#5931: Allow 'Any' to be passed to a foreign prim function.
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Reporter: nomeata | Owner:
Type: feature request | Status: new
Priority: normal | Component: Compiler (FFI)
Version: 7.4.1 | Keywords:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: None/Unknown | Testcase:
Blockedby: | Blocking:
Related: |
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Real primops can take boxed arguments, and the Cmm code will receive the
pointer to the object on the Haskell heap, e.g. for unpackClosure#. To be
able to implement such a function in a "foreign prim" call, this needs to
be allowed there as well, and the attached patch does that.
By only allowing Any here (instead of arbitrary types), it is clearer that
the function will not receive the value in any marshalled form, but just
the raw pointer. Haskell code using such functions are likely to use
unsafeCoerce# to turn a Haskell value into a value of type Any.
I am working on code that helps investigating the heap, similar to vacuum,
and unwrapClosure was not sufficient. With this patch in GHC I do not have
to modify the compiler further to create an improved version.
If applied, the documentation at wiki:Commentary/PrimOps#Foreignout-of-
linePrimOps needs to be updated. I did not find any documentation in the
GHC tree to updated accordingly.
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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5931>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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