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 ( vanillaIdInfo )
24 import Literal ( Literal(..) )
25 import Module ( Module, moduleUserString )
26 import Name ( mkGlobalName, nameModule, nameOccName, getOccString,
27 mkForeignExportOcc, isLocalName,
30 import Type ( repType, eqType )
31 import TcType ( Type, mkFunTys, mkForAllTys, mkTyConApp,
33 tcSplitForAllTys, tcSplitFunTys, tcTyConAppArgs,
34 tcSplitTyConApp_maybe, tcSplitAppTy,
38 import ForeignCall ( ForeignCall(..), CCallSpec(..),
41 CCallConv(..), ccallConvToInt
43 import CStrings ( CLabelString )
44 import TysWiredIn ( addrTy, unitTy, stablePtrTyCon )
45 import TysPrim ( addrPrimTy )
46 import PrelNames ( hasKey, ioTyConKey, deRefStablePtrName, newStablePtrName,
47 bindIOName, returnIOName
49 import BasicTypes ( Activation( NeverActive ) )
51 import Maybe ( fromJust )
54 Desugaring of @foreign@ declarations is naturally split up into
55 parts, an @import@ and an @export@ part. A @foreign import@
58 foreign import cc nm f :: prim_args -> IO prim_res
62 f :: prim_args -> IO prim_res
63 f a1 ... an = _ccall_ nm cc a1 ... an
65 so we reuse the desugaring code in @DsCCall@ to deal with these.
68 type Binding = (Id, CoreExpr) -- No rec/nonrec structure;
69 -- the occurrence analyser will sort it all out
72 -> [TypecheckedForeignDecl]
73 -> DsM ( [Id] -- Foreign-exported binders;
74 -- we have to generate code to register these
76 , SDoc -- Header file prototypes for
77 -- "foreign exported" functions.
78 , SDoc -- C stubs to use when calling
79 -- "foreign exported" functions.
81 dsForeigns mod_name fos
82 = foldlDs combine ([], [], empty, empty) fos
84 combine (acc_feb, acc_f, acc_h, acc_c) (ForeignImport id _ spec _)
85 = dsFImport mod_name id spec `thenDs` \ (bs, h, c) ->
86 returnDs (acc_feb, bs ++ acc_f, h $$ acc_h, c $$ acc_c)
88 combine (acc_feb, acc_f, acc_h, acc_c) (ForeignExport id _ (CExport (CExportStatic ext_nm cconv)) _)
89 = dsFExport mod_name id (idType id) ext_nm cconv False `thenDs` \ (feb, b, h, c) ->
90 returnDs (feb:acc_feb, b : acc_f, h $$ acc_h, c $$ acc_c)
94 %************************************************************************
96 \subsection{Foreign import}
98 %************************************************************************
100 Desugaring foreign imports is just the matter of creating a binding
101 that on its RHS unboxes its arguments, performs the external call
102 (using the @CCallOp@ primop), before boxing the result up and returning it.
104 However, we create a worker/wrapper pair, thus:
106 foreign import f :: Int -> IO Int
108 f x = IO ( \s -> case x of { I# x# ->
109 case fw s x# of { (# s1, y# #) ->
112 fw s x# = ccall f s x#
114 The strictness/CPR analyser won't do this automatically because it doesn't look
115 inside returned tuples; but inlining this wrapper is a Really Good Idea
116 because it exposes the boxing to the call site.
123 -> DsM ([Binding], SDoc, SDoc)
124 dsFImport mod_name lbl_id (LblImport ext_nm)
125 = ASSERT(fromJust res_ty `eqType` addrPrimTy) -- typechecker ensures this
126 returnDs ([(lbl_id, rhs)], empty, empty)
128 (res_ty, fo_rhs) = resultWrapper (idType lbl_id)
129 rhs = fo_rhs (mkLit (MachLabel ext_nm))
131 dsFImport mod_name fn_id (CImport spec) = dsFCall mod_name fn_id (CCall spec)
132 dsFImport mod_name fn_id (DNImport spec) = dsFCall mod_name fn_id (DNCall spec)
133 dsFImport mod_name fn_id (CDynImport cconv) = dsFExportDynamic mod_name fn_id cconv
137 %************************************************************************
139 \subsection{Foreign calls}
141 %************************************************************************
144 dsFCall mod_Name fn_id fcall
147 (tvs, fun_ty) = tcSplitForAllTys ty
148 (arg_tys, io_res_ty) = tcSplitFunTys fun_ty
149 -- Must use tcSplit* functions because we want to
150 -- see that (IO t) in the corner
152 newSysLocalsDs arg_tys `thenDs` \ args ->
153 mapAndUnzipDs unboxArg (map Var args) `thenDs` \ (val_args, arg_wrappers) ->
156 work_arg_ids = [v | Var v <- val_args] -- All guaranteed to be vars
158 -- These are the ids we pass to boxResult, which are used to decide
159 -- whether to touch# an argument after the call (used to keep
160 -- ForeignObj#s live across a 'safe' foreign import).
161 maybe_arg_ids | unsafe_call fcall = work_arg_ids
164 boxResult maybe_arg_ids io_res_ty `thenDs` \ (ccall_result_ty, res_wrapper) ->
166 getUniqueDs `thenDs` \ ccall_uniq ->
167 getUniqueDs `thenDs` \ work_uniq ->
170 worker_ty = mkForAllTys tvs (mkFunTys (map idType work_arg_ids) ccall_result_ty)
171 the_ccall_app = mkFCall ccall_uniq fcall val_args ccall_result_ty
172 work_rhs = mkLams tvs (mkLams work_arg_ids the_ccall_app)
173 work_id = mkSysLocal SLIT("$wccall") work_uniq worker_ty
176 work_app = mkApps (mkVarApps (Var work_id) tvs) val_args
177 wrapper_body = foldr ($) (res_wrapper work_app) arg_wrappers
178 wrap_rhs = mkInlineMe (mkLams (tvs ++ args) wrapper_body)
180 returnDs ([(work_id, work_rhs), (fn_id, wrap_rhs)], empty, empty)
182 unsafe_call (CCall (CCallSpec _ _ safety)) = playSafe safety
183 unsafe_call (DNCall _) = False
187 %************************************************************************
189 \subsection{Foreign export}
191 %************************************************************************
193 The function that does most of the work for `@foreign export@' declarations.
194 (see below for the boilerplate code a `@foreign export@' declaration expands
197 For each `@foreign export foo@' in a module M we generate:
199 \item a C function `@foo@', which calls
200 \item a Haskell stub `@M.$ffoo@', which calls
202 the user-written Haskell function `@M.foo@'.
206 -> Id -- Either the exported Id,
207 -- or the foreign-export-dynamic constructor
208 -> Type -- The type of the thing callable from C
209 -> CLabelString -- The name to export to C land
211 -> Bool -- True => foreign export dynamic
212 -- so invoke IO action that's hanging off
213 -- the first argument's stable pointer
214 -> DsM ( Id -- The foreign-exported Id
219 dsFExport mod_name fn_id ty ext_name cconv isDyn
220 = -- BUILD THE returnIO WRAPPER, if necessary
221 -- Look at the result type of the exported function, orig_res_ty
222 -- If it's IO t, return (\x.x, IO t, t)
223 -- If it's plain t, return (\x.returnIO x, IO t, t)
224 (case tcSplitTyConApp_maybe orig_res_ty of
225 -- We must use tcSplit here so that we see the (IO t) in
226 -- the type. [IO t is transparent to plain splitTyConApp.]
228 Just (ioTyCon, [res_ty])
229 -> ASSERT( ioTyCon `hasKey` ioTyConKey )
230 -- The function already returns IO t
231 returnDs (\body -> body, orig_res_ty, res_ty)
233 other -> -- The function returns t, so wrap the call in returnIO
234 dsLookupGlobalValue returnIOName `thenDs` \ retIOId ->
235 returnDs (\body -> mkApps (Var retIOId) [Type orig_res_ty, body],
236 tcFunResultTy (applyTy (idType retIOId) orig_res_ty),
237 -- We don't have ioTyCon conveniently to hand
240 ) `thenDs` \ (return_io_wrapper, -- Either identity or returnIO
245 -- BUILD THE deRefStablePtr WRAPPER, if necessary
247 newSysLocalDs stbl_ptr_ty `thenDs` \ stbl_ptr ->
248 newSysLocalDs stbl_ptr_to_ty `thenDs` \ stbl_value ->
249 dsLookupGlobalValue deRefStablePtrName `thenDs` \ deRefStablePtrId ->
250 dsLookupGlobalValue bindIOName `thenDs` \ bindIOId ->
252 the_deref_app = mkApps (Var deRefStablePtrId)
253 [ Type stbl_ptr_to_ty, Var stbl_ptr ]
255 stbl_app cont = mkApps (Var bindIOId)
256 [ Type stbl_ptr_to_ty
259 , mkLams [stbl_value] cont]
261 returnDs (stbl_value, stbl_app, stbl_ptr)
265 panic "stbl_ptr" -- should never be touched.
266 )) `thenDs` \ (i, getFun_wrapper, stbl_ptr) ->
270 getModuleDs `thenDs` \ mod ->
271 getUniqueDs `thenDs` \ uniq ->
272 getSrcLocDs `thenDs` \ src_loc ->
273 newSysLocalsDs fe_arg_tys `thenDs` \ fe_args ->
275 wrapper_args | isDyn = stbl_ptr:fe_args
276 | otherwise = fe_args
278 wrapper_arg_tys | isDyn = stbl_ptr_ty:fe_arg_tys
279 | otherwise = fe_arg_tys
281 helper_ty = mkForAllTys tvs $
282 mkFunTys wrapper_arg_tys io_res_ty
284 f_helper_glob = mkVanillaGlobal helper_name helper_ty vanillaIdInfo
288 | isLocalName name = mod_name
289 | otherwise = nameModule name
291 occ = mkForeignExportOcc (nameOccName name)
292 helper_name = mkGlobalName uniq mod occ src_loc
294 the_app = getFun_wrapper (return_io_wrapper (mkVarApps (Var i) (tvs ++ fe_args)))
295 the_body = mkLams (tvs ++ wrapper_args) the_app
297 (h_stub, c_stub) = fexportEntry (moduleUserString mod)
298 ext_name f_helper_glob
299 wrapper_arg_tys res_ty cconv isDyn
301 returnDs (f_helper_glob, (f_helper_glob, the_body), h_stub, c_stub)
304 (tvs,sans_foralls) = tcSplitForAllTys ty
305 (fe_arg_tys', orig_res_ty) = tcSplitFunTys sans_foralls
306 -- We must use tcSplits here, because we want to see
307 -- the (IO t) in the corner of the type!
309 fe_arg_tys | isDyn = tail fe_arg_tys'
310 | otherwise = fe_arg_tys'
312 stbl_ptr_ty | isDyn = head fe_arg_tys'
313 | otherwise = error "stbl_ptr_ty"
315 (_, stbl_ptr_ty') = tcSplitForAllTys stbl_ptr_ty
316 (_, stbl_ptr_to_ty) = tcSplitAppTy stbl_ptr_ty'
317 -- Again, stable pointers are just newtypes,
318 -- so we must see them! Hence tcSplit*
321 @foreign export dynamic@ lets you dress up Haskell IO actions
322 of some fixed type behind an externally callable interface (i.e.,
323 as a C function pointer). Useful for callbacks and stuff.
326 foreign export dynamic f :: (Addr -> Int -> IO Int) -> IO Addr
328 -- Haskell-visible constructor, which is generated from the above:
329 -- SUP: No check for NULL from createAdjustor anymore???
331 f :: (Addr -> Int -> IO Int) -> IO Addr
333 bindIO (newStablePtr cback)
334 (\StablePtr sp# -> IO (\s1# ->
335 case _ccall_ createAdjustor cconv sp# ``f_helper'' s1# of
336 (# s2#, a# #) -> (# s2#, A# a# #)))
338 foreign export "f_helper" f_helper :: StablePtr (Addr -> Int -> IO Int) -> Addr -> Int -> IO Int
339 -- `special' foreign export that invokes the closure pointed to by the
344 dsFExportDynamic :: Module
347 -> DsM ([Binding], SDoc, SDoc)
348 dsFExportDynamic mod_name id cconv
349 = newSysLocalDs ty `thenDs` \ fe_id ->
351 -- hack: need to get at the name of the C stub we're about to generate.
352 fe_nm = _PK_ (moduleUserString mod_name ++ "_" ++ toCName fe_id)
354 dsFExport mod_name id export_ty fe_nm cconv True `thenDs` \ (feb, fe, h_code, c_code) ->
355 newSysLocalDs arg_ty `thenDs` \ cback ->
356 dsLookupGlobalValue newStablePtrName `thenDs` \ newStablePtrId ->
358 mk_stbl_ptr_app = mkApps (Var newStablePtrId) [ Type arg_ty, Var cback ]
360 dsLookupGlobalValue bindIOName `thenDs` \ bindIOId ->
361 newSysLocalDs (mkTyConApp stablePtrTyCon [arg_ty]) `thenDs` \ stbl_value ->
364 = mkApps (Var bindIOId)
365 [ Type (mkTyConApp stablePtrTyCon [arg_ty])
372 The arguments to the external function which will
373 create a little bit of (template) code on the fly
374 for allowing the (stable pointed) Haskell closure
375 to be entered using an external calling convention
378 adj_args = [ mkIntLitInt (ccallConvToInt cconv)
380 , mkLit (MachLabel fe_nm)
382 -- name of external entry point providing these services.
383 -- (probably in the RTS.)
384 adjustor = SLIT("createAdjustor")
386 dsCCall adjustor adj_args PlayRisky False io_res_ty `thenDs` \ ccall_adj ->
387 -- PlayRisky: the adjustor doesn't allocate in the Haskell heap or do a callback
388 let ccall_adj_ty = exprType ccall_adj
389 ccall_io_adj = mkLams [stbl_value] $
390 Note (Coerce io_res_ty ccall_adj_ty)
392 io_app = mkLams tvs $
394 stbl_app ccall_io_adj res_ty
395 fed = (id `setInlinePragma` NeverActive, io_app)
396 -- Never inline the f.e.d. function, because the litlit
397 -- might not be in scope in other modules.
399 returnDs ([fed, fe], h_code, c_code)
403 (tvs,sans_foralls) = tcSplitForAllTys ty
404 ([arg_ty], io_res_ty) = tcSplitFunTys sans_foralls
405 [res_ty] = tcTyConAppArgs io_res_ty
406 -- Must use tcSplit* to see the (IO t), which is a newtype
407 export_ty = mkFunTy (mkTyConApp stablePtrTyCon [arg_ty]) arg_ty
409 toCName :: Id -> String
410 toCName i = showSDoc (pprCode CStyle (ppr (idName i)))
415 \subsection{Generating @foreign export@ stubs}
419 For each @foreign export@ function, a C stub function is generated.
420 The C stub constructs the application of the exported Haskell function
421 using the hugs/ghc rts invocation API.
424 fexportEntry :: String
432 fexportEntry mod_nm c_nm helper args res_ty cc isDyn = (header_bits, c_bits)
434 -- name of the (Haskell) helper function generated by the desugarer.
435 h_nm = ppr helper <> text "_closure"
436 -- prototype for the exported function.
437 header_bits = ptext SLIT("extern") <+> fun_proto <> semi
439 fun_proto = cResType <+> pprCconv <+> ptext c_nm <>
440 parens (hsep (punctuate comma (zipWith (<+>) cParamTypes proto_args)))
447 , text "SchedulerStatus rc;"
449 -- create the application + perform it.
450 , text "rc=rts_evalIO" <>
451 parens (foldl appArg (text "(StgClosure*)&" <> h_nm) (zip args c_args) <> comma <> text "&ret") <> semi
452 , text "rts_checkSchedStatus" <> parens (doubleQuotes (ptext c_nm)
453 <> comma <> text "rc") <> semi
454 , text "return" <> return_what <> semi
459 text "rts_apply" <> parens (acc <> comma <> mkHObj a <> parens c_a)
461 cParamTypes = map showStgType real_args
463 res_ty_is_unit = res_ty `eqType` unitTy -- Look through any newtypes
465 cResType | res_ty_is_unit = text "void"
466 | otherwise = showStgType res_ty
468 pprCconv = case cc of
470 StdCallConv -> ppr cc
472 declareResult = text "HaskellObj ret;"
474 externDecl = mkExtern (text "HaskellObj") h_nm
476 mkExtern ty nm = text "extern" <+> ty <+> nm <> semi
478 return_what | res_ty_is_unit = empty
479 | otherwise = parens (unpackHObj res_ty <> parens (text "ret"))
481 c_args = mkCArgNames 0 args
484 If we're generating an entry point for a 'foreign export ccall dynamic',
485 then we receive the return address of the C function that wants to
486 invoke a Haskell function as any other C function, as second arg.
487 This arg is unused within the body of the generated C stub, but
488 needed by the Adjustor.c code to get the stack cleanup right.
490 (proto_args, real_args)
492 CCallConv | isDyn -> ( text "a0" : text "a_" : mkCArgNames 1 (tail args)
493 , head args : addrTy : tail args)
494 other -> (mkCArgNames 0 args, args)
496 mkCArgNames :: Int -> [a] -> [SDoc]
497 mkCArgNames n as = zipWith (\ _ n -> text ('a':show n)) as [n..]
499 mkHObj :: Type -> SDoc
500 mkHObj t = text "rts_mk" <> text (showFFIType t)
502 unpackHObj :: Type -> SDoc
503 unpackHObj t = text "rts_get" <> text (showFFIType t)
505 showStgType :: Type -> SDoc
506 showStgType t = text "Hs" <> text (showFFIType t)
508 showFFIType :: Type -> String
509 showFFIType t = getOccString (getName tc)
511 tc = case tcSplitTyConApp_maybe (repType t) of
513 Nothing -> pprPanic "showFFIType" (ppr t)