#5529: Newtypes with hidden constructors cannot be passed as FFI arguments
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Reporter: mikhail.vorozhtsov | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 7.3
Keywords: | Testcase:
Blockedby: | Difficulty:
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: None/Unknown
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Comment(by simonmar):
I think GHC is correct now. This was discussed a long time ago on the FFI
list (no link handy, sorry), and I think the principle is that in order to
use a newtype in an FFI declaration you have to know its representation,
because you're linking against some known C code that depends on the
representation. So if we allowed that to happen with an abstract newtype,
it would constitute leakage of the abstraction.
We ought to change `Foreign.C.Types` to export the types non-abstractly.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5529#comment:3>
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