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 ( moduleFS )
32 import Name ( getOccString, NamedThing(..) )
33 import Type ( repType, coreEqType )
34 import TcType ( Type, mkFunTys, mkForAllTys, mkTyConApp,
35 mkFunTy, tcSplitTyConApp_maybe,
36 tcSplitForAllTys, tcSplitFunTys, tcTyConAppArgs,
39 import BasicTypes ( Boxity(..) )
40 import HscTypes ( ForeignStubs(..) )
41 import ForeignCall ( ForeignCall(..), CCallSpec(..),
43 CExportSpec(..), CLabelString,
44 CCallConv(..), ccallConvToInt,
47 import TysWiredIn ( unitTy, tupleTyCon )
48 import TysPrim ( addrPrimTy, mkStablePtrPrimTy, alphaTy )
49 import PrelNames ( hasKey, ioTyConKey, stablePtrTyConName, newStablePtrName, bindIOName,
51 import BasicTypes ( Activation( NeverActive ) )
52 import SrcLoc ( Located(..), unLoc )
54 import Maybe ( fromJust, isNothing )
58 Desugaring of @foreign@ declarations is naturally split up into
59 parts, an @import@ and an @export@ part. A @foreign import@
62 foreign import cc nm f :: prim_args -> IO prim_res
66 f :: prim_args -> IO prim_res
67 f a1 ... an = _ccall_ nm cc a1 ... an
69 so we reuse the desugaring code in @DsCCall@ to deal with these.
72 type Binding = (Id, CoreExpr) -- No rec/nonrec structure;
73 -- the occurrence analyser will sort it all out
75 dsForeigns :: [LForeignDecl Id]
76 -> DsM (ForeignStubs, [Binding])
78 = returnDs (NoStubs, [])
80 = foldlDs combine (ForeignStubs empty empty [] [], []) fos
82 combine stubs (L loc decl) = putSrcSpanDs loc (combine1 stubs decl)
84 combine1 (ForeignStubs acc_h acc_c acc_hdrs acc_feb, acc_f)
85 (ForeignImport id _ spec depr)
86 = traceIf (text "fi start" <+> ppr id) `thenDs` \ _ ->
87 dsFImport (unLoc id) spec `thenDs` \ (bs, h, c, mbhd) ->
88 warnDepr depr `thenDs` \ _ ->
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)) depr)
98 = dsFExport id (idType id)
99 ext_nm cconv False `thenDs` \(h, c, _, _) ->
100 warnDepr depr `thenDs` \_ ->
101 returnDs (ForeignStubs (h $$ acc_h) (c $$ acc_c) acc_hdrs (id:acc_feb),
109 warnDepr False = returnDs ()
110 warnDepr True = dsWarn msg
112 msg = ptext SLIT("foreign declaration uses deprecated non-standard syntax")
116 %************************************************************************
118 \subsection{Foreign import}
120 %************************************************************************
122 Desugaring foreign imports is just the matter of creating a binding
123 that on its RHS unboxes its arguments, performs the external call
124 (using the @CCallOp@ primop), before boxing the result up and returning it.
126 However, we create a worker/wrapper pair, thus:
128 foreign import f :: Int -> IO Int
130 f x = IO ( \s -> case x of { I# x# ->
131 case fw s x# of { (# s1, y# #) ->
134 fw s x# = ccall f s x#
136 The strictness/CPR analyser won't do this automatically because it doesn't look
137 inside returned tuples; but inlining this wrapper is a Really Good Idea
138 because it exposes the boxing to the call site.
143 -> DsM ([Binding], SDoc, SDoc, Maybe FastString)
144 dsFImport id (CImport cconv safety header lib spec)
145 = dsCImport id spec cconv safety no_hdrs `thenDs` \(ids, h, c) ->
146 returnDs (ids, h, c, if no_hdrs then Nothing else Just header)
148 no_hdrs = nullFS header
150 -- FIXME: the `lib' field is needed for .NET ILX generation when invoking
151 -- routines that are external to the .NET runtime, but GHC doesn't
152 -- support such calls yet; if `nullFastString lib', the value was not given
153 dsFImport id (DNImport spec)
154 = dsFCall id (DNCall spec) True {- No headers -} `thenDs` \(ids, h, c) ->
155 returnDs (ids, h, c, Nothing)
161 -> Bool -- True <=> no headers in the f.i decl
162 -> DsM ([Binding], SDoc, SDoc)
163 dsCImport id (CLabel cid) _ _ no_hdrs
164 = resultWrapper (idType id) `thenDs` \ (resTy, foRhs) ->
165 ASSERT(fromJust resTy `coreEqType` addrPrimTy) -- typechecker ensures this
166 let rhs = foRhs (mkLit (MachLabel cid Nothing)) in
167 returnDs ([(setImpInline no_hdrs id, rhs)], empty, empty)
168 dsCImport id (CFunction target) cconv safety no_hdrs
169 = dsFCall id (CCall (CCallSpec target cconv safety)) no_hdrs
170 dsCImport id CWrapper cconv _ _
171 = dsFExportDynamic id cconv
173 setImpInline :: Bool -- True <=> No #include headers
174 -- in the foreign import declaration
176 -- If there is a #include header in the foreign import
177 -- we make the worker non-inlinable, because we currently
178 -- don't keep the #include stuff in the CCallId, and hence
179 -- it won't be visible in the importing module, which can be
181 -- (The #include stuff is just collected from the foreign import
182 -- decls in a module.)
183 -- If you want to do cross-module inlining of the c-calls themselves,
184 -- put the #include stuff in the package spec, not the foreign
186 setImpInline True id = id
187 setImpInline False id = id `setInlinePragma` NeverActive
191 %************************************************************************
193 \subsection{Foreign calls}
195 %************************************************************************
198 dsFCall fn_id fcall no_hdrs
201 (tvs, fun_ty) = tcSplitForAllTys ty
202 (arg_tys, io_res_ty) = tcSplitFunTys fun_ty
203 -- Must use tcSplit* functions because we want to
204 -- see that (IO t) in the corner
206 newSysLocalsDs arg_tys `thenDs` \ args ->
207 mapAndUnzipDs unboxArg (map Var args) `thenDs` \ (val_args, arg_wrappers) ->
210 work_arg_ids = [v | Var v <- val_args] -- All guaranteed to be vars
219 dsLookupGlobalId checkDotnetResName `thenDs` \ check_id ->
220 return (Just check_id)
221 | otherwise = return Nothing
225 newSysLocalDs addrPrimTy `thenDs` \ err_res ->
226 returnDs (\ (mb_res_ty, resWrap) ->
228 Nothing -> (Just (mkTyConApp (tupleTyCon Unboxed 1)
231 Just x -> (Just (mkTyConApp (tupleTyCon Unboxed 2)
234 | otherwise = returnDs id
236 augmentResultDs `thenDs` \ augment ->
237 topConDs `thenDs` \ topCon ->
238 boxResult augment topCon io_res_ty `thenDs` \ (ccall_result_ty, res_wrapper) ->
240 newUnique `thenDs` \ ccall_uniq ->
241 newUnique `thenDs` \ work_uniq ->
244 worker_ty = mkForAllTys tvs (mkFunTys (map idType work_arg_ids) ccall_result_ty)
245 the_ccall_app = mkFCall ccall_uniq fcall val_args ccall_result_ty
246 work_rhs = mkLams tvs (mkLams work_arg_ids the_ccall_app)
247 work_id = setImpInline no_hdrs $ -- See comments with setImpInline
248 mkSysLocal FSLIT("$wccall") work_uniq worker_ty
251 work_app = mkApps (mkVarApps (Var work_id) tvs) val_args
252 wrapper_body = foldr ($) (res_wrapper work_app) arg_wrappers
253 wrap_rhs = mkInlineMe (mkLams (tvs ++ args) wrapper_body)
255 returnDs ([(work_id, work_rhs), (fn_id, wrap_rhs)], empty, empty)
257 unsafe_call (CCall (CCallSpec _ _ safety)) = playSafe safety
258 unsafe_call (DNCall _) = False
262 %************************************************************************
264 \subsection{Foreign export}
266 %************************************************************************
268 The function that does most of the work for `@foreign export@' declarations.
269 (see below for the boilerplate code a `@foreign export@' declaration expands
272 For each `@foreign export foo@' in a module M we generate:
274 \item a C function `@foo@', which calls
275 \item a Haskell stub `@M.$ffoo@', which calls
277 the user-written Haskell function `@M.foo@'.
280 dsFExport :: Id -- Either the exported Id,
281 -- or the foreign-export-dynamic constructor
282 -> Type -- The type of the thing callable from C
283 -> CLabelString -- The name to export to C land
285 -> Bool -- True => foreign export dynamic
286 -- so invoke IO action that's hanging off
287 -- the first argument's stable pointer
288 -> DsM ( SDoc -- contents of Module_stub.h
289 , SDoc -- contents of Module_stub.c
290 , [MachRep] -- primitive arguments expected by stub function
291 , Int -- size of args to stub function
294 dsFExport fn_id ty ext_name cconv isDyn
297 (_tvs,sans_foralls) = tcSplitForAllTys ty
298 (fe_arg_tys', orig_res_ty) = tcSplitFunTys sans_foralls
299 -- We must use tcSplits here, because we want to see
300 -- the (IO t) in the corner of the type!
301 fe_arg_tys | isDyn = tail fe_arg_tys'
302 | otherwise = fe_arg_tys'
304 -- Look at the result type of the exported function, orig_res_ty
305 -- If it's IO t, return (t, True)
306 -- If it's plain t, return (t, False)
307 (case tcSplitTyConApp_maybe orig_res_ty of
308 -- We must use tcSplit here so that we see the (IO t) in
309 -- the type. [IO t is transparent to plain splitTyConApp.]
311 Just (ioTyCon, [res_ty])
312 -> ASSERT( ioTyCon `hasKey` ioTyConKey )
313 -- The function already returns IO t
314 returnDs (res_ty, True)
316 other -> -- The function returns t
317 returnDs (orig_res_ty, False)
319 `thenDs` \ (res_ty, -- t
320 is_IO_res_ty) -> -- Bool
322 mkFExportCBits ext_name
323 (if isDyn then Nothing else Just fn_id)
324 fe_arg_tys res_ty is_IO_res_ty cconv
327 @foreign export dynamic@ lets you dress up Haskell IO actions
328 of some fixed type behind an externally callable interface (i.e.,
329 as a C function pointer). Useful for callbacks and stuff.
332 foreign export dynamic f :: (Addr -> Int -> IO Int) -> IO Addr
334 -- Haskell-visible constructor, which is generated from the above:
335 -- SUP: No check for NULL from createAdjustor anymore???
337 f :: (Addr -> Int -> IO Int) -> IO Addr
339 bindIO (newStablePtr cback)
340 (\StablePtr sp# -> IO (\s1# ->
341 case _ccall_ createAdjustor cconv sp# ``f_helper'' s1# of
342 (# s2#, a# #) -> (# s2#, A# a# #)))
344 foreign export "f_helper" f_helper :: StablePtr (Addr -> Int -> IO Int) -> Addr -> Int -> IO Int
345 -- `special' foreign export that invokes the closure pointed to by the
350 dsFExportDynamic :: Id
352 -> DsM ([Binding], SDoc, SDoc)
353 dsFExportDynamic id cconv
354 = newSysLocalDs ty `thenDs` \ fe_id ->
355 getModuleDs `thenDs` \ mod_name ->
357 -- hack: need to get at the name of the C stub we're about to generate.
358 fe_nm = mkFastString (unpackFS (zEncodeFS (moduleFS mod_name)) ++ "_" ++ toCName fe_id)
360 newSysLocalDs arg_ty `thenDs` \ cback ->
361 dsLookupGlobalId newStablePtrName `thenDs` \ newStablePtrId ->
362 dsLookupTyCon stablePtrTyConName `thenDs` \ stable_ptr_tycon ->
364 mk_stbl_ptr_app = mkApps (Var newStablePtrId) [ Type arg_ty, Var cback ]
365 stable_ptr_ty = mkTyConApp stable_ptr_tycon [arg_ty]
366 export_ty = mkFunTy stable_ptr_ty arg_ty
368 dsLookupGlobalId bindIOName `thenDs` \ bindIOId ->
369 newSysLocalDs stable_ptr_ty `thenDs` \ stbl_value ->
370 dsFExport id export_ty fe_nm cconv True
371 `thenDs` \ (h_code, c_code, arg_reps, args_size) ->
373 stbl_app cont ret_ty = mkApps (Var bindIOId)
380 The arguments to the external function which will
381 create a little bit of (template) code on the fly
382 for allowing the (stable pointed) Haskell closure
383 to be entered using an external calling convention
386 adj_args = [ mkIntLitInt (ccallConvToInt cconv)
388 , mkLit (MachLabel fe_nm mb_sz_args)
389 , mkLit (mkStringLit arg_type_info)
391 -- name of external entry point providing these services.
392 -- (probably in the RTS.)
393 adjustor = FSLIT("createAdjustor")
395 arg_type_info = map repCharCode arg_reps
396 repCharCode F32 = 'f'
397 repCharCode F64 = 'd'
398 repCharCode I64 = 'l'
401 -- Determine the number of bytes of arguments to the stub function,
402 -- so that we can attach the '@N' suffix to its label if it is a
403 -- stdcall on Windows.
404 mb_sz_args = case cconv of
405 StdCallConv -> Just args_size
409 dsCCall adjustor adj_args PlayRisky io_res_ty `thenDs` \ ccall_adj ->
410 -- PlayRisky: the adjustor doesn't allocate in the Haskell heap or do a callback
411 let ccall_adj_ty = exprType ccall_adj
412 ccall_io_adj = mkLams [stbl_value] $
413 Note (Coerce io_res_ty ccall_adj_ty)
415 io_app = mkLams tvs $
417 stbl_app ccall_io_adj res_ty
418 fed = (id `setInlinePragma` NeverActive, io_app)
419 -- Never inline the f.e.d. function, because the litlit
420 -- might not be in scope in other modules.
422 returnDs ([fed], h_code, c_code)
426 (tvs,sans_foralls) = tcSplitForAllTys ty
427 ([arg_ty], io_res_ty) = tcSplitFunTys sans_foralls
428 [res_ty] = tcTyConAppArgs io_res_ty
429 -- Must use tcSplit* to see the (IO t), which is a newtype
431 toCName :: Id -> String
432 toCName i = showSDoc (pprCode CStyle (ppr (idName i)))
437 \subsection{Generating @foreign export@ stubs}
441 For each @foreign export@ function, a C stub function is generated.
442 The C stub constructs the application of the exported Haskell function
443 using the hugs/ghc rts invocation API.
446 mkFExportCBits :: FastString
447 -> Maybe Id -- Just==static, Nothing==dynamic
450 -> Bool -- True <=> returns an IO type
454 [MachRep], -- the argument reps
455 Int -- total size of arguments
457 mkFExportCBits c_nm maybe_target arg_htys res_hty is_IO_res_ty cc
458 = (header_bits, c_bits,
459 [rep | (_,_,_,rep) <- arg_info], -- just the real args
460 sum [ machRepByteWidth rep | (_,_,_,rep) <- aug_arg_info] -- all the args
463 -- list the arguments to the C function
464 arg_info :: [(SDoc, -- arg name
466 Type, -- Haskell type
467 MachRep)] -- the MachRep
468 arg_info = [ (text ('a':show n), showStgType ty, ty,
469 typeMachRep (getPrimTyOf ty))
470 | (ty,n) <- zip arg_htys [1..] ]
472 -- add some auxiliary args; the stable ptr in the wrapper case, and
473 -- a slot for the dummy return address in the wrapper + ccall case
475 | isNothing maybe_target = stable_ptr_arg : insertRetAddr cc arg_info
476 | otherwise = arg_info
479 (text "the_stableptr", text "StgStablePtr", undefined,
480 typeMachRep (mkStablePtrPrimTy alphaTy))
482 -- stuff to do with the return type of the C function
483 res_hty_is_unit = res_hty `coreEqType` unitTy -- Look through any newtypes
485 cResType | res_hty_is_unit = text "void"
486 | otherwise = showStgType res_hty
488 -- Now we can cook up the prototype for the exported function.
489 pprCconv = case cc of
491 StdCallConv -> text (ccallConvAttribute cc)
493 header_bits = ptext SLIT("extern") <+> fun_proto <> semi
495 fun_proto = cResType <+> pprCconv <+> ftext c_nm <>
496 parens (hsep (punctuate comma (map (\(nm,ty,_,_) -> ty <+> nm)
499 -- the target which will form the root of what we ask rts_evalIO to run
501 = case maybe_target of
502 Nothing -> text "(StgClosure*)deRefStablePtr(the_stableptr)"
503 Just hs_fn -> char '&' <> ppr hs_fn <> text "_closure"
505 cap = text "cap" <> comma
507 -- the expression we give to rts_evalIO
509 = foldl appArg the_cfun arg_info -- NOT aug_arg_info
511 appArg acc (arg_cname, _, arg_hty, _)
513 <> parens (cap <> acc <> comma <> mkHObj arg_hty <> parens (cap <> arg_cname))
515 -- various other bits for inside the fn
516 declareResult = text "HaskellObj ret;"
517 declareCResult | res_hty_is_unit = empty
518 | otherwise = cResType <+> text "cret;"
520 assignCResult | res_hty_is_unit = empty
522 text "cret=" <> unpackHObj res_hty <> parens (text "ret") <> semi
524 -- an extern decl for the fn being called
526 = case maybe_target of
528 Just hs_fn -> text "extern StgClosure " <> ppr hs_fn <> text "_closure" <> semi
531 -- Initialise foreign exports by registering a stable pointer from an
532 -- __attribute__((constructor)) function.
533 -- The alternative is to do this from stginit functions generated in
534 -- codeGen/CodeGen.lhs; however, stginit functions have a negative impact
535 -- on binary sizes and link times because the static linker will think that
536 -- all modules that are imported directly or indirectly are actually used by
538 -- (this is bad for big umbrella modules like Graphics.Rendering.OpenGL)
541 = case maybe_target of
545 [ text "static void stginit_export_" <> ppr hs_fn
546 <> text "() __attribute__((constructor));"
547 , text "static void stginit_export_" <> ppr hs_fn <> text "()"
548 , braces (text "getStablePtr"
549 <> parens (text "(StgPtr) &" <> ppr hs_fn <> text "_closure")
553 -- finally, the whole darn thing
560 , text "Capability *cap;"
563 , text "cap = rts_lock();"
564 -- create the application + perform it.
565 , text "cap=rts_evalIO" <> parens (
567 text "rts_apply" <> parens (
570 <> text (if is_IO_res_ty
572 else "runNonIO_closure")
578 , text "rts_checkSchedStatus" <> parens (doubleQuotes (ftext c_nm)
579 <> comma <> text "cap") <> semi
581 , text "rts_unlock(cap);"
582 , if res_hty_is_unit then empty
583 else text "return cret;"
588 -- NB. the calculation here isn't strictly speaking correct.
589 -- We have a primitive Haskell type (eg. Int#, Double#), and
590 -- we want to know the size, when passed on the C stack, of
591 -- the associated C type (eg. HsInt, HsDouble). We don't have
592 -- this information to hand, but we know what GHC's conventions
593 -- are for passing around the primitive Haskell types, so we
594 -- use that instead. I hope the two coincide --SDM
595 typeMachRep ty = argMachRep (typeCgRep ty)
597 mkHObj :: Type -> SDoc
598 mkHObj t = text "rts_mk" <> text (showFFIType t)
600 unpackHObj :: Type -> SDoc
601 unpackHObj t = text "rts_get" <> text (showFFIType t)
603 showStgType :: Type -> SDoc
604 showStgType t = text "Hs" <> text (showFFIType t)
606 showFFIType :: Type -> String
607 showFFIType t = getOccString (getName tc)
609 tc = case tcSplitTyConApp_maybe (repType t) of
611 Nothing -> pprPanic "showFFIType" (ppr t)
613 #if !defined(x86_64_TARGET_ARCH)
614 insertRetAddr CCallConv args = ret_addr_arg : args
615 insertRetAddr _ args = args
617 -- On x86_64 we insert the return address after the 6th
618 -- integer argument, because this is the point at which we
619 -- need to flush a register argument to the stack (See rts/Adjustor.c for
621 insertRetAddr CCallConv args = go 0 args
622 where go 6 args = ret_addr_arg : args
623 go n (arg@(_,_,_,rep):args)
624 | I64 <- rep = arg : go (n+1) args
625 | otherwise = arg : go n args
627 insertRetAddr _ args = args
630 ret_addr_arg = (text "original_return_addr", text "void*", undefined,
631 typeMachRep addrPrimTy)
633 -- This function returns the primitive type associated with the boxed
634 -- type argument to a foreign export (eg. Int ==> Int#). It assumes
635 -- that all the types we are interested in have a single constructor
636 -- with a single primitive-typed argument, which is true for all of the legal
637 -- foreign export argument types (see TcType.legalFEArgTyCon).
638 getPrimTyOf :: Type -> Type
640 case splitProductType_maybe (repType ty) of
641 Just (_, _, data_con, [prim_ty]) ->
642 ASSERT(dataConSourceArity data_con == 1)
643 ASSERT2(isUnLiftedType prim_ty, ppr prim_ty)
645 _other -> pprPanic "DsForeign.getPrimTyOf" (ppr ty)