizeof(tuple<char,tuple<char,int>>) is currently 16, that's twice as much as necessary (in case someone wonders, the unexpected extra 4 is there for the same reason that tuple<tuple<tuple<int>>> has size 12, ie derivation from the empty tuple<>). Note that it is not obvious how to efficiently (you can't try all n! orders...) determine the best layout. In the code I just put all the empty types first and then the rest sorted by decreasing alignment, but that heuristic is not optimal for several reasons: - there can be hidden empty types in the bigger types - if we use derivation also for non-empty types, the size (without tail padding) is not a multiple of the alignment anymore and the heuristic doesn't make much sense anymore.
