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 )
28 import TcType ( Type, mkFunTys, mkForAllTys, mkTyConApp,
29 mkFunTy, tcSplitTyConApp_maybe,
30 tcSplitForAllTys, tcSplitFunTys, tcTyConAppArgs,
33 import HscTypes ( ForeignStubs(..) )
34 import ForeignCall ( ForeignCall(..), CCallSpec(..),
37 CCallConv(..), ccallConvToInt,
40 import CStrings ( CLabelString )
41 import TysWiredIn ( unitTy, stablePtrTyCon )
42 import TysPrim ( addrPrimTy )
43 import PrelNames ( hasKey, ioTyConKey, newStablePtrName, bindIOName )
44 import BasicTypes ( Activation( NeverActive ) )
46 import Maybe ( fromJust )
50 Desugaring of @foreign@ declarations is naturally split up into
51 parts, an @import@ and an @export@ part. A @foreign import@
54 foreign import cc nm f :: prim_args -> IO prim_res
58 f :: prim_args -> IO prim_res
59 f a1 ... an = _ccall_ nm cc a1 ... an
61 so we reuse the desugaring code in @DsCCall@ to deal with these.
64 type Binding = (Id, CoreExpr) -- No rec/nonrec structure;
65 -- the occurrence analyser will sort it all out
67 dsForeigns :: [TypecheckedForeignDecl]
68 -> DsM (ForeignStubs, [Binding])
70 = returnDs (NoStubs, [])
72 = foldlDs combine (ForeignStubs empty empty [] [], []) fos
74 combine (ForeignStubs acc_h acc_c acc_hdrs acc_feb, acc_f)
75 (ForeignImport id _ spec depr loc)
76 = dsFImport id spec `thenDs` \ (bs, h, c, mbhd) ->
77 warnDepr depr loc `thenDs` \ _ ->
78 returnDs (ForeignStubs (h $$ acc_h)
84 combine (ForeignStubs acc_h acc_c acc_hdrs acc_feb, acc_f)
85 (ForeignExport id _ (CExport (CExportStatic ext_nm cconv)) depr loc)
86 = dsFExport id (idType id)
87 ext_nm cconv False `thenDs` \(h, c) ->
88 warnDepr depr loc `thenDs` \_ ->
89 returnDs (ForeignStubs (h $$ acc_h) (c $$ acc_c) acc_hdrs (id:acc_feb),
97 warnDepr False _ = returnDs ()
98 warnDepr True loc = dsWarn (loc, msg)
100 msg = ptext SLIT("foreign declaration uses deprecated non-standard syntax")
104 %************************************************************************
106 \subsection{Foreign import}
108 %************************************************************************
110 Desugaring foreign imports is just the matter of creating a binding
111 that on its RHS unboxes its arguments, performs the external call
112 (using the @CCallOp@ primop), before boxing the result up and returning it.
114 However, we create a worker/wrapper pair, thus:
116 foreign import f :: Int -> IO Int
118 f x = IO ( \s -> case x of { I# x# ->
119 case fw s x# of { (# s1, y# #) ->
122 fw s x# = ccall f s x#
124 The strictness/CPR analyser won't do this automatically because it doesn't look
125 inside returned tuples; but inlining this wrapper is a Really Good Idea
126 because it exposes the boxing to the call site.
131 -> DsM ([Binding], SDoc, SDoc, Maybe FastString)
132 dsFImport id (CImport cconv safety header lib spec)
133 = dsCImport id spec cconv safety no_hdrs `thenDs` \(ids, h, c) ->
134 returnDs (ids, h, c, if no_hdrs then Nothing else Just header)
136 no_hdrs = nullFastString header
138 -- FIXME: the `lib' field is needed for .NET ILX generation when invoking
139 -- routines that are external to the .NET runtime, but GHC doesn't
140 -- support such calls yet; if `nullFastString lib', the value was not given
141 dsFImport id (DNImport spec)
142 = dsFCall id (DNCall spec) True {- No headers -} `thenDs` \(ids, h, c) ->
143 returnDs (ids, h, c, Nothing)
149 -> Bool -- True <=> no headers in the f.i decl
150 -> DsM ([Binding], SDoc, SDoc)
151 dsCImport id (CLabel cid) _ _ no_hdrs
152 = ASSERT(fromJust resTy `eqType` addrPrimTy) -- typechecker ensures this
153 returnDs ([(setImpInline no_hdrs id, rhs)], empty, empty)
155 (resTy, foRhs) = resultWrapper (idType id)
156 rhs = foRhs (mkLit (MachLabel cid))
157 dsCImport id (CFunction target) cconv safety no_hdrs
158 = dsFCall id (CCall (CCallSpec target cconv safety)) no_hdrs
159 dsCImport id CWrapper cconv _ _
160 = dsFExportDynamic id cconv
162 setImpInline :: Bool -- True <=> No #include headers
163 -- in the foreign import declaration
165 -- If there is a #include header in the foreign import
166 -- we make the worker non-inlinable, because we currently
167 -- don't keep the #include stuff in the CCallId, and hence
168 -- it won't be visible in the importing module, which can be
170 -- (The #include stuff is just collected from the foreign import
171 -- decls in a module.)
172 -- If you want to do cross-module inlining of the c-calls themselves,
173 -- put the #include stuff in the package spec, not the foreign
175 setImpInline True id = id
176 setImpInline False id = id `setInlinePragma` NeverActive
180 %************************************************************************
182 \subsection{Foreign calls}
184 %************************************************************************
187 dsFCall fn_id fcall no_hdrs
190 (tvs, fun_ty) = tcSplitForAllTys ty
191 (arg_tys, io_res_ty) = tcSplitFunTys fun_ty
192 -- Must use tcSplit* functions because we want to
193 -- see that (IO t) in the corner
195 newSysLocalsDs arg_tys `thenDs` \ args ->
196 mapAndUnzipDs unboxArg (map Var args) `thenDs` \ (val_args, arg_wrappers) ->
199 work_arg_ids = [v | Var v <- val_args] -- All guaranteed to be vars
201 -- These are the ids we pass to boxResult, which are used to decide
202 -- whether to touch# an argument after the call (used to keep
203 -- ForeignObj#s live across a 'safe' foreign import).
204 maybe_arg_ids | unsafe_call fcall = work_arg_ids
207 boxResult maybe_arg_ids io_res_ty `thenDs` \ (ccall_result_ty, res_wrapper) ->
209 getUniqueDs `thenDs` \ ccall_uniq ->
210 getUniqueDs `thenDs` \ work_uniq ->
213 worker_ty = mkForAllTys tvs (mkFunTys (map idType work_arg_ids) ccall_result_ty)
214 the_ccall_app = mkFCall ccall_uniq fcall val_args ccall_result_ty
215 work_rhs = mkLams tvs (mkLams work_arg_ids the_ccall_app)
216 work_id = setImpInline no_hdrs $ -- See comments with setImpInline
217 mkSysLocal (encodeFS FSLIT("$wccall")) work_uniq worker_ty
220 work_app = mkApps (mkVarApps (Var work_id) tvs) val_args
221 wrapper_body = foldr ($) (res_wrapper work_app) arg_wrappers
222 wrap_rhs = mkInlineMe (mkLams (tvs ++ args) wrapper_body)
224 returnDs ([(work_id, work_rhs), (fn_id, wrap_rhs)], empty, empty)
226 unsafe_call (CCall (CCallSpec _ _ safety)) = playSafe safety
227 unsafe_call (DNCall _) = False
231 %************************************************************************
233 \subsection{Foreign export}
235 %************************************************************************
237 The function that does most of the work for `@foreign export@' declarations.
238 (see below for the boilerplate code a `@foreign export@' declaration expands
241 For each `@foreign export foo@' in a module M we generate:
243 \item a C function `@foo@', which calls
244 \item a Haskell stub `@M.$ffoo@', which calls
246 the user-written Haskell function `@M.foo@'.
249 dsFExport :: Id -- Either the exported Id,
250 -- or the foreign-export-dynamic constructor
251 -> Type -- The type of the thing callable from C
252 -> CLabelString -- The name to export to C land
254 -> Bool -- True => foreign export dynamic
255 -- so invoke IO action that's hanging off
256 -- the first argument's stable pointer
257 -> DsM ( SDoc -- contents of Module_stub.h
258 , SDoc -- contents of Module_stub.c
261 dsFExport fn_id ty ext_name cconv isDyn
264 (tvs,sans_foralls) = tcSplitForAllTys ty
265 (fe_arg_tys', orig_res_ty) = tcSplitFunTys sans_foralls
266 -- We must use tcSplits here, because we want to see
267 -- the (IO t) in the corner of the type!
268 fe_arg_tys | isDyn = tail fe_arg_tys'
269 | otherwise = fe_arg_tys'
271 -- Look at the result type of the exported function, orig_res_ty
272 -- If it's IO t, return (t, True)
273 -- If it's plain t, return (t, False)
274 (case tcSplitTyConApp_maybe orig_res_ty of
275 -- We must use tcSplit here so that we see the (IO t) in
276 -- the type. [IO t is transparent to plain splitTyConApp.]
278 Just (ioTyCon, [res_ty])
279 -> ASSERT( ioTyCon `hasKey` ioTyConKey )
280 -- The function already returns IO t
281 returnDs (res_ty, True)
283 other -> -- The function returns t
284 returnDs (orig_res_ty, False)
286 `thenDs` \ (res_ty, -- t
287 is_IO_res_ty) -> -- Bool
290 = mkFExportCBits ext_name
291 (if isDyn then Nothing else Just fn_id)
292 fe_arg_tys res_ty is_IO_res_ty cconv
294 returnDs (h_stub, c_stub)
297 @foreign export dynamic@ lets you dress up Haskell IO actions
298 of some fixed type behind an externally callable interface (i.e.,
299 as a C function pointer). Useful for callbacks and stuff.
302 foreign export dynamic f :: (Addr -> Int -> IO Int) -> IO Addr
304 -- Haskell-visible constructor, which is generated from the above:
305 -- SUP: No check for NULL from createAdjustor anymore???
307 f :: (Addr -> Int -> IO Int) -> IO Addr
309 bindIO (newStablePtr cback)
310 (\StablePtr sp# -> IO (\s1# ->
311 case _ccall_ createAdjustor cconv sp# ``f_helper'' s1# of
312 (# s2#, a# #) -> (# s2#, A# a# #)))
314 foreign export "f_helper" f_helper :: StablePtr (Addr -> Int -> IO Int) -> Addr -> Int -> IO Int
315 -- `special' foreign export that invokes the closure pointed to by the
320 dsFExportDynamic :: Id
322 -> DsM ([Binding], SDoc, SDoc)
323 dsFExportDynamic id cconv
324 = newSysLocalDs ty `thenDs` \ fe_id ->
325 getModuleDs `thenDs` \ mod_name ->
327 -- hack: need to get at the name of the C stub we're about to generate.
328 fe_nm = mkFastString (moduleString mod_name ++ "_" ++ toCName fe_id)
330 dsFExport id export_ty fe_nm cconv True `thenDs` \ (h_code, c_code) ->
331 newSysLocalDs arg_ty `thenDs` \ cback ->
332 dsLookupGlobalId newStablePtrName `thenDs` \ newStablePtrId ->
334 mk_stbl_ptr_app = mkApps (Var newStablePtrId) [ Type arg_ty, Var cback ]
336 dsLookupGlobalId bindIOName `thenDs` \ bindIOId ->
337 newSysLocalDs (mkTyConApp stablePtrTyCon [arg_ty]) `thenDs` \ stbl_value ->
340 = mkApps (Var bindIOId)
341 [ Type (mkTyConApp stablePtrTyCon [arg_ty])
348 The arguments to the external function which will
349 create a little bit of (template) code on the fly
350 for allowing the (stable pointed) Haskell closure
351 to be entered using an external calling convention
354 adj_args = [ mkIntLitInt (ccallConvToInt cconv)
356 , mkLit (MachLabel fe_nm)
358 -- name of external entry point providing these services.
359 -- (probably in the RTS.)
360 adjustor = FSLIT("createAdjustor")
362 dsCCall adjustor adj_args PlayRisky False io_res_ty `thenDs` \ ccall_adj ->
363 -- PlayRisky: the adjustor doesn't allocate in the Haskell heap or do a callback
364 let ccall_adj_ty = exprType ccall_adj
365 ccall_io_adj = mkLams [stbl_value] $
366 Note (Coerce io_res_ty ccall_adj_ty)
368 io_app = mkLams tvs $
370 stbl_app ccall_io_adj res_ty
371 fed = (id `setInlinePragma` NeverActive, io_app)
372 -- Never inline the f.e.d. function, because the litlit
373 -- might not be in scope in other modules.
375 returnDs ([fed], h_code, c_code)
379 (tvs,sans_foralls) = tcSplitForAllTys ty
380 ([arg_ty], io_res_ty) = tcSplitFunTys sans_foralls
381 [res_ty] = tcTyConAppArgs io_res_ty
382 -- Must use tcSplit* to see the (IO t), which is a newtype
383 export_ty = mkFunTy (mkTyConApp stablePtrTyCon [arg_ty]) arg_ty
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 mkFExportCBits :: FastString
401 -> Maybe Id -- Just==static, Nothing==dynamic
404 -> Bool -- True <=> returns an IO type
407 mkFExportCBits c_nm maybe_target arg_htys res_hty is_IO_res_ty cc
408 = (header_bits, c_bits)
410 -- Create up types and names for the real args
411 arg_cnames, arg_ctys :: [SDoc]
412 arg_cnames = mkCArgNames 1 arg_htys
413 arg_ctys = map showStgType arg_htys
415 -- and also for auxiliary ones; the stable ptr in the dynamic case, and
416 -- a slot for the dummy return address in the dynamic + ccall case
417 extra_cnames_and_ctys
418 = case maybe_target of
419 Nothing -> [(text "the_stableptr", text "StgStablePtr")]
422 case (maybe_target, cc) of
423 (Nothing, CCallConv) -> [(text "original_return_addr", text "void*")]
426 all_cnames_and_ctys :: [(SDoc, SDoc)]
428 = extra_cnames_and_ctys ++ zip arg_cnames arg_ctys
430 -- stuff to do with the return type of the C function
431 res_hty_is_unit = res_hty `eqType` unitTy -- Look through any newtypes
433 cResType | res_hty_is_unit = text "void"
434 | otherwise = showStgType res_hty
436 -- Now we can cook up the prototype for the exported function.
437 pprCconv = case cc of
439 StdCallConv -> text (ccallConvAttribute cc)
441 header_bits = ptext SLIT("extern") <+> fun_proto <> semi
443 fun_proto = cResType <+> pprCconv <+> ftext c_nm <>
444 parens (hsep (punctuate comma (map (\(nm,ty) -> ty <+> nm)
445 all_cnames_and_ctys)))
447 -- the target which will form the root of what we ask rts_evalIO to run
449 = case maybe_target of
450 Nothing -> text "(StgClosure*)deRefStablePtr(the_stableptr)"
451 Just hs_fn -> char '&' <> ppr hs_fn <> text "_closure"
453 -- the expression we give to rts_evalIO
455 = foldl appArg the_cfun (zip arg_cnames arg_htys)
457 appArg acc (arg_cname, arg_hty)
459 <> parens (acc <> comma <> mkHObj arg_hty <> parens arg_cname)
461 -- various other bits for inside the fn
462 declareResult = text "HaskellObj ret;"
463 declareCResult | res_hty_is_unit = empty
464 | otherwise = cResType <+> text "cret;"
466 assignCResult | res_hty_is_unit = empty
468 text "cret=" <> unpackHObj res_hty <> parens (text "ret") <> semi
470 -- an extern decl for the fn being called
472 = case maybe_target of
474 Just hs_fn -> text "extern StgClosure " <> ppr hs_fn <> text "_closure" <> semi
476 -- finally, the whole darn thing
483 , text "SchedulerStatus rc;"
487 -- create the application + perform it.
488 , text "rc=rts_evalIO" <> parens (
489 text "rts_apply" <> parens (
491 <> text (if is_IO_res_ty
493 else "runNonIO_closure")
499 , text "rts_checkSchedStatus" <> parens (doubleQuotes (ftext c_nm)
500 <> comma <> text "rc") <> semi
502 , text "rts_unlock();"
503 , if res_hty_is_unit then empty
504 else text "return cret;"
509 mkCArgNames :: Int -> [a] -> [SDoc]
510 mkCArgNames n as = zipWith (\ _ n -> text ('a':show n)) as [n..]
512 mkHObj :: Type -> SDoc
513 mkHObj t = text "rts_mk" <> text (showFFIType t)
515 unpackHObj :: Type -> SDoc
516 unpackHObj t = text "rts_get" <> text (showFFIType t)
518 showStgType :: Type -> SDoc
519 showStgType t = text "Hs" <> text (showFFIType t)
521 showFFIType :: Type -> String
522 showFFIType t = getOccString (getName tc)
524 tc = case tcSplitTyConApp_maybe (repType t) of
526 Nothing -> pprPanic "showFFIType" (ppr t)