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, mkCCall, boxResult, unboxArg, resultWrapper )
18 import HsSyn ( ExtName(..), ForeignDecl(..), isDynamicExtName, ForKind(..) )
19 import HsDecls ( extNameStatic )
21 import TcHsSyn ( TypecheckedForeignDecl )
22 import CoreUtils ( exprType, mkInlineMe )
23 import Id ( Id, idType, idName, mkVanillaGlobal, mkSysLocal,
25 import IdInfo ( neverInlinePrag, vanillaIdInfo )
26 import Literal ( Literal(..) )
27 import Module ( Module, moduleUserString )
28 import Name ( mkGlobalName, nameModule, nameOccName, getOccString,
29 mkForeignExportOcc, isLocalName,
32 import Type ( repType, splitTyConApp_maybe,
33 tyConAppTyCon, splitFunTys, splitForAllTys,
34 Type, mkFunTys, mkForAllTys, mkTyConApp,
35 mkFunTy, splitAppTy, applyTy, funResultTy
37 import PrimOp ( CCall(..), CCallTarget(..), dynamicTarget )
38 import TysWiredIn ( unitTy, addrTy, stablePtrTyCon )
39 import TysPrim ( addrPrimTy )
40 import PrelNames ( hasKey, ioTyConKey, deRefStablePtrName, newStablePtrName,
41 bindIOName, returnIOName
45 import Maybe ( fromJust )
48 Desugaring of @foreign@ declarations is naturally split up into
49 parts, an @import@ and an @export@ part. A @foreign import@
52 foreign import cc nm f :: prim_args -> IO prim_res
56 f :: prim_args -> IO prim_res
57 f a1 ... an = _ccall_ nm cc a1 ... an
59 so we reuse the desugaring code in @DsCCall@ to deal with these.
62 type Binding = (Id, CoreExpr) -- No rec/nonrec structure;
63 -- the occurrence analyser will sort it all out
66 -> [TypecheckedForeignDecl]
67 -> DsM ( [Id] -- Foreign-exported binders;
68 -- we have to generate code to register these
70 , SDoc -- Header file prototypes for
71 -- "foreign exported" functions.
72 , SDoc -- C stubs to use when calling
73 -- "foreign exported" functions.
75 dsForeigns mod_name fos = foldlDs combine ([], [], empty, empty) fos
77 combine (acc_feb, acc_f, acc_h, acc_c) fo@(ForeignDecl i imp_exp _ ext_nm cconv _)
78 | isForeignImport = -- foreign import (dynamic)?
79 dsFImport i (idType i) uns ext_nm cconv `thenDs` \ bs ->
80 returnDs (acc_feb, bs ++ acc_f, acc_h, acc_c)
82 dsFLabel i (idType i) ext_nm `thenDs` \ b ->
83 returnDs (acc_feb, b:acc_f, acc_h, acc_c)
84 | isDynamicExtName ext_nm =
85 dsFExportDynamic i (idType i) mod_name ext_nm cconv `thenDs` \ (feb,bs,h,c) ->
86 returnDs (feb:acc_feb, bs ++ acc_f, h $$ acc_h, c $$ acc_c)
88 | otherwise = -- foreign export
89 dsFExport i (idType i) mod_name ext_nm cconv False `thenDs` \ (feb,fe,h,c) ->
90 returnDs (feb:acc_feb, fe:acc_f, h $$ acc_h, c $$ acc_c)
102 (FoImport uns) = imp_exp
106 Desugaring foreign imports is just the matter of creating a binding
107 that on its RHS unboxes its arguments, performs the external call
108 (using the @CCallOp@ primop), before boxing the result up and returning it.
110 However, we create a worker/wrapper pair, thus:
112 foreign import f :: Int -> IO Int
114 f x = IO ( \s -> case x of { I# x# ->
115 case fw s x# of { (# s1, y# #) ->
118 fw s x# = ccall f s x#
120 The strictness/CPR analyser won't do this automatically because it doesn't look
121 inside returned tuples; but inlining this wrapper is a Really Good Idea
122 because it exposes the boxing to the call site.
127 -> Type -- Type of foreign import.
128 -> Bool -- True <=> might cause Haskell GC
132 dsFImport fn_id ty may_not_gc ext_name cconv
134 (tvs, fun_ty) = splitForAllTys ty
135 (arg_tys, io_res_ty) = splitFunTys fun_ty
137 newSysLocalsDs arg_tys `thenDs` \ args ->
138 mapAndUnzipDs unboxArg (map Var args) `thenDs` \ (val_args, arg_wrappers) ->
139 boxResult io_res_ty `thenDs` \ (ccall_result_ty, res_wrapper) ->
141 getUniqueDs `thenDs` \ ccall_uniq ->
142 getUniqueDs `thenDs` \ work_uniq ->
144 lbl = case ext_name of
145 Dynamic -> dynamicTarget
146 ExtName fs _ -> StaticTarget fs
149 work_arg_ids = [v | Var v <- val_args] -- All guaranteed to be vars
150 worker_ty = mkForAllTys tvs (mkFunTys (map idType work_arg_ids) ccall_result_ty)
151 the_ccall = CCall lbl False (not may_not_gc) cconv
152 the_ccall_app = mkCCall ccall_uniq the_ccall val_args ccall_result_ty
153 work_rhs = mkLams tvs (mkLams work_arg_ids the_ccall_app)
154 work_id = mkSysLocal SLIT("$wccall") work_uniq worker_ty
157 work_app = mkApps (mkVarApps (Var work_id) tvs) val_args
158 wrapper_body = foldr ($) (res_wrapper work_app) arg_wrappers
159 wrap_rhs = mkInlineMe (mkLams (tvs ++ args) wrapper_body)
161 returnDs [(work_id, work_rhs), (fn_id, wrap_rhs)]
167 dsFLabel :: Id -> Type -> ExtName -> DsM Binding
168 dsFLabel nm ty ext_name =
169 ASSERT(fromJust res_ty == addrPrimTy) -- typechecker ensures this
170 returnDs (nm, fo_rhs (mkLit (MachLabel enm)))
172 (res_ty, fo_rhs) = resultWrapper ty
173 enm = extNameStatic ext_name
176 The function that does most of the work for `@foreign export@' declarations.
177 (see below for the boilerplate code a `@foreign export@' declaration expands
180 For each `@foreign export foo@' in a module M we generate:
182 \item a C function `@foo@', which calls
183 \item a Haskell stub `@M.$ffoo@', which calls
185 the user-written Haskell function `@M.foo@'.
189 -> Type -- Type of foreign export.
193 -> Bool -- True => invoke IO action that's hanging off
194 -- the first argument's stable pointer
195 -> DsM ( Id -- The foreign-exported Id
200 dsFExport fn_id ty mod_name ext_name cconv isDyn
201 = -- BUILD THE returnIO WRAPPER, if necessary
202 -- Look at the result type of the exported function, orig_res_ty
203 -- If it's IO t, return (\x.x, IO t, t)
204 -- If it's plain t, return (\x.returnIO x, IO t, t)
205 (case splitTyConApp_maybe orig_res_ty of
206 Just (ioTyCon, [res_ty])
207 -> ASSERT( ioTyCon `hasKey` ioTyConKey )
208 -- The function already returns IO t
209 returnDs (\body -> body, orig_res_ty, res_ty)
211 other -> -- The function returns t, so wrap the call in returnIO
212 dsLookupGlobalValue returnIOName `thenDs` \ retIOId ->
213 returnDs (\body -> mkApps (Var retIOId) [Type orig_res_ty, body],
214 funResultTy (applyTy (idType retIOId) orig_res_ty),
215 -- We don't have ioTyCon conveniently to hand
218 ) `thenDs` \ (return_io_wrapper, -- Either identity or returnIO
223 -- BUILD THE deRefStablePtr WRAPPER, if necessary
225 newSysLocalDs stbl_ptr_ty `thenDs` \ stbl_ptr ->
226 newSysLocalDs stbl_ptr_to_ty `thenDs` \ stbl_value ->
227 dsLookupGlobalValue deRefStablePtrName `thenDs` \ deRefStablePtrId ->
228 dsLookupGlobalValue bindIOName `thenDs` \ bindIOId ->
230 the_deref_app = mkApps (Var deRefStablePtrId)
231 [ Type stbl_ptr_to_ty, Var stbl_ptr ]
233 stbl_app cont = mkApps (Var bindIOId)
234 [ Type stbl_ptr_to_ty
237 , mkLams [stbl_value] cont]
239 returnDs (stbl_value, stbl_app, stbl_ptr)
243 panic "stbl_ptr" -- should never be touched.
244 )) `thenDs` \ (i, getFun_wrapper, stbl_ptr) ->
248 getModuleDs `thenDs` \ mod ->
249 getUniqueDs `thenDs` \ uniq ->
250 getSrcLocDs `thenDs` \ src_loc ->
251 newSysLocalsDs fe_arg_tys `thenDs` \ fe_args ->
253 wrapper_args | isDyn = stbl_ptr:fe_args
254 | otherwise = fe_args
256 wrapper_arg_tys | isDyn = stbl_ptr_ty:fe_arg_tys
257 | otherwise = fe_arg_tys
259 helper_ty = mkForAllTys tvs $
260 mkFunTys wrapper_arg_tys io_res_ty
262 f_helper_glob = mkVanillaGlobal helper_name helper_ty vanillaIdInfo
266 | isLocalName name = mod_name
267 | otherwise = nameModule name
269 occ = mkForeignExportOcc (nameOccName name)
270 helper_name = mkGlobalName uniq mod occ src_loc
272 the_app = getFun_wrapper (return_io_wrapper (mkVarApps (Var i) (tvs ++ fe_args)))
273 the_body = mkLams (tvs ++ wrapper_args) the_app
274 c_nm = extNameStatic ext_name
276 (h_stub, c_stub) = fexportEntry (moduleUserString mod)
278 wrapper_arg_tys res_ty cconv isDyn
280 returnDs (f_helper_glob, (f_helper_glob, the_body), h_stub, c_stub)
283 (tvs,sans_foralls) = splitForAllTys ty
284 (fe_arg_tys', orig_res_ty) = splitFunTys sans_foralls
286 (_, stbl_ptr_ty') = splitForAllTys stbl_ptr_ty
287 (_, stbl_ptr_to_ty) = splitAppTy stbl_ptr_ty'
289 fe_arg_tys | isDyn = tail fe_arg_tys'
290 | otherwise = fe_arg_tys'
292 stbl_ptr_ty | isDyn = head fe_arg_tys'
293 | otherwise = error "stbl_ptr_ty"
296 @foreign export dynamic@ lets you dress up Haskell IO actions
297 of some fixed type behind an externally callable interface (i.e.,
298 as a C function pointer). Useful for callbacks and stuff.
301 foreign export dynamic f :: (Addr -> Int -> IO Int) -> IO Addr
303 -- Haskell-visible constructor, which is generated from the above:
304 -- SUP: No check for NULL from createAdjustor anymore???
306 f :: (Addr -> Int -> IO Int) -> IO Addr
308 bindIO (newStablePtr cback)
309 (\StablePtr sp# -> IO (\s1# ->
310 case _ccall_ createAdjustor cconv sp# ``f_helper'' s1# of
311 (# s2#, a# #) -> (# s2#, A# a# #)))
313 foreign export "f_helper" f_helper :: StablePtr (Addr -> Int -> IO Int) -> Addr -> Int -> IO Int
314 -- `special' foreign export that invokes the closure pointed to by the
319 dsFExportDynamic :: Id
320 -> Type -- Type of foreign export.
324 -> DsM (Id, [Binding], SDoc, SDoc)
325 dsFExportDynamic i ty mod_name ext_name cconv =
326 newSysLocalDs ty `thenDs` \ fe_id ->
328 -- hack: need to get at the name of the C stub we're about to generate.
329 fe_nm = moduleUserString mod_name ++ "_" ++ toCName fe_id
330 fe_ext_name = ExtName (_PK_ fe_nm) Nothing
332 dsFExport i export_ty mod_name fe_ext_name cconv True
333 `thenDs` \ (feb, fe, h_code, c_code) ->
334 newSysLocalDs arg_ty `thenDs` \ cback ->
335 dsLookupGlobalValue newStablePtrName `thenDs` \ newStablePtrId ->
337 mk_stbl_ptr_app = mkApps (Var newStablePtrId) [ Type arg_ty, Var cback ]
339 dsLookupGlobalValue bindIOName `thenDs` \ bindIOId ->
340 newSysLocalDs (mkTyConApp stablePtrTyCon [arg_ty]) `thenDs` \ stbl_value ->
343 = mkApps (Var bindIOId)
344 [ Type (mkTyConApp stablePtrTyCon [arg_ty])
351 The arguments to the external function which will
352 create a little bit of (template) code on the fly
353 for allowing the (stable pointed) Haskell closure
354 to be entered using an external calling convention
357 adj_args = [ mkIntLitInt (callConvToInt cconv)
359 , mkLit (MachLabel (_PK_ fe_nm))
361 -- name of external entry point providing these services.
362 -- (probably in the RTS.)
363 adjustor = SLIT("createAdjustor")
365 dsCCall adjustor adj_args False False io_res_ty `thenDs` \ ccall_adj ->
366 let ccall_adj_ty = exprType ccall_adj
367 ccall_io_adj = mkLams [stbl_value] $
368 Note (Coerce io_res_ty ccall_adj_ty)
371 let io_app = mkLams tvs $
373 stbl_app ccall_io_adj res_ty
374 fed = (i `setInlinePragma` neverInlinePrag, io_app)
375 -- Never inline the f.e.d. function, because the litlit
376 -- might not be in scope in other modules.
378 returnDs (feb, [fed, fe], h_code, c_code)
381 (tvs,sans_foralls) = splitForAllTys ty
382 ([arg_ty], io_res_ty) = splitFunTys sans_foralls
384 Just (ioTyCon, [res_ty]) = splitTyConApp_maybe io_res_ty
386 export_ty = mkFunTy (mkTyConApp stablePtrTyCon [arg_ty]) arg_ty
388 ioAddrTy :: Type -- IO Addr
389 ioAddrTy = mkTyConApp ioTyCon [addrTy]
391 toCName :: Id -> String
392 toCName i = showSDoc (pprCode CStyle (ppr (idName i)))
397 \subsection{Generating @foreign export@ stubs}
401 For each @foreign export@ function, a C stub function is generated.
402 The C stub constructs the application of the exported Haskell function
403 using the hugs/ghc rts invocation API.
406 fexportEntry :: String
414 fexportEntry mod_nm c_nm helper args res_ty cc isDyn = (header_bits, c_bits)
416 -- name of the (Haskell) helper function generated by the desugarer.
417 h_nm = ppr helper <> text "_closure"
418 -- prototype for the exported function.
419 header_bits = ptext SLIT("extern") <+> fun_proto <> semi
421 fun_proto = cResType <+> pprCconv <+> ptext c_nm <>
422 parens (hsep (punctuate comma (zipWith (<+>) cParamTypes proto_args)))
429 , text "SchedulerStatus rc;"
431 -- create the application + perform it.
432 , text "rc=rts_evalIO" <>
433 parens (foldl appArg (text "(StgClosure*)&" <> h_nm) (zip args c_args) <> comma <> text "&ret") <> semi
434 , text "rts_checkSchedStatus" <> parens (doubleQuotes (ptext c_nm)
435 <> comma <> text "rc") <> semi
436 , text "return" <> return_what <> semi
441 text "rts_apply" <> parens (acc <> comma <> mkHObj a <> parens c_a)
443 cParamTypes = map showStgType real_args
445 res_ty_is_unit = res_ty == unitTy
447 cResType | res_ty_is_unit = text "void"
448 | otherwise = showStgType res_ty
451 | cc == cCallConv = empty
452 | otherwise = pprCallConv cc
454 declareResult = text "HaskellObj ret;"
456 externDecl = mkExtern (text "HaskellObj") h_nm
458 mkExtern ty nm = text "extern" <+> ty <+> nm <> semi
460 return_what | res_ty_is_unit = empty
461 | otherwise = parens (unpackHObj res_ty <> parens (text "ret"))
463 c_args = mkCArgNames 0 args
466 If we're generating an entry point for a 'foreign export ccall dynamic',
467 then we receive the return address of the C function that wants to
468 invoke a Haskell function as any other C function, as second arg.
469 This arg is unused within the body of the generated C stub, but
470 needed by the Adjustor.c code to get the stack cleanup right.
472 (proto_args, real_args)
473 | cc == cCallConv && isDyn = ( text "a0" : text "a_" : mkCArgNames 1 (tail args)
474 , head args : addrTy : tail args)
475 | otherwise = (mkCArgNames 0 args, args)
477 mkCArgNames :: Int -> [a] -> [SDoc]
478 mkCArgNames n as = zipWith (\ _ n -> text ('a':show n)) as [n..]
480 mkHObj :: Type -> SDoc
481 mkHObj t = text "rts_mk" <> text (showFFIType t)
483 unpackHObj :: Type -> SDoc
484 unpackHObj t = text "rts_get" <> text (showFFIType t)
486 showStgType :: Type -> SDoc
487 showStgType t = text "Hs" <> text (showFFIType t)
489 showFFIType :: Type -> String
490 showFFIType t = getOccString (getName tc)
492 tc = case splitTyConApp_maybe (repType t) of
494 Nothing -> pprPanic "showFFIType" (ppr t)