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, mkVanillaGlobal, mkSysLocal,
24 import IdInfo ( vanillaIdInfo )
25 import Literal ( Literal(..) )
26 import Module ( Module, moduleUserString )
27 import Name ( mkGlobalName, nameModule, nameOccName, getOccString,
28 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,
45 import CStrings ( CLabelString )
46 import TysWiredIn ( addrTy, unitTy, stablePtrTyCon )
47 import TysPrim ( addrPrimTy )
48 import PrelNames ( hasKey, ioTyConKey, deRefStablePtrName, newStablePtrName,
49 bindIOName, returnIOName
51 import BasicTypes ( Activation( NeverActive ) )
52 import ErrUtils ( addShortWarnLocLine )
54 import Maybe ( fromJust )
57 Desugaring of @foreign@ declarations is naturally split up into
58 parts, an @import@ and an @export@ part. A @foreign import@
61 foreign import cc nm f :: prim_args -> IO prim_res
65 f :: prim_args -> IO prim_res
66 f a1 ... an = _ccall_ nm cc a1 ... an
68 so we reuse the desugaring code in @DsCCall@ to deal with these.
71 type Binding = (Id, CoreExpr) -- No rec/nonrec structure;
72 -- the occurrence analyser will sort it all out
75 -> [TypecheckedForeignDecl]
76 -> DsM ( [Id] -- Foreign-exported binders;
77 -- we have to generate code to register these
79 , SDoc -- Header file prototypes for
80 -- "foreign exported" functions.
81 , SDoc -- C stubs to use when calling
82 -- "foreign exported" functions.
83 , [FAST_STRING] -- headers that need to be included
84 -- into C code generated for this module
86 dsForeigns mod_name fos
87 = foldlDs combine ([], [], empty, empty, []) fos
89 combine (acc_feb, acc_f, acc_h, acc_c, acc_header)
90 (ForeignImport id _ spec depr loc)
91 = dsFImport mod_name id spec `thenDs` \(bs, h, c, hd) ->
92 warnDepr depr loc `thenDs` \_ ->
93 returnDs (acc_feb, bs ++ acc_f, h $$ acc_h, c $$ acc_c, hd ++ acc_header)
95 combine (acc_feb, acc_f, acc_h, acc_c, acc_header)
96 (ForeignExport id _ (CExport (CExportStatic ext_nm cconv)) depr loc)
97 = dsFExport mod_name id (idType id)
98 ext_nm cconv False `thenDs` \(h, c) ->
99 warnDepr depr loc `thenDs` \_ ->
100 returnDs (acc_feb, acc_f, h $$ acc_h, c $$ acc_c, acc_header)
102 warnDepr False _ = returnDs ()
103 warnDepr True loc = dsWarn (addShortWarnLocLine loc msg)
105 msg = ptext SLIT("foreign declaration uses deprecated non-standard syntax")
109 %************************************************************************
111 \subsection{Foreign import}
113 %************************************************************************
115 Desugaring foreign imports is just the matter of creating a binding
116 that on its RHS unboxes its arguments, performs the external call
117 (using the @CCallOp@ primop), before boxing the result up and returning it.
119 However, we create a worker/wrapper pair, thus:
121 foreign import f :: Int -> IO Int
123 f x = IO ( \s -> case x of { I# x# ->
124 case fw s x# of { (# s1, y# #) ->
127 fw s x# = ccall f s x#
129 The strictness/CPR analyser won't do this automatically because it doesn't look
130 inside returned tuples; but inlining this wrapper is a Really Good Idea
131 because it exposes the boxing to the call site.
137 -> DsM ([Binding], SDoc, SDoc, [FAST_STRING])
138 dsFImport modName id (CImport cconv safety header lib spec)
139 = dsCImport modName id spec cconv safety `thenDs` \(ids, h, c) ->
140 returnDs (ids, h, c, if _NULL_ header then [] else [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 `_NULL_ lib', the value was not given
144 dsFImport modName id (DNImport spec)
145 = dsFCall modName id (DNCall spec) `thenDs` \(ids, h, c) ->
146 returnDs (ids, h, c, [])
153 -> DsM ([Binding], SDoc, SDoc)
154 dsCImport modName id (CLabel cid) _ _
155 = ASSERT(fromJust resTy `eqType` addrPrimTy) -- typechecker ensures this
156 returnDs ([(id, rhs)], empty, empty)
158 (resTy, foRhs) = resultWrapper (idType id)
159 rhs = foRhs (mkLit (MachLabel cid))
160 dsCImport modName id (CFunction target) cconv safety
161 = dsFCall modName id (CCall (CCallSpec target cconv safety))
162 dsCImport modName id CWrapper cconv _
163 = dsFExportDynamic modName id cconv
167 %************************************************************************
169 \subsection{Foreign calls}
171 %************************************************************************
174 dsFCall mod_Name fn_id fcall
177 (tvs, fun_ty) = tcSplitForAllTys ty
178 (arg_tys, io_res_ty) = tcSplitFunTys fun_ty
179 -- Must use tcSplit* functions because we want to
180 -- see that (IO t) in the corner
182 newSysLocalsDs arg_tys `thenDs` \ args ->
183 mapAndUnzipDs unboxArg (map Var args) `thenDs` \ (val_args, arg_wrappers) ->
186 work_arg_ids = [v | Var v <- val_args] -- All guaranteed to be vars
188 -- These are the ids we pass to boxResult, which are used to decide
189 -- whether to touch# an argument after the call (used to keep
190 -- ForeignObj#s live across a 'safe' foreign import).
191 maybe_arg_ids | unsafe_call fcall = work_arg_ids
194 boxResult maybe_arg_ids io_res_ty `thenDs` \ (ccall_result_ty, res_wrapper) ->
196 getUniqueDs `thenDs` \ ccall_uniq ->
197 getUniqueDs `thenDs` \ work_uniq ->
200 worker_ty = mkForAllTys tvs (mkFunTys (map idType work_arg_ids) ccall_result_ty)
201 the_ccall_app = mkFCall ccall_uniq fcall val_args ccall_result_ty
202 work_rhs = mkLams tvs (mkLams work_arg_ids the_ccall_app)
203 work_id = mkSysLocal SLIT("$wccall") work_uniq worker_ty
206 work_app = mkApps (mkVarApps (Var work_id) tvs) val_args
207 wrapper_body = foldr ($) (res_wrapper work_app) arg_wrappers
208 wrap_rhs = mkInlineMe (mkLams (tvs ++ args) wrapper_body)
210 returnDs ([(work_id, work_rhs), (fn_id, wrap_rhs)], empty, empty)
212 unsafe_call (CCall (CCallSpec _ _ safety)) = playSafe safety
213 unsafe_call (DNCall _) = False
217 %************************************************************************
219 \subsection{Foreign export}
221 %************************************************************************
223 The function that does most of the work for `@foreign export@' declarations.
224 (see below for the boilerplate code a `@foreign export@' declaration expands
227 For each `@foreign export foo@' in a module M we generate:
229 \item a C function `@foo@', which calls
230 \item a Haskell stub `@M.$ffoo@', which calls
232 the user-written Haskell function `@M.foo@'.
236 -> Id -- Either the exported Id,
237 -- or the foreign-export-dynamic constructor
238 -> Type -- The type of the thing callable from C
239 -> CLabelString -- The name to export to C land
241 -> Bool -- True => foreign export dynamic
242 -- so invoke IO action that's hanging off
243 -- the first argument's stable pointer
244 -> DsM ( SDoc -- contents of Module_stub.h
245 , SDoc -- contents of Module_stub.c
248 dsFExport mod_name fn_id ty ext_name cconv isDyn
251 (tvs,sans_foralls) = tcSplitForAllTys ty
252 (fe_arg_tys', orig_res_ty) = tcSplitFunTys sans_foralls
253 -- We must use tcSplits here, because we want to see
254 -- the (IO t) in the corner of the type!
255 fe_arg_tys | isDyn = tail fe_arg_tys'
256 | otherwise = fe_arg_tys'
258 -- Look at the result type of the exported function, orig_res_ty
259 -- If it's IO t, return (t, True)
260 -- If it's plain t, return (t, False)
261 (case tcSplitTyConApp_maybe orig_res_ty of
262 -- We must use tcSplit here so that we see the (IO t) in
263 -- the type. [IO t is transparent to plain splitTyConApp.]
265 Just (ioTyCon, [res_ty])
266 -> ASSERT( ioTyCon `hasKey` ioTyConKey )
267 -- The function already returns IO t
268 returnDs (res_ty, True)
270 other -> -- The function returns t
271 returnDs (orig_res_ty, False)
273 `thenDs` \ (res_ty, -- t
274 is_IO_res_ty) -> -- Bool
279 = mkFExportCBits (moduleUserString mod) ext_name
280 (if isDyn then Nothing else Just fn_id)
281 fe_arg_tys res_ty is_IO_res_ty cconv
283 returnDs (h_stub, c_stub)
286 @foreign export dynamic@ lets you dress up Haskell IO actions
287 of some fixed type behind an externally callable interface (i.e.,
288 as a C function pointer). Useful for callbacks and stuff.
291 foreign export dynamic f :: (Addr -> Int -> IO Int) -> IO Addr
293 -- Haskell-visible constructor, which is generated from the above:
294 -- SUP: No check for NULL from createAdjustor anymore???
296 f :: (Addr -> Int -> IO Int) -> IO Addr
298 bindIO (newStablePtr cback)
299 (\StablePtr sp# -> IO (\s1# ->
300 case _ccall_ createAdjustor cconv sp# ``f_helper'' s1# of
301 (# s2#, a# #) -> (# s2#, A# a# #)))
303 foreign export "f_helper" f_helper :: StablePtr (Addr -> Int -> IO Int) -> Addr -> Int -> IO Int
304 -- `special' foreign export that invokes the closure pointed to by the
309 dsFExportDynamic :: Module
312 -> DsM ([Binding], SDoc, SDoc)
313 dsFExportDynamic mod_name id cconv
314 = newSysLocalDs ty `thenDs` \ fe_id ->
316 -- hack: need to get at the name of the C stub we're about to generate.
317 fe_nm = _PK_ (moduleUserString mod_name ++ "_" ++ toCName fe_id)
319 dsFExport mod_name id export_ty fe_nm cconv True `thenDs` \ (h_code, c_code) ->
320 newSysLocalDs arg_ty `thenDs` \ cback ->
321 dsLookupGlobalValue newStablePtrName `thenDs` \ newStablePtrId ->
323 mk_stbl_ptr_app = mkApps (Var newStablePtrId) [ Type arg_ty, Var cback ]
325 dsLookupGlobalValue bindIOName `thenDs` \ bindIOId ->
326 newSysLocalDs (mkTyConApp stablePtrTyCon [arg_ty]) `thenDs` \ stbl_value ->
329 = mkApps (Var bindIOId)
330 [ Type (mkTyConApp stablePtrTyCon [arg_ty])
337 The arguments to the external function which will
338 create a little bit of (template) code on the fly
339 for allowing the (stable pointed) Haskell closure
340 to be entered using an external calling convention
343 adj_args = [ mkIntLitInt (ccallConvToInt cconv)
345 , mkLit (MachLabel fe_nm)
347 -- name of external entry point providing these services.
348 -- (probably in the RTS.)
349 adjustor = SLIT("createAdjustor")
351 dsCCall adjustor adj_args PlayRisky False io_res_ty `thenDs` \ ccall_adj ->
352 -- PlayRisky: the adjustor doesn't allocate in the Haskell heap or do a callback
353 let ccall_adj_ty = exprType ccall_adj
354 ccall_io_adj = mkLams [stbl_value] $
355 Note (Coerce io_res_ty ccall_adj_ty)
357 io_app = mkLams tvs $
359 stbl_app ccall_io_adj res_ty
360 fed = (id `setInlinePragma` NeverActive, io_app)
361 -- Never inline the f.e.d. function, because the litlit
362 -- might not be in scope in other modules.
364 returnDs ([fed], h_code, c_code)
368 (tvs,sans_foralls) = tcSplitForAllTys ty
369 ([arg_ty], io_res_ty) = tcSplitFunTys sans_foralls
370 [res_ty] = tcTyConAppArgs io_res_ty
371 -- Must use tcSplit* to see the (IO t), which is a newtype
372 export_ty = mkFunTy (mkTyConApp stablePtrTyCon [arg_ty]) arg_ty
374 toCName :: Id -> String
375 toCName i = showSDoc (pprCode CStyle (ppr (idName i)))
380 \subsection{Generating @foreign export@ stubs}
384 For each @foreign export@ function, a C stub function is generated.
385 The C stub constructs the application of the exported Haskell function
386 using the hugs/ghc rts invocation API.
389 mkFExportCBits :: String
391 -> Maybe Id -- Just==static, Nothing==dynamic
394 -> Bool -- True <=> returns an IO type
397 mkFExportCBits mod_nm c_nm maybe_target arg_htys res_hty is_IO_res_ty cc
398 = (header_bits, c_bits)
400 -- Create up types and names for the real args
401 arg_cnames, arg_ctys :: [SDoc]
402 arg_cnames = mkCArgNames 1 arg_htys
403 arg_ctys = map showStgType arg_htys
405 -- and also for auxiliary ones; the stable ptr in the dynamic case, and
406 -- a slot for the dummy return address in the dynamic + ccall case
407 extra_cnames_and_ctys
408 = case maybe_target of
409 Nothing -> [(text "the_stableptr", text "StgStablePtr")]
412 case (maybe_target, cc) of
413 (Nothing, CCallConv) -> [(text "original_return_addr", text "void*")]
416 all_cnames_and_ctys :: [(SDoc, SDoc)]
418 = extra_cnames_and_ctys ++ zip arg_cnames arg_ctys
420 -- stuff to do with the return type of the C function
421 res_hty_is_unit = res_hty `eqType` unitTy -- Look through any newtypes
423 cResType | res_hty_is_unit = text "void"
424 | otherwise = showStgType res_hty
426 -- Now we can cook up the prototype for the exported function.
427 pprCconv = case cc of
429 StdCallConv -> text (ccallConvAttribute cc)
431 header_bits = ptext SLIT("extern") <+> fun_proto <> semi
433 fun_proto = cResType <+> pprCconv <+> ptext c_nm <>
434 parens (hsep (punctuate comma (map (\(nm,ty) -> ty <+> nm)
435 all_cnames_and_ctys)))
437 -- the target which will form the root of what we ask rts_evalIO to run
439 = case maybe_target of
440 Nothing -> text "(StgClosure*)deRefStablePtr(the_stableptr)"
441 Just hs_fn -> ppr hs_fn <> text "_closure"
443 -- the expression we give to rts_evalIO
445 = foldl appArg the_cfun (zip arg_cnames arg_htys)
447 appArg acc (arg_cname, arg_hty)
449 <> parens (acc <> comma <> mkHObj arg_hty <> parens arg_cname)
451 -- various other bits for inside the fn
452 declareResult = text "HaskellObj ret;"
454 return_what | res_hty_is_unit = empty
455 | otherwise = parens (unpackHObj res_hty <> parens (text "ret"))
457 -- an extern decl for the fn being called
459 = case maybe_target of
461 Just hs_fn -> text "extern StgClosure* " <> ppr hs_fn <> text "_closure" <> semi
463 -- finally, the whole darn thing
470 , text "SchedulerStatus rc;"
472 -- create the application + perform it.
473 , text (if is_IO_res_ty then "rc=rts_evalIO" else "rc=rts_eval")
474 <> parens (expr_to_run <+> comma <> text "&ret")
476 , text "rts_checkSchedStatus" <> parens (doubleQuotes (ptext c_nm)
477 <> comma <> text "rc") <> semi
478 , text "return" <> return_what <> semi
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 tcSplitTyConApp_maybe (repType t) of
500 Nothing -> pprPanic "showFFIType" (ppr t)