2 % (c) The AQUA Project, Glasgow University, 1998
4 \section[DsCCall]{Desugaring \tr{foreign} declarations}
6 Expanding out @foreign import@ and @foreign export@ declarations.
9 module DsForeign ( dsForeigns ) where
11 #include "HsVersions.h"
15 import DsCCall ( dsCCall, mkFCall, boxResult, unboxArg, resultWrapper )
18 import HsSyn ( ForeignDecl(..), ForeignExport(..),
19 ForeignImport(..), CImportSpec(..) )
20 import TcHsSyn ( TypecheckedForeignDecl )
21 import CoreUtils ( exprType, mkInlineMe )
22 import Id ( Id, idType, idName, mkSysLocal, setInlinePragma )
23 import Literal ( Literal(..) )
24 import Module ( moduleString )
25 import Name ( getOccString, NamedThing(..) )
26 import OccName ( encodeFS )
27 import Type ( repType, eqType )
28 import TcType ( Type, mkFunTys, mkForAllTys, mkTyConApp,
29 mkFunTy, tcSplitTyConApp_maybe,
30 tcSplitForAllTys, tcSplitFunTys, tcTyConAppArgs,
33 import HscTypes ( ForeignStubs(..) )
34 import ForeignCall ( ForeignCall(..), CCallSpec(..),
37 CCallConv(..), ccallConvToInt,
40 import CStrings ( CLabelString )
41 import TysWiredIn ( unitTy, stablePtrTyCon )
42 import TysPrim ( addrPrimTy )
43 import PrelNames ( hasKey, ioTyConKey, newStablePtrName, bindIOName )
44 import BasicTypes ( Activation( NeverActive ) )
46 import Maybe ( fromJust )
50 Desugaring of @foreign@ declarations is naturally split up into
51 parts, an @import@ and an @export@ part. A @foreign import@
54 foreign import cc nm f :: prim_args -> IO prim_res
58 f :: prim_args -> IO prim_res
59 f a1 ... an = _ccall_ nm cc a1 ... an
61 so we reuse the desugaring code in @DsCCall@ to deal with these.
64 type Binding = (Id, CoreExpr) -- No rec/nonrec structure;
65 -- the occurrence analyser will sort it all out
67 dsForeigns :: [TypecheckedForeignDecl]
68 -> DsM (ForeignStubs, [Binding])
70 = foldlDs combine (ForeignStubs empty empty [] [], []) fos
72 combine (ForeignStubs acc_h acc_c acc_hdrs acc_feb, acc_f)
73 (ForeignImport id _ spec depr loc)
74 = dsFImport id spec `thenDs` \(bs, h, c, hd) ->
75 warnDepr depr loc `thenDs` \_ ->
76 returnDs (ForeignStubs (h $$ acc_h) (c $$ acc_c) (hd ++ acc_hdrs) acc_feb,
79 combine (ForeignStubs acc_h acc_c acc_hdrs acc_feb, acc_f)
80 (ForeignExport id _ (CExport (CExportStatic ext_nm cconv)) depr loc)
81 = dsFExport id (idType id)
82 ext_nm cconv False `thenDs` \(h, c) ->
83 warnDepr depr loc `thenDs` \_ ->
84 returnDs (ForeignStubs (h $$ acc_h) (c $$ acc_c) acc_hdrs (id:acc_feb),
87 warnDepr False _ = returnDs ()
88 warnDepr True loc = dsWarn (loc, msg)
90 msg = ptext SLIT("foreign declaration uses deprecated non-standard syntax")
94 %************************************************************************
96 \subsection{Foreign import}
98 %************************************************************************
100 Desugaring foreign imports is just the matter of creating a binding
101 that on its RHS unboxes its arguments, performs the external call
102 (using the @CCallOp@ primop), before boxing the result up and returning it.
104 However, we create a worker/wrapper pair, thus:
106 foreign import f :: Int -> IO Int
108 f x = IO ( \s -> case x of { I# x# ->
109 case fw s x# of { (# s1, y# #) ->
112 fw s x# = ccall f s x#
114 The strictness/CPR analyser won't do this automatically because it doesn't look
115 inside returned tuples; but inlining this wrapper is a Really Good Idea
116 because it exposes the boxing to the call site.
121 -> DsM ([Binding], SDoc, SDoc, [FastString])
122 dsFImport id (CImport cconv safety header lib spec)
123 = dsCImport id spec cconv safety `thenDs` \(ids, h, c) ->
124 returnDs (ids, h, c, if nullFastString header then [] else [header])
125 -- FIXME: the `lib' field is needed for .NET ILX generation when invoking
126 -- routines that are external to the .NET runtime, but GHC doesn't
127 -- support such calls yet; if `nullFastString lib', the value was not given
128 dsFImport id (DNImport spec)
129 = dsFCall id (DNCall spec) `thenDs` \(ids, h, c) ->
130 returnDs (ids, h, c, [])
136 -> DsM ([Binding], SDoc, SDoc)
137 dsCImport id (CLabel cid) _ _
138 = ASSERT(fromJust resTy `eqType` addrPrimTy) -- typechecker ensures this
139 returnDs ([(id, rhs)], empty, empty)
141 (resTy, foRhs) = resultWrapper (idType id)
142 rhs = foRhs (mkLit (MachLabel cid))
143 dsCImport id (CFunction target) cconv safety
144 = dsFCall id (CCall (CCallSpec target cconv safety))
145 dsCImport id CWrapper cconv _
146 = dsFExportDynamic id cconv
150 %************************************************************************
152 \subsection{Foreign calls}
154 %************************************************************************
160 (tvs, fun_ty) = tcSplitForAllTys ty
161 (arg_tys, io_res_ty) = tcSplitFunTys fun_ty
162 -- Must use tcSplit* functions because we want to
163 -- see that (IO t) in the corner
165 newSysLocalsDs arg_tys `thenDs` \ args ->
166 mapAndUnzipDs unboxArg (map Var args) `thenDs` \ (val_args, arg_wrappers) ->
169 work_arg_ids = [v | Var v <- val_args] -- All guaranteed to be vars
171 -- These are the ids we pass to boxResult, which are used to decide
172 -- whether to touch# an argument after the call (used to keep
173 -- ForeignObj#s live across a 'safe' foreign import).
174 maybe_arg_ids | unsafe_call fcall = work_arg_ids
177 boxResult maybe_arg_ids io_res_ty `thenDs` \ (ccall_result_ty, res_wrapper) ->
179 getUniqueDs `thenDs` \ ccall_uniq ->
180 getUniqueDs `thenDs` \ work_uniq ->
183 worker_ty = mkForAllTys tvs (mkFunTys (map idType work_arg_ids) ccall_result_ty)
184 the_ccall_app = mkFCall ccall_uniq fcall val_args ccall_result_ty
185 work_rhs = mkLams tvs (mkLams work_arg_ids the_ccall_app)
186 work_id = mkSysLocal (encodeFS FSLIT("$wccall")) work_uniq worker_ty
189 work_app = mkApps (mkVarApps (Var work_id) tvs) val_args
190 wrapper_body = foldr ($) (res_wrapper work_app) arg_wrappers
191 wrap_rhs = mkInlineMe (mkLams (tvs ++ args) wrapper_body)
193 returnDs ([(work_id, work_rhs), (fn_id, wrap_rhs)], empty, empty)
195 unsafe_call (CCall (CCallSpec _ _ safety)) = playSafe safety
196 unsafe_call (DNCall _) = False
200 %************************************************************************
202 \subsection{Foreign export}
204 %************************************************************************
206 The function that does most of the work for `@foreign export@' declarations.
207 (see below for the boilerplate code a `@foreign export@' declaration expands
210 For each `@foreign export foo@' in a module M we generate:
212 \item a C function `@foo@', which calls
213 \item a Haskell stub `@M.$ffoo@', which calls
215 the user-written Haskell function `@M.foo@'.
218 dsFExport :: Id -- Either the exported Id,
219 -- or the foreign-export-dynamic constructor
220 -> Type -- The type of the thing callable from C
221 -> CLabelString -- The name to export to C land
223 -> Bool -- True => foreign export dynamic
224 -- so invoke IO action that's hanging off
225 -- the first argument's stable pointer
226 -> DsM ( SDoc -- contents of Module_stub.h
227 , SDoc -- contents of Module_stub.c
230 dsFExport fn_id ty ext_name cconv isDyn
233 (tvs,sans_foralls) = tcSplitForAllTys ty
234 (fe_arg_tys', orig_res_ty) = tcSplitFunTys sans_foralls
235 -- We must use tcSplits here, because we want to see
236 -- the (IO t) in the corner of the type!
237 fe_arg_tys | isDyn = tail fe_arg_tys'
238 | otherwise = fe_arg_tys'
240 -- Look at the result type of the exported function, orig_res_ty
241 -- If it's IO t, return (t, True)
242 -- If it's plain t, return (t, False)
243 (case tcSplitTyConApp_maybe orig_res_ty of
244 -- We must use tcSplit here so that we see the (IO t) in
245 -- the type. [IO t is transparent to plain splitTyConApp.]
247 Just (ioTyCon, [res_ty])
248 -> ASSERT( ioTyCon `hasKey` ioTyConKey )
249 -- The function already returns IO t
250 returnDs (res_ty, True)
252 other -> -- The function returns t
253 returnDs (orig_res_ty, False)
255 `thenDs` \ (res_ty, -- t
256 is_IO_res_ty) -> -- Bool
259 = mkFExportCBits ext_name
260 (if isDyn then Nothing else Just fn_id)
261 fe_arg_tys res_ty is_IO_res_ty cconv
263 returnDs (h_stub, c_stub)
266 @foreign export dynamic@ lets you dress up Haskell IO actions
267 of some fixed type behind an externally callable interface (i.e.,
268 as a C function pointer). Useful for callbacks and stuff.
271 foreign export dynamic f :: (Addr -> Int -> IO Int) -> IO Addr
273 -- Haskell-visible constructor, which is generated from the above:
274 -- SUP: No check for NULL from createAdjustor anymore???
276 f :: (Addr -> Int -> IO Int) -> IO Addr
278 bindIO (newStablePtr cback)
279 (\StablePtr sp# -> IO (\s1# ->
280 case _ccall_ createAdjustor cconv sp# ``f_helper'' s1# of
281 (# s2#, a# #) -> (# s2#, A# a# #)))
283 foreign export "f_helper" f_helper :: StablePtr (Addr -> Int -> IO Int) -> Addr -> Int -> IO Int
284 -- `special' foreign export that invokes the closure pointed to by the
289 dsFExportDynamic :: Id
291 -> DsM ([Binding], SDoc, SDoc)
292 dsFExportDynamic id cconv
293 = newSysLocalDs ty `thenDs` \ fe_id ->
294 getModuleDs `thenDs` \ mod_name ->
296 -- hack: need to get at the name of the C stub we're about to generate.
297 fe_nm = mkFastString (moduleString mod_name ++ "_" ++ toCName fe_id)
299 dsFExport id export_ty fe_nm cconv True `thenDs` \ (h_code, c_code) ->
300 newSysLocalDs arg_ty `thenDs` \ cback ->
301 dsLookupGlobalId newStablePtrName `thenDs` \ newStablePtrId ->
303 mk_stbl_ptr_app = mkApps (Var newStablePtrId) [ Type arg_ty, Var cback ]
305 dsLookupGlobalId bindIOName `thenDs` \ bindIOId ->
306 newSysLocalDs (mkTyConApp stablePtrTyCon [arg_ty]) `thenDs` \ stbl_value ->
309 = mkApps (Var bindIOId)
310 [ Type (mkTyConApp stablePtrTyCon [arg_ty])
317 The arguments to the external function which will
318 create a little bit of (template) code on the fly
319 for allowing the (stable pointed) Haskell closure
320 to be entered using an external calling convention
323 adj_args = [ mkIntLitInt (ccallConvToInt cconv)
325 , mkLit (MachLabel fe_nm)
327 -- name of external entry point providing these services.
328 -- (probably in the RTS.)
329 adjustor = FSLIT("createAdjustor")
331 dsCCall adjustor adj_args PlayRisky False io_res_ty `thenDs` \ ccall_adj ->
332 -- PlayRisky: the adjustor doesn't allocate in the Haskell heap or do a callback
333 let ccall_adj_ty = exprType ccall_adj
334 ccall_io_adj = mkLams [stbl_value] $
335 Note (Coerce io_res_ty ccall_adj_ty)
337 io_app = mkLams tvs $
339 stbl_app ccall_io_adj res_ty
340 fed = (id `setInlinePragma` NeverActive, io_app)
341 -- Never inline the f.e.d. function, because the litlit
342 -- might not be in scope in other modules.
344 returnDs ([fed], h_code, c_code)
348 (tvs,sans_foralls) = tcSplitForAllTys ty
349 ([arg_ty], io_res_ty) = tcSplitFunTys sans_foralls
350 [res_ty] = tcTyConAppArgs io_res_ty
351 -- Must use tcSplit* to see the (IO t), which is a newtype
352 export_ty = mkFunTy (mkTyConApp stablePtrTyCon [arg_ty]) arg_ty
354 toCName :: Id -> String
355 toCName i = showSDoc (pprCode CStyle (ppr (idName i)))
360 \subsection{Generating @foreign export@ stubs}
364 For each @foreign export@ function, a C stub function is generated.
365 The C stub constructs the application of the exported Haskell function
366 using the hugs/ghc rts invocation API.
369 mkFExportCBits :: FastString
370 -> Maybe Id -- Just==static, Nothing==dynamic
373 -> Bool -- True <=> returns an IO type
376 mkFExportCBits c_nm maybe_target arg_htys res_hty is_IO_res_ty cc
377 = (header_bits, c_bits)
379 -- Create up types and names for the real args
380 arg_cnames, arg_ctys :: [SDoc]
381 arg_cnames = mkCArgNames 1 arg_htys
382 arg_ctys = map showStgType arg_htys
384 -- and also for auxiliary ones; the stable ptr in the dynamic case, and
385 -- a slot for the dummy return address in the dynamic + ccall case
386 extra_cnames_and_ctys
387 = case maybe_target of
388 Nothing -> [(text "the_stableptr", text "StgStablePtr")]
391 case (maybe_target, cc) of
392 (Nothing, CCallConv) -> [(text "original_return_addr", text "void*")]
395 all_cnames_and_ctys :: [(SDoc, SDoc)]
397 = extra_cnames_and_ctys ++ zip arg_cnames arg_ctys
399 -- stuff to do with the return type of the C function
400 res_hty_is_unit = res_hty `eqType` unitTy -- Look through any newtypes
402 cResType | res_hty_is_unit = text "void"
403 | otherwise = showStgType res_hty
405 -- Now we can cook up the prototype for the exported function.
406 pprCconv = case cc of
408 StdCallConv -> text (ccallConvAttribute cc)
410 header_bits = ptext SLIT("extern") <+> fun_proto <> semi
412 fun_proto = cResType <+> pprCconv <+> ftext c_nm <>
413 parens (hsep (punctuate comma (map (\(nm,ty) -> ty <+> nm)
414 all_cnames_and_ctys)))
416 -- the target which will form the root of what we ask rts_evalIO to run
418 = case maybe_target of
419 Nothing -> text "(StgClosure*)deRefStablePtr(the_stableptr)"
420 Just hs_fn -> char '&' <> ppr hs_fn <> text "_closure"
422 -- the expression we give to rts_evalIO
424 = foldl appArg the_cfun (zip arg_cnames arg_htys)
426 appArg acc (arg_cname, arg_hty)
428 <> parens (acc <> comma <> mkHObj arg_hty <> parens arg_cname)
430 -- various other bits for inside the fn
431 declareResult = text "HaskellObj ret;"
433 return_what | res_hty_is_unit = empty
434 | otherwise = parens (unpackHObj res_hty <> parens (text "ret"))
436 -- an extern decl for the fn being called
438 = case maybe_target of
440 Just hs_fn -> text "extern StgClosure " <> ppr hs_fn <> text "_closure" <> semi
442 -- finally, the whole darn thing
449 , text "SchedulerStatus rc;"
451 -- create the application + perform it.
452 , text "rc=rts_evalIO" <> parens (
453 text "rts_apply" <> parens (
455 <> text (if is_IO_res_ty
457 else "runNonIO_closure")
463 , text "rts_checkSchedStatus" <> parens (doubleQuotes (ftext c_nm)
464 <> comma <> text "rc") <> semi
465 , text "return" <> return_what <> semi
470 mkCArgNames :: Int -> [a] -> [SDoc]
471 mkCArgNames n as = zipWith (\ _ n -> text ('a':show n)) as [n..]
473 mkHObj :: Type -> SDoc
474 mkHObj t = text "rts_mk" <> text (showFFIType t)
476 unpackHObj :: Type -> SDoc
477 unpackHObj t = text "rts_get" <> text (showFFIType t)
479 showStgType :: Type -> SDoc
480 showStgType t = text "Hs" <> text (showFFIType t)
482 showFFIType :: Type -> String
483 showFFIType t = getOccString (getName tc)
485 tc = case tcSplitTyConApp_maybe (repType t) of
487 Nothing -> pprPanic "showFFIType" (ppr t)