GHCi doesn't work Any and missing RealWorld foreign prim imports

Here are two issues with our GHCi support for foreign prim imports:

Here is a program that works:

{-# LANGUAGE GHCForeignImportPrim, MagicHash, UnliftedFFITypes, UnboxedTuples #-}
module Serum where
import GHC.Exts

foreign import prim "cheneycopy" cheneycopy :: Word# -> State# RealWorld -> (# State# RealWorld, Word# #)

If I remove the world token passing, as in here:

{-# LANGUAGE GHCForeignImportPrim, MagicHash, UnliftedFFITypes, UnboxedTuples #-}
module Serum where
import GHC.Exts

foreign import prim "cheneycopy" cheneycopy :: Word# -> Word#

I get:

  (GHC version 7.10.1 for x86_64-unknown-linux):
	ByteCodeGen.generateCCall: missing or invalid World token?

Another error is if I try to pass Any as an argument:

{-# LANGUAGE GHCForeignImportPrim, MagicHash, UnliftedFFITypes, UnboxedTuples #-}
module Serum where
import GHC.Exts

foreign import prim "cheneycopy" cheneycopy :: Any -> State# RealWorld -> (# State# RealWorld, Word# #)

Then I get:

ghc: panic! (the 'impossible' happened)
  (GHC version 7.10.1 for x86_64-unknown-linux):
	primRepToFFIType

Note to anyone who is running into this problem: an easy workaround is to use -fobject-code which bypasses bytecode generation.

Trac metadata

Trac field	Value
Version	7.10.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	GHCi
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	hvr
Operating system
Architecture

changed weight to 5

added GHCi Tbug Trac import labels

changed weight to 3

Trac metadata

Trac field	Value
Priority	normal → low

I don't think your first example works as expected. It type checks but the calling convention is silently ignored and replaced by the default CCall one (see #3336 (closed) and "convToABI" in compiler/ghci/LibFFI.hsc). The other examples fail because "generateCCall" from compiler/ghci/ByteCodeGen.hs shouldn't be called at all for primops and there are errors when parameters are pushed (your first case) or when parameters are converted into types understandable by libffi (second case).

I attach a patch with an additional check which fails sooner and in a nicer way (similarily to #1257 (closed)).

Attached file 0001-ghci-indicate-that-foreign-primops-are-not-supported.patch (download).

changed milestone to %8.0.1

Trac metadata

Trac field	Value
Component	GHCi → Compiler (CodeGen)
Test case	- → prog014
Differential revisions	- → D1458

mentioned in commit badf5d54

closed

Marking this as fixed, I guess...

Trac metadata

Trac field	Value
Resolution	Unresolved → ResolvedFixed

added compiler crash label

added Plow label