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(..), FoExport(..), FoImport(..) )
19 import TcHsSyn ( TypecheckedForeignDecl )
20 import CoreUtils ( exprType, mkInlineMe )
21 import Id ( Id, idType, idName, mkVanillaGlobal, mkSysLocal,
23 import IdInfo ( neverInlinePrag, vanillaIdInfo )
24 import Literal ( Literal(..) )
25 import Module ( Module, moduleUserString )
26 import Name ( mkGlobalName, nameModule, nameOccName, getOccString,
27 mkForeignExportOcc, isLocalName,
30 import TcType ( tcSplitTyConApp_maybe, tcFunResultTy,
31 tcSplitFunTys, tcSplitForAllTys,
32 Type, mkFunTys, mkForAllTys, mkTyConApp,
33 mkFunTy, tcSplitAppTy, applyTy, tcEqType, isUnitTy
35 import Type ( repType )
36 import ForeignCall ( ForeignCall(..), CCallSpec(..),
39 CCallConv(..), ccallConvToInt
41 import CStrings ( CLabelString )
42 import TysWiredIn ( addrTy, stablePtrTyCon )
43 import TysPrim ( addrPrimTy )
44 import PrelNames ( hasKey, ioTyConKey, deRefStablePtrName, newStablePtrName,
45 bindIOName, returnIOName
49 import Maybe ( fromJust )
52 Desugaring of @foreign@ declarations is naturally split up into
53 parts, an @import@ and an @export@ part. A @foreign import@
56 foreign import cc nm f :: prim_args -> IO prim_res
60 f :: prim_args -> IO prim_res
61 f a1 ... an = _ccall_ nm cc a1 ... an
63 so we reuse the desugaring code in @DsCCall@ to deal with these.
66 type Binding = (Id, CoreExpr) -- No rec/nonrec structure;
67 -- the occurrence analyser will sort it all out
70 -> [TypecheckedForeignDecl]
71 -> DsM ( [Id] -- Foreign-exported binders;
72 -- we have to generate code to register these
74 , SDoc -- Header file prototypes for
75 -- "foreign exported" functions.
76 , SDoc -- C stubs to use when calling
77 -- "foreign exported" functions.
79 dsForeigns mod_name fos
80 = foldlDs combine ([], [], empty, empty) fos
82 combine (acc_feb, acc_f, acc_h, acc_c) (ForeignImport id _ spec _)
83 = dsFImport mod_name id spec `thenDs` \ (bs, h, c) ->
84 returnDs (acc_feb, bs ++ acc_f, h $$ acc_h, c $$ acc_c)
86 combine (acc_feb, acc_f, acc_h, acc_c) (ForeignExport id _ (CExport (CExportStatic ext_nm cconv)) _)
87 = dsFExport mod_name id (idType id) ext_nm cconv False `thenDs` \ (feb, b, h, c) ->
88 returnDs (feb:acc_feb, b : acc_f, h $$ acc_h, c $$ acc_c)
92 %************************************************************************
94 \subsection{Foreign import}
96 %************************************************************************
98 Desugaring foreign imports is just the matter of creating a binding
99 that on its RHS unboxes its arguments, performs the external call
100 (using the @CCallOp@ primop), before boxing the result up and returning it.
102 However, we create a worker/wrapper pair, thus:
104 foreign import f :: Int -> IO Int
106 f x = IO ( \s -> case x of { I# x# ->
107 case fw s x# of { (# s1, y# #) ->
110 fw s x# = ccall f s x#
112 The strictness/CPR analyser won't do this automatically because it doesn't look
113 inside returned tuples; but inlining this wrapper is a Really Good Idea
114 because it exposes the boxing to the call site.
121 -> DsM ([Binding], SDoc, SDoc)
122 dsFImport mod_name lbl_id (LblImport ext_nm)
123 = ASSERT(fromJust res_ty `tcEqType` addrPrimTy) -- typechecker ensures this
124 returnDs ([(lbl_id, rhs)], empty, empty)
126 (res_ty, fo_rhs) = resultWrapper (idType lbl_id)
127 rhs = fo_rhs (mkLit (MachLabel ext_nm))
129 dsFImport mod_name fn_id (CImport spec) = dsFCall mod_name fn_id (CCall spec)
130 dsFImport mod_name fn_id (DNImport spec) = dsFCall mod_name fn_id (DNCall spec)
131 dsFImport mod_name fn_id (CDynImport cconv) = dsFExportDynamic mod_name fn_id cconv
135 %************************************************************************
137 \subsection{Foreign calls}
139 %************************************************************************
142 dsFCall mod_Name fn_id fcall
145 (tvs, fun_ty) = tcSplitForAllTys ty
146 (arg_tys, io_res_ty) = tcSplitFunTys fun_ty
148 newSysLocalsDs arg_tys `thenDs` \ args ->
149 mapAndUnzipDs unboxArg (map Var args) `thenDs` \ (val_args, arg_wrappers) ->
152 work_arg_ids = [v | Var v <- val_args] -- All guaranteed to be vars
154 -- These are the ids we pass to boxResult, which are used to decide
155 -- whether to touch# an argument after the call (used to keep
156 -- ForeignObj#s live across a 'safe' foreign import).
157 maybe_arg_ids | unsafe_call fcall = work_arg_ids
160 boxResult maybe_arg_ids io_res_ty `thenDs` \ (ccall_result_ty, res_wrapper) ->
162 getUniqueDs `thenDs` \ ccall_uniq ->
163 getUniqueDs `thenDs` \ work_uniq ->
166 worker_ty = mkForAllTys tvs (mkFunTys (map idType work_arg_ids) ccall_result_ty)
167 the_ccall_app = mkFCall ccall_uniq fcall val_args ccall_result_ty
168 work_rhs = mkLams tvs (mkLams work_arg_ids the_ccall_app)
169 work_id = mkSysLocal SLIT("$wccall") work_uniq worker_ty
172 work_app = mkApps (mkVarApps (Var work_id) tvs) val_args
173 wrapper_body = foldr ($) (res_wrapper work_app) arg_wrappers
174 wrap_rhs = mkInlineMe (mkLams (tvs ++ args) wrapper_body)
176 returnDs ([(work_id, work_rhs), (fn_id, wrap_rhs)], empty, empty)
178 unsafe_call (CCall (CCallSpec _ _ safety)) = playSafe safety
179 unsafe_call (DNCall _) = False
183 %************************************************************************
185 \subsection{Foreign export}
187 %************************************************************************
189 The function that does most of the work for `@foreign export@' declarations.
190 (see below for the boilerplate code a `@foreign export@' declaration expands
193 For each `@foreign export foo@' in a module M we generate:
195 \item a C function `@foo@', which calls
196 \item a Haskell stub `@M.$ffoo@', which calls
198 the user-written Haskell function `@M.foo@'.
202 -> Id -- Either the exported Id,
203 -- or the foreign-export-dynamic constructor
204 -> Type -- The type of the thing callable from C
205 -> CLabelString -- The name to export to C land
207 -> Bool -- True => foreign export dynamic
208 -- so invoke IO action that's hanging off
209 -- the first argument's stable pointer
210 -> DsM ( Id -- The foreign-exported Id
215 dsFExport mod_name fn_id ty ext_name cconv isDyn
216 = -- BUILD THE returnIO WRAPPER, if necessary
217 -- Look at the result type of the exported function, orig_res_ty
218 -- If it's IO t, return (\x.x, IO t, t)
219 -- If it's plain t, return (\x.returnIO x, IO t, t)
220 (case tcSplitTyConApp_maybe orig_res_ty of
221 Just (ioTyCon, [res_ty])
222 -> ASSERT( ioTyCon `hasKey` ioTyConKey )
223 -- The function already returns IO t
224 returnDs (\body -> body, orig_res_ty, res_ty)
226 other -> -- The function returns t, so wrap the call in returnIO
227 dsLookupGlobalValue returnIOName `thenDs` \ retIOId ->
228 returnDs (\body -> mkApps (Var retIOId) [Type orig_res_ty, body],
229 tcFunResultTy (applyTy (idType retIOId) orig_res_ty),
230 -- We don't have ioTyCon conveniently to hand
233 ) `thenDs` \ (return_io_wrapper, -- Either identity or returnIO
238 -- BUILD THE deRefStablePtr WRAPPER, if necessary
240 newSysLocalDs stbl_ptr_ty `thenDs` \ stbl_ptr ->
241 newSysLocalDs stbl_ptr_to_ty `thenDs` \ stbl_value ->
242 dsLookupGlobalValue deRefStablePtrName `thenDs` \ deRefStablePtrId ->
243 dsLookupGlobalValue bindIOName `thenDs` \ bindIOId ->
245 the_deref_app = mkApps (Var deRefStablePtrId)
246 [ Type stbl_ptr_to_ty, Var stbl_ptr ]
248 stbl_app cont = mkApps (Var bindIOId)
249 [ Type stbl_ptr_to_ty
252 , mkLams [stbl_value] cont]
254 returnDs (stbl_value, stbl_app, stbl_ptr)
258 panic "stbl_ptr" -- should never be touched.
259 )) `thenDs` \ (i, getFun_wrapper, stbl_ptr) ->
263 getModuleDs `thenDs` \ mod ->
264 getUniqueDs `thenDs` \ uniq ->
265 getSrcLocDs `thenDs` \ src_loc ->
266 newSysLocalsDs fe_arg_tys `thenDs` \ fe_args ->
268 wrapper_args | isDyn = stbl_ptr:fe_args
269 | otherwise = fe_args
271 wrapper_arg_tys | isDyn = stbl_ptr_ty:fe_arg_tys
272 | otherwise = fe_arg_tys
274 helper_ty = mkForAllTys tvs $
275 mkFunTys wrapper_arg_tys io_res_ty
277 f_helper_glob = mkVanillaGlobal helper_name helper_ty vanillaIdInfo
281 | isLocalName name = mod_name
282 | otherwise = nameModule name
284 occ = mkForeignExportOcc (nameOccName name)
285 helper_name = mkGlobalName uniq mod occ src_loc
287 the_app = getFun_wrapper (return_io_wrapper (mkVarApps (Var i) (tvs ++ fe_args)))
288 the_body = mkLams (tvs ++ wrapper_args) the_app
290 (h_stub, c_stub) = fexportEntry (moduleUserString mod)
291 ext_name f_helper_glob
292 wrapper_arg_tys res_ty cconv isDyn
294 returnDs (f_helper_glob, (f_helper_glob, the_body), h_stub, c_stub)
297 (tvs,sans_foralls) = tcSplitForAllTys ty
298 (fe_arg_tys', orig_res_ty) = tcSplitFunTys sans_foralls
300 (_, stbl_ptr_ty') = tcSplitForAllTys stbl_ptr_ty
301 (_, stbl_ptr_to_ty) = tcSplitAppTy stbl_ptr_ty'
303 fe_arg_tys | isDyn = tail fe_arg_tys'
304 | otherwise = fe_arg_tys'
306 stbl_ptr_ty | isDyn = head fe_arg_tys'
307 | otherwise = error "stbl_ptr_ty"
310 @foreign export dynamic@ lets you dress up Haskell IO actions
311 of some fixed type behind an externally callable interface (i.e.,
312 as a C function pointer). Useful for callbacks and stuff.
315 foreign export dynamic f :: (Addr -> Int -> IO Int) -> IO Addr
317 -- Haskell-visible constructor, which is generated from the above:
318 -- SUP: No check for NULL from createAdjustor anymore???
320 f :: (Addr -> Int -> IO Int) -> IO Addr
322 bindIO (newStablePtr cback)
323 (\StablePtr sp# -> IO (\s1# ->
324 case _ccall_ createAdjustor cconv sp# ``f_helper'' s1# of
325 (# s2#, a# #) -> (# s2#, A# a# #)))
327 foreign export "f_helper" f_helper :: StablePtr (Addr -> Int -> IO Int) -> Addr -> Int -> IO Int
328 -- `special' foreign export that invokes the closure pointed to by the
333 dsFExportDynamic :: Module
336 -> DsM ([Binding], SDoc, SDoc)
337 dsFExportDynamic mod_name id cconv
338 = newSysLocalDs ty `thenDs` \ fe_id ->
340 -- hack: need to get at the name of the C stub we're about to generate.
341 fe_nm = _PK_ (moduleUserString mod_name ++ "_" ++ toCName fe_id)
343 dsFExport mod_name id export_ty fe_nm cconv True `thenDs` \ (feb, fe, h_code, c_code) ->
344 newSysLocalDs arg_ty `thenDs` \ cback ->
345 dsLookupGlobalValue newStablePtrName `thenDs` \ newStablePtrId ->
347 mk_stbl_ptr_app = mkApps (Var newStablePtrId) [ Type arg_ty, Var cback ]
349 dsLookupGlobalValue bindIOName `thenDs` \ bindIOId ->
350 newSysLocalDs (mkTyConApp stablePtrTyCon [arg_ty]) `thenDs` \ stbl_value ->
353 = mkApps (Var bindIOId)
354 [ Type (mkTyConApp stablePtrTyCon [arg_ty])
361 The arguments to the external function which will
362 create a little bit of (template) code on the fly
363 for allowing the (stable pointed) Haskell closure
364 to be entered using an external calling convention
367 adj_args = [ mkIntLitInt (ccallConvToInt cconv)
369 , mkLit (MachLabel fe_nm)
371 -- name of external entry point providing these services.
372 -- (probably in the RTS.)
373 adjustor = SLIT("createAdjustor")
375 dsCCall adjustor adj_args PlayRisky False io_res_ty `thenDs` \ ccall_adj ->
376 -- PlayRisky: the adjustor doesn't allocate in the Haskell heap or do a callback
377 let ccall_adj_ty = exprType ccall_adj
378 ccall_io_adj = mkLams [stbl_value] $
379 Note (Coerce io_res_ty ccall_adj_ty)
381 io_app = mkLams tvs $
383 stbl_app ccall_io_adj res_ty
384 fed = (id `setInlinePragma` neverInlinePrag, io_app)
385 -- Never inline the f.e.d. function, because the litlit
386 -- might not be in scope in other modules.
388 returnDs ([fed, fe], h_code, c_code)
392 (tvs,sans_foralls) = tcSplitForAllTys ty
393 ([arg_ty], io_res_ty) = tcSplitFunTys sans_foralls
394 Just (ioTyCon, [res_ty]) = tcSplitTyConApp_maybe io_res_ty
395 export_ty = mkFunTy (mkTyConApp stablePtrTyCon [arg_ty]) arg_ty
397 toCName :: Id -> String
398 toCName i = showSDoc (pprCode CStyle (ppr (idName i)))
403 \subsection{Generating @foreign export@ stubs}
407 For each @foreign export@ function, a C stub function is generated.
408 The C stub constructs the application of the exported Haskell function
409 using the hugs/ghc rts invocation API.
412 fexportEntry :: String
420 fexportEntry mod_nm c_nm helper args res_ty cc isDyn = (header_bits, c_bits)
422 -- name of the (Haskell) helper function generated by the desugarer.
423 h_nm = ppr helper <> text "_closure"
424 -- prototype for the exported function.
425 header_bits = ptext SLIT("extern") <+> fun_proto <> semi
427 fun_proto = cResType <+> pprCconv <+> ptext c_nm <>
428 parens (hsep (punctuate comma (zipWith (<+>) cParamTypes proto_args)))
435 , text "SchedulerStatus rc;"
437 -- create the application + perform it.
438 , text "rc=rts_evalIO" <>
439 parens (foldl appArg (text "(StgClosure*)&" <> h_nm) (zip args c_args) <> comma <> text "&ret") <> semi
440 , text "rts_checkSchedStatus" <> parens (doubleQuotes (ptext c_nm)
441 <> comma <> text "rc") <> semi
442 , text "return" <> return_what <> semi
447 text "rts_apply" <> parens (acc <> comma <> mkHObj a <> parens c_a)
449 cParamTypes = map showStgType real_args
451 res_ty_is_unit = isUnitTy res_ty
453 cResType | res_ty_is_unit = text "void"
454 | otherwise = showStgType res_ty
456 pprCconv = case cc of
458 StdCallConv -> ppr cc
460 declareResult = text "HaskellObj ret;"
462 externDecl = mkExtern (text "HaskellObj") h_nm
464 mkExtern ty nm = text "extern" <+> ty <+> nm <> semi
466 return_what | res_ty_is_unit = empty
467 | otherwise = parens (unpackHObj res_ty <> parens (text "ret"))
469 c_args = mkCArgNames 0 args
472 If we're generating an entry point for a 'foreign export ccall dynamic',
473 then we receive the return address of the C function that wants to
474 invoke a Haskell function as any other C function, as second arg.
475 This arg is unused within the body of the generated C stub, but
476 needed by the Adjustor.c code to get the stack cleanup right.
478 (proto_args, real_args)
480 CCallConv | isDyn -> ( text "a0" : text "a_" : mkCArgNames 1 (tail args)
481 , head args : addrTy : tail args)
482 other -> (mkCArgNames 0 args, args)
484 mkCArgNames :: Int -> [a] -> [SDoc]
485 mkCArgNames n as = zipWith (\ _ n -> text ('a':show n)) as [n..]
487 mkHObj :: Type -> SDoc
488 mkHObj t = text "rts_mk" <> text (showFFIType t)
490 unpackHObj :: Type -> SDoc
491 unpackHObj t = text "rts_get" <> text (showFFIType t)
493 showStgType :: Type -> SDoc
494 showStgType t = text "Hs" <> text (showFFIType t)
496 showFFIType :: Type -> String
497 showFFIType t = getOccString (getName tc)
499 tc = case tcSplitTyConApp_maybe (repType t) of
501 Nothing -> pprPanic "showFFIType" (ppr t)