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, mkVanillaGlobal, mkSysLocal,
24 import IdInfo ( vanillaIdInfo )
25 import Literal ( Literal(..) )
26 import Module ( Module, moduleUserString )
27 import Name ( mkGlobalName, nameModule, nameOccName, getOccString,
28 mkForeignExportOcc, isLocalName,
31 import Type ( repType, eqType )
32 import TcType ( Type, mkFunTys, mkForAllTys, mkTyConApp,
34 tcSplitForAllTys, tcSplitFunTys, tcTyConAppArgs,
35 tcSplitTyConApp_maybe, tcSplitAppTy,
39 import ForeignCall ( ForeignCall(..), CCallSpec(..),
42 CCallConv(..), ccallConvToInt
44 import CStrings ( CLabelString )
45 import TysWiredIn ( addrTy, unitTy, stablePtrTyCon )
46 import TysPrim ( addrPrimTy )
47 import PrelNames ( hasKey, ioTyConKey, deRefStablePtrName, newStablePtrName,
48 bindIOName, returnIOName
50 import BasicTypes ( Activation( NeverActive ) )
51 import ErrUtils ( addShortWarnLocLine )
53 import Maybe ( fromJust )
56 Desugaring of @foreign@ declarations is naturally split up into
57 parts, an @import@ and an @export@ part. A @foreign import@
60 foreign import cc nm f :: prim_args -> IO prim_res
64 f :: prim_args -> IO prim_res
65 f a1 ... an = _ccall_ nm cc a1 ... an
67 so we reuse the desugaring code in @DsCCall@ to deal with these.
70 type Binding = (Id, CoreExpr) -- No rec/nonrec structure;
71 -- the occurrence analyser will sort it all out
74 -> [TypecheckedForeignDecl]
75 -> DsM ( [Id] -- Foreign-exported binders;
76 -- we have to generate code to register these
78 , SDoc -- Header file prototypes for
79 -- "foreign exported" functions.
80 , SDoc -- C stubs to use when calling
81 -- "foreign exported" functions.
82 , [FAST_STRING] -- headers that need to be included
83 -- into C code generated for this module
85 dsForeigns mod_name fos
86 = foldlDs combine ([], [], empty, empty, []) fos
88 combine (acc_feb, acc_f, acc_h, acc_c, acc_header)
89 (ForeignImport id _ spec depr loc)
90 = dsFImport mod_name id spec `thenDs` \(bs, h, c, hd) ->
91 warnDepr depr loc `thenDs` \_ ->
92 returnDs (acc_feb, bs ++ acc_f, h $$ acc_h, c $$ acc_c, hd ++ acc_header)
94 combine (acc_feb, acc_f, acc_h, acc_c, acc_header)
95 (ForeignExport id _ (CExport (CExportStatic ext_nm cconv)) depr loc)
96 = dsFExport mod_name id (idType id)
97 ext_nm cconv False `thenDs` \(feb, b, h, c) ->
98 warnDepr depr loc `thenDs` \_ ->
99 returnDs (feb:acc_feb, b : acc_f, h $$ acc_h, c $$ acc_c, acc_header)
101 warnDepr False _ = returnDs ()
102 warnDepr True loc = dsWarn (addShortWarnLocLine loc msg)
104 msg = ptext SLIT("foreign declaration uses deprecated non-standard syntax")
108 %************************************************************************
110 \subsection{Foreign import}
112 %************************************************************************
114 Desugaring foreign imports is just the matter of creating a binding
115 that on its RHS unboxes its arguments, performs the external call
116 (using the @CCallOp@ primop), before boxing the result up and returning it.
118 However, we create a worker/wrapper pair, thus:
120 foreign import f :: Int -> IO Int
122 f x = IO ( \s -> case x of { I# x# ->
123 case fw s x# of { (# s1, y# #) ->
126 fw s x# = ccall f s x#
128 The strictness/CPR analyser won't do this automatically because it doesn't look
129 inside returned tuples; but inlining this wrapper is a Really Good Idea
130 because it exposes the boxing to the call site.
136 -> DsM ([Binding], SDoc, SDoc, [FAST_STRING])
137 dsFImport modName id (CImport cconv safety header lib spec)
138 = dsCImport modName id spec cconv safety `thenDs` \(ids, h, c) ->
139 returnDs (ids, h, c, if _NULL_ header then [] else [header])
140 -- FIXME: the `lib' field is needed for .NET ILX generation when invoking
141 -- routines that are external to the .NET runtime, but GHC doesn't
142 -- support such calls yet; if `_NULL_ lib', the value was not given
143 dsFImport modName id (DNImport spec)
144 = dsFCall modName id (DNCall spec) `thenDs` \(ids, h, c) ->
145 returnDs (ids, h, c, [])
152 -> DsM ([Binding], SDoc, SDoc)
153 dsCImport modName id (CLabel cid) _ _
154 = ASSERT(fromJust resTy `eqType` addrPrimTy) -- typechecker ensures this
155 returnDs ([(id, rhs)], empty, empty)
157 (resTy, foRhs) = resultWrapper (idType id)
158 rhs = foRhs (mkLit (MachLabel cid))
159 dsCImport modName id (CFunction target) cconv safety
160 = dsFCall modName id (CCall (CCallSpec target cconv safety))
161 dsCImport modName id CWrapper cconv _
162 = dsFExportDynamic modName id cconv
166 %************************************************************************
168 \subsection{Foreign calls}
170 %************************************************************************
173 dsFCall mod_Name fn_id fcall
176 (tvs, fun_ty) = tcSplitForAllTys ty
177 (arg_tys, io_res_ty) = tcSplitFunTys fun_ty
178 -- Must use tcSplit* functions because we want to
179 -- see that (IO t) in the corner
181 newSysLocalsDs arg_tys `thenDs` \ args ->
182 mapAndUnzipDs unboxArg (map Var args) `thenDs` \ (val_args, arg_wrappers) ->
185 work_arg_ids = [v | Var v <- val_args] -- All guaranteed to be vars
187 -- These are the ids we pass to boxResult, which are used to decide
188 -- whether to touch# an argument after the call (used to keep
189 -- ForeignObj#s live across a 'safe' foreign import).
190 maybe_arg_ids | unsafe_call fcall = work_arg_ids
193 boxResult maybe_arg_ids io_res_ty `thenDs` \ (ccall_result_ty, res_wrapper) ->
195 getUniqueDs `thenDs` \ ccall_uniq ->
196 getUniqueDs `thenDs` \ work_uniq ->
199 worker_ty = mkForAllTys tvs (mkFunTys (map idType work_arg_ids) ccall_result_ty)
200 the_ccall_app = mkFCall ccall_uniq fcall val_args ccall_result_ty
201 work_rhs = mkLams tvs (mkLams work_arg_ids the_ccall_app)
202 work_id = mkSysLocal SLIT("$wccall") work_uniq worker_ty
205 work_app = mkApps (mkVarApps (Var work_id) tvs) val_args
206 wrapper_body = foldr ($) (res_wrapper work_app) arg_wrappers
207 wrap_rhs = mkInlineMe (mkLams (tvs ++ args) wrapper_body)
209 returnDs ([(work_id, work_rhs), (fn_id, wrap_rhs)], empty, empty)
211 unsafe_call (CCall (CCallSpec _ _ safety)) = playSafe safety
212 unsafe_call (DNCall _) = False
216 %************************************************************************
218 \subsection{Foreign export}
220 %************************************************************************
222 The function that does most of the work for `@foreign export@' declarations.
223 (see below for the boilerplate code a `@foreign export@' declaration expands
226 For each `@foreign export foo@' in a module M we generate:
228 \item a C function `@foo@', which calls
229 \item a Haskell stub `@M.$ffoo@', which calls
231 the user-written Haskell function `@M.foo@'.
235 -> Id -- Either the exported Id,
236 -- or the foreign-export-dynamic constructor
237 -> Type -- The type of the thing callable from C
238 -> CLabelString -- The name to export to C land
240 -> Bool -- True => foreign export dynamic
241 -- so invoke IO action that's hanging off
242 -- the first argument's stable pointer
243 -> DsM ( Id -- The foreign-exported Id
248 dsFExport mod_name fn_id ty ext_name cconv isDyn
249 = -- BUILD THE returnIO WRAPPER, if necessary
250 -- Look at the result type of the exported function, orig_res_ty
251 -- If it's IO t, return (\x.x, IO t, t)
252 -- If it's plain t, return (\x.returnIO x, IO t, t)
253 (case tcSplitTyConApp_maybe orig_res_ty of
254 -- We must use tcSplit here so that we see the (IO t) in
255 -- the type. [IO t is transparent to plain splitTyConApp.]
257 Just (ioTyCon, [res_ty])
258 -> ASSERT( ioTyCon `hasKey` ioTyConKey )
259 -- The function already returns IO t
260 returnDs (\body -> body, orig_res_ty, res_ty)
262 other -> -- The function returns t, so wrap the call in returnIO
263 dsLookupGlobalValue returnIOName `thenDs` \ retIOId ->
264 returnDs (\body -> mkApps (Var retIOId) [Type orig_res_ty, body],
265 tcFunResultTy (applyTy (idType retIOId) orig_res_ty),
266 -- We don't have ioTyCon conveniently to hand
269 ) `thenDs` \ (return_io_wrapper, -- Either identity or returnIO
274 -- BUILD THE deRefStablePtr WRAPPER, if necessary
276 newSysLocalDs stbl_ptr_ty `thenDs` \ stbl_ptr ->
277 newSysLocalDs stbl_ptr_to_ty `thenDs` \ stbl_value ->
278 dsLookupGlobalValue deRefStablePtrName `thenDs` \ deRefStablePtrId ->
279 dsLookupGlobalValue bindIOName `thenDs` \ bindIOId ->
281 the_deref_app = mkApps (Var deRefStablePtrId)
282 [ Type stbl_ptr_to_ty, Var stbl_ptr ]
284 stbl_app cont = mkApps (Var bindIOId)
285 [ Type stbl_ptr_to_ty
288 , mkLams [stbl_value] cont]
290 returnDs (stbl_value, stbl_app, stbl_ptr)
294 panic "stbl_ptr" -- should never be touched.
295 )) `thenDs` \ (i, getFun_wrapper, stbl_ptr) ->
299 getModuleDs `thenDs` \ mod ->
300 getUniqueDs `thenDs` \ uniq ->
301 getSrcLocDs `thenDs` \ src_loc ->
302 newSysLocalsDs fe_arg_tys `thenDs` \ fe_args ->
304 wrapper_args | isDyn = stbl_ptr:fe_args
305 | otherwise = fe_args
307 wrapper_arg_tys | isDyn = stbl_ptr_ty:fe_arg_tys
308 | otherwise = fe_arg_tys
310 helper_ty = mkForAllTys tvs $
311 mkFunTys wrapper_arg_tys io_res_ty
313 f_helper_glob = mkVanillaGlobal helper_name helper_ty vanillaIdInfo
317 | isLocalName name = mod_name
318 | otherwise = nameModule name
320 occ = mkForeignExportOcc (nameOccName name)
321 helper_name = mkGlobalName uniq mod occ src_loc
323 the_app = getFun_wrapper (return_io_wrapper (mkVarApps (Var i) (tvs ++ fe_args)))
324 the_body = mkLams (tvs ++ wrapper_args) the_app
326 (h_stub, c_stub) = fexportEntry (moduleUserString mod)
327 ext_name f_helper_glob
328 wrapper_arg_tys res_ty cconv isDyn
330 returnDs (f_helper_glob, (f_helper_glob, the_body), h_stub, c_stub)
333 (tvs,sans_foralls) = tcSplitForAllTys ty
334 (fe_arg_tys', orig_res_ty) = tcSplitFunTys sans_foralls
335 -- We must use tcSplits here, because we want to see
336 -- the (IO t) in the corner of the type!
338 fe_arg_tys | isDyn = tail fe_arg_tys'
339 | otherwise = fe_arg_tys'
341 stbl_ptr_ty | isDyn = head fe_arg_tys'
342 | otherwise = error "stbl_ptr_ty"
344 (_, stbl_ptr_ty') = tcSplitForAllTys stbl_ptr_ty
345 (_, stbl_ptr_to_ty) = tcSplitAppTy stbl_ptr_ty'
346 -- Again, stable pointers are just newtypes,
347 -- so we must see them! Hence tcSplit*
350 @foreign export dynamic@ lets you dress up Haskell IO actions
351 of some fixed type behind an externally callable interface (i.e.,
352 as a C function pointer). Useful for callbacks and stuff.
355 foreign export dynamic f :: (Addr -> Int -> IO Int) -> IO Addr
357 -- Haskell-visible constructor, which is generated from the above:
358 -- SUP: No check for NULL from createAdjustor anymore???
360 f :: (Addr -> Int -> IO Int) -> IO Addr
362 bindIO (newStablePtr cback)
363 (\StablePtr sp# -> IO (\s1# ->
364 case _ccall_ createAdjustor cconv sp# ``f_helper'' s1# of
365 (# s2#, a# #) -> (# s2#, A# a# #)))
367 foreign export "f_helper" f_helper :: StablePtr (Addr -> Int -> IO Int) -> Addr -> Int -> IO Int
368 -- `special' foreign export that invokes the closure pointed to by the
373 dsFExportDynamic :: Module
376 -> DsM ([Binding], SDoc, SDoc)
377 dsFExportDynamic mod_name id cconv
378 = newSysLocalDs ty `thenDs` \ fe_id ->
380 -- hack: need to get at the name of the C stub we're about to generate.
381 fe_nm = _PK_ (moduleUserString mod_name ++ "_" ++ toCName fe_id)
383 dsFExport mod_name id export_ty fe_nm cconv True `thenDs` \ (feb, fe, h_code, c_code) ->
384 newSysLocalDs arg_ty `thenDs` \ cback ->
385 dsLookupGlobalValue newStablePtrName `thenDs` \ newStablePtrId ->
387 mk_stbl_ptr_app = mkApps (Var newStablePtrId) [ Type arg_ty, Var cback ]
389 dsLookupGlobalValue bindIOName `thenDs` \ bindIOId ->
390 newSysLocalDs (mkTyConApp stablePtrTyCon [arg_ty]) `thenDs` \ stbl_value ->
393 = mkApps (Var bindIOId)
394 [ Type (mkTyConApp stablePtrTyCon [arg_ty])
401 The arguments to the external function which will
402 create a little bit of (template) code on the fly
403 for allowing the (stable pointed) Haskell closure
404 to be entered using an external calling convention
407 adj_args = [ mkIntLitInt (ccallConvToInt cconv)
409 , mkLit (MachLabel fe_nm)
411 -- name of external entry point providing these services.
412 -- (probably in the RTS.)
413 adjustor = SLIT("createAdjustor")
415 dsCCall adjustor adj_args PlayRisky False io_res_ty `thenDs` \ ccall_adj ->
416 -- PlayRisky: the adjustor doesn't allocate in the Haskell heap or do a callback
417 let ccall_adj_ty = exprType ccall_adj
418 ccall_io_adj = mkLams [stbl_value] $
419 Note (Coerce io_res_ty ccall_adj_ty)
421 io_app = mkLams tvs $
423 stbl_app ccall_io_adj res_ty
424 fed = (id `setInlinePragma` NeverActive, io_app)
425 -- Never inline the f.e.d. function, because the litlit
426 -- might not be in scope in other modules.
428 returnDs ([fed, fe], h_code, c_code)
432 (tvs,sans_foralls) = tcSplitForAllTys ty
433 ([arg_ty], io_res_ty) = tcSplitFunTys sans_foralls
434 [res_ty] = tcTyConAppArgs io_res_ty
435 -- Must use tcSplit* to see the (IO t), which is a newtype
436 export_ty = mkFunTy (mkTyConApp stablePtrTyCon [arg_ty]) arg_ty
438 toCName :: Id -> String
439 toCName i = showSDoc (pprCode CStyle (ppr (idName i)))
444 \subsection{Generating @foreign export@ stubs}
448 For each @foreign export@ function, a C stub function is generated.
449 The C stub constructs the application of the exported Haskell function
450 using the hugs/ghc rts invocation API.
453 fexportEntry :: String
461 fexportEntry mod_nm c_nm helper args res_ty cc isDyn = (header_bits, c_bits)
463 -- name of the (Haskell) helper function generated by the desugarer.
464 h_nm = ppr helper <> text "_closure"
465 -- prototype for the exported function.
466 header_bits = ptext SLIT("extern") <+> fun_proto <> semi
468 fun_proto = cResType <+> pprCconv <+> ptext c_nm <>
469 parens (hsep (punctuate comma (zipWith (<+>) cParamTypes proto_args)))
476 , text "SchedulerStatus rc;"
478 -- create the application + perform it.
479 , text "rc=rts_evalIO" <>
480 parens (foldl appArg (text "(StgClosure*)&" <> h_nm) (zip args c_args) <> comma <> text "&ret") <> semi
481 , text "rts_checkSchedStatus" <> parens (doubleQuotes (ptext c_nm)
482 <> comma <> text "rc") <> semi
483 , text "return" <> return_what <> semi
488 text "rts_apply" <> parens (acc <> comma <> mkHObj a <> parens c_a)
490 cParamTypes = map showStgType real_args
492 res_ty_is_unit = res_ty `eqType` unitTy -- Look through any newtypes
494 cResType | res_ty_is_unit = text "void"
495 | otherwise = showStgType res_ty
497 pprCconv = case cc of
499 StdCallConv -> ppr cc
501 declareResult = text "HaskellObj ret;"
503 externDecl = mkExtern (text "HaskellObj") h_nm
505 mkExtern ty nm = text "extern" <+> ty <+> nm <> semi
507 return_what | res_ty_is_unit = empty
508 | otherwise = parens (unpackHObj res_ty <> parens (text "ret"))
510 c_args = mkCArgNames 0 args
513 If we're generating an entry point for a 'foreign export ccall dynamic',
514 then we receive the return address of the C function that wants to
515 invoke a Haskell function as any other C function, as second arg.
516 This arg is unused within the body of the generated C stub, but
517 needed by the Adjustor.c code to get the stack cleanup right.
519 (proto_args, real_args)
521 CCallConv | isDyn -> ( text "a0" : text "a_" : mkCArgNames 1 (tail args)
522 , head args : addrTy : tail args)
523 other -> (mkCArgNames 0 args, args)
525 mkCArgNames :: Int -> [a] -> [SDoc]
526 mkCArgNames n as = zipWith (\ _ n -> text ('a':show n)) as [n..]
528 mkHObj :: Type -> SDoc
529 mkHObj t = text "rts_mk" <> text (showFFIType t)
531 unpackHObj :: Type -> SDoc
532 unpackHObj t = text "rts_get" <> text (showFFIType t)
534 showStgType :: Type -> SDoc
535 showStgType t = text "Hs" <> text (showFFIType t)
537 showFFIType :: Type -> String
538 showFFIType t = getOccString (getName tc)
540 tc = case tcSplitTyConApp_maybe (repType t) of
542 Nothing -> pprPanic "showFFIType" (ppr t)