Re: [GHC] #5659: hsc2hs should add explicit type annotations to peeks and pokes

2011-12-14 Thread GHC 
#5659: hsc2hs should add explicit type annotations to peeks and pokes
--+-
  Reporter:  ezyang   |  Owner:  
  Type:  bug  | Status:  closed  
  Priority:  normal   |  Milestone:  
 Component:  hsc2hs   |Version:  7.0.2   
Resolution:  wontfix  |   Keywords:  
Os:  Unknown/Multiple |   Architecture:  Unknown/Multiple
   Failure:  GHC accepts invalid program  | Difficulty:  
  Testcase:   |  Blockedby:  
  Blocking:   |Related:  
--+-
Changes (by PHO):

 * cc: pho@… (added)


-- 
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/5659#comment:3
GHC http://www.haskell.org/ghc/
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Re: [GHC] #5659: hsc2hs should add explicit type annotations to peeks and pokes

2011-11-26 Thread GHC 
#5659: hsc2hs should add explicit type annotations to peeks and pokes
--+-
  Reporter:  ezyang   |  Owner:  
  Type:  bug  | Status:  closed  
  Priority:  normal   |  Milestone:  
 Component:  hsc2hs   |Version:  7.0.2   
Resolution:  wontfix  |   Keywords:  
  Testcase:   |  Blockedby:  
Difficulty:   | Os:  Unknown/Multiple
  Blocking:   |   Architecture:  Unknown/Multiple
   Failure:  GHC accepts invalid program  |  
--+-

Comment(by ezyang):

 Keegan and I had a brief discussion about this, and we think that one
 fundamental issue here is that Int really shouldn't be in Storable, in the
 sense that it doesn't have reasonable portability semantics (even on the
 same machine) for C code. So you could instead have

 {{{
 class Storable a where ... -- as now
 class (Storable a) = CStorable a  -- no body
 }}}

 where CStorable instances are proofs that the type corresponds directly to
 a specific C type. This won't save you if you mix up your types too much,
 but avoids Int/CInt heartache.

 Perhaps we could also permit people to more easily explicitly specify the
 type of peeks and pokes, maybe as an extra optional arg (you can do it by
 hand but it's kind of annoying in do-notation).

-- 
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/5659#comment:2
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[GHC] #5659: hsc2hs should add explicit type annotations to peeks and pokes

2011-11-25 Thread GHC 
#5659: hsc2hs should add explicit type annotations to peeks and pokes
-+--
Reporter:  ezyang|   Owner: 
Type:  bug   |  Status:  new
Priority:  normal|   Component:  hsc2hs 
 Version:  7.0.2 |Keywords: 
Testcase:|   Blockedby: 
  Os:  Unknown/Multiple  |Blocking: 
Architecture:  Unknown/Multiple  | Failure:  GHC accepts invalid program
-+--
 Can you guess what is wrong with this piece of code?

 {{{
   c_len   - #{peek ZNotice_t, z_message_len} c_note
   c_msg   - #{peek ZNotice_t, z_message} c_note
   message - B.packCStringLen (c_msg, c_len)
 }}}

 The problem here is that ``c_len`` needs to be interpreted as type
 ``CInt``, but packCStringLen takes an ``Int`` as an argument. Inference
 happens, and it so happens that in circumstances when CInt does not equal
 Int, this will read out too much or little, with no type errors!

 Probably the right thing to do here is to add an explicit type annotation
 to the resulting Haskell code, so peekByteOff is forced to read out the
 correct amount of information. This will break any code that was reading
 directly to Haskell level types, but one could make the reasonable
 argument that these programs were supposed to be ill-typed anyway.

 It's not obvious to me if hsc2hs actually has access to this information.
 So that might make this difficult to implement.

-- 
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/5659
GHC http://www.haskell.org/ghc/
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Re: [GHC] #5659: hsc2hs should add explicit type annotations to peeks and pokes

2011-11-25 Thread GHC 
#5659: hsc2hs should add explicit type annotations to peeks and pokes
--+-
  Reporter:  ezyang   |  Owner:  
  Type:  bug  | Status:  closed  
  Priority:  normal   |  Milestone:  
 Component:  hsc2hs   |Version:  7.0.2   
Resolution:  wontfix  |   Keywords:  
  Testcase:   |  Blockedby:  
Difficulty:   | Os:  Unknown/Multiple
  Blocking:   |   Architecture:  Unknown/Multiple
   Failure:  GHC accepts invalid program  |  
--+-
Changes (by igloo):

  * status:  new = closed
  * resolution:  = wontfix


Comment:

 You mean the correct code is this, right?:
 {{{
   c_len   - #{peek ZNotice_t, z_message_len} c_note
   c_msg   - #{peek ZNotice_t, z_message} c_note
   message - B.packCStringLen (c_msg, fromIntegral (c_len :: CInt))
 }}}

 I don't think there's anything we can do. You can `peek` anything that is
 `Storable`, and while that does have a `sizeof` method I don't see a
 reasonable way for `hsc2hs` to call it with the right type.

-- 
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/5659#comment:1
GHC http://www.haskell.org/ghc/
The Glasgow Haskell Compiler

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