#8299: Add richer data model address arithmetic: AddrDiff and AddrInt (ie d Int_ptr_diff and Int_ptr_size) ----------------------------+---------------------------------------------- Reporter: carter | Owner: Type: feature | Status: new request | Milestone: 7.10.1 Priority: high | Version: 7.6.3 Component: | Keywords: Compiler | Architecture: Unknown/Multiple Resolution: | Difficulty: Project (more than a week) Operating System: | Blocked By: Unknown/Multiple | Related Tickets: Type of failure: | None/Unknown | Test Case: | Blocking: 8287 | ----------------------------+---------------------------------------------- Comment (by rwbarton): On point 2: It seems to me that the current Foreign.Ptr API {{{ plusPtr :: Ptr a -> Int -> Ptr b minusPtr :: Ptr a -> Ptr b -> Int }}} pretty much forces `Int` to be the same size as a C pointer, on any architecture. For a real x32 executable, this would mean 32-bit `Int`, while for a "fake x32" mode which maintains a heap below 4G and stores heap pointers as 4 bytes, but otherwise is a normal x86_64 executable, this would mean 64-bit `Int`. There doesn't seem to be a good reason why the `Int` used for normal arithmetic, and used to count things in data structures like `Map`, should be tied to that C pointer size. As a matter of fact, an appropriate replacement for those `Int`s in Foreign.Ptr already exists in Foreign.C.Types: `CPtrdiff`, "Haskell type representing the C `ptrdiff_t` type". -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8299#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#8299: Add richer data model address arithmetic: AddrDiff and AddrInt (ie d Int_ptr_diff and Int_ptr_size) ----------------------------+---------------------------------------------- Reporter: carter | Owner: Type: feature | Status: new request | Milestone: 7.10.1 Priority: high | Version: 7.6.3 Component: | Keywords: Compiler | Architecture: Unknown/Multiple Resolution: | Difficulty: Project (more than a week) Operating System: | Blocked By: Unknown/Multiple | Related Tickets: Type of failure: | None/Unknown | Test Case: | Blocking: 8287 | ----------------------------+---------------------------------------------- Comment (by simonpj): Presumably an `Addr#` is wide enough to contain an offset? So perhaps we should use `Addr#` instead of `Int#` for address differences? We could have and `AddrDiff#` type, but then we'd need arithmetic over it etc. Maybe just a type synonym for `Addr#`? Anyway feel free to propose a concrete design. Simon -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8299#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#8299: Add richer data model address arithmetic: AddrDiff and AddrInt (ie d Int_ptr_diff and Int_ptr_size) ----------------------------+---------------------------------------------- Reporter: carter | Owner: Type: feature | Status: new request | Milestone: 7.10.1 Priority: high | Version: 7.6.3 Component: | Keywords: Compiler | Architecture: Unknown/Multiple Resolution: | Difficulty: Project (more than a week) Operating System: | Blocked By: Unknown/Multiple | Related Tickets: Type of failure: | None/Unknown | Test Case: | Blocking: 8287 | ----------------------------+---------------------------------------------- Comment (by carter): Reid Barton (who's been experimenting with an x32 ABI) made an observation yesterday evening on IRC #ghc about address vs int sizes for ghc {{{ [09:24:34] <rwbarton> ugh, I didn't think about the fact that integer- gmp exposes its representation to the world [09:24:43] <rwbarton> that means potentially anybody is assuming that Int is the same size as mp_limb_t [09:24:47] dcoutts_: fwiw, bytestring w/ ghc-head/linux/i386 passed too [09:55:47] <rwbarton> I guess ghcjs has the same problem [09:56:07] <rwbarton> can't support exporting the J# constructor [09:56:25] rwbarton: what problem exactly? [09:57:11] <rwbarton> so my problem that I just realized is on x32 [09:57:34] <rwbarton> where Int is 4 bytes, but gmp uses 8 byte limbs [09:57:59] <rwbarton> I can't have people going around constructing Integers with J#, because first of all they might not provide a ByteArray# that's a multiple of 8 bytes long [09:59:49] <rwbarton> so ideally (for me) there would be a type with the S# and J# constructors for pattern matching on, that was distinct from Integer [10:00:14] <rwbarton> that former type exported, the constructors of Integer not exported [10:00:29] <rwbarton> with conversions between them that on "ordinary" platforms are zero-cost [10:04:34] rwbarton: btw, I've been wishing for some bignum- only type [10:04:45] i.e. an Integer only w/ J# [10:05:38] then the proper Integer type could use that unboxed as single field in its J# constructor }}} This is just another data point to consider in any design constraints -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8299#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#8299: Add richer data model address arithmetic: AddrDiff and AddrInt (ie d Int_ptr_diff and Int_ptr_size) -------------------------------------+------------------------------------- Reporter: carter | Owner: Type: feature request | Status: new Priority: normal | Milestone: 8.2.1 Component: Compiler | Version: 7.6.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: 8287 Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by bgamari): * priority: high => normal * milestone: 8.0.1 => 8.2.1 Comment: This won't be happening for 8.0 I'm afraid. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8299#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler