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 Type ( repType, splitTyConApp_maybe,
31 splitFunTys, splitForAllTys,
32 Type, mkFunTys, mkForAllTys, mkTyConApp,
33 mkFunTy, splitAppTy, applyTy, funResultTy
35 import ForeignCall ( ForeignCall(..), CCallSpec(..),
38 CCallConv(..), ccallConvToInt
40 import CStrings ( CLabelString )
41 import TysWiredIn ( unitTy, addrTy, stablePtrTyCon )
42 import TysPrim ( addrPrimTy )
43 import PrelNames ( hasKey, ioTyConKey, deRefStablePtrName, newStablePtrName,
44 bindIOName, returnIOName
48 import Maybe ( fromJust )
51 Desugaring of @foreign@ declarations is naturally split up into
52 parts, an @import@ and an @export@ part. A @foreign import@
55 foreign import cc nm f :: prim_args -> IO prim_res
59 f :: prim_args -> IO prim_res
60 f a1 ... an = _ccall_ nm cc a1 ... an
62 so we reuse the desugaring code in @DsCCall@ to deal with these.
65 type Binding = (Id, CoreExpr) -- No rec/nonrec structure;
66 -- the occurrence analyser will sort it all out
69 -> [TypecheckedForeignDecl]
70 -> DsM ( [Id] -- Foreign-exported binders;
71 -- we have to generate code to register these
73 , SDoc -- Header file prototypes for
74 -- "foreign exported" functions.
75 , SDoc -- C stubs to use when calling
76 -- "foreign exported" functions.
78 dsForeigns mod_name fos
79 = foldlDs combine ([], [], empty, empty) fos
81 combine (acc_feb, acc_f, acc_h, acc_c) (ForeignImport id _ spec _)
82 = dsFImport mod_name id spec `thenDs` \ (bs, h, c) ->
83 returnDs (acc_feb, bs ++ acc_f, h $$ acc_h, c $$ acc_c)
85 combine (acc_feb, acc_f, acc_h, acc_c) (ForeignExport id _ (CExport (CExportStatic ext_nm cconv)) _)
86 = dsFExport mod_name id (idType id) ext_nm cconv False `thenDs` \ (feb, b, h, c) ->
87 returnDs (feb:acc_feb, b : acc_f, h $$ acc_h, c $$ acc_c)
91 %************************************************************************
93 \subsection{Foreign import}
95 %************************************************************************
97 Desugaring foreign imports is just the matter of creating a binding
98 that on its RHS unboxes its arguments, performs the external call
99 (using the @CCallOp@ primop), before boxing the result up and returning it.
101 However, we create a worker/wrapper pair, thus:
103 foreign import f :: Int -> IO Int
105 f x = IO ( \s -> case x of { I# x# ->
106 case fw s x# of { (# s1, y# #) ->
109 fw s x# = ccall f s x#
111 The strictness/CPR analyser won't do this automatically because it doesn't look
112 inside returned tuples; but inlining this wrapper is a Really Good Idea
113 because it exposes the boxing to the call site.
120 -> DsM ([Binding], SDoc, SDoc)
121 dsFImport mod_name lbl_id (LblImport ext_nm)
122 = ASSERT(fromJust res_ty == addrPrimTy) -- typechecker ensures this
123 returnDs ([(lbl_id, rhs)], empty, empty)
125 (res_ty, fo_rhs) = resultWrapper (idType lbl_id)
126 rhs = fo_rhs (mkLit (MachLabel ext_nm))
128 dsFImport mod_name fn_id (CImport spec) = dsFCall mod_name fn_id (CCall spec)
129 dsFImport mod_name fn_id (DNImport spec) = dsFCall mod_name fn_id (DNCall spec)
130 dsFImport mod_name fn_id (CDynImport cconv) = dsFExportDynamic mod_name fn_id cconv
134 %************************************************************************
136 \subsection{Foreign calls}
138 %************************************************************************
141 dsFCall mod_Name fn_id fcall
144 (tvs, fun_ty) = splitForAllTys ty
145 (arg_tys, io_res_ty) = splitFunTys fun_ty
147 newSysLocalsDs arg_tys `thenDs` \ args ->
148 mapAndUnzipDs unboxArg (map Var args) `thenDs` \ (val_args, arg_wrappers) ->
151 work_arg_ids = [v | Var v <- val_args] -- All guaranteed to be vars
153 -- These are the ids we pass to boxResult, which are used to decide
154 -- whether to touch# an argument after the call (used to keep
155 -- ForeignObj#s live across a 'safe' foreign import).
156 maybe_arg_ids | unsafe_call fcall = work_arg_ids
159 boxResult maybe_arg_ids io_res_ty `thenDs` \ (ccall_result_ty, res_wrapper) ->
161 getUniqueDs `thenDs` \ ccall_uniq ->
162 getUniqueDs `thenDs` \ work_uniq ->
165 worker_ty = mkForAllTys tvs (mkFunTys (map idType work_arg_ids) ccall_result_ty)
166 the_ccall_app = mkFCall ccall_uniq fcall val_args ccall_result_ty
167 work_rhs = mkLams tvs (mkLams work_arg_ids the_ccall_app)
168 work_id = mkSysLocal SLIT("$wccall") work_uniq worker_ty
171 work_app = mkApps (mkVarApps (Var work_id) tvs) val_args
172 wrapper_body = foldr ($) (res_wrapper work_app) arg_wrappers
173 wrap_rhs = mkInlineMe (mkLams (tvs ++ args) wrapper_body)
175 returnDs ([(work_id, work_rhs), (fn_id, wrap_rhs)], empty, empty)
177 unsafe_call (CCall (CCallSpec _ _ safety)) = playSafe safety
178 unsafe_call (DNCall _) = False
182 %************************************************************************
184 \subsection{Foreign export}
186 %************************************************************************
188 The function that does most of the work for `@foreign export@' declarations.
189 (see below for the boilerplate code a `@foreign export@' declaration expands
192 For each `@foreign export foo@' in a module M we generate:
194 \item a C function `@foo@', which calls
195 \item a Haskell stub `@M.$ffoo@', which calls
197 the user-written Haskell function `@M.foo@'.
201 -> Id -- Either the exported Id,
202 -- or the foreign-export-dynamic constructor
203 -> Type -- The type of the thing callable from C
204 -> CLabelString -- The name to export to C land
206 -> Bool -- True => foreign export dynamic
207 -- so invoke IO action that's hanging off
208 -- the first argument's stable pointer
209 -> DsM ( Id -- The foreign-exported Id
214 dsFExport mod_name fn_id ty ext_name cconv isDyn
215 = -- BUILD THE returnIO WRAPPER, if necessary
216 -- Look at the result type of the exported function, orig_res_ty
217 -- If it's IO t, return (\x.x, IO t, t)
218 -- If it's plain t, return (\x.returnIO x, IO t, t)
219 (case splitTyConApp_maybe orig_res_ty of
220 Just (ioTyCon, [res_ty])
221 -> ASSERT( ioTyCon `hasKey` ioTyConKey )
222 -- The function already returns IO t
223 returnDs (\body -> body, orig_res_ty, res_ty)
225 other -> -- The function returns t, so wrap the call in returnIO
226 dsLookupGlobalValue returnIOName `thenDs` \ retIOId ->
227 returnDs (\body -> mkApps (Var retIOId) [Type orig_res_ty, body],
228 funResultTy (applyTy (idType retIOId) orig_res_ty),
229 -- We don't have ioTyCon conveniently to hand
232 ) `thenDs` \ (return_io_wrapper, -- Either identity or returnIO
237 -- BUILD THE deRefStablePtr WRAPPER, if necessary
239 newSysLocalDs stbl_ptr_ty `thenDs` \ stbl_ptr ->
240 newSysLocalDs stbl_ptr_to_ty `thenDs` \ stbl_value ->
241 dsLookupGlobalValue deRefStablePtrName `thenDs` \ deRefStablePtrId ->
242 dsLookupGlobalValue bindIOName `thenDs` \ bindIOId ->
244 the_deref_app = mkApps (Var deRefStablePtrId)
245 [ Type stbl_ptr_to_ty, Var stbl_ptr ]
247 stbl_app cont = mkApps (Var bindIOId)
248 [ Type stbl_ptr_to_ty
251 , mkLams [stbl_value] cont]
253 returnDs (stbl_value, stbl_app, stbl_ptr)
257 panic "stbl_ptr" -- should never be touched.
258 )) `thenDs` \ (i, getFun_wrapper, stbl_ptr) ->
262 getModuleDs `thenDs` \ mod ->
263 getUniqueDs `thenDs` \ uniq ->
264 getSrcLocDs `thenDs` \ src_loc ->
265 newSysLocalsDs fe_arg_tys `thenDs` \ fe_args ->
267 wrapper_args | isDyn = stbl_ptr:fe_args
268 | otherwise = fe_args
270 wrapper_arg_tys | isDyn = stbl_ptr_ty:fe_arg_tys
271 | otherwise = fe_arg_tys
273 helper_ty = mkForAllTys tvs $
274 mkFunTys wrapper_arg_tys io_res_ty
276 f_helper_glob = mkVanillaGlobal helper_name helper_ty vanillaIdInfo
280 | isLocalName name = mod_name
281 | otherwise = nameModule name
283 occ = mkForeignExportOcc (nameOccName name)
284 helper_name = mkGlobalName uniq mod occ src_loc
286 the_app = getFun_wrapper (return_io_wrapper (mkVarApps (Var i) (tvs ++ fe_args)))
287 the_body = mkLams (tvs ++ wrapper_args) the_app
289 (h_stub, c_stub) = fexportEntry (moduleUserString mod)
290 ext_name f_helper_glob
291 wrapper_arg_tys res_ty cconv isDyn
293 returnDs (f_helper_glob, (f_helper_glob, the_body), h_stub, c_stub)
296 (tvs,sans_foralls) = splitForAllTys ty
297 (fe_arg_tys', orig_res_ty) = splitFunTys sans_foralls
299 (_, stbl_ptr_ty') = splitForAllTys stbl_ptr_ty
300 (_, stbl_ptr_to_ty) = splitAppTy stbl_ptr_ty'
302 fe_arg_tys | isDyn = tail fe_arg_tys'
303 | otherwise = fe_arg_tys'
305 stbl_ptr_ty | isDyn = head fe_arg_tys'
306 | otherwise = error "stbl_ptr_ty"
309 @foreign export dynamic@ lets you dress up Haskell IO actions
310 of some fixed type behind an externally callable interface (i.e.,
311 as a C function pointer). Useful for callbacks and stuff.
314 foreign export dynamic f :: (Addr -> Int -> IO Int) -> IO Addr
316 -- Haskell-visible constructor, which is generated from the above:
317 -- SUP: No check for NULL from createAdjustor anymore???
319 f :: (Addr -> Int -> IO Int) -> IO Addr
321 bindIO (newStablePtr cback)
322 (\StablePtr sp# -> IO (\s1# ->
323 case _ccall_ createAdjustor cconv sp# ``f_helper'' s1# of
324 (# s2#, a# #) -> (# s2#, A# a# #)))
326 foreign export "f_helper" f_helper :: StablePtr (Addr -> Int -> IO Int) -> Addr -> Int -> IO Int
327 -- `special' foreign export that invokes the closure pointed to by the
332 dsFExportDynamic :: Module
335 -> DsM ([Binding], SDoc, SDoc)
336 dsFExportDynamic mod_name id cconv
337 = newSysLocalDs ty `thenDs` \ fe_id ->
339 -- hack: need to get at the name of the C stub we're about to generate.
340 fe_nm = _PK_ (moduleUserString mod_name ++ "_" ++ toCName fe_id)
342 dsFExport mod_name id export_ty fe_nm cconv True `thenDs` \ (feb, fe, h_code, c_code) ->
343 newSysLocalDs arg_ty `thenDs` \ cback ->
344 dsLookupGlobalValue newStablePtrName `thenDs` \ newStablePtrId ->
346 mk_stbl_ptr_app = mkApps (Var newStablePtrId) [ Type arg_ty, Var cback ]
348 dsLookupGlobalValue bindIOName `thenDs` \ bindIOId ->
349 newSysLocalDs (mkTyConApp stablePtrTyCon [arg_ty]) `thenDs` \ stbl_value ->
352 = mkApps (Var bindIOId)
353 [ Type (mkTyConApp stablePtrTyCon [arg_ty])
360 The arguments to the external function which will
361 create a little bit of (template) code on the fly
362 for allowing the (stable pointed) Haskell closure
363 to be entered using an external calling convention
366 adj_args = [ mkIntLitInt (ccallConvToInt cconv)
368 , mkLit (MachLabel fe_nm)
370 -- name of external entry point providing these services.
371 -- (probably in the RTS.)
372 adjustor = SLIT("createAdjustor")
374 dsCCall adjustor adj_args PlayRisky False io_res_ty `thenDs` \ ccall_adj ->
375 -- PlayRisky: the adjustor doesn't allocate in the Haskell heap or do a callback
376 let ccall_adj_ty = exprType ccall_adj
377 ccall_io_adj = mkLams [stbl_value] $
378 Note (Coerce io_res_ty ccall_adj_ty)
380 io_app = mkLams tvs $
382 stbl_app ccall_io_adj res_ty
383 fed = (id `setInlinePragma` neverInlinePrag, io_app)
384 -- Never inline the f.e.d. function, because the litlit
385 -- might not be in scope in other modules.
387 returnDs ([fed, fe], h_code, c_code)
391 (tvs,sans_foralls) = splitForAllTys ty
392 ([arg_ty], io_res_ty) = splitFunTys sans_foralls
393 Just (ioTyCon, [res_ty]) = splitTyConApp_maybe io_res_ty
394 export_ty = mkFunTy (mkTyConApp stablePtrTyCon [arg_ty]) arg_ty
396 toCName :: Id -> String
397 toCName i = showSDoc (pprCode CStyle (ppr (idName i)))
402 \subsection{Generating @foreign export@ stubs}
406 For each @foreign export@ function, a C stub function is generated.
407 The C stub constructs the application of the exported Haskell function
408 using the hugs/ghc rts invocation API.
411 fexportEntry :: String
419 fexportEntry mod_nm c_nm helper args res_ty cc isDyn = (header_bits, c_bits)
421 -- name of the (Haskell) helper function generated by the desugarer.
422 h_nm = ppr helper <> text "_closure"
423 -- prototype for the exported function.
424 header_bits = ptext SLIT("extern") <+> fun_proto <> semi
426 fun_proto = cResType <+> pprCconv <+> ptext c_nm <>
427 parens (hsep (punctuate comma (zipWith (<+>) cParamTypes proto_args)))
434 , text "SchedulerStatus rc;"
436 -- create the application + perform it.
437 , text "rc=rts_evalIO" <>
438 parens (foldl appArg (text "(StgClosure*)&" <> h_nm) (zip args c_args) <> comma <> text "&ret") <> semi
439 , text "rts_checkSchedStatus" <> parens (doubleQuotes (ptext c_nm)
440 <> comma <> text "rc") <> semi
441 , text "return" <> return_what <> semi
446 text "rts_apply" <> parens (acc <> comma <> mkHObj a <> parens c_a)
448 cParamTypes = map showStgType real_args
450 res_ty_is_unit = res_ty == unitTy
452 cResType | res_ty_is_unit = text "void"
453 | otherwise = showStgType res_ty
455 pprCconv = case cc of
457 StdCallConv -> ppr cc
459 declareResult = text "HaskellObj ret;"
461 externDecl = mkExtern (text "HaskellObj") h_nm
463 mkExtern ty nm = text "extern" <+> ty <+> nm <> semi
465 return_what | res_ty_is_unit = empty
466 | otherwise = parens (unpackHObj res_ty <> parens (text "ret"))
468 c_args = mkCArgNames 0 args
471 If we're generating an entry point for a 'foreign export ccall dynamic',
472 then we receive the return address of the C function that wants to
473 invoke a Haskell function as any other C function, as second arg.
474 This arg is unused within the body of the generated C stub, but
475 needed by the Adjustor.c code to get the stack cleanup right.
477 (proto_args, real_args)
479 CCallConv | isDyn -> ( text "a0" : text "a_" : mkCArgNames 1 (tail args)
480 , head args : addrTy : tail args)
481 other -> (mkCArgNames 0 args, args)
483 mkCArgNames :: Int -> [a] -> [SDoc]
484 mkCArgNames n as = zipWith (\ _ n -> text ('a':show n)) as [n..]
486 mkHObj :: Type -> SDoc
487 mkHObj t = text "rts_mk" <> text (showFFIType t)
489 unpackHObj :: Type -> SDoc
490 unpackHObj t = text "rts_get" <> text (showFFIType t)
492 showStgType :: Type -> SDoc
493 showStgType t = text "Hs" <> text (showFFIType t)
495 showFFIType :: Type -> String
496 showFFIType t = getOccString (getName tc)
498 tc = case splitTyConApp_maybe (repType t) of
500 Nothing -> pprPanic "showFFIType" (ppr t)