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"
12 import TcRnMonad -- temp
16 import DsCCall ( dsCCall, mkFCall, boxResult, unboxArg, resultWrapper )
19 import HsSyn ( ForeignDecl(..), ForeignExport(..), LForeignDecl,
20 ForeignImport(..), CImportSpec(..) )
21 import DataCon ( splitProductType_maybe )
23 import DataCon ( dataConSourceArity )
24 import Type ( isUnLiftedType )
26 import MachOp ( machRepByteWidth, MachRep(..) )
27 import SMRep ( argMachRep, typeCgRep )
28 import CoreUtils ( exprType, mkInlineMe )
29 import Id ( Id, idType, idName, mkSysLocal, setInlinePragma )
30 import Literal ( Literal(..), mkStringLit )
31 import Module ( moduleNameFS, moduleName )
32 import Name ( getOccString, NamedThing(..) )
33 import Type ( repType, coreEqType )
34 import TcType ( Type, mkFunTys, mkForAllTys, mkTyConApp,
35 mkFunTy, tcSplitTyConApp_maybe, tcSplitIOType_maybe,
36 tcSplitForAllTys, tcSplitFunTys, tcTyConAppArgs,
40 import BasicTypes ( Boxity(..) )
41 import HscTypes ( ForeignStubs(..) )
42 import ForeignCall ( ForeignCall(..), CCallSpec(..),
44 CExportSpec(..), CLabelString,
45 CCallConv(..), ccallConvToInt,
48 import TysWiredIn ( unitTy, tupleTyCon )
49 import TysPrim ( addrPrimTy, mkStablePtrPrimTy, alphaTy, intPrimTy )
50 import PrelNames ( stablePtrTyConName, newStablePtrName, bindIOName,
52 import BasicTypes ( Activation( NeverActive ) )
53 import SrcLoc ( Located(..), unLoc )
55 import Maybe ( fromJust, isNothing )
59 Desugaring of @foreign@ declarations is naturally split up into
60 parts, an @import@ and an @export@ part. A @foreign import@
63 foreign import cc nm f :: prim_args -> IO prim_res
67 f :: prim_args -> IO prim_res
68 f a1 ... an = _ccall_ nm cc a1 ... an
70 so we reuse the desugaring code in @DsCCall@ to deal with these.
73 type Binding = (Id, CoreExpr) -- No rec/nonrec structure;
74 -- the occurrence analyser will sort it all out
76 dsForeigns :: [LForeignDecl Id]
77 -> DsM (ForeignStubs, [Binding])
79 = returnDs (NoStubs, [])
81 = foldlDs combine (ForeignStubs empty empty [] [], []) fos
83 combine stubs (L loc decl) = putSrcSpanDs loc (combine1 stubs decl)
85 combine1 (ForeignStubs acc_h acc_c acc_hdrs acc_feb, acc_f)
86 (ForeignImport id _ spec)
87 = traceIf (text "fi start" <+> ppr id) `thenDs` \ _ ->
88 dsFImport (unLoc id) spec `thenDs` \ (bs, h, c, mbhd) ->
89 traceIf (text "fi end" <+> ppr id) `thenDs` \ _ ->
90 returnDs (ForeignStubs (h $$ acc_h)
96 combine1 (ForeignStubs acc_h acc_c acc_hdrs acc_feb, acc_f)
97 (ForeignExport (L _ id) _ (CExport (CExportStatic ext_nm cconv)))
98 = dsFExport id (idType id)
99 ext_nm cconv False `thenDs` \(h, c, _, _) ->
100 returnDs (ForeignStubs (h $$ acc_h) (c $$ acc_c) acc_hdrs (id:acc_feb),
110 %************************************************************************
112 \subsection{Foreign import}
114 %************************************************************************
116 Desugaring foreign imports is just the matter of creating a binding
117 that on its RHS unboxes its arguments, performs the external call
118 (using the @CCallOp@ primop), before boxing the result up and returning it.
120 However, we create a worker/wrapper pair, thus:
122 foreign import f :: Int -> IO Int
124 f x = IO ( \s -> case x of { I# x# ->
125 case fw s x# of { (# s1, y# #) ->
128 fw s x# = ccall f s x#
130 The strictness/CPR analyser won't do this automatically because it doesn't look
131 inside returned tuples; but inlining this wrapper is a Really Good Idea
132 because it exposes the boxing to the call site.
137 -> DsM ([Binding], SDoc, SDoc, Maybe FastString)
138 dsFImport id (CImport cconv safety header lib spec)
139 = dsCImport id spec cconv safety no_hdrs `thenDs` \(ids, h, c) ->
140 returnDs (ids, h, c, if no_hdrs then Nothing else Just header)
142 no_hdrs = nullFS header
144 -- FIXME: the `lib' field is needed for .NET ILX generation when invoking
145 -- routines that are external to the .NET runtime, but GHC doesn't
146 -- support such calls yet; if `nullFastString lib', the value was not given
147 dsFImport id (DNImport spec)
148 = dsFCall id (DNCall spec) True {- No headers -} `thenDs` \(ids, h, c) ->
149 returnDs (ids, h, c, Nothing)
155 -> Bool -- True <=> no headers in the f.i decl
156 -> DsM ([Binding], SDoc, SDoc)
157 dsCImport id (CLabel cid) _ _ no_hdrs
158 = resultWrapper (idType id) `thenDs` \ (resTy, foRhs) ->
159 ASSERT(fromJust resTy `coreEqType` addrPrimTy) -- typechecker ensures this
160 let rhs = foRhs (mkLit (MachLabel cid Nothing)) in
161 returnDs ([(setImpInline no_hdrs id, rhs)], empty, empty)
162 dsCImport id (CFunction target) cconv safety no_hdrs
163 = dsFCall id (CCall (CCallSpec target cconv safety)) no_hdrs
164 dsCImport id CWrapper cconv _ _
165 = dsFExportDynamic id cconv
167 setImpInline :: Bool -- True <=> No #include headers
168 -- in the foreign import declaration
170 -- If there is a #include header in the foreign import
171 -- we make the worker non-inlinable, because we currently
172 -- don't keep the #include stuff in the CCallId, and hence
173 -- it won't be visible in the importing module, which can be
175 -- (The #include stuff is just collected from the foreign import
176 -- decls in a module.)
177 -- If you want to do cross-module inlining of the c-calls themselves,
178 -- put the #include stuff in the package spec, not the foreign
180 setImpInline True id = id
181 setImpInline False id = id `setInlinePragma` NeverActive
185 %************************************************************************
187 \subsection{Foreign calls}
189 %************************************************************************
192 dsFCall fn_id fcall no_hdrs
195 (tvs, fun_ty) = tcSplitForAllTys ty
196 (arg_tys, io_res_ty) = tcSplitFunTys fun_ty
197 -- Must use tcSplit* functions because we want to
198 -- see that (IO t) in the corner
200 newSysLocalsDs arg_tys `thenDs` \ args ->
201 mapAndUnzipDs unboxArg (map Var args) `thenDs` \ (val_args, arg_wrappers) ->
204 work_arg_ids = [v | Var v <- val_args] -- All guaranteed to be vars
213 dsLookupGlobalId checkDotnetResName `thenDs` \ check_id ->
214 return (Just check_id)
215 | otherwise = return Nothing
219 newSysLocalDs addrPrimTy `thenDs` \ err_res ->
220 returnDs (\ (mb_res_ty, resWrap) ->
222 Nothing -> (Just (mkTyConApp (tupleTyCon Unboxed 1)
225 Just x -> (Just (mkTyConApp (tupleTyCon Unboxed 2)
228 | otherwise = returnDs id
230 augmentResultDs `thenDs` \ augment ->
231 topConDs `thenDs` \ topCon ->
232 boxResult augment topCon io_res_ty `thenDs` \ (ccall_result_ty, res_wrapper) ->
234 newUnique `thenDs` \ ccall_uniq ->
235 newUnique `thenDs` \ work_uniq ->
238 worker_ty = mkForAllTys tvs (mkFunTys (map idType work_arg_ids) ccall_result_ty)
239 the_ccall_app = mkFCall ccall_uniq fcall val_args ccall_result_ty
240 work_rhs = mkLams tvs (mkLams work_arg_ids the_ccall_app)
241 work_id = setImpInline no_hdrs $ -- See comments with setImpInline
242 mkSysLocal FSLIT("$wccall") work_uniq worker_ty
245 work_app = mkApps (mkVarApps (Var work_id) tvs) val_args
246 wrapper_body = foldr ($) (res_wrapper work_app) arg_wrappers
247 wrap_rhs = mkInlineMe (mkLams (tvs ++ args) wrapper_body)
249 returnDs ([(work_id, work_rhs), (fn_id, wrap_rhs)], empty, empty)
253 %************************************************************************
255 \subsection{Foreign export}
257 %************************************************************************
259 The function that does most of the work for `@foreign export@' declarations.
260 (see below for the boilerplate code a `@foreign export@' declaration expands
263 For each `@foreign export foo@' in a module M we generate:
265 \item a C function `@foo@', which calls
266 \item a Haskell stub `@M.$ffoo@', which calls
268 the user-written Haskell function `@M.foo@'.
271 dsFExport :: Id -- Either the exported Id,
272 -- or the foreign-export-dynamic constructor
273 -> Type -- The type of the thing callable from C
274 -> CLabelString -- The name to export to C land
276 -> Bool -- True => foreign export dynamic
277 -- so invoke IO action that's hanging off
278 -- the first argument's stable pointer
279 -> DsM ( SDoc -- contents of Module_stub.h
280 , SDoc -- contents of Module_stub.c
281 , [MachRep] -- primitive arguments expected by stub function
282 , Int -- size of args to stub function
285 dsFExport fn_id ty ext_name cconv isDyn
288 (_tvs,sans_foralls) = tcSplitForAllTys ty
289 (fe_arg_tys', orig_res_ty) = tcSplitFunTys sans_foralls
290 -- We must use tcSplits here, because we want to see
291 -- the (IO t) in the corner of the type!
292 fe_arg_tys | isDyn = tail fe_arg_tys'
293 | otherwise = fe_arg_tys'
295 -- Look at the result type of the exported function, orig_res_ty
296 -- If it's IO t, return (t, True)
297 -- If it's plain t, return (t, False)
298 (case tcSplitIOType_maybe orig_res_ty of
299 Just (ioTyCon, res_ty) -> returnDs (res_ty, True)
300 -- The function already returns IO t
301 Nothing -> returnDs (orig_res_ty, False)
302 -- The function returns t
303 ) `thenDs` \ (res_ty, -- t
304 is_IO_res_ty) -> -- Bool
306 mkFExportCBits ext_name
307 (if isDyn then Nothing else Just fn_id)
308 fe_arg_tys res_ty is_IO_res_ty cconv
311 @foreign import "wrapper"@ (previously "foreign export dynamic") lets
312 you dress up Haskell IO actions of some fixed type behind an
313 externally callable interface (i.e., as a C function pointer). Useful
314 for callbacks and stuff.
317 type Fun = Bool -> Int -> IO Int
318 foreign import "wrapper" f :: Fun -> IO (FunPtr Fun)
320 -- Haskell-visible constructor, which is generated from the above:
321 -- SUP: No check for NULL from createAdjustor anymore???
323 f :: Fun -> IO (FunPtr Fun)
325 bindIO (newStablePtr cback)
326 (\StablePtr sp# -> IO (\s1# ->
327 case _ccall_ createAdjustor cconv sp# ``f_helper'' s1# of
328 (# s2#, a# #) -> (# s2#, A# a# #)))
330 foreign import "&f_helper" f_helper :: FunPtr (StablePtr Fun -> Fun)
332 -- and the helper in C:
334 f_helper(StablePtr s, HsBool b, HsInt i)
336 rts_evalIO(rts_apply(rts_apply(deRefStablePtr(s),
337 rts_mkBool(b)), rts_mkInt(i)));
342 dsFExportDynamic :: Id
344 -> DsM ([Binding], SDoc, SDoc)
345 dsFExportDynamic id cconv
346 = newSysLocalDs ty `thenDs` \ fe_id ->
347 getModuleDs `thenDs` \ mod ->
349 -- hack: need to get at the name of the C stub we're about to generate.
350 fe_nm = mkFastString (unpackFS (zEncodeFS (moduleNameFS (moduleName mod))) ++ "_" ++ toCName fe_id)
352 newSysLocalDs arg_ty `thenDs` \ cback ->
353 dsLookupGlobalId newStablePtrName `thenDs` \ newStablePtrId ->
354 dsLookupTyCon stablePtrTyConName `thenDs` \ stable_ptr_tycon ->
356 mk_stbl_ptr_app = mkApps (Var newStablePtrId) [ Type arg_ty, Var cback ]
357 stable_ptr_ty = mkTyConApp stable_ptr_tycon [arg_ty]
358 export_ty = mkFunTy stable_ptr_ty arg_ty
360 dsLookupGlobalId bindIOName `thenDs` \ bindIOId ->
361 newSysLocalDs stable_ptr_ty `thenDs` \ stbl_value ->
362 dsFExport id export_ty fe_nm cconv True
363 `thenDs` \ (h_code, c_code, arg_reps, args_size) ->
365 stbl_app cont ret_ty = mkApps (Var bindIOId)
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 mb_sz_args)
381 , mkLit (mkStringLit arg_type_info)
383 -- name of external entry point providing these services.
384 -- (probably in the RTS.)
385 adjustor = FSLIT("createAdjustor")
387 arg_type_info = map repCharCode arg_reps
388 repCharCode F32 = 'f'
389 repCharCode F64 = 'd'
390 repCharCode I64 = 'l'
393 -- Determine the number of bytes of arguments to the stub function,
394 -- so that we can attach the '@N' suffix to its label if it is a
395 -- stdcall on Windows.
396 mb_sz_args = case cconv of
397 StdCallConv -> Just args_size
401 dsCCall adjustor adj_args PlayRisky io_res_ty `thenDs` \ ccall_adj ->
402 -- PlayRisky: the adjustor doesn't allocate in the Haskell heap or do a callback
403 let ccall_adj_ty = exprType ccall_adj
404 ccall_io_adj = mkLams [stbl_value] $
405 Note (Coerce io_res_ty ccall_adj_ty)
407 io_app = mkLams tvs $
409 stbl_app ccall_io_adj res_ty
410 fed = (id `setInlinePragma` NeverActive, io_app)
411 -- Never inline the f.e.d. function, because the litlit
412 -- might not be in scope in other modules.
414 returnDs ([fed], h_code, c_code)
418 (tvs,sans_foralls) = tcSplitForAllTys ty
419 ([arg_ty], io_res_ty) = tcSplitFunTys sans_foralls
420 [res_ty] = tcTyConAppArgs io_res_ty
421 -- Must use tcSplit* to see the (IO t), which is a newtype
423 toCName :: Id -> String
424 toCName i = showSDoc (pprCode CStyle (ppr (idName i)))
429 \subsection{Generating @foreign export@ stubs}
433 For each @foreign export@ function, a C stub function is generated.
434 The C stub constructs the application of the exported Haskell function
435 using the hugs/ghc rts invocation API.
438 mkFExportCBits :: FastString
439 -> Maybe Id -- Just==static, Nothing==dynamic
442 -> Bool -- True <=> returns an IO type
446 [MachRep], -- the argument reps
447 Int -- total size of arguments
449 mkFExportCBits c_nm maybe_target arg_htys res_hty is_IO_res_ty cc
450 = (header_bits, c_bits,
451 [rep | (_,_,_,rep) <- arg_info], -- just the real args
452 sum [ machRepByteWidth rep | (_,_,_,rep) <- aug_arg_info] -- all the args
455 -- list the arguments to the C function
456 arg_info :: [(SDoc, -- arg name
458 Type, -- Haskell type
459 MachRep)] -- the MachRep
460 arg_info = [ (text ('a':show n), showStgType ty, ty,
461 typeMachRep (getPrimTyOf ty))
462 | (ty,n) <- zip arg_htys [1..] ]
464 -- add some auxiliary args; the stable ptr in the wrapper case, and
465 -- a slot for the dummy return address in the wrapper + ccall case
467 | isNothing maybe_target = stable_ptr_arg : insertRetAddr cc arg_info
468 | otherwise = arg_info
471 (text "the_stableptr", text "StgStablePtr", undefined,
472 typeMachRep (mkStablePtrPrimTy alphaTy))
474 -- stuff to do with the return type of the C function
475 res_hty_is_unit = res_hty `coreEqType` unitTy -- Look through any newtypes
477 cResType | res_hty_is_unit = text "void"
478 | otherwise = showStgType res_hty
480 -- Now we can cook up the prototype for the exported function.
481 pprCconv = case cc of
483 StdCallConv -> text (ccallConvAttribute cc)
485 header_bits = ptext SLIT("extern") <+> fun_proto <> semi
487 fun_proto = cResType <+> pprCconv <+> ftext c_nm <>
488 parens (hsep (punctuate comma (map (\(nm,ty,_,_) -> ty <+> nm)
491 -- the target which will form the root of what we ask rts_evalIO to run
493 = case maybe_target of
494 Nothing -> text "(StgClosure*)deRefStablePtr(the_stableptr)"
495 Just hs_fn -> char '&' <> ppr hs_fn <> text "_closure"
497 cap = text "cap" <> comma
499 -- the expression we give to rts_evalIO
501 = foldl appArg the_cfun arg_info -- NOT aug_arg_info
503 appArg acc (arg_cname, _, arg_hty, _)
505 <> parens (cap <> acc <> comma <> mkHObj arg_hty <> parens (cap <> arg_cname))
507 -- various other bits for inside the fn
508 declareResult = text "HaskellObj ret;"
509 declareCResult | res_hty_is_unit = empty
510 | otherwise = cResType <+> text "cret;"
512 assignCResult | res_hty_is_unit = empty
514 text "cret=" <> unpackHObj res_hty <> parens (text "ret") <> semi
516 -- an extern decl for the fn being called
518 = case maybe_target of
520 Just hs_fn -> text "extern StgClosure " <> ppr hs_fn <> text "_closure" <> semi
523 -- Initialise foreign exports by registering a stable pointer from an
524 -- __attribute__((constructor)) function.
525 -- The alternative is to do this from stginit functions generated in
526 -- codeGen/CodeGen.lhs; however, stginit functions have a negative impact
527 -- on binary sizes and link times because the static linker will think that
528 -- all modules that are imported directly or indirectly are actually used by
530 -- (this is bad for big umbrella modules like Graphics.Rendering.OpenGL)
533 = case maybe_target of
537 [ text "static void stginit_export_" <> ppr hs_fn
538 <> text "() __attribute__((constructor));"
539 , text "static void stginit_export_" <> ppr hs_fn <> text "()"
540 , braces (text "getStablePtr"
541 <> parens (text "(StgPtr) &" <> ppr hs_fn <> text "_closure")
545 -- finally, the whole darn thing
552 , text "Capability *cap;"
555 , text "cap = rts_lock();"
556 -- create the application + perform it.
557 , text "cap=rts_evalIO" <> parens (
559 text "rts_apply" <> parens (
562 <> text (if is_IO_res_ty
564 else "runNonIO_closure")
570 , text "rts_checkSchedStatus" <> parens (doubleQuotes (ftext c_nm)
571 <> comma <> text "cap") <> semi
573 , text "rts_unlock(cap);"
574 , if res_hty_is_unit then empty
575 else text "return cret;"
580 -- NB. the calculation here isn't strictly speaking correct.
581 -- We have a primitive Haskell type (eg. Int#, Double#), and
582 -- we want to know the size, when passed on the C stack, of
583 -- the associated C type (eg. HsInt, HsDouble). We don't have
584 -- this information to hand, but we know what GHC's conventions
585 -- are for passing around the primitive Haskell types, so we
586 -- use that instead. I hope the two coincide --SDM
587 typeMachRep ty = argMachRep (typeCgRep ty)
589 mkHObj :: Type -> SDoc
590 mkHObj t = text "rts_mk" <> text (showFFIType t)
592 unpackHObj :: Type -> SDoc
593 unpackHObj t = text "rts_get" <> text (showFFIType t)
595 showStgType :: Type -> SDoc
596 showStgType t = text "Hs" <> text (showFFIType t)
598 showFFIType :: Type -> String
599 showFFIType t = getOccString (getName tc)
601 tc = case tcSplitTyConApp_maybe (repType t) of
603 Nothing -> pprPanic "showFFIType" (ppr t)
605 #if !defined(x86_64_TARGET_ARCH)
606 insertRetAddr CCallConv args = ret_addr_arg : args
607 insertRetAddr _ args = args
609 -- On x86_64 we insert the return address after the 6th
610 -- integer argument, because this is the point at which we
611 -- need to flush a register argument to the stack (See rts/Adjustor.c for
613 insertRetAddr CCallConv args = go 0 args
614 where go 6 args = ret_addr_arg : args
615 go n (arg@(_,_,_,rep):args)
616 | I64 <- rep = arg : go (n+1) args
617 | otherwise = arg : go n args
619 insertRetAddr _ args = args
622 ret_addr_arg = (text "original_return_addr", text "void*", undefined,
623 typeMachRep addrPrimTy)
625 -- This function returns the primitive type associated with the boxed
626 -- type argument to a foreign export (eg. Int ==> Int#).
627 getPrimTyOf :: Type -> Type
629 | isBoolTy rep_ty = intPrimTy
630 -- Except for Bool, the types we are interested in have a single constructor
631 -- with a single primitive-typed argument (see TcType.legalFEArgTyCon).
633 case splitProductType_maybe rep_ty of
634 Just (_, _, data_con, [prim_ty]) ->
635 ASSERT(dataConSourceArity data_con == 1)
636 ASSERT2(isUnLiftedType prim_ty, ppr prim_ty)
638 _other -> pprPanic "DsForeign.getPrimTyOf" (ppr ty)