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 )
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,
30 NamedThing(..), Provenance(..), ExportFlag(..)
32 import Type ( unUsgTy, repType,
33 splitTyConApp_maybe, splitFunTys, splitForAllTys,
34 Type, mkFunTys, mkForAllTys, mkTyConApp,
35 mkTyVarTy, mkFunTy, splitAppTy, applyTy, funResultTy
37 import PrimOp ( PrimOp(..), CCall(..),
38 CCallTarget(..), dynamicTarget )
39 import TysWiredIn ( unitTy, addrTy, stablePtrTyCon,
42 import Unique ( Uniquable(..), hasKey,
43 ioTyConKey, deRefStablePtrIdKey, returnIOIdKey,
44 bindIOIdKey, makeStablePtrIdKey
49 Desugaring of @foreign@ declarations is naturally split up into
50 parts, an @import@ and an @export@ part. A @foreign import@
53 foreign import cc nm f :: prim_args -> IO prim_res
57 f :: prim_args -> IO prim_res
58 f a1 ... an = _ccall_ nm cc a1 ... an
60 so we reuse the desugaring code in @DsCCall@ to deal with these.
64 -> [TypecheckedForeignDecl]
65 -> DsM ( [CoreBind] -- desugared foreign imports
66 , [CoreBind] -- helper functions for foreign exports
67 , SDoc -- Header file prototypes for
68 -- "foreign exported" functions.
69 , SDoc -- C stubs to use when calling
70 -- "foreign exported" functions.
72 dsForeigns mod_name fos = foldlDs combine ([],[],empty,empty) fos
74 combine (acc_fi, acc_fe, acc_h, acc_c) fo@(ForeignDecl i imp_exp _ ext_nm cconv _)
75 | isForeignImport = -- foreign import (dynamic)?
76 dsFImport i (idType i) uns ext_nm cconv `thenDs` \ bs ->
77 returnDs (bs ++ acc_fi, acc_fe, acc_h, acc_c)
79 dsFLabel i ext_nm `thenDs` \ b ->
80 returnDs (b:acc_fi, acc_fe, acc_h, acc_c)
81 | isDynamicExtName ext_nm =
82 dsFExportDynamic i (idType i) mod_name ext_nm cconv `thenDs` \ (fi,fe,h,c) ->
83 returnDs (fi:acc_fi, fe:acc_fe, h $$ acc_h, c $$ acc_c)
85 | otherwise = -- foreign export
86 dsFExport i (idType i) mod_name ext_nm cconv False `thenDs` \ (fe,h,c) ->
87 returnDs (acc_fi, fe:acc_fe, h $$ acc_h, c $$ acc_c)
99 (FoImport uns) = imp_exp
103 Desugaring foreign imports is just the matter of creating a binding
104 that on its RHS unboxes its arguments, performs the external call
105 (using the @CCallOp@ primop), before boxing the result up and returning it.
107 However, we create a worker/wrapper pair, thus:
109 foreign import f :: Int -> IO Int
111 f x = IO ( \s -> case x of { I# x# ->
112 case fw s x# of { (# s1, y# #) ->
115 fw s x# = ccall f s x#
117 The strictness/CPR analyser won't do this automatically because it doesn't look
118 inside returned tuples; but inlining this wrapper is a Really Good Idea
119 because it exposes the boxing to the call site.
124 -> Type -- Type of foreign import.
125 -> Bool -- True <=> might cause Haskell GC
129 dsFImport fn_id ty may_not_gc ext_name cconv
131 (tvs, fun_ty) = splitForAllTys ty
132 (arg_tys, io_res_ty) = splitFunTys fun_ty
134 newSysLocalsDs arg_tys `thenDs` \ args ->
135 mapAndUnzipDs unboxArg (map Var args) `thenDs` \ (val_args, arg_wrappers) ->
136 boxResult io_res_ty `thenDs` \ (ccall_result_ty, res_wrapper) ->
138 getUniqueDs `thenDs` \ ccall_uniq ->
139 getUniqueDs `thenDs` \ work_uniq ->
141 lbl = case ext_name of
142 Dynamic -> dynamicTarget
143 ExtName fs _ -> StaticTarget fs
146 work_arg_ids = [v | Var v <- val_args] -- All guaranteed to be vars
147 worker_ty = mkForAllTys tvs (mkFunTys (map idType work_arg_ids) ccall_result_ty)
148 the_ccall = CCall lbl False (not may_not_gc) cconv
149 the_ccall_app = mkCCall ccall_uniq the_ccall val_args ccall_result_ty
150 work_rhs = mkLams tvs (mkLams work_arg_ids the_ccall_app)
151 work_id = mkSysLocal SLIT("$wccall") work_uniq worker_ty
154 work_app = mkApps (mkVarApps (Var work_id) tvs) val_args
155 wrapper_body = foldr ($) (res_wrapper work_app) arg_wrappers
156 wrap_rhs = mkInlineMe (mkLams (tvs ++ args) wrapper_body)
158 returnDs [NonRec fn_id wrap_rhs, NonRec work_id work_rhs]
164 dsFLabel :: Id -> ExtName -> DsM CoreBind
165 dsFLabel nm ext_name = returnDs (NonRec nm fo_rhs)
167 fo_rhs = mkConApp addrDataCon [mkLit (MachLabel enm)]
168 enm = extNameStatic ext_name
171 The function that does most of the work for `@foreign export@' declarations.
172 (see below for the boilerplate code a `@foreign export@' declaration expands
175 For each `@foreign export foo@' in a module M we generate:
177 \item a C function `@foo@', which calls
178 \item a Haskell stub `@M.$ffoo@', which calls
180 the user-written Haskell function `@M.foo@'.
184 -> Type -- Type of foreign export.
188 -> Bool -- True => invoke IO action that's hanging off
189 -- the first argument's stable pointer
194 dsFExport fn_id ty mod_name ext_name cconv isDyn
195 = -- BUILD THE returnIO WRAPPER, if necessary
196 -- Look at the result type of the exported function, orig_res_ty
197 -- If it's IO t, return (\x.x, IO t, t)
198 -- If it's plain t, return (\x.returnIO x, IO t, t)
199 (case splitTyConApp_maybe orig_res_ty of
200 Just (ioTyCon, [res_ty])
201 -> ASSERT( ioTyCon `hasKey` ioTyConKey )
202 -- The function already returns IO t
203 returnDs (\body -> body, orig_res_ty, res_ty)
205 other -> -- The function returns t, so wrap the call in returnIO
206 dsLookupGlobalValue returnIOIdKey `thenDs` \ retIOId ->
207 returnDs (\body -> mkApps (Var retIOId) [Type orig_res_ty, body],
208 funResultTy (applyTy (idType retIOId) orig_res_ty),
209 -- We don't have ioTyCon conveniently to hand
212 ) `thenDs` \ (return_io_wrapper, -- Either identity or returnIO
217 -- BUILD THE deRefStablePtr WRAPPER, if necessary
219 newSysLocalDs stbl_ptr_ty `thenDs` \ stbl_ptr ->
220 newSysLocalDs stbl_ptr_to_ty `thenDs` \ stbl_value ->
221 dsLookupGlobalValue deRefStablePtrIdKey `thenDs` \ deRefStablePtrId ->
222 dsLookupGlobalValue bindIOIdKey `thenDs` \ bindIOId ->
224 the_deref_app = mkApps (Var deRefStablePtrId)
225 [ Type stbl_ptr_to_ty, Var stbl_ptr ]
227 stbl_app cont = mkApps (Var bindIOId)
228 [ Type stbl_ptr_to_ty
231 , mkLams [stbl_value] cont]
233 returnDs (stbl_value, stbl_app, stbl_ptr)
237 panic "stbl_ptr" -- should never be touched.
238 )) `thenDs` \ (i, getFun_wrapper, stbl_ptr) ->
242 getModuleDs `thenDs` \ mod ->
243 getUniqueDs `thenDs` \ uniq ->
244 getSrcLocDs `thenDs` \ src_loc ->
245 newSysLocalsDs fe_arg_tys `thenDs` \ fe_args ->
247 wrapper_args | isDyn = stbl_ptr:fe_args
248 | otherwise = fe_args
250 wrapper_arg_tys | isDyn = stbl_ptr_ty:fe_arg_tys
251 | otherwise = fe_arg_tys
253 helper_ty = mkForAllTys tvs $
254 mkFunTys wrapper_arg_tys io_res_ty
256 f_helper_glob = mkVanillaId helper_name helper_ty
260 | isLocalName name = mod_name
261 | otherwise = nameModule name
263 occ = mkForeignExportOcc (nameOccName name)
264 prov = LocalDef src_loc Exported
265 helper_name = mkGlobalName uniq mod occ prov
267 the_app = getFun_wrapper (return_io_wrapper (mkVarApps (Var i) (tvs ++ fe_args)))
268 the_body = mkLams (tvs ++ wrapper_args) the_app
269 c_nm = extNameStatic ext_name
271 (h_stub, c_stub) = fexportEntry (moduleUserString mod)
273 wrapper_arg_tys res_ty cconv isDyn
275 returnDs (NonRec f_helper_glob the_body, h_stub, c_stub)
278 (tvs,sans_foralls) = splitForAllTys ty
279 (fe_arg_tys', orig_res_ty) = splitFunTys sans_foralls
281 (_, stbl_ptr_ty') = splitForAllTys stbl_ptr_ty
282 (_, stbl_ptr_to_ty) = splitAppTy stbl_ptr_ty'
284 fe_arg_tys | isDyn = tail fe_arg_tys'
285 | otherwise = fe_arg_tys'
287 stbl_ptr_ty | isDyn = head fe_arg_tys'
288 | otherwise = error "stbl_ptr_ty"
291 @foreign export dynamic@ lets you dress up Haskell IO actions
292 of some fixed type behind an externally callable interface (i.e.,
293 as a C function pointer). Useful for callbacks and stuff.
296 foreign export dynamic f :: (Addr -> Int -> IO Int) -> IO Addr
298 -- Haskell-visible constructor, which is generated from the above:
299 -- SUP: No check for NULL from createAdjustor anymore???
301 f :: (Addr -> Int -> IO Int) -> IO Addr
303 bindIO (makeStablePtr cback)
304 (\StablePtr sp# -> IO (\s1# ->
305 case _ccall_ createAdjustor cconv sp# ``f_helper'' s1# of
306 (# s2#, a# #) -> (# s2#, A# a# #)))
308 foreign export "f_helper" f_helper :: StablePtr (Addr -> Int -> IO Int) -> Addr -> Int -> IO Int
309 -- `special' foreign export that invokes the closure pointed to by the
314 dsFExportDynamic :: Id
315 -> Type -- Type of foreign export.
319 -> DsM (CoreBind, CoreBind, SDoc, SDoc)
320 dsFExportDynamic i ty mod_name ext_name cconv =
321 newSysLocalDs ty `thenDs` \ fe_id ->
323 -- hack: need to get at the name of the C stub we're about to generate.
324 fe_nm = moduleUserString mod_name ++ "_" ++ toCName fe_id
325 fe_ext_name = ExtName (_PK_ fe_nm) Nothing
327 dsFExport i export_ty mod_name fe_ext_name cconv True
328 `thenDs` \ (fe@(NonRec fe_helper fe_expr), h_code, c_code) ->
329 newSysLocalDs arg_ty `thenDs` \ cback ->
330 dsLookupGlobalValue makeStablePtrIdKey `thenDs` \ makeStablePtrId ->
332 mk_stbl_ptr_app = mkApps (Var makeStablePtrId) [ Type arg_ty, Var cback ]
334 dsLookupGlobalValue bindIOIdKey `thenDs` \ bindIOId ->
335 newSysLocalDs (mkTyConApp stablePtrTyCon [arg_ty]) `thenDs` \ stbl_value ->
338 = mkApps (Var bindIOId)
339 [ Type (mkTyConApp stablePtrTyCon [arg_ty])
346 The arguments to the external function which will
347 create a little bit of (template) code on the fly
348 for allowing the (stable pointed) Haskell closure
349 to be entered using an external calling convention
352 adj_args = [ mkIntLitInt (callConvToInt cconv)
354 , mkLit (MachLabel (_PK_ fe_nm))
356 -- name of external entry point providing these services.
357 -- (probably in the RTS.)
358 adjustor = SLIT("createAdjustor")
360 dsCCall adjustor adj_args False False ioAddrTy `thenDs` \ ccall_adj ->
361 let ccall_adj_ty = exprType ccall_adj
362 ccall_io_adj = mkLams [stbl_value] $
363 Note (Coerce io_res_ty (unUsgTy ccall_adj_ty))
366 let io_app = mkLams tvs $
368 stbl_app ccall_io_adj addrTy
370 -- Never inline the f.e.d. function, because the litlit might not be in scope
372 returnDs (NonRec (i `setInlinePragma` neverInlinePrag) io_app, fe, h_code, c_code)
375 (tvs,sans_foralls) = splitForAllTys ty
376 ([arg_ty], io_res_ty) = splitFunTys sans_foralls
378 Just (ioTyCon, [res_ty]) = splitTyConApp_maybe io_res_ty
380 export_ty = mkFunTy (mkTyConApp stablePtrTyCon [arg_ty]) arg_ty
382 ioAddrTy :: Type -- IO Addr
383 ioAddrTy = mkTyConApp ioTyCon [addrTy]
385 toCName :: Id -> String
386 toCName i = showSDoc (pprCode CStyle (ppr (idName i)))
391 \subsection{Generating @foreign export@ stubs}
395 For each @foreign export@ function, a C stub function is generated.
396 The C stub constructs the application of the exported Haskell function
397 using the hugs/ghc rts invocation API.
400 fexportEntry :: String
408 fexportEntry mod_nm c_nm helper args res_ty cc isDyn = (header_bits, c_bits)
410 -- name of the (Haskell) helper function generated by the desugarer.
411 h_nm = ppr helper <> text "_closure"
412 -- prototype for the exported function.
413 header_bits = ptext SLIT("extern") <+> fun_proto <> semi
415 fun_proto = cResType <+> pprCconv <+> ptext c_nm <>
416 parens (hsep (punctuate comma (zipWith (<+>) cParamTypes proto_args)))
423 , text "SchedulerStatus rc;"
425 -- create the application + perform it.
426 , text "rc=rts_evalIO" <>
427 parens (foldl appArg (text "(StgClosure*)&" <> h_nm) (zip args c_args) <> comma <> text "&ret") <> semi
428 , text "rts_checkSchedStatus" <> parens (doubleQuotes (ptext c_nm)
429 <> comma <> text "rc") <> semi
430 , text "return" <> return_what <> semi
435 text "rts_apply" <> parens (acc <> comma <> mkHObj a <> parens c_a)
437 cParamTypes = map showStgType real_args
439 res_ty_is_unit = res_ty == unitTy
441 cResType | res_ty_is_unit = text "void"
442 | otherwise = showStgType res_ty
445 | cc == cCallConv = empty
446 | otherwise = pprCallConv cc
448 declareResult = text "HaskellObj ret;"
450 externDecl = mkExtern (text "HaskellObj") h_nm
452 mkExtern ty nm = text "extern" <+> ty <+> nm <> semi
454 return_what | res_ty_is_unit = empty
455 | otherwise = parens (unpackHObj res_ty <> parens (text "ret"))
457 c_args = mkCArgNames 0 args
460 If we're generating an entry point for a 'foreign export ccall dynamic',
461 then we receive the return address of the C function that wants to
462 invoke a Haskell function as any other C function, as second arg.
463 This arg is unused within the body of the generated C stub, but
464 needed by the Adjustor.c code to get the stack cleanup right.
466 (proto_args, real_args)
467 | cc == cCallConv && isDyn = ( text "a0" : text "a_" : mkCArgNames 1 (tail args)
468 , head args : addrTy : tail args)
469 | otherwise = (mkCArgNames 0 args, args)
471 mkCArgNames :: Int -> [a] -> [SDoc]
472 mkCArgNames n as = zipWith (\ _ n -> text ('a':show n)) as [n..]
474 mkHObj :: Type -> SDoc
475 mkHObj t = text "rts_mk" <> text (showFFIType t)
477 unpackHObj :: Type -> SDoc
478 unpackHObj t = text "rts_get" <> text (showFFIType t)
480 showStgType :: Type -> SDoc
481 showStgType t = text "Stg" <> text (showFFIType t)
483 showFFIType :: Type -> String
484 showFFIType t = getOccString (getName tc)
486 tc = case splitTyConApp_maybe (repType t) of
488 Nothing -> pprPanic "showFFIType" (ppr t)