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"
12 import TcRnMonad -- temp
16 import DsCCall ( dsCCall, mkFCall, boxResult, unboxArg, resultWrapper )
19 import HsSyn ( ForeignDecl(..), ForeignExport(..), LForeignDecl,
20 ForeignImport(..), CImportSpec(..) )
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, typePrimRep )
28 import TcType ( Type, mkFunTys, mkForAllTys, mkTyConApp,
29 mkFunTy, tcSplitTyConApp_maybe,
30 tcSplitForAllTys, tcSplitFunTys, tcTyConAppArgs,
33 import BasicTypes ( Boxity(..) )
34 import HscTypes ( ForeignStubs(..) )
35 import ForeignCall ( ForeignCall(..), CCallSpec(..),
38 CCallConv(..), ccallConvToInt,
41 import CStrings ( CLabelString )
42 import TysWiredIn ( unitTy, tupleTyCon )
43 import TysPrim ( addrPrimTy, mkStablePtrPrimTy, alphaTy )
44 import PrimRep ( getPrimRepSizeInBytes )
45 import PrelNames ( hasKey, ioTyConKey, stablePtrTyConName, newStablePtrName, bindIOName,
47 import BasicTypes ( Activation( NeverActive ) )
48 import SrcLoc ( Located(..), unLoc )
50 import Maybe ( fromJust )
54 Desugaring of @foreign@ declarations is naturally split up into
55 parts, an @import@ and an @export@ part. A @foreign import@
58 foreign import cc nm f :: prim_args -> IO prim_res
62 f :: prim_args -> IO prim_res
63 f a1 ... an = _ccall_ nm cc a1 ... an
65 so we reuse the desugaring code in @DsCCall@ to deal with these.
68 type Binding = (Id, CoreExpr) -- No rec/nonrec structure;
69 -- the occurrence analyser will sort it all out
71 dsForeigns :: [LForeignDecl Id]
72 -> DsM (ForeignStubs, [Binding])
74 = returnDs (NoStubs, [])
76 = foldlDs combine (ForeignStubs empty empty [] [], []) fos
78 combine (ForeignStubs acc_h acc_c acc_hdrs acc_feb, acc_f)
79 (L loc (ForeignImport id _ spec depr))
80 = traceIf (text "fi start" <+> ppr id) `thenDs` \ _ ->
81 dsFImport (unLoc id) spec `thenDs` \ (bs, h, c, mbhd) ->
82 warnDepr depr loc `thenDs` \ _ ->
83 traceIf (text "fi end" <+> ppr id) `thenDs` \ _ ->
84 returnDs (ForeignStubs (h $$ acc_h)
90 combine (ForeignStubs acc_h acc_c acc_hdrs acc_feb, acc_f)
91 (L loc (ForeignExport (L _ id) _ (CExport (CExportStatic ext_nm cconv)) depr))
92 = dsFExport id (idType id)
93 ext_nm cconv False `thenDs` \(h, c, _) ->
94 warnDepr depr loc `thenDs` \_ ->
95 returnDs (ForeignStubs (h $$ acc_h) (c $$ acc_c) acc_hdrs (id:acc_feb),
103 warnDepr False _ = returnDs ()
104 warnDepr True loc = dsWarn (loc, msg)
106 msg = ptext SLIT("foreign declaration uses deprecated non-standard syntax")
110 %************************************************************************
112 \subsection{Foreign import}
114 %************************************************************************
116 Desugaring foreign imports is just the matter of creating a binding
117 that on its RHS unboxes its arguments, performs the external call
118 (using the @CCallOp@ primop), before boxing the result up and returning it.
120 However, we create a worker/wrapper pair, thus:
122 foreign import f :: Int -> IO Int
124 f x = IO ( \s -> case x of { I# x# ->
125 case fw s x# of { (# s1, y# #) ->
128 fw s x# = ccall f s x#
130 The strictness/CPR analyser won't do this automatically because it doesn't look
131 inside returned tuples; but inlining this wrapper is a Really Good Idea
132 because it exposes the boxing to the call site.
137 -> DsM ([Binding], SDoc, SDoc, Maybe FastString)
138 dsFImport id (CImport cconv safety header lib spec)
139 = dsCImport id spec cconv safety no_hdrs `thenDs` \(ids, h, c) ->
140 returnDs (ids, h, c, if no_hdrs then Nothing else Just header)
142 no_hdrs = nullFastString header
144 -- FIXME: the `lib' field is needed for .NET ILX generation when invoking
145 -- routines that are external to the .NET runtime, but GHC doesn't
146 -- support such calls yet; if `nullFastString lib', the value was not given
147 dsFImport id (DNImport spec)
148 = dsFCall id (DNCall spec) True {- No headers -} `thenDs` \(ids, h, c) ->
149 returnDs (ids, h, c, Nothing)
155 -> Bool -- True <=> no headers in the f.i decl
156 -> DsM ([Binding], SDoc, SDoc)
157 dsCImport id (CLabel cid) _ _ no_hdrs
158 = resultWrapper (idType id) `thenDs` \ (resTy, foRhs) ->
159 ASSERT(fromJust resTy `eqType` addrPrimTy) -- typechecker ensures this
160 let rhs = foRhs (mkLit (MachLabel cid Nothing)) in
161 returnDs ([(setImpInline no_hdrs id, rhs)], empty, empty)
162 dsCImport id (CFunction target) cconv safety no_hdrs
163 = dsFCall id (CCall (CCallSpec target cconv safety)) no_hdrs
164 dsCImport id CWrapper cconv _ _
165 = dsFExportDynamic id cconv
167 setImpInline :: Bool -- True <=> No #include headers
168 -- in the foreign import declaration
170 -- If there is a #include header in the foreign import
171 -- we make the worker non-inlinable, because we currently
172 -- don't keep the #include stuff in the CCallId, and hence
173 -- it won't be visible in the importing module, which can be
175 -- (The #include stuff is just collected from the foreign import
176 -- decls in a module.)
177 -- If you want to do cross-module inlining of the c-calls themselves,
178 -- put the #include stuff in the package spec, not the foreign
180 setImpInline True id = id
181 setImpInline False id = id `setInlinePragma` NeverActive
185 %************************************************************************
187 \subsection{Foreign calls}
189 %************************************************************************
192 dsFCall fn_id fcall no_hdrs
195 (tvs, fun_ty) = tcSplitForAllTys ty
196 (arg_tys, io_res_ty) = tcSplitFunTys fun_ty
197 -- Must use tcSplit* functions because we want to
198 -- see that (IO t) in the corner
200 newSysLocalsDs arg_tys `thenDs` \ args ->
201 mapAndUnzipDs unboxArg (map Var args) `thenDs` \ (val_args, arg_wrappers) ->
204 work_arg_ids = [v | Var v <- val_args] -- All guaranteed to be vars
206 -- These are the ids we pass to boxResult, which are used to decide
207 -- whether to touch# an argument after the call (used to keep
208 -- ForeignObj#s live across a 'safe' foreign import).
209 maybe_arg_ids | unsafe_call fcall = work_arg_ids
219 dsLookupGlobalId checkDotnetResName `thenDs` \ check_id ->
220 return (Just check_id)
221 | otherwise = return Nothing
225 newSysLocalDs addrPrimTy `thenDs` \ err_res ->
226 returnDs (\ (mb_res_ty, resWrap) ->
228 Nothing -> (Just (mkTyConApp (tupleTyCon Unboxed 1)
231 Just x -> (Just (mkTyConApp (tupleTyCon Unboxed 2)
234 | otherwise = returnDs id
236 augmentResultDs `thenDs` \ augment ->
237 topConDs `thenDs` \ topCon ->
238 boxResult maybe_arg_ids augment topCon io_res_ty `thenDs` \ (ccall_result_ty, res_wrapper) ->
240 newUnique `thenDs` \ ccall_uniq ->
241 newUnique `thenDs` \ work_uniq ->
244 worker_ty = mkForAllTys tvs (mkFunTys (map idType work_arg_ids) ccall_result_ty)
245 the_ccall_app = mkFCall ccall_uniq fcall val_args ccall_result_ty
246 work_rhs = mkLams tvs (mkLams work_arg_ids the_ccall_app)
247 work_id = setImpInline no_hdrs $ -- See comments with setImpInline
248 mkSysLocal (encodeFS FSLIT("$wccall")) work_uniq worker_ty
251 work_app = mkApps (mkVarApps (Var work_id) tvs) val_args
252 wrapper_body = foldr ($) (res_wrapper work_app) arg_wrappers
253 wrap_rhs = mkInlineMe (mkLams (tvs ++ args) wrapper_body)
255 returnDs ([(work_id, work_rhs), (fn_id, wrap_rhs)], empty, empty)
257 unsafe_call (CCall (CCallSpec _ _ safety)) = playSafe safety
258 unsafe_call (DNCall _) = False
262 %************************************************************************
264 \subsection{Foreign export}
266 %************************************************************************
268 The function that does most of the work for `@foreign export@' declarations.
269 (see below for the boilerplate code a `@foreign export@' declaration expands
272 For each `@foreign export foo@' in a module M we generate:
274 \item a C function `@foo@', which calls
275 \item a Haskell stub `@M.$ffoo@', which calls
277 the user-written Haskell function `@M.foo@'.
280 dsFExport :: Id -- Either the exported Id,
281 -- or the foreign-export-dynamic constructor
282 -> Type -- The type of the thing callable from C
283 -> CLabelString -- The name to export to C land
285 -> Bool -- True => foreign export dynamic
286 -- so invoke IO action that's hanging off
287 -- the first argument's stable pointer
288 -> DsM ( SDoc -- contents of Module_stub.h
289 , SDoc -- contents of Module_stub.c
290 , [Type] -- arguments expected by stub function.
293 dsFExport fn_id ty ext_name cconv isDyn
296 (_tvs,sans_foralls) = tcSplitForAllTys ty
297 (fe_arg_tys', orig_res_ty) = tcSplitFunTys sans_foralls
298 -- We must use tcSplits here, because we want to see
299 -- the (IO t) in the corner of the type!
300 fe_arg_tys | isDyn = tail fe_arg_tys'
301 | otherwise = fe_arg_tys'
303 -- Look at the result type of the exported function, orig_res_ty
304 -- If it's IO t, return (t, True)
305 -- If it's plain t, return (t, False)
306 (case tcSplitTyConApp_maybe orig_res_ty of
307 -- We must use tcSplit here so that we see the (IO t) in
308 -- the type. [IO t is transparent to plain splitTyConApp.]
310 Just (ioTyCon, [res_ty])
311 -> ASSERT( ioTyCon `hasKey` ioTyConKey )
312 -- The function already returns IO t
313 returnDs (res_ty, True)
315 other -> -- The function returns t
316 returnDs (orig_res_ty, False)
318 `thenDs` \ (res_ty, -- t
319 is_IO_res_ty) -> -- Bool
321 mkFExportCBits ext_name
322 (if isDyn then Nothing else Just fn_id)
323 fe_arg_tys res_ty is_IO_res_ty cconv
326 @foreign export dynamic@ lets you dress up Haskell IO actions
327 of some fixed type behind an externally callable interface (i.e.,
328 as a C function pointer). Useful for callbacks and stuff.
331 foreign export dynamic f :: (Addr -> Int -> IO Int) -> IO Addr
333 -- Haskell-visible constructor, which is generated from the above:
334 -- SUP: No check for NULL from createAdjustor anymore???
336 f :: (Addr -> Int -> IO Int) -> IO Addr
338 bindIO (newStablePtr cback)
339 (\StablePtr sp# -> IO (\s1# ->
340 case _ccall_ createAdjustor cconv sp# ``f_helper'' s1# of
341 (# s2#, a# #) -> (# s2#, A# a# #)))
343 foreign export "f_helper" f_helper :: StablePtr (Addr -> Int -> IO Int) -> Addr -> Int -> IO Int
344 -- `special' foreign export that invokes the closure pointed to by the
349 dsFExportDynamic :: Id
351 -> DsM ([Binding], SDoc, SDoc)
352 dsFExportDynamic id cconv
353 = newSysLocalDs ty `thenDs` \ fe_id ->
354 getModuleDs `thenDs` \ mod_name ->
356 -- hack: need to get at the name of the C stub we're about to generate.
357 fe_nm = mkFastString (moduleString mod_name ++ "_" ++ toCName fe_id)
359 newSysLocalDs arg_ty `thenDs` \ cback ->
360 dsLookupGlobalId newStablePtrName `thenDs` \ newStablePtrId ->
361 dsLookupTyCon stablePtrTyConName `thenDs` \ stable_ptr_tycon ->
363 mk_stbl_ptr_app = mkApps (Var newStablePtrId) [ Type arg_ty, Var cback ]
364 stable_ptr_ty = mkTyConApp stable_ptr_tycon [arg_ty]
365 export_ty = mkFunTy stable_ptr_ty arg_ty
367 dsLookupGlobalId bindIOName `thenDs` \ bindIOId ->
368 newSysLocalDs stable_ptr_ty `thenDs` \ stbl_value ->
369 dsFExport id export_ty fe_nm cconv True `thenDs` \ (h_code, c_code, stub_args) ->
371 stbl_app cont ret_ty = mkApps (Var bindIOId)
378 The arguments to the external function which will
379 create a little bit of (template) code on the fly
380 for allowing the (stable pointed) Haskell closure
381 to be entered using an external calling convention
384 adj_args = [ mkIntLitInt (ccallConvToInt cconv)
386 , mkLit (MachLabel fe_nm mb_sz_args)
388 -- name of external entry point providing these services.
389 -- (probably in the RTS.)
390 adjustor = FSLIT("createAdjustor")
392 sz_args = sum (map (getPrimRepSizeInBytes . typePrimRep) stub_args)
393 mb_sz_args = case cconv of
394 StdCallConv -> Just sz_args
397 dsCCall adjustor adj_args PlayRisky io_res_ty `thenDs` \ ccall_adj ->
398 -- PlayRisky: the adjustor doesn't allocate in the Haskell heap or do a callback
399 let ccall_adj_ty = exprType ccall_adj
400 ccall_io_adj = mkLams [stbl_value] $
401 Note (Coerce io_res_ty ccall_adj_ty)
403 io_app = mkLams tvs $
405 stbl_app ccall_io_adj res_ty
406 fed = (id `setInlinePragma` NeverActive, io_app)
407 -- Never inline the f.e.d. function, because the litlit
408 -- might not be in scope in other modules.
410 returnDs ([fed], h_code, c_code)
414 (tvs,sans_foralls) = tcSplitForAllTys ty
415 ([arg_ty], io_res_ty) = tcSplitFunTys sans_foralls
416 [res_ty] = tcTyConAppArgs io_res_ty
417 -- Must use tcSplit* to see the (IO t), which is a newtype
419 toCName :: Id -> String
420 toCName i = showSDoc (pprCode CStyle (ppr (idName i)))
425 \subsection{Generating @foreign export@ stubs}
429 For each @foreign export@ function, a C stub function is generated.
430 The C stub constructs the application of the exported Haskell function
431 using the hugs/ghc rts invocation API.
434 mkFExportCBits :: FastString
435 -> Maybe Id -- Just==static, Nothing==dynamic
438 -> Bool -- True <=> returns an IO type
440 -> (SDoc, SDoc, [Type])
441 mkFExportCBits c_nm maybe_target arg_htys res_hty is_IO_res_ty cc
442 = (header_bits, c_bits, all_arg_tys)
444 -- Create up types and names for the real args
445 arg_cnames, arg_ctys :: [SDoc]
446 arg_cnames = mkCArgNames 1 arg_htys
447 arg_ctys = map showStgType arg_htys
449 -- and also for auxiliary ones; the stable ptr in the dynamic case, and
450 -- a slot for the dummy return address in the dynamic + ccall case
452 = case maybe_target of
453 Nothing -> [((text "the_stableptr", text "StgStablePtr"), mkStablePtrPrimTy alphaTy)]
456 case (maybe_target, cc) of
457 (Nothing, CCallConv) -> [((text "original_return_addr", text "void*"), addrPrimTy)]
460 all_cnames_and_ctys :: [(SDoc, SDoc)]
462 = map fst extra_cnames_and_tys ++ zip arg_cnames arg_ctys
465 = map snd extra_cnames_and_tys ++ arg_htys
467 -- stuff to do with the return type of the C function
468 res_hty_is_unit = res_hty `eqType` unitTy -- Look through any newtypes
470 cResType | res_hty_is_unit = text "void"
471 | otherwise = showStgType res_hty
473 -- Now we can cook up the prototype for the exported function.
474 pprCconv = case cc of
476 StdCallConv -> text (ccallConvAttribute cc)
478 header_bits = ptext SLIT("extern") <+> fun_proto <> semi
480 fun_proto = cResType <+> pprCconv <+> ftext c_nm <>
481 parens (hsep (punctuate comma (map (\(nm,ty) -> ty <+> nm)
482 all_cnames_and_ctys)))
484 -- the target which will form the root of what we ask rts_evalIO to run
486 = case maybe_target of
487 Nothing -> text "(StgClosure*)deRefStablePtr(the_stableptr)"
488 Just hs_fn -> char '&' <> ppr hs_fn <> text "_closure"
490 -- the expression we give to rts_evalIO
492 = foldl appArg the_cfun (zip arg_cnames arg_htys)
494 appArg acc (arg_cname, arg_hty)
496 <> parens (acc <> comma <> mkHObj arg_hty <> parens arg_cname)
498 -- various other bits for inside the fn
499 declareResult = text "HaskellObj ret;"
500 declareCResult | res_hty_is_unit = empty
501 | otherwise = cResType <+> text "cret;"
503 assignCResult | res_hty_is_unit = empty
505 text "cret=" <> unpackHObj res_hty <> parens (text "ret") <> semi
507 -- an extern decl for the fn being called
509 = case maybe_target of
511 Just hs_fn -> text "extern StgClosure " <> ppr hs_fn <> text "_closure" <> semi
513 -- finally, the whole darn thing
520 , text "SchedulerStatus rc;"
524 -- create the application + perform it.
525 , text "rc=rts_evalIO" <> parens (
526 text "rts_apply" <> parens (
528 <> text (if is_IO_res_ty
530 else "runNonIO_closure")
536 , text "rts_checkSchedStatus" <> parens (doubleQuotes (ftext c_nm)
537 <> comma <> text "rc") <> semi
539 , text "rts_unlock();"
540 , if res_hty_is_unit then empty
541 else text "return cret;"
546 mkCArgNames :: Int -> [a] -> [SDoc]
547 mkCArgNames n as = zipWith (\ _ n -> text ('a':show n)) as [n..]
549 mkHObj :: Type -> SDoc
550 mkHObj t = text "rts_mk" <> text (showFFIType t)
552 unpackHObj :: Type -> SDoc
553 unpackHObj t = text "rts_get" <> text (showFFIType t)
555 showStgType :: Type -> SDoc
556 showStgType t = text "Hs" <> text (showFFIType t)
558 showFFIType :: Type -> String
559 showFFIType t = getOccString (getName tc)
561 tc = case tcSplitTyConApp_maybe (repType t) of
563 Nothing -> pprPanic "showFFIType" (ppr t)