[GHC] #2594: Wrong size for Int in arguments to functions wrapped to FunPtr by FFI wrappers (on 64-bit machine)

[GHC]

#2594: Wrong size for Int in arguments to functions wrapped to FunPtr by FFI
wrappers (on 64-bit machine)
-------------------------------+--------------------------------------------
    Reporter:  shahn           |        Owner:         
        Type:  bug             |       Status:  closed 
    Priority:  normal          |    Milestone:         
   Component:  Compiler        |      Version:  6.8.3  
    Severity:  normal          |   Resolution:  invalid
    Keywords:                  |     Testcase:         
Architecture:  x86_64 (amd64)  |           Os:  Linux  
-------------------------------+--------------------------------------------
Changes (by duncan):

  * status:  new => closed
  * resolution:  => invalid

Comment:

 I think this is an incorrect use of the FFI. The example uses  Haskell
 `Int` and passes it to C code which uses it at C's type `int`. These are
 not the same types, though they do happen to coincide on x86 32bit. The
 example should be using `CInt` on the Haskell side. Alternatively, if the
 intention really is to use the Haskell `Int` type then the C side code
 must use `HsInt` (which is defined in `HsFFI.h`).

 The reason we get the observed result is because on x86-64, GHC uses a
 64-bit `Int` while C's `int` remains 32bit so `-1` in a 32bit int is all
 `1` bits but that bit pattern as a larger int is `2^32-1`.

 So I'm closing the ticket as invalid. If anyone thinks this is incorrect
 then please do re-open it.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2594#comment:1>
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