Sorry, I confused 'DynamicGhcPrograms' merely with 'DynamicGhc'. In
other words: DynamicGhc means exactly what I said before - dynamic
GHC, static everything else.
As for the reason why the switch wasn't made for x86, I was not privvy
to the decision at the time, but I imagine it's one of consistency. To
ship a x64 GHC with these features (where it was acceptable) but not a
32bit one means essentially you force 32bit users into one of two
situations:
- Your compiled program may not work in GHCi, or at all in some
corner cases, and most of the bugs that were there are effectively
unfixed.
- Your compiled program suffers a noticeable performance hit, due to
register theft.
Which is rather unfortunate. On the other hand, if you dynamically
link GHC only, only GHC itself pays a hit on the dynamic linking, and
your remaining programs are unaffected.
On Mon, Oct 20, 2014 at 9:32 AM, Jeremy
Austin Seipp
writes: As far as I'm aware, Dynamic-by-default GHC is actually broken, and I don't know for how long this has been the case.
For some history: originally when all this was being decided to try and fix the linker issues in GHC, dynamic by default was considered an option, but was rejected in favor of DynamicGhcPrograms. Why was it rejected? Well, dynamic by default particularly hurts 32bit x86, which suffers from a very pathetic set of registers, and dynamic programs steal one of these for the GOT (%ebx IIRC).
On the other hand, DynamicGhcPrograms instead means GHC builds everything statically, *except itself*, which it builds as a dynamically linked executable. The idea is you dynamically link GHC itself to fix linker issues, and end-user programs remain static, which is the expected mode of operation.
Thank you for the detailed explanation (although I still don't understand why DYNAMIC_BY_DEFAULT by default wasn't kept for x64.)
Where does GhcDynamic fit into this?
_______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
-- Regards, Austin Seipp, Haskell Consultant Well-Typed LLP, http://www.well-typed.com/