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,
31 import Type ( repType, eqType )
32 import TcType ( Type, mkFunTys, mkForAllTys, mkTyConApp,
34 tcSplitForAllTys, tcSplitFunTys, tcTyConAppArgs,
35 tcSplitTyConApp_maybe, tcSplitAppTy,
39 import ForeignCall ( ForeignCall(..), CCallSpec(..),
42 CCallConv(..), ccallConvToInt
44 import CStrings ( CLabelString )
45 import TysWiredIn ( addrTy, unitTy, stablePtrTyCon )
46 import TysPrim ( addrPrimTy )
47 import PrelNames ( hasKey, ioTyConKey, deRefStablePtrName, newStablePtrName,
48 bindIOName, returnIOName
52 import Maybe ( fromJust )
55 Desugaring of @foreign@ declarations is naturally split up into
56 parts, an @import@ and an @export@ part. A @foreign import@
59 foreign import cc nm f :: prim_args -> IO prim_res
63 f :: prim_args -> IO prim_res
64 f a1 ... an = _ccall_ nm cc a1 ... an
66 so we reuse the desugaring code in @DsCCall@ to deal with these.
69 type Binding = (Id, CoreExpr) -- No rec/nonrec structure;
70 -- the occurrence analyser will sort it all out
73 -> [TypecheckedForeignDecl]
74 -> DsM ( [Id] -- Foreign-exported binders;
75 -- we have to generate code to register these
77 , SDoc -- Header file prototypes for
78 -- "foreign exported" functions.
79 , SDoc -- C stubs to use when calling
80 -- "foreign exported" functions.
82 dsForeigns mod_name fos
83 = foldlDs combine ([], [], empty, empty) fos
85 combine (acc_feb, acc_f, acc_h, acc_c) (ForeignImport id _ spec _)
86 = dsFImport mod_name id spec `thenDs` \ (bs, h, c) ->
87 returnDs (acc_feb, bs ++ acc_f, h $$ acc_h, c $$ acc_c)
89 combine (acc_feb, acc_f, acc_h, acc_c) (ForeignExport id _ (CExport (CExportStatic ext_nm cconv)) _)
90 = dsFExport mod_name id (idType id) ext_nm cconv False `thenDs` \ (feb, b, h, c) ->
91 returnDs (feb:acc_feb, b : acc_f, h $$ acc_h, c $$ acc_c)
95 %************************************************************************
97 \subsection{Foreign import}
99 %************************************************************************
101 Desugaring foreign imports is just the matter of creating a binding
102 that on its RHS unboxes its arguments, performs the external call
103 (using the @CCallOp@ primop), before boxing the result up and returning it.
105 However, we create a worker/wrapper pair, thus:
107 foreign import f :: Int -> IO Int
109 f x = IO ( \s -> case x of { I# x# ->
110 case fw s x# of { (# s1, y# #) ->
113 fw s x# = ccall f s x#
115 The strictness/CPR analyser won't do this automatically because it doesn't look
116 inside returned tuples; but inlining this wrapper is a Really Good Idea
117 because it exposes the boxing to the call site.
124 -> DsM ([Binding], SDoc, SDoc)
125 dsFImport mod_name lbl_id (LblImport ext_nm)
126 = ASSERT(fromJust res_ty `eqType` addrPrimTy) -- typechecker ensures this
127 returnDs ([(lbl_id, rhs)], empty, empty)
129 (res_ty, fo_rhs) = resultWrapper (idType lbl_id)
130 rhs = fo_rhs (mkLit (MachLabel ext_nm))
132 dsFImport mod_name fn_id (CImport spec) = dsFCall mod_name fn_id (CCall spec)
133 dsFImport mod_name fn_id (DNImport spec) = dsFCall mod_name fn_id (DNCall spec)
134 dsFImport mod_name fn_id (CDynImport cconv) = dsFExportDynamic mod_name fn_id cconv
138 %************************************************************************
140 \subsection{Foreign calls}
142 %************************************************************************
145 dsFCall mod_Name fn_id fcall
148 (tvs, fun_ty) = tcSplitForAllTys ty
149 (arg_tys, io_res_ty) = tcSplitFunTys fun_ty
150 -- Must use tcSplit* functions because we want to
151 -- see that (IO t) in the corner
153 newSysLocalsDs arg_tys `thenDs` \ args ->
154 mapAndUnzipDs unboxArg (map Var args) `thenDs` \ (val_args, arg_wrappers) ->
157 work_arg_ids = [v | Var v <- val_args] -- All guaranteed to be vars
159 -- These are the ids we pass to boxResult, which are used to decide
160 -- whether to touch# an argument after the call (used to keep
161 -- ForeignObj#s live across a 'safe' foreign import).
162 maybe_arg_ids | unsafe_call fcall = work_arg_ids
165 boxResult maybe_arg_ids io_res_ty `thenDs` \ (ccall_result_ty, res_wrapper) ->
167 getUniqueDs `thenDs` \ ccall_uniq ->
168 getUniqueDs `thenDs` \ work_uniq ->
171 worker_ty = mkForAllTys tvs (mkFunTys (map idType work_arg_ids) ccall_result_ty)
172 the_ccall_app = mkFCall ccall_uniq fcall val_args ccall_result_ty
173 work_rhs = mkLams tvs (mkLams work_arg_ids the_ccall_app)
174 work_id = mkSysLocal SLIT("$wccall") work_uniq worker_ty
177 work_app = mkApps (mkVarApps (Var work_id) tvs) val_args
178 wrapper_body = foldr ($) (res_wrapper work_app) arg_wrappers
179 wrap_rhs = mkInlineMe (mkLams (tvs ++ args) wrapper_body)
181 returnDs ([(work_id, work_rhs), (fn_id, wrap_rhs)], empty, empty)
183 unsafe_call (CCall (CCallSpec _ _ safety)) = playSafe safety
184 unsafe_call (DNCall _) = False
188 %************************************************************************
190 \subsection{Foreign export}
192 %************************************************************************
194 The function that does most of the work for `@foreign export@' declarations.
195 (see below for the boilerplate code a `@foreign export@' declaration expands
198 For each `@foreign export foo@' in a module M we generate:
200 \item a C function `@foo@', which calls
201 \item a Haskell stub `@M.$ffoo@', which calls
203 the user-written Haskell function `@M.foo@'.
207 -> Id -- Either the exported Id,
208 -- or the foreign-export-dynamic constructor
209 -> Type -- The type of the thing callable from C
210 -> CLabelString -- The name to export to C land
212 -> Bool -- True => foreign export dynamic
213 -- so invoke IO action that's hanging off
214 -- the first argument's stable pointer
215 -> DsM ( Id -- The foreign-exported Id
220 dsFExport mod_name fn_id ty ext_name cconv isDyn
221 = -- BUILD THE returnIO WRAPPER, if necessary
222 -- Look at the result type of the exported function, orig_res_ty
223 -- If it's IO t, return (\x.x, IO t, t)
224 -- If it's plain t, return (\x.returnIO x, IO t, t)
225 (case tcSplitTyConApp_maybe orig_res_ty of
226 -- We must use tcSplit here so that we see the (IO t) in
227 -- the type. [IO t is transparent to plain splitTyConApp.]
229 Just (ioTyCon, [res_ty])
230 -> ASSERT( ioTyCon `hasKey` ioTyConKey )
231 -- The function already returns IO t
232 returnDs (\body -> body, orig_res_ty, res_ty)
234 other -> -- The function returns t, so wrap the call in returnIO
235 dsLookupGlobalValue returnIOName `thenDs` \ retIOId ->
236 returnDs (\body -> mkApps (Var retIOId) [Type orig_res_ty, body],
237 tcFunResultTy (applyTy (idType retIOId) orig_res_ty),
238 -- We don't have ioTyCon conveniently to hand
241 ) `thenDs` \ (return_io_wrapper, -- Either identity or returnIO
246 -- BUILD THE deRefStablePtr WRAPPER, if necessary
248 newSysLocalDs stbl_ptr_ty `thenDs` \ stbl_ptr ->
249 newSysLocalDs stbl_ptr_to_ty `thenDs` \ stbl_value ->
250 dsLookupGlobalValue deRefStablePtrName `thenDs` \ deRefStablePtrId ->
251 dsLookupGlobalValue bindIOName `thenDs` \ bindIOId ->
253 the_deref_app = mkApps (Var deRefStablePtrId)
254 [ Type stbl_ptr_to_ty, Var stbl_ptr ]
256 stbl_app cont = mkApps (Var bindIOId)
257 [ Type stbl_ptr_to_ty
260 , mkLams [stbl_value] cont]
262 returnDs (stbl_value, stbl_app, stbl_ptr)
266 panic "stbl_ptr" -- should never be touched.
267 )) `thenDs` \ (i, getFun_wrapper, stbl_ptr) ->
271 getModuleDs `thenDs` \ mod ->
272 getUniqueDs `thenDs` \ uniq ->
273 getSrcLocDs `thenDs` \ src_loc ->
274 newSysLocalsDs fe_arg_tys `thenDs` \ fe_args ->
276 wrapper_args | isDyn = stbl_ptr:fe_args
277 | otherwise = fe_args
279 wrapper_arg_tys | isDyn = stbl_ptr_ty:fe_arg_tys
280 | otherwise = fe_arg_tys
282 helper_ty = mkForAllTys tvs $
283 mkFunTys wrapper_arg_tys io_res_ty
285 f_helper_glob = mkVanillaGlobal helper_name helper_ty vanillaIdInfo
289 | isLocalName name = mod_name
290 | otherwise = nameModule name
292 occ = mkForeignExportOcc (nameOccName name)
293 helper_name = mkGlobalName uniq mod occ src_loc
295 the_app = getFun_wrapper (return_io_wrapper (mkVarApps (Var i) (tvs ++ fe_args)))
296 the_body = mkLams (tvs ++ wrapper_args) the_app
298 (h_stub, c_stub) = fexportEntry (moduleUserString mod)
299 ext_name f_helper_glob
300 wrapper_arg_tys res_ty cconv isDyn
302 returnDs (f_helper_glob, (f_helper_glob, the_body), h_stub, c_stub)
305 (tvs,sans_foralls) = tcSplitForAllTys ty
306 (fe_arg_tys', orig_res_ty) = tcSplitFunTys sans_foralls
307 -- We must use tcSplits here, because we want to see
308 -- the (IO t) in the corner of the type!
310 fe_arg_tys | isDyn = tail fe_arg_tys'
311 | otherwise = fe_arg_tys'
313 stbl_ptr_ty | isDyn = head fe_arg_tys'
314 | otherwise = error "stbl_ptr_ty"
316 (_, stbl_ptr_ty') = tcSplitForAllTys stbl_ptr_ty
317 (_, stbl_ptr_to_ty) = tcSplitAppTy stbl_ptr_ty'
318 -- Again, stable pointers are just newtypes,
319 -- so we must see them! Hence tcSplit*
322 @foreign export dynamic@ lets you dress up Haskell IO actions
323 of some fixed type behind an externally callable interface (i.e.,
324 as a C function pointer). Useful for callbacks and stuff.
327 foreign export dynamic f :: (Addr -> Int -> IO Int) -> IO Addr
329 -- Haskell-visible constructor, which is generated from the above:
330 -- SUP: No check for NULL from createAdjustor anymore???
332 f :: (Addr -> Int -> IO Int) -> IO Addr
334 bindIO (newStablePtr cback)
335 (\StablePtr sp# -> IO (\s1# ->
336 case _ccall_ createAdjustor cconv sp# ``f_helper'' s1# of
337 (# s2#, a# #) -> (# s2#, A# a# #)))
339 foreign export "f_helper" f_helper :: StablePtr (Addr -> Int -> IO Int) -> Addr -> Int -> IO Int
340 -- `special' foreign export that invokes the closure pointed to by the
345 dsFExportDynamic :: Module
348 -> DsM ([Binding], SDoc, SDoc)
349 dsFExportDynamic mod_name id cconv
350 = newSysLocalDs ty `thenDs` \ fe_id ->
352 -- hack: need to get at the name of the C stub we're about to generate.
353 fe_nm = _PK_ (moduleUserString mod_name ++ "_" ++ toCName fe_id)
355 dsFExport mod_name id export_ty fe_nm cconv True `thenDs` \ (feb, fe, h_code, c_code) ->
356 newSysLocalDs arg_ty `thenDs` \ cback ->
357 dsLookupGlobalValue newStablePtrName `thenDs` \ newStablePtrId ->
359 mk_stbl_ptr_app = mkApps (Var newStablePtrId) [ Type arg_ty, Var cback ]
361 dsLookupGlobalValue bindIOName `thenDs` \ bindIOId ->
362 newSysLocalDs (mkTyConApp stablePtrTyCon [arg_ty]) `thenDs` \ stbl_value ->
365 = mkApps (Var bindIOId)
366 [ Type (mkTyConApp stablePtrTyCon [arg_ty])
373 The arguments to the external function which will
374 create a little bit of (template) code on the fly
375 for allowing the (stable pointed) Haskell closure
376 to be entered using an external calling convention
379 adj_args = [ mkIntLitInt (ccallConvToInt cconv)
381 , mkLit (MachLabel fe_nm)
383 -- name of external entry point providing these services.
384 -- (probably in the RTS.)
385 adjustor = SLIT("createAdjustor")
387 dsCCall adjustor adj_args PlayRisky False io_res_ty `thenDs` \ ccall_adj ->
388 -- PlayRisky: the adjustor doesn't allocate in the Haskell heap or do a callback
389 let ccall_adj_ty = exprType ccall_adj
390 ccall_io_adj = mkLams [stbl_value] $
391 Note (Coerce io_res_ty ccall_adj_ty)
393 io_app = mkLams tvs $
395 stbl_app ccall_io_adj res_ty
396 fed = (id `setInlinePragma` neverInlinePrag, io_app)
397 -- Never inline the f.e.d. function, because the litlit
398 -- might not be in scope in other modules.
400 returnDs ([fed, fe], h_code, c_code)
404 (tvs,sans_foralls) = tcSplitForAllTys ty
405 ([arg_ty], io_res_ty) = tcSplitFunTys sans_foralls
406 [res_ty] = tcTyConAppArgs io_res_ty
407 -- Must use tcSplit* to see the (IO t), which is a newtype
408 export_ty = mkFunTy (mkTyConApp stablePtrTyCon [arg_ty]) arg_ty
410 toCName :: Id -> String
411 toCName i = showSDoc (pprCode CStyle (ppr (idName i)))
416 \subsection{Generating @foreign export@ stubs}
420 For each @foreign export@ function, a C stub function is generated.
421 The C stub constructs the application of the exported Haskell function
422 using the hugs/ghc rts invocation API.
425 fexportEntry :: String
433 fexportEntry mod_nm c_nm helper args res_ty cc isDyn = (header_bits, c_bits)
435 -- name of the (Haskell) helper function generated by the desugarer.
436 h_nm = ppr helper <> text "_closure"
437 -- prototype for the exported function.
438 header_bits = ptext SLIT("extern") <+> fun_proto <> semi
440 fun_proto = cResType <+> pprCconv <+> ptext c_nm <>
441 parens (hsep (punctuate comma (zipWith (<+>) cParamTypes proto_args)))
448 , text "SchedulerStatus rc;"
450 -- create the application + perform it.
451 , text "rc=rts_evalIO" <>
452 parens (foldl appArg (text "(StgClosure*)&" <> h_nm) (zip args c_args) <> comma <> text "&ret") <> semi
453 , text "rts_checkSchedStatus" <> parens (doubleQuotes (ptext c_nm)
454 <> comma <> text "rc") <> semi
455 , text "return" <> return_what <> semi
460 text "rts_apply" <> parens (acc <> comma <> mkHObj a <> parens c_a)
462 cParamTypes = map showStgType real_args
464 res_ty_is_unit = res_ty `eqType` unitTy -- Look through any newtypes
466 cResType | res_ty_is_unit = text "void"
467 | otherwise = showStgType res_ty
469 pprCconv = case cc of
471 StdCallConv -> ppr cc
473 declareResult = text "HaskellObj ret;"
475 externDecl = mkExtern (text "HaskellObj") h_nm
477 mkExtern ty nm = text "extern" <+> ty <+> nm <> semi
479 return_what | res_ty_is_unit = empty
480 | otherwise = parens (unpackHObj res_ty <> parens (text "ret"))
482 c_args = mkCArgNames 0 args
485 If we're generating an entry point for a 'foreign export ccall dynamic',
486 then we receive the return address of the C function that wants to
487 invoke a Haskell function as any other C function, as second arg.
488 This arg is unused within the body of the generated C stub, but
489 needed by the Adjustor.c code to get the stack cleanup right.
491 (proto_args, real_args)
493 CCallConv | isDyn -> ( text "a0" : text "a_" : mkCArgNames 1 (tail args)
494 , head args : addrTy : tail args)
495 other -> (mkCArgNames 0 args, args)
497 mkCArgNames :: Int -> [a] -> [SDoc]
498 mkCArgNames n as = zipWith (\ _ n -> text ('a':show n)) as [n..]
500 mkHObj :: Type -> SDoc
501 mkHObj t = text "rts_mk" <> text (showFFIType t)
503 unpackHObj :: Type -> SDoc
504 unpackHObj t = text "rts_get" <> text (showFFIType t)
506 showStgType :: Type -> SDoc
507 showStgType t = text "Hs" <> text (showFFIType t)
509 showFFIType :: Type -> String
510 showFFIType t = getOccString (getName tc)
512 tc = case tcSplitTyConApp_maybe (repType t) of
514 Nothing -> pprPanic "showFFIType" (ppr t)