Before we bike shed these details, let’s evaluate / document the pieces of base that should also be moved to using Addr.  Though that module where

1) What exported types / data definitions / functions will have changes ?

2) what internal apis need to change?

as a lower bound estimate of work surface area, i grepped for "Ptr ()"  and "Addr#" in a fresh recursive clone of ghc at commit 503514b94f8dc7bd9eab5392206649aee45f140b,
limiting my search to .hs and .hsc files

THERES A LOT of uses of Ptr (), and its siblings StablePtr () and RemotePtr () ,   The latter two dont have a simple Addr# underneath, 

heres the list of files that match that search   rg 'Ptr \(\)' --type haskell -c

ghc/GHCi/Leak.hs:1
utils/hsc2hs/Main.hs:1
utils/runghc/Main.hs:1
compiler/ghci/GHCi.hs:4
compiler/ghci/ByteCodeLink.hs:3
compiler/ghci/ByteCodeGen.hs:4
compiler/ghci/ByteCodeTypes.hs:1
compiler/ghci/ByteCodeAsm.hs:2
compiler/main/HscTypes.hs:1
libraries/ghci/GHCi/ObjLink.hs:3
libraries/ghci/GHCi/StaticPtrTable.hs:1
libraries/ghci/GHCi/ResolvedBCO.hs:1
libraries/ghci/GHCi/RemoteTypes.hs:2
libraries/ghci/GHCi/Run.hs:2
libraries/ghci/GHCi/Message.hs:5
libraries/base/GHC/Stable.hs:2
libraries/base/GHC/StaticPtr.hs:1
libraries/base/GHC/Generics.hs:2
libraries/base/GHC/TopHandler.hs:1
libraries/base/GHC/Windows.hs:1
libraries/base/tests/dynamic002.hs:2
utils/haddock/haddock-api/src/Haddock.hs:1
libraries/array/Data/Array/IO.hs:2
libraries/base/Foreign/Marshal/Pool.hs:1
libraries/bytestring/Data/ByteString/Builder/Extra.hs:1
libraries/base/GHC/IO/Handle/Text.hs:1
testsuite/tests/rts/T7160.hs:1
testsuite/tests/rts/overflow3.hs:1
testsuite/tests/rts/overflow2.hs:1
testsuite/tests/rts/T5250.hs:1
testsuite/tests/rts/T10296b.hs:2
testsuite/tests/th/T3319.hs:1
testsuite/tests/th/TH_foreignInterruptible.hs:1
testsuite/tests/th/TH_foreignCallingConventions.hs:1
libraries/Cabal/cabal-install/Distribution/Client/Win32SelfUpgrade.hs:1
libraries/Cabal/Cabal/Distribution/Simple/InstallDirs.hs:2
testsuite/tests/llvm/should_compile/T5486.hs:2
testsuite/tests/codeGen/should_run/cgrun070.hs:5
testsuite/tests/codeGen/should_run/cgrun026.hs:3
testsuite/tests/primops/should_run/T4442.hs:1
testsuite/tests/ffi/should_fail/T7243.hs:1
testsuite/tests/ffi/should_fail/T3066.hs:1
testsuite/tests/ffi/should_compile/cc009.hs:1
testsuite/tests/ffi/should_run/ffi021.hs:1
testsuite/tests/typecheck/should_compile/T7408.hs:1
libraries/Cabal/cabal-install/Distribution/Client/Compat/ExecutablePath.hs:1
libraries/Cabal/Cabal/Distribution/Simple/Build/PathsModule.hs:1
libraries/time/lib/Data/Time/Clock/Internal/CTimeval.hs:1
testsuite/tests/rename/should_compile/T3103/Foreign/Ptr.hs:1

likewise the locations where Addr# comes up are as follows (some of these perhaps should be an Addr? )

$ rg 'Addr#' --type haskell -c
utils/genprimopcode/Main.hs:2
ghc/GHCi/Leak.hs:2
compiler/cmm/CmmMachOp.hs:1
compiler/cmm/CmmUtils.hs:1
compiler/specialise/Rules.hs:2
compiler/basicTypes/MkId.hs:2
compiler/basicTypes/Literal.hs:6
compiler/basicTypes/Unique.hs:2
compiler/utils/StringBuffer.hs:1
compiler/utils/FastString.hs:4
compiler/utils/Encoding.hs:9
compiler/codeGen/StgCmmPrim.hs:3
compiler/coreSyn/MkCore.hs:5
compiler/coreSyn/CoreLint.hs:2
compiler/coreSyn/CoreSyn.hs:4
compiler/coreSyn/CorePrep.hs:1
compiler/stranal/WwLib.hs:1
compiler/simplCore/CSE.hs:1
compiler/simplCore/Simplify.hs:2
compiler/deSugar/DsExpr.hs:1
compiler/typecheck/TcGenDeriv.hs:5
compiler/prelude/ForeignCall.hs:1
compiler/prelude/PrelNames.hs:1
compiler/prelude/TysPrim.hs:1
compiler/ghci/ByteCodeGen.hs:8
libraries/bytestring/tests/revcomp.hs:1
libraries/bytestring/Data/ByteString.hs:5
libraries/ghc-heap/tests/heap_all.hs:1
libraries/ghc-prim/GHC/CString.hs:17
libraries/ghc-prim/GHC/Classes.hs:1
libraries/ghc-prim/GHC/Types.hs:3
libraries/ghci/GHCi/BinaryArray.hs:1
libraries/ghci/GHCi/CreateBCO.hs:5
libraries/base/codepages/MakeTable.hs:1
libraries/base/GHC/Ptr.hs:8
libraries/base/GHC/Generics.hs:5
libraries/base/GHC/Storable.hs:32
libraries/base/GHC/ForeignPtr.hs:6
libraries/base/Foreign/Ptr.hs:2
libraries/bytestring/Data/ByteString/Unsafe.hs:6
libraries/bytestring/Data/ByteString/Internal.hs:7
libraries/ghc-heap/GHC/Exts/Heap.hs:1
libraries/text/Data/Text/Show.hs:2
libraries/text/Data/Text/Lazy.hs:2
libraries/containers/Data/IntSet/Internal.hs:4
libraries/ghc-compact/GHC/Compact/Serialized.hs:11
libraries/base/GHC/IO/Exception.hs:1
libraries/base/Data/Typeable/Internal.hs:3
libraries/base/Control/Exception/Base.hs:1
utils/haddock/html-test/src/Ticket112.hs:1
testsuite/tests/rts/T8242.hs:19
testsuite/tests/ghci.debugger/HappyTest.hs:3
testsuite/tests/arityanal/Main.hs:3
testsuite/tests/th/TH_StringPrimL.hs:2
testsuite/tests/th/T1830_3a.hs:2
libraries/template-haskell/Language/Haskell/TH/Syntax.hs:1
libraries/bytestring/Data/ByteString/Short/Internal.hs:16
libraries/integer-gmp/src/GHC/Integer/Type.hs:11
libraries/base/GHC/IO/Encoding/CodePage.hs:3
libraries/Cabal/Cabal/Distribution/Parsec/Lexer.hs:9
testsuite/tests/generics/GEq/GEq1A.hs:1
testsuite/tests/generics/GEq/GEq1.hs:2
testsuite/tests/codeGen/should_compile/cg008.hs:1
testsuite/tests/codeGen/should_run/cgrun070.hs:4
testsuite/tests/codeGen/should_run/T9577.hs:1
testsuite/tests/codeGen/should_run/cgrun066.hs:1
testsuite/tests/codeGen/should_run/cgrun026.hs:2
testsuite/tests/codeGen/should_run/T2080.hs:2
testsuite/tests/codeGen/should_run/T9577_A.hs:1
testsuite/tests/primops/should_run/T4442.hs:4
testsuite/tests/simplCore/should_compile/T13367.hs:1
testsuite/tests/simplCore/should_compile/T13155.hs:2
testsuite/tests/simplCore/should_compile/T14779a.hs:1
testsuite/tests/simplCore/should_compile/T14779b.hs:2
testsuite/tests/simplCore/should_compile/spec001.hs:1
testsuite/tests/lib/integer/integerGmpInternals.hs:9
testsuite/tests/perf/compiler/T14683.hs:3
testsuite/tests/ghci/should_run/T2589.hs:1
libraries/integer-gmp/src/GHC/Integer/GMP/Internals.hs:7
libraries/text/Data/Text/Internal/Fusion/Common.hs:3
libraries/base/GHC/IO/Encoding/CodePage/Table.hs:1



On Fri, Oct 26, 2018 at 11:01 AM Daniel Cartwright <chessai1996@gmail.com> wrote:
Also, where in base should Addr go?

On Fri, Oct 26, 2018 at 10:15 AM Daniel Cartwright <chessai1996@gmail.com> wrote:
I would, yeah. Should the next version of `primitive` just re-export `Addr` from base in `Data.Primitive.Addr`?

On Fri, Oct 26, 2018 at 10:14 AM Carter Schonwald <carter.schonwald@gmail.com> wrote:
Daniel or David, would either of you be interested/willing to do the legwork on this patch wise (subject to sanity checking whats the impact surface area?)

On Fri, Oct 26, 2018 at 12:04 AM Carter Schonwald <carter.schonwald@gmail.com> wrote:
Cool. What apis in base should move to use Addr from fake pointer ? Cause just adding it in isolation seems lame! 

I guess I’m just trying to say “what would the impact on base, if every fake Ptr was moved to be Addr?” Because it’s not something which should be done by halves. 

1) what apis would be changed?

2) what internal things would be changed albeit not Api visible 

3). Address arithmetic for Addr is very different from addres arithmetic on larger than word8 size storable values, is there anything which would move representations where the change to byte indexed would change the calculations ?


If we can layout what the impact / scope of changes needed for these and other considerations, I guess I’d be all for it. Assuming there’s the corresponding interest in executing changes. (I just have this worry in my head that it might be one of those icebergs.. like the split base effort )



On Thu, Oct 25, 2018 at 11:33 PM David Feuer <david.feuer@gmail.com> wrote:
On Thu, Oct 25, 2018, 11:28 PM Carter Schonwald <carter.schonwald@gmail.com> wrote:
Pretending we’re talking about this with storable as our example semantics : 

Ptr Void 
Corresponds to a memory address you don’t want to read or write to.

This is not so easy to think about (there's not much utility in such a type). Perhaps Ptr Void is a reasonable type for pointers known to be null or outside the address space, but I'm not sure.


Ptr () corresponds to a memory location that’s pretty boring to read / write to

Yes! In other words, it's *not* what people should be using for a pointer to an arbitrary non-Haskell address. That's precisely what Addr is for.


On Thu, Oct 25, 2018 at 11:22 PM Carter Schonwald <carter.schonwald@gmail.com> wrote:
... when is a valid pointer not going to point at byte addressable memory on memory architectures ghc can support or target? 

On Thu, Oct 25, 2018 at 8:27 PM Daniel Cartwright <chessai1996@gmail.com> wrote:
Now, one could argue that `Ptr ()` isn't a lie, it sort of reads like C's void pointer. But surely something like `Ptr Word8` is a lie, when it is not actually a Ptr to Word8 values.

On Thu, Oct 25, 2018 at 8:11 PM Daniel Cartwright <chessai1996@gmail.com> wrote:
yes, only the type and its instances should be moved as far as i'm aware.

Also, it's more than just base.

in GHC.Stats, the foreign import "getRTSStats" has `Ptr () -> IO ()`, this Ptr () is also a lie

These are just off the top of my head, there are more


On Thu, Oct 25, 2018 at 6:46 PM Carter Schonwald <carter.schonwald@gmail.com> wrote:
hrmm, what are the pieces of base that are using Ptr when they really should be using Addr? This would help me understand what would be made better in base :) 

On Thu, Oct 25, 2018 at 6:19 PM David Feuer <david.feuer@gmail.com> wrote:
We shouldn't really need to move anything into base except Addr and its base instances.

On Oct 25, 2018 5:59 PM, "Carter Schonwald" <carter.schonwald@gmail.com> wrote:
Indeed.  The monad transformer instances for primmonad need to live in primmonad OR transformers to avoid orphans. 

Either way, unless transformers moves into base (unlikely), no way anything using prim monad will. 

On Thu, Oct 25, 2018 at 3:34 PM Andrew Martin <andrew.thaddeus@gmail.com> wrote:
I like the idea of moving the type Addr into base. But we cannot move the entire module since it has functions that talk about PrimMonad, and we definitely don't want to move that into base.

On Thu, Oct 25, 2018 at 11:25 AM Daniel Cartwright <chessai1996@gmail.com> wrote:
Motivation: There are a lot of places in base where 'Ptr a' is used in place of 'Addr', because in base there is no 'Addr', only 'Addr#'. The problem lies in the fact that many of these uses of 'Ptr a' are lying; the 'a' value is meaningless. Authors of functions therein have used things like 'Ptr ()', 'Ptr Word8', 'Ptr a', but these types do not mean what they say they mean - they're just Addr. There are probably other motivations for this that I can't think of off the top of my head right now.
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