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(..), ForeignExport(..),
19 ForeignImport(..), CImportSpec(..) )
20 import TcHsSyn ( TypecheckedForeignDecl )
21 import CoreUtils ( exprType, mkInlineMe )
22 import Id ( Id, idType, idName, mkSysLocal, setInlinePragma )
23 import Literal ( Literal(..) )
24 import Module ( moduleString )
25 import Name ( getOccString, NamedThing(..) )
26 import OccName ( encodeFS )
27 import Type ( repType, eqType, typePrimRep )
28 import TcType ( Type, mkFunTys, mkForAllTys, mkTyConApp,
29 mkFunTy, tcSplitTyConApp_maybe,
30 tcSplitForAllTys, tcSplitFunTys, tcTyConAppArgs,
33 import BasicTypes ( Boxity(..) )
34 import HscTypes ( ForeignStubs(..) )
35 import ForeignCall ( ForeignCall(..), CCallSpec(..),
38 CCallConv(..), ccallConvToInt,
41 import CStrings ( CLabelString )
42 import TysWiredIn ( unitTy, tupleTyCon )
43 import TysPrim ( addrPrimTy, mkStablePtrPrimTy, alphaTy )
44 import PrimRep ( getPrimRepSizeInBytes )
45 import PrelNames ( hasKey, ioTyConKey, stablePtrTyConName, newStablePtrName, bindIOName,
47 import BasicTypes ( Activation( NeverActive ) )
49 import Maybe ( fromJust )
53 Desugaring of @foreign@ declarations is naturally split up into
54 parts, an @import@ and an @export@ part. A @foreign import@
57 foreign import cc nm f :: prim_args -> IO prim_res
61 f :: prim_args -> IO prim_res
62 f a1 ... an = _ccall_ nm cc a1 ... an
64 so we reuse the desugaring code in @DsCCall@ to deal with these.
67 type Binding = (Id, CoreExpr) -- No rec/nonrec structure;
68 -- the occurrence analyser will sort it all out
70 dsForeigns :: [TypecheckedForeignDecl]
71 -> DsM (ForeignStubs, [Binding])
73 = returnDs (NoStubs, [])
75 = foldlDs combine (ForeignStubs empty empty [] [], []) fos
77 combine (ForeignStubs acc_h acc_c acc_hdrs acc_feb, acc_f)
78 (ForeignImport id _ spec depr loc)
79 = dsFImport id spec `thenDs` \ (bs, h, c, mbhd) ->
80 warnDepr depr loc `thenDs` \ _ ->
81 returnDs (ForeignStubs (h $$ acc_h)
87 combine (ForeignStubs acc_h acc_c acc_hdrs acc_feb, acc_f)
88 (ForeignExport id _ (CExport (CExportStatic ext_nm cconv)) depr loc)
89 = dsFExport id (idType id)
90 ext_nm cconv False `thenDs` \(h, c, _) ->
91 warnDepr depr loc `thenDs` \_ ->
92 returnDs (ForeignStubs (h $$ acc_h) (c $$ acc_c) acc_hdrs (id:acc_feb),
100 warnDepr False _ = returnDs ()
101 warnDepr True loc = dsWarn (loc, msg)
103 msg = ptext SLIT("foreign declaration uses deprecated non-standard syntax")
107 %************************************************************************
109 \subsection{Foreign import}
111 %************************************************************************
113 Desugaring foreign imports is just the matter of creating a binding
114 that on its RHS unboxes its arguments, performs the external call
115 (using the @CCallOp@ primop), before boxing the result up and returning it.
117 However, we create a worker/wrapper pair, thus:
119 foreign import f :: Int -> IO Int
121 f x = IO ( \s -> case x of { I# x# ->
122 case fw s x# of { (# s1, y# #) ->
125 fw s x# = ccall f s x#
127 The strictness/CPR analyser won't do this automatically because it doesn't look
128 inside returned tuples; but inlining this wrapper is a Really Good Idea
129 because it exposes the boxing to the call site.
134 -> DsM ([Binding], SDoc, SDoc, Maybe FastString)
135 dsFImport id (CImport cconv safety header lib spec)
136 = dsCImport id spec cconv safety no_hdrs `thenDs` \(ids, h, c) ->
137 returnDs (ids, h, c, if no_hdrs then Nothing else Just header)
139 no_hdrs = nullFastString header
141 -- FIXME: the `lib' field is needed for .NET ILX generation when invoking
142 -- routines that are external to the .NET runtime, but GHC doesn't
143 -- support such calls yet; if `nullFastString lib', the value was not given
144 dsFImport id (DNImport spec)
145 = dsFCall id (DNCall spec) True {- No headers -} `thenDs` \(ids, h, c) ->
146 returnDs (ids, h, c, Nothing)
152 -> Bool -- True <=> no headers in the f.i decl
153 -> DsM ([Binding], SDoc, SDoc)
154 dsCImport id (CLabel cid) _ _ no_hdrs
155 = resultWrapper (idType id) `thenDs` \ (resTy, foRhs) ->
156 ASSERT(fromJust resTy `eqType` addrPrimTy) -- typechecker ensures this
157 let rhs = foRhs (mkLit (MachLabel cid Nothing)) in
158 returnDs ([(setImpInline no_hdrs id, rhs)], empty, empty)
159 dsCImport id (CFunction target) cconv safety no_hdrs
160 = dsFCall id (CCall (CCallSpec target cconv safety)) no_hdrs
161 dsCImport id CWrapper cconv _ _
162 = dsFExportDynamic id cconv
164 setImpInline :: Bool -- True <=> No #include headers
165 -- in the foreign import declaration
167 -- If there is a #include header in the foreign import
168 -- we make the worker non-inlinable, because we currently
169 -- don't keep the #include stuff in the CCallId, and hence
170 -- it won't be visible in the importing module, which can be
172 -- (The #include stuff is just collected from the foreign import
173 -- decls in a module.)
174 -- If you want to do cross-module inlining of the c-calls themselves,
175 -- put the #include stuff in the package spec, not the foreign
177 setImpInline True id = id
178 setImpInline False id = id `setInlinePragma` NeverActive
182 %************************************************************************
184 \subsection{Foreign calls}
186 %************************************************************************
189 dsFCall fn_id fcall no_hdrs
192 (tvs, fun_ty) = tcSplitForAllTys ty
193 (arg_tys, io_res_ty) = tcSplitFunTys fun_ty
194 -- Must use tcSplit* functions because we want to
195 -- see that (IO t) in the corner
197 newSysLocalsDs arg_tys `thenDs` \ args ->
198 mapAndUnzipDs unboxArg (map Var args) `thenDs` \ (val_args, arg_wrappers) ->
201 work_arg_ids = [v | Var v <- val_args] -- All guaranteed to be vars
203 -- These are the ids we pass to boxResult, which are used to decide
204 -- whether to touch# an argument after the call (used to keep
205 -- ForeignObj#s live across a 'safe' foreign import).
206 maybe_arg_ids | unsafe_call fcall = work_arg_ids
216 dsLookupGlobalId checkDotnetResName `thenDs` \ check_id ->
217 return (Just check_id)
218 | otherwise = return Nothing
222 newSysLocalDs addrPrimTy `thenDs` \ err_res ->
223 returnDs (\ (mb_res_ty, resWrap) ->
225 Nothing -> (Just (mkTyConApp (tupleTyCon Unboxed 1)
228 Just x -> (Just (mkTyConApp (tupleTyCon Unboxed 2)
231 | otherwise = returnDs id
233 augmentResultDs `thenDs` \ augment ->
234 topConDs `thenDs` \ topCon ->
235 boxResult maybe_arg_ids augment topCon io_res_ty `thenDs` \ (ccall_result_ty, res_wrapper) ->
237 getUniqueDs `thenDs` \ ccall_uniq ->
238 getUniqueDs `thenDs` \ work_uniq ->
241 worker_ty = mkForAllTys tvs (mkFunTys (map idType work_arg_ids) ccall_result_ty)
242 the_ccall_app = mkFCall ccall_uniq fcall val_args ccall_result_ty
243 work_rhs = mkLams tvs (mkLams work_arg_ids the_ccall_app)
244 work_id = setImpInline no_hdrs $ -- See comments with setImpInline
245 mkSysLocal (encodeFS FSLIT("$wccall")) work_uniq worker_ty
248 work_app = mkApps (mkVarApps (Var work_id) tvs) val_args
249 wrapper_body = foldr ($) (res_wrapper work_app) arg_wrappers
250 wrap_rhs = mkInlineMe (mkLams (tvs ++ args) wrapper_body)
252 returnDs ([(work_id, work_rhs), (fn_id, wrap_rhs)], empty, empty)
254 unsafe_call (CCall (CCallSpec _ _ safety)) = playSafe safety
255 unsafe_call (DNCall _) = False
259 %************************************************************************
261 \subsection{Foreign export}
263 %************************************************************************
265 The function that does most of the work for `@foreign export@' declarations.
266 (see below for the boilerplate code a `@foreign export@' declaration expands
269 For each `@foreign export foo@' in a module M we generate:
271 \item a C function `@foo@', which calls
272 \item a Haskell stub `@M.$ffoo@', which calls
274 the user-written Haskell function `@M.foo@'.
277 dsFExport :: Id -- Either the exported Id,
278 -- or the foreign-export-dynamic constructor
279 -> Type -- The type of the thing callable from C
280 -> CLabelString -- The name to export to C land
282 -> Bool -- True => foreign export dynamic
283 -- so invoke IO action that's hanging off
284 -- the first argument's stable pointer
285 -> DsM ( SDoc -- contents of Module_stub.h
286 , SDoc -- contents of Module_stub.c
287 , [Type] -- arguments expected by stub function.
290 dsFExport fn_id ty ext_name cconv isDyn
293 (tvs,sans_foralls) = tcSplitForAllTys ty
294 (fe_arg_tys', orig_res_ty) = tcSplitFunTys sans_foralls
295 -- We must use tcSplits here, because we want to see
296 -- the (IO t) in the corner of the type!
297 fe_arg_tys | isDyn = tail fe_arg_tys'
298 | otherwise = fe_arg_tys'
300 -- Look at the result type of the exported function, orig_res_ty
301 -- If it's IO t, return (t, True)
302 -- If it's plain t, return (t, False)
303 (case tcSplitTyConApp_maybe orig_res_ty of
304 -- We must use tcSplit here so that we see the (IO t) in
305 -- the type. [IO t is transparent to plain splitTyConApp.]
307 Just (ioTyCon, [res_ty])
308 -> ASSERT( ioTyCon `hasKey` ioTyConKey )
309 -- The function already returns IO t
310 returnDs (res_ty, True)
312 other -> -- The function returns t
313 returnDs (orig_res_ty, False)
315 `thenDs` \ (res_ty, -- t
316 is_IO_res_ty) -> -- Bool
318 mkFExportCBits ext_name
319 (if isDyn then Nothing else Just fn_id)
320 fe_arg_tys res_ty is_IO_res_ty cconv
323 @foreign export dynamic@ lets you dress up Haskell IO actions
324 of some fixed type behind an externally callable interface (i.e.,
325 as a C function pointer). Useful for callbacks and stuff.
328 foreign export dynamic f :: (Addr -> Int -> IO Int) -> IO Addr
330 -- Haskell-visible constructor, which is generated from the above:
331 -- SUP: No check for NULL from createAdjustor anymore???
333 f :: (Addr -> Int -> IO Int) -> IO Addr
335 bindIO (newStablePtr cback)
336 (\StablePtr sp# -> IO (\s1# ->
337 case _ccall_ createAdjustor cconv sp# ``f_helper'' s1# of
338 (# s2#, a# #) -> (# s2#, A# a# #)))
340 foreign export "f_helper" f_helper :: StablePtr (Addr -> Int -> IO Int) -> Addr -> Int -> IO Int
341 -- `special' foreign export that invokes the closure pointed to by the
346 dsFExportDynamic :: Id
348 -> DsM ([Binding], SDoc, SDoc)
349 dsFExportDynamic id cconv
350 = newSysLocalDs ty `thenDs` \ fe_id ->
351 getModuleDs `thenDs` \ mod_name ->
353 -- hack: need to get at the name of the C stub we're about to generate.
354 fe_nm = mkFastString (moduleString mod_name ++ "_" ++ toCName fe_id)
356 newSysLocalDs arg_ty `thenDs` \ cback ->
357 dsLookupGlobalId newStablePtrName `thenDs` \ newStablePtrId ->
358 dsLookupTyCon stablePtrTyConName `thenDs` \ stable_ptr_tycon ->
360 mk_stbl_ptr_app = mkApps (Var newStablePtrId) [ Type arg_ty, Var cback ]
361 stable_ptr_ty = mkTyConApp stable_ptr_tycon [arg_ty]
362 export_ty = mkFunTy stable_ptr_ty arg_ty
364 dsLookupGlobalId bindIOName `thenDs` \ bindIOId ->
365 newSysLocalDs stable_ptr_ty `thenDs` \ stbl_value ->
366 dsFExport id export_ty fe_nm cconv True `thenDs` \ (h_code, c_code, stub_args) ->
368 stbl_app cont ret_ty = mkApps (Var bindIOId)
375 The arguments to the external function which will
376 create a little bit of (template) code on the fly
377 for allowing the (stable pointed) Haskell closure
378 to be entered using an external calling convention
381 adj_args = [ mkIntLitInt (ccallConvToInt cconv)
383 , mkLit (MachLabel fe_nm mb_sz_args)
385 -- name of external entry point providing these services.
386 -- (probably in the RTS.)
387 adjustor = FSLIT("createAdjustor")
389 sz_args = sum (map (getPrimRepSizeInBytes . typePrimRep) stub_args)
390 mb_sz_args = case cconv of
391 StdCallConv -> Just sz_args
394 dsCCall adjustor adj_args PlayRisky False io_res_ty `thenDs` \ ccall_adj ->
395 -- PlayRisky: the adjustor doesn't allocate in the Haskell heap or do a callback
396 let ccall_adj_ty = exprType ccall_adj
397 ccall_io_adj = mkLams [stbl_value] $
398 Note (Coerce io_res_ty ccall_adj_ty)
400 io_app = mkLams tvs $
402 stbl_app ccall_io_adj res_ty
403 fed = (id `setInlinePragma` NeverActive, io_app)
404 -- Never inline the f.e.d. function, because the litlit
405 -- might not be in scope in other modules.
407 returnDs ([fed], h_code, c_code)
411 (tvs,sans_foralls) = tcSplitForAllTys ty
412 ([arg_ty], io_res_ty) = tcSplitFunTys sans_foralls
413 [res_ty] = tcTyConAppArgs io_res_ty
414 -- Must use tcSplit* to see the (IO t), which is a newtype
416 toCName :: Id -> String
417 toCName i = showSDoc (pprCode CStyle (ppr (idName i)))
422 \subsection{Generating @foreign export@ stubs}
426 For each @foreign export@ function, a C stub function is generated.
427 The C stub constructs the application of the exported Haskell function
428 using the hugs/ghc rts invocation API.
431 mkFExportCBits :: FastString
432 -> Maybe Id -- Just==static, Nothing==dynamic
435 -> Bool -- True <=> returns an IO type
437 -> (SDoc, SDoc, [Type])
438 mkFExportCBits c_nm maybe_target arg_htys res_hty is_IO_res_ty cc
439 = (header_bits, c_bits, all_arg_tys)
441 -- Create up types and names for the real args
442 arg_cnames, arg_ctys :: [SDoc]
443 arg_cnames = mkCArgNames 1 arg_htys
444 arg_ctys = map showStgType arg_htys
446 -- and also for auxiliary ones; the stable ptr in the dynamic case, and
447 -- a slot for the dummy return address in the dynamic + ccall case
449 = case maybe_target of
450 Nothing -> [((text "the_stableptr", text "StgStablePtr"), mkStablePtrPrimTy alphaTy)]
453 case (maybe_target, cc) of
454 (Nothing, CCallConv) -> [((text "original_return_addr", text "void*"), addrPrimTy)]
457 all_cnames_and_ctys :: [(SDoc, SDoc)]
459 = map fst extra_cnames_and_tys ++ zip arg_cnames arg_ctys
462 = map snd extra_cnames_and_tys ++ arg_htys
464 -- stuff to do with the return type of the C function
465 res_hty_is_unit = res_hty `eqType` unitTy -- Look through any newtypes
467 cResType | res_hty_is_unit = text "void"
468 | otherwise = showStgType res_hty
470 -- Now we can cook up the prototype for the exported function.
471 pprCconv = case cc of
473 StdCallConv -> text (ccallConvAttribute cc)
475 header_bits = ptext SLIT("extern") <+> fun_proto <> semi
477 fun_proto = cResType <+> pprCconv <+> ftext c_nm <>
478 parens (hsep (punctuate comma (map (\(nm,ty) -> ty <+> nm)
479 all_cnames_and_ctys)))
481 -- the target which will form the root of what we ask rts_evalIO to run
483 = case maybe_target of
484 Nothing -> text "(StgClosure*)deRefStablePtr(the_stableptr)"
485 Just hs_fn -> char '&' <> ppr hs_fn <> text "_closure"
487 -- the expression we give to rts_evalIO
489 = foldl appArg the_cfun (zip arg_cnames arg_htys)
491 appArg acc (arg_cname, arg_hty)
493 <> parens (acc <> comma <> mkHObj arg_hty <> parens arg_cname)
495 -- various other bits for inside the fn
496 declareResult = text "HaskellObj ret;"
497 declareCResult | res_hty_is_unit = empty
498 | otherwise = cResType <+> text "cret;"
500 assignCResult | res_hty_is_unit = empty
502 text "cret=" <> unpackHObj res_hty <> parens (text "ret") <> semi
504 -- an extern decl for the fn being called
506 = case maybe_target of
508 Just hs_fn -> text "extern StgClosure " <> ppr hs_fn <> text "_closure" <> semi
510 -- finally, the whole darn thing
517 , text "SchedulerStatus rc;"
521 -- create the application + perform it.
522 , text "rc=rts_evalIO" <> parens (
523 text "rts_apply" <> parens (
525 <> text (if is_IO_res_ty
527 else "runNonIO_closure")
533 , text "rts_checkSchedStatus" <> parens (doubleQuotes (ftext c_nm)
534 <> comma <> text "rc") <> semi
536 , text "rts_unlock();"
537 , if res_hty_is_unit then empty
538 else text "return cret;"
543 mkCArgNames :: Int -> [a] -> [SDoc]
544 mkCArgNames n as = zipWith (\ _ n -> text ('a':show n)) as [n..]
546 mkHObj :: Type -> SDoc
547 mkHObj t = text "rts_mk" <> text (showFFIType t)
549 unpackHObj :: Type -> SDoc
550 unpackHObj t = text "rts_get" <> text (showFFIType t)
552 showStgType :: Type -> SDoc
553 showStgType t = text "Hs" <> text (showFFIType t)
555 showFFIType :: Type -> String
556 showFFIType t = getOccString (getName tc)
558 tc = case tcSplitTyConApp_maybe (repType t) of
560 Nothing -> pprPanic "showFFIType" (ppr t)