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, mkVanillaId, mkSysLocal,
25 import IdInfo ( neverInlinePrag )
26 import Literal ( Literal(..) )
27 import Module ( Module, moduleUserString )
28 import Name ( mkGlobalName, nameModule, nameOccName, getOccString,
29 mkForeignExportOcc, isLocalName,
32 import Type ( splitTyConApp_maybe, tyConAppTyCon, splitFunTys, splitForAllTys,
33 Type, mkFunTys, mkForAllTys, mkTyConApp,
34 mkFunTy, splitAppTy, applyTy, funResultTy
36 import PrimOp ( CCall(..), CCallTarget(..), dynamicTarget )
37 import TysWiredIn ( unitTy, addrTy, stablePtrTyCon )
38 import TysPrim ( addrPrimTy )
39 import PrelNames ( hasKey, ioTyConKey, deRefStablePtrName, newStablePtrName,
40 bindIOName, returnIOName
44 import Maybe ( fromJust )
47 Desugaring of @foreign@ declarations is naturally split up into
48 parts, an @import@ and an @export@ part. A @foreign import@
51 foreign import cc nm f :: prim_args -> IO prim_res
55 f :: prim_args -> IO prim_res
56 f a1 ... an = _ccall_ nm cc a1 ... an
58 so we reuse the desugaring code in @DsCCall@ to deal with these.
61 type Binding = (Id, CoreExpr) -- No rec/nonrec structure;
62 -- the occurrence analyser will sort it all out
65 -> [TypecheckedForeignDecl]
66 -> DsM ( [Id] -- Foreign-exported binders;
67 -- we have to generate code to register these
69 , SDoc -- Header file prototypes for
70 -- "foreign exported" functions.
71 , SDoc -- C stubs to use when calling
72 -- "foreign exported" functions.
74 dsForeigns mod_name fos = foldlDs combine ([], [], empty, empty) fos
76 combine (acc_feb, acc_f, acc_h, acc_c) fo@(ForeignDecl i imp_exp _ ext_nm cconv _)
77 | isForeignImport = -- foreign import (dynamic)?
78 dsFImport i (idType i) uns ext_nm cconv `thenDs` \ bs ->
79 returnDs (acc_feb, bs ++ acc_f, acc_h, acc_c)
81 dsFLabel i (idType i) ext_nm `thenDs` \ b ->
82 returnDs (acc_feb, b:acc_f, acc_h, acc_c)
83 | isDynamicExtName ext_nm =
84 dsFExportDynamic i (idType i) mod_name ext_nm cconv `thenDs` \ (feb,bs,h,c) ->
85 returnDs (feb:acc_feb, bs ++ acc_f, h $$ acc_h, c $$ acc_c)
87 | otherwise = -- foreign export
88 dsFExport i (idType i) mod_name ext_nm cconv False `thenDs` \ (feb,fe,h,c) ->
89 returnDs (feb:acc_feb, fe:acc_f, h $$ acc_h, c $$ acc_c)
101 (FoImport uns) = imp_exp
105 Desugaring foreign imports is just the matter of creating a binding
106 that on its RHS unboxes its arguments, performs the external call
107 (using the @CCallOp@ primop), before boxing the result up and returning it.
109 However, we create a worker/wrapper pair, thus:
111 foreign import f :: Int -> IO Int
113 f x = IO ( \s -> case x of { I# x# ->
114 case fw s x# of { (# s1, y# #) ->
117 fw s x# = ccall f s x#
119 The strictness/CPR analyser won't do this automatically because it doesn't look
120 inside returned tuples; but inlining this wrapper is a Really Good Idea
121 because it exposes the boxing to the call site.
126 -> Type -- Type of foreign import.
127 -> Bool -- True <=> might cause Haskell GC
131 dsFImport fn_id ty may_not_gc ext_name cconv
133 (tvs, fun_ty) = splitForAllTys ty
134 (arg_tys, io_res_ty) = splitFunTys fun_ty
136 newSysLocalsDs arg_tys `thenDs` \ args ->
137 mapAndUnzipDs unboxArg (map Var args) `thenDs` \ (val_args, arg_wrappers) ->
138 boxResult io_res_ty `thenDs` \ (ccall_result_ty, res_wrapper) ->
140 getUniqueDs `thenDs` \ ccall_uniq ->
141 getUniqueDs `thenDs` \ work_uniq ->
143 lbl = case ext_name of
144 Dynamic -> dynamicTarget
145 ExtName fs _ -> StaticTarget fs
148 work_arg_ids = [v | Var v <- val_args] -- All guaranteed to be vars
149 worker_ty = mkForAllTys tvs (mkFunTys (map idType work_arg_ids) ccall_result_ty)
150 the_ccall = CCall lbl False (not may_not_gc) cconv
151 the_ccall_app = mkCCall ccall_uniq the_ccall val_args ccall_result_ty
152 work_rhs = mkLams tvs (mkLams work_arg_ids the_ccall_app)
153 work_id = mkSysLocal SLIT("$wccall") work_uniq worker_ty
156 work_app = mkApps (mkVarApps (Var work_id) tvs) val_args
157 wrapper_body = foldr ($) (res_wrapper work_app) arg_wrappers
158 wrap_rhs = mkInlineMe (mkLams (tvs ++ args) wrapper_body)
160 returnDs [(work_id, work_rhs), (fn_id, wrap_rhs)]
166 dsFLabel :: Id -> Type -> ExtName -> DsM Binding
167 dsFLabel nm ty ext_name =
168 ASSERT(fromJust res_ty == addrPrimTy) -- typechecker ensures this
169 returnDs (nm, fo_rhs (mkLit (MachLabel enm)))
171 (res_ty, fo_rhs) = resultWrapper ty
172 enm = extNameStatic ext_name
175 The function that does most of the work for `@foreign export@' declarations.
176 (see below for the boilerplate code a `@foreign export@' declaration expands
179 For each `@foreign export foo@' in a module M we generate:
181 \item a C function `@foo@', which calls
182 \item a Haskell stub `@M.$ffoo@', which calls
184 the user-written Haskell function `@M.foo@'.
188 -> Type -- Type of foreign export.
192 -> Bool -- True => invoke IO action that's hanging off
193 -- the first argument's stable pointer
194 -> DsM ( Id -- The foreign-exported Id
199 dsFExport fn_id ty mod_name ext_name cconv isDyn
200 = -- BUILD THE returnIO WRAPPER, if necessary
201 -- Look at the result type of the exported function, orig_res_ty
202 -- If it's IO t, return (\x.x, IO t, t)
203 -- If it's plain t, return (\x.returnIO x, IO t, t)
204 (case splitTyConApp_maybe orig_res_ty of
205 Just (ioTyCon, [res_ty])
206 -> ASSERT( ioTyCon `hasKey` ioTyConKey )
207 -- The function already returns IO t
208 returnDs (\body -> body, orig_res_ty, res_ty)
210 other -> -- The function returns t, so wrap the call in returnIO
211 dsLookupGlobalValue returnIOName `thenDs` \ retIOId ->
212 returnDs (\body -> mkApps (Var retIOId) [Type orig_res_ty, body],
213 funResultTy (applyTy (idType retIOId) orig_res_ty),
214 -- We don't have ioTyCon conveniently to hand
217 ) `thenDs` \ (return_io_wrapper, -- Either identity or returnIO
222 -- BUILD THE deRefStablePtr WRAPPER, if necessary
224 newSysLocalDs stbl_ptr_ty `thenDs` \ stbl_ptr ->
225 newSysLocalDs stbl_ptr_to_ty `thenDs` \ stbl_value ->
226 dsLookupGlobalValue deRefStablePtrName `thenDs` \ deRefStablePtrId ->
227 dsLookupGlobalValue bindIOName `thenDs` \ bindIOId ->
229 the_deref_app = mkApps (Var deRefStablePtrId)
230 [ Type stbl_ptr_to_ty, Var stbl_ptr ]
232 stbl_app cont = mkApps (Var bindIOId)
233 [ Type stbl_ptr_to_ty
236 , mkLams [stbl_value] cont]
238 returnDs (stbl_value, stbl_app, stbl_ptr)
242 panic "stbl_ptr" -- should never be touched.
243 )) `thenDs` \ (i, getFun_wrapper, stbl_ptr) ->
247 getModuleDs `thenDs` \ mod ->
248 getUniqueDs `thenDs` \ uniq ->
249 getSrcLocDs `thenDs` \ src_loc ->
250 newSysLocalsDs fe_arg_tys `thenDs` \ fe_args ->
252 wrapper_args | isDyn = stbl_ptr:fe_args
253 | otherwise = fe_args
255 wrapper_arg_tys | isDyn = stbl_ptr_ty:fe_arg_tys
256 | otherwise = fe_arg_tys
258 helper_ty = mkForAllTys tvs $
259 mkFunTys wrapper_arg_tys io_res_ty
261 f_helper_glob = mkVanillaId helper_name helper_ty
265 | isLocalName name = mod_name
266 | otherwise = nameModule name
268 occ = mkForeignExportOcc (nameOccName name)
269 helper_name = mkGlobalName uniq mod occ src_loc
271 the_app = getFun_wrapper (return_io_wrapper (mkVarApps (Var i) (tvs ++ fe_args)))
272 the_body = mkLams (tvs ++ wrapper_args) the_app
273 c_nm = extNameStatic ext_name
275 (h_stub, c_stub) = fexportEntry (moduleUserString mod)
277 wrapper_arg_tys res_ty cconv isDyn
279 returnDs (f_helper_glob, (f_helper_glob, the_body), h_stub, c_stub)
282 (tvs,sans_foralls) = splitForAllTys ty
283 (fe_arg_tys', orig_res_ty) = splitFunTys sans_foralls
285 (_, stbl_ptr_ty') = splitForAllTys stbl_ptr_ty
286 (_, stbl_ptr_to_ty) = splitAppTy stbl_ptr_ty'
288 fe_arg_tys | isDyn = tail fe_arg_tys'
289 | otherwise = fe_arg_tys'
291 stbl_ptr_ty | isDyn = head fe_arg_tys'
292 | otherwise = error "stbl_ptr_ty"
295 @foreign export dynamic@ lets you dress up Haskell IO actions
296 of some fixed type behind an externally callable interface (i.e.,
297 as a C function pointer). Useful for callbacks and stuff.
300 foreign export dynamic f :: (Addr -> Int -> IO Int) -> IO Addr
302 -- Haskell-visible constructor, which is generated from the above:
303 -- SUP: No check for NULL from createAdjustor anymore???
305 f :: (Addr -> Int -> IO Int) -> IO Addr
307 bindIO (newStablePtr cback)
308 (\StablePtr sp# -> IO (\s1# ->
309 case _ccall_ createAdjustor cconv sp# ``f_helper'' s1# of
310 (# s2#, a# #) -> (# s2#, A# a# #)))
312 foreign export "f_helper" f_helper :: StablePtr (Addr -> Int -> IO Int) -> Addr -> Int -> IO Int
313 -- `special' foreign export that invokes the closure pointed to by the
318 dsFExportDynamic :: Id
319 -> Type -- Type of foreign export.
323 -> DsM (Id, [Binding], SDoc, SDoc)
324 dsFExportDynamic i ty mod_name ext_name cconv =
325 newSysLocalDs ty `thenDs` \ fe_id ->
327 -- hack: need to get at the name of the C stub we're about to generate.
328 fe_nm = moduleUserString mod_name ++ "_" ++ toCName fe_id
329 fe_ext_name = ExtName (_PK_ fe_nm) Nothing
331 dsFExport i export_ty mod_name fe_ext_name cconv True
332 `thenDs` \ (feb, fe, h_code, c_code) ->
333 newSysLocalDs arg_ty `thenDs` \ cback ->
334 dsLookupGlobalValue newStablePtrName `thenDs` \ newStablePtrId ->
336 mk_stbl_ptr_app = mkApps (Var newStablePtrId) [ Type arg_ty, Var cback ]
338 dsLookupGlobalValue bindIOName `thenDs` \ bindIOId ->
339 newSysLocalDs (mkTyConApp stablePtrTyCon [arg_ty]) `thenDs` \ stbl_value ->
342 = mkApps (Var bindIOId)
343 [ Type (mkTyConApp stablePtrTyCon [arg_ty])
350 The arguments to the external function which will
351 create a little bit of (template) code on the fly
352 for allowing the (stable pointed) Haskell closure
353 to be entered using an external calling convention
356 adj_args = [ mkIntLitInt (callConvToInt cconv)
358 , mkLit (MachLabel (_PK_ fe_nm))
360 -- name of external entry point providing these services.
361 -- (probably in the RTS.)
362 adjustor = SLIT("createAdjustor")
364 dsCCall adjustor adj_args False False io_res_ty `thenDs` \ ccall_adj ->
365 let ccall_adj_ty = exprType ccall_adj
366 ccall_io_adj = mkLams [stbl_value] $
367 Note (Coerce io_res_ty ccall_adj_ty)
370 let io_app = mkLams tvs $
372 stbl_app ccall_io_adj res_ty
373 fed = (i `setInlinePragma` neverInlinePrag, io_app)
374 -- Never inline the f.e.d. function, because the litlit
375 -- might not be in scope in other modules.
377 returnDs (feb, [fed, fe], h_code, c_code)
380 (tvs,sans_foralls) = splitForAllTys ty
381 ([arg_ty], io_res_ty) = splitFunTys sans_foralls
383 Just (ioTyCon, [res_ty]) = splitTyConApp_maybe io_res_ty
385 export_ty = mkFunTy (mkTyConApp stablePtrTyCon [arg_ty]) arg_ty
387 ioAddrTy :: Type -- IO Addr
388 ioAddrTy = mkTyConApp ioTyCon [addrTy]
390 toCName :: Id -> String
391 toCName i = showSDoc (pprCode CStyle (ppr (idName i)))
396 \subsection{Generating @foreign export@ stubs}
400 For each @foreign export@ function, a C stub function is generated.
401 The C stub constructs the application of the exported Haskell function
402 using the hugs/ghc rts invocation API.
405 fexportEntry :: String
413 fexportEntry mod_nm c_nm helper args res_ty cc isDyn = (header_bits, c_bits)
415 -- name of the (Haskell) helper function generated by the desugarer.
416 h_nm = ppr helper <> text "_closure"
417 -- prototype for the exported function.
418 header_bits = ptext SLIT("extern") <+> fun_proto <> semi
420 fun_proto = cResType <+> pprCconv <+> ptext c_nm <>
421 parens (hsep (punctuate comma (zipWith (<+>) cParamTypes proto_args)))
428 , text "SchedulerStatus rc;"
430 -- create the application + perform it.
431 , text "rc=rts_evalIO" <>
432 parens (foldl appArg (text "(StgClosure*)&" <> h_nm) (zip args c_args) <> comma <> text "&ret") <> semi
433 , text "rts_checkSchedStatus" <> parens (doubleQuotes (ptext c_nm)
434 <> comma <> text "rc") <> semi
435 , text "return" <> return_what <> semi
440 text "rts_apply" <> parens (acc <> comma <> mkHObj a <> parens c_a)
442 cParamTypes = map showStgType real_args
444 res_ty_is_unit = res_ty == unitTy
446 cResType | res_ty_is_unit = text "void"
447 | otherwise = showStgType res_ty
450 | cc == cCallConv = empty
451 | otherwise = pprCallConv cc
453 declareResult = text "HaskellObj ret;"
455 externDecl = mkExtern (text "HaskellObj") h_nm
457 mkExtern ty nm = text "extern" <+> ty <+> nm <> semi
459 return_what | res_ty_is_unit = empty
460 | otherwise = parens (unpackHObj res_ty <> parens (text "ret"))
462 c_args = mkCArgNames 0 args
465 If we're generating an entry point for a 'foreign export ccall dynamic',
466 then we receive the return address of the C function that wants to
467 invoke a Haskell function as any other C function, as second arg.
468 This arg is unused within the body of the generated C stub, but
469 needed by the Adjustor.c code to get the stack cleanup right.
471 (proto_args, real_args)
472 | cc == cCallConv && isDyn = ( text "a0" : text "a_" : mkCArgNames 1 (tail args)
473 , head args : addrTy : tail args)
474 | otherwise = (mkCArgNames 0 args, args)
476 mkCArgNames :: Int -> [a] -> [SDoc]
477 mkCArgNames n as = zipWith (\ _ n -> text ('a':show n)) as [n..]
479 mkHObj :: Type -> SDoc
480 mkHObj t = text "rts_mk" <> text (showFFIType t)
482 unpackHObj :: Type -> SDoc
483 unpackHObj t = text "rts_get" <> text (showFFIType t)
485 showStgType :: Type -> SDoc
486 showStgType t = text "Hs" <> text (showFFIType t)
488 showFFIType :: Type -> String
489 showFFIType t = getOccString (getName (tyConAppTyCon t))