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 Coercion ( mkUnsafeCoercion )
35 import TcType ( Type, mkFunTys, mkForAllTys, mkTyConApp,
36 mkFunTy, tcSplitTyConApp_maybe, tcSplitIOType_maybe,
37 tcSplitForAllTys, tcSplitFunTys, tcTyConAppArgs,
41 import BasicTypes ( Boxity(..) )
42 import HscTypes ( ForeignStubs(..) )
43 import ForeignCall ( ForeignCall(..), CCallSpec(..),
45 CExportSpec(..), CLabelString,
46 CCallConv(..), ccallConvToInt,
49 import TysWiredIn ( unitTy, tupleTyCon )
50 import TysPrim ( addrPrimTy, mkStablePtrPrimTy, alphaTy, intPrimTy )
51 import PrelNames ( stablePtrTyConName, newStablePtrName, bindIOName,
53 import BasicTypes ( Activation( NeverActive ) )
54 import SrcLoc ( Located(..), unLoc )
56 import Maybe ( fromJust, isNothing )
60 Desugaring of @foreign@ declarations is naturally split up into
61 parts, an @import@ and an @export@ part. A @foreign import@
64 foreign import cc nm f :: prim_args -> IO prim_res
68 f :: prim_args -> IO prim_res
69 f a1 ... an = _ccall_ nm cc a1 ... an
71 so we reuse the desugaring code in @DsCCall@ to deal with these.
74 type Binding = (Id, CoreExpr) -- No rec/nonrec structure;
75 -- the occurrence analyser will sort it all out
77 dsForeigns :: [LForeignDecl Id]
78 -> DsM (ForeignStubs, [Binding])
80 = returnDs (NoStubs, [])
82 = foldlDs combine (ForeignStubs empty empty [] [], []) fos
84 combine stubs (L loc decl) = putSrcSpanDs loc (combine1 stubs decl)
86 combine1 (ForeignStubs acc_h acc_c acc_hdrs acc_feb, acc_f)
87 (ForeignImport id _ spec)
88 = traceIf (text "fi start" <+> ppr id) `thenDs` \ _ ->
89 dsFImport (unLoc id) spec `thenDs` \ (bs, h, c, mbhd) ->
90 traceIf (text "fi end" <+> ppr id) `thenDs` \ _ ->
91 returnDs (ForeignStubs (h $$ acc_h)
97 combine1 (ForeignStubs acc_h acc_c acc_hdrs acc_feb, acc_f)
98 (ForeignExport (L _ id) _ (CExport (CExportStatic ext_nm cconv)))
99 = dsFExport id (idType id)
100 ext_nm cconv False `thenDs` \(h, c, _, _) ->
101 returnDs (ForeignStubs (h $$ acc_h) (c $$ acc_c) acc_hdrs (id:acc_feb),
111 %************************************************************************
113 \subsection{Foreign import}
115 %************************************************************************
117 Desugaring foreign imports is just the matter of creating a binding
118 that on its RHS unboxes its arguments, performs the external call
119 (using the @CCallOp@ primop), before boxing the result up and returning it.
121 However, we create a worker/wrapper pair, thus:
123 foreign import f :: Int -> IO Int
125 f x = IO ( \s -> case x of { I# x# ->
126 case fw s x# of { (# s1, y# #) ->
129 fw s x# = ccall f s x#
131 The strictness/CPR analyser won't do this automatically because it doesn't look
132 inside returned tuples; but inlining this wrapper is a Really Good Idea
133 because it exposes the boxing to the call site.
138 -> DsM ([Binding], SDoc, SDoc, Maybe FastString)
139 dsFImport id (CImport cconv safety header lib spec)
140 = dsCImport id spec cconv safety no_hdrs `thenDs` \(ids, h, c) ->
141 returnDs (ids, h, c, if no_hdrs then Nothing else Just header)
143 no_hdrs = nullFS header
145 -- FIXME: the `lib' field is needed for .NET ILX generation when invoking
146 -- routines that are external to the .NET runtime, but GHC doesn't
147 -- support such calls yet; if `nullFastString lib', the value was not given
148 dsFImport id (DNImport spec)
149 = dsFCall id (DNCall spec) True {- No headers -} `thenDs` \(ids, h, c) ->
150 returnDs (ids, h, c, Nothing)
156 -> Bool -- True <=> no headers in the f.i decl
157 -> DsM ([Binding], SDoc, SDoc)
158 dsCImport id (CLabel cid) _ _ no_hdrs
159 = resultWrapper (idType id) `thenDs` \ (resTy, foRhs) ->
160 ASSERT(fromJust resTy `coreEqType` addrPrimTy) -- typechecker ensures this
161 let rhs = foRhs (mkLit (MachLabel cid Nothing)) in
162 returnDs ([(setImpInline no_hdrs id, rhs)], empty, empty)
163 dsCImport id (CFunction target) cconv safety no_hdrs
164 = dsFCall id (CCall (CCallSpec target cconv safety)) no_hdrs
165 dsCImport id CWrapper cconv _ _
166 = dsFExportDynamic id cconv
168 setImpInline :: Bool -- True <=> No #include headers
169 -- in the foreign import declaration
171 -- If there is a #include header in the foreign import
172 -- we make the worker non-inlinable, because we currently
173 -- don't keep the #include stuff in the CCallId, and hence
174 -- it won't be visible in the importing module, which can be
176 -- (The #include stuff is just collected from the foreign import
177 -- decls in a module.)
178 -- If you want to do cross-module inlining of the c-calls themselves,
179 -- put the #include stuff in the package spec, not the foreign
181 setImpInline True id = id
182 setImpInline False id = id `setInlinePragma` NeverActive
186 %************************************************************************
188 \subsection{Foreign calls}
190 %************************************************************************
193 dsFCall fn_id fcall no_hdrs
196 (tvs, fun_ty) = tcSplitForAllTys ty
197 (arg_tys, io_res_ty) = tcSplitFunTys fun_ty
198 -- Must use tcSplit* functions because we want to
199 -- see that (IO t) in the corner
201 newSysLocalsDs arg_tys `thenDs` \ args ->
202 mapAndUnzipDs unboxArg (map Var args) `thenDs` \ (val_args, arg_wrappers) ->
205 work_arg_ids = [v | Var v <- val_args] -- All guaranteed to be vars
214 dsLookupGlobalId checkDotnetResName `thenDs` \ check_id ->
215 return (Just check_id)
216 | otherwise = return Nothing
220 newSysLocalDs addrPrimTy `thenDs` \ err_res ->
221 returnDs (\ (mb_res_ty, resWrap) ->
223 Nothing -> (Just (mkTyConApp (tupleTyCon Unboxed 1)
226 Just x -> (Just (mkTyConApp (tupleTyCon Unboxed 2)
229 | otherwise = returnDs id
231 augmentResultDs `thenDs` \ augment ->
232 topConDs `thenDs` \ topCon ->
233 boxResult augment topCon io_res_ty `thenDs` \ (ccall_result_ty, res_wrapper) ->
235 newUnique `thenDs` \ ccall_uniq ->
236 newUnique `thenDs` \ work_uniq ->
239 worker_ty = mkForAllTys tvs (mkFunTys (map idType work_arg_ids) ccall_result_ty)
240 the_ccall_app = mkFCall ccall_uniq fcall val_args ccall_result_ty
241 work_rhs = mkLams tvs (mkLams work_arg_ids the_ccall_app)
242 work_id = setImpInline no_hdrs $ -- See comments with setImpInline
243 mkSysLocal FSLIT("$wccall") work_uniq worker_ty
246 work_app = mkApps (mkVarApps (Var work_id) tvs) val_args
247 wrapper_body = foldr ($) (res_wrapper work_app) arg_wrappers
248 wrap_rhs = mkInlineMe (mkLams (tvs ++ args) wrapper_body)
250 returnDs ([(work_id, work_rhs), (fn_id, wrap_rhs)], empty, empty)
254 %************************************************************************
256 \subsection{Foreign export}
258 %************************************************************************
260 The function that does most of the work for `@foreign export@' declarations.
261 (see below for the boilerplate code a `@foreign export@' declaration expands
264 For each `@foreign export foo@' in a module M we generate:
266 \item a C function `@foo@', which calls
267 \item a Haskell stub `@M.$ffoo@', which calls
269 the user-written Haskell function `@M.foo@'.
272 dsFExport :: Id -- Either the exported Id,
273 -- or the foreign-export-dynamic constructor
274 -> Type -- The type of the thing callable from C
275 -> CLabelString -- The name to export to C land
277 -> Bool -- True => foreign export dynamic
278 -- so invoke IO action that's hanging off
279 -- the first argument's stable pointer
280 -> DsM ( SDoc -- contents of Module_stub.h
281 , SDoc -- contents of Module_stub.c
282 , [MachRep] -- primitive arguments expected by stub function
283 , Int -- size of args to stub function
286 dsFExport fn_id ty ext_name cconv isDyn
289 (_tvs,sans_foralls) = tcSplitForAllTys ty
290 (fe_arg_tys', orig_res_ty) = tcSplitFunTys sans_foralls
291 -- We must use tcSplits here, because we want to see
292 -- the (IO t) in the corner of the type!
293 fe_arg_tys | isDyn = tail fe_arg_tys'
294 | otherwise = fe_arg_tys'
296 -- Look at the result type of the exported function, orig_res_ty
297 -- If it's IO t, return (t, True)
298 -- If it's plain t, return (t, False)
299 (case tcSplitIOType_maybe orig_res_ty of
300 Just (ioTyCon, res_ty) -> returnDs (res_ty, True)
301 -- The function already returns IO t
302 Nothing -> returnDs (orig_res_ty, False)
303 -- The function returns t
304 ) `thenDs` \ (res_ty, -- t
305 is_IO_res_ty) -> -- Bool
307 mkFExportCBits ext_name
308 (if isDyn then Nothing else Just fn_id)
309 fe_arg_tys res_ty is_IO_res_ty cconv
312 @foreign import "wrapper"@ (previously "foreign export dynamic") lets
313 you dress up Haskell IO actions of some fixed type behind an
314 externally callable interface (i.e., as a C function pointer). Useful
315 for callbacks and stuff.
318 type Fun = Bool -> Int -> IO Int
319 foreign import "wrapper" f :: Fun -> IO (FunPtr Fun)
321 -- Haskell-visible constructor, which is generated from the above:
322 -- SUP: No check for NULL from createAdjustor anymore???
324 f :: Fun -> IO (FunPtr Fun)
326 bindIO (newStablePtr cback)
327 (\StablePtr sp# -> IO (\s1# ->
328 case _ccall_ createAdjustor cconv sp# ``f_helper'' <arg info> s1# of
329 (# s2#, a# #) -> (# s2#, A# a# #)))
331 foreign import "&f_helper" f_helper :: FunPtr (StablePtr Fun -> Fun)
333 -- and the helper in C:
335 f_helper(StablePtr s, HsBool b, HsInt i)
337 rts_evalIO(rts_apply(rts_apply(deRefStablePtr(s),
338 rts_mkBool(b)), rts_mkInt(i)));
343 dsFExportDynamic :: Id
345 -> DsM ([Binding], SDoc, SDoc)
346 dsFExportDynamic id cconv
347 = newSysLocalDs ty `thenDs` \ fe_id ->
348 getModuleDs `thenDs` \ mod ->
350 -- hack: need to get at the name of the C stub we're about to generate.
351 fe_nm = mkFastString (unpackFS (zEncodeFS (moduleNameFS (moduleName mod))) ++ "_" ++ toCName fe_id)
353 newSysLocalDs arg_ty `thenDs` \ cback ->
354 dsLookupGlobalId newStablePtrName `thenDs` \ newStablePtrId ->
355 dsLookupTyCon stablePtrTyConName `thenDs` \ stable_ptr_tycon ->
357 mk_stbl_ptr_app = mkApps (Var newStablePtrId) [ Type arg_ty, Var cback ]
358 stable_ptr_ty = mkTyConApp stable_ptr_tycon [arg_ty]
359 export_ty = mkFunTy stable_ptr_ty arg_ty
361 dsLookupGlobalId bindIOName `thenDs` \ bindIOId ->
362 newSysLocalDs stable_ptr_ty `thenDs` \ stbl_value ->
363 dsFExport id export_ty fe_nm cconv True
364 `thenDs` \ (h_code, c_code, arg_reps, args_size) ->
366 stbl_app cont ret_ty = mkApps (Var bindIOId)
373 The arguments to the external function which will
374 create a little bit of (template) code on the fly
375 for allowing the (stable pointed) Haskell closure
376 to be entered using an external calling convention
379 adj_args = [ mkIntLitInt (ccallConvToInt cconv)
381 , mkLit (MachLabel fe_nm mb_sz_args)
382 , mkLit (mkStringLit arg_type_info)
384 -- name of external entry point providing these services.
385 -- (probably in the RTS.)
386 adjustor = FSLIT("createAdjustor")
388 arg_type_info = map repCharCode arg_reps
389 repCharCode F32 = 'f'
390 repCharCode F64 = 'd'
391 repCharCode I64 = 'l'
394 -- Determine the number of bytes of arguments to the stub function,
395 -- so that we can attach the '@N' suffix to its label if it is a
396 -- stdcall on Windows.
397 mb_sz_args = case cconv of
398 StdCallConv -> Just args_size
402 dsCCall adjustor adj_args PlayRisky io_res_ty `thenDs` \ ccall_adj ->
403 -- PlayRisky: the adjustor doesn't allocate in the Haskell heap or do a callback
404 let ccall_adj_ty = exprType ccall_adj
405 ccall_io_adj = mkLams [stbl_value] $
406 (pprTrace "DsForeign: why is there an unsafeCoerce here?" (text "") $
407 (Cast ccall_adj (mkUnsafeCoercion ccall_adj_ty io_res_ty )))
409 io_app = mkLams tvs $
411 stbl_app ccall_io_adj res_ty
412 fed = (id `setInlinePragma` NeverActive, io_app)
413 -- Never inline the f.e.d. function, because the litlit
414 -- might not be in scope in other modules.
416 returnDs ([fed], h_code, c_code)
420 (tvs,sans_foralls) = tcSplitForAllTys ty
421 ([arg_ty], io_res_ty) = tcSplitFunTys sans_foralls
422 [res_ty] = tcTyConAppArgs io_res_ty
423 -- Must use tcSplit* to see the (IO t), which is a newtype
425 toCName :: Id -> String
426 toCName i = showSDoc (pprCode CStyle (ppr (idName i)))
431 \subsection{Generating @foreign export@ stubs}
435 For each @foreign export@ function, a C stub function is generated.
436 The C stub constructs the application of the exported Haskell function
437 using the hugs/ghc rts invocation API.
440 mkFExportCBits :: FastString
441 -> Maybe Id -- Just==static, Nothing==dynamic
444 -> Bool -- True <=> returns an IO type
448 [MachRep], -- the argument reps
449 Int -- total size of arguments
451 mkFExportCBits c_nm maybe_target arg_htys res_hty is_IO_res_ty cc
452 = (header_bits, c_bits,
453 [rep | (_,_,_,rep) <- arg_info], -- just the real args
454 sum [ machRepByteWidth rep | (_,_,_,rep) <- aug_arg_info] -- all the args
457 -- list the arguments to the C function
458 arg_info :: [(SDoc, -- arg name
460 Type, -- Haskell type
461 MachRep)] -- the MachRep
462 arg_info = [ (text ('a':show n), showStgType ty, ty,
463 typeMachRep (getPrimTyOf ty))
464 | (ty,n) <- zip arg_htys [1..] ]
466 -- add some auxiliary args; the stable ptr in the wrapper case, and
467 -- a slot for the dummy return address in the wrapper + ccall case
469 | isNothing maybe_target = stable_ptr_arg : insertRetAddr cc arg_info
470 | otherwise = arg_info
473 (text "the_stableptr", text "StgStablePtr", undefined,
474 typeMachRep (mkStablePtrPrimTy alphaTy))
476 -- stuff to do with the return type of the C function
477 res_hty_is_unit = res_hty `coreEqType` unitTy -- Look through any newtypes
479 cResType | res_hty_is_unit = text "void"
480 | otherwise = showStgType res_hty
482 -- Now we can cook up the prototype for the exported function.
483 pprCconv = case cc of
485 StdCallConv -> text (ccallConvAttribute cc)
487 header_bits = ptext SLIT("extern") <+> fun_proto <> semi
489 fun_proto = cResType <+> pprCconv <+> ftext c_nm <>
490 parens (hsep (punctuate comma (map (\(nm,ty,_,_) -> ty <+> nm)
493 -- the target which will form the root of what we ask rts_evalIO to run
495 = case maybe_target of
496 Nothing -> text "(StgClosure*)deRefStablePtr(the_stableptr)"
497 Just hs_fn -> char '&' <> ppr hs_fn <> text "_closure"
499 cap = text "cap" <> comma
501 -- the expression we give to rts_evalIO
503 = foldl appArg the_cfun arg_info -- NOT aug_arg_info
505 appArg acc (arg_cname, _, arg_hty, _)
507 <> parens (cap <> acc <> comma <> mkHObj arg_hty <> parens (cap <> arg_cname))
509 -- various other bits for inside the fn
510 declareResult = text "HaskellObj ret;"
511 declareCResult | res_hty_is_unit = empty
512 | otherwise = cResType <+> text "cret;"
514 assignCResult | res_hty_is_unit = empty
516 text "cret=" <> unpackHObj res_hty <> parens (text "ret") <> semi
518 -- an extern decl for the fn being called
520 = case maybe_target of
522 Just hs_fn -> text "extern StgClosure " <> ppr hs_fn <> text "_closure" <> semi
525 -- Initialise foreign exports by registering a stable pointer from an
526 -- __attribute__((constructor)) function.
527 -- The alternative is to do this from stginit functions generated in
528 -- codeGen/CodeGen.lhs; however, stginit functions have a negative impact
529 -- on binary sizes and link times because the static linker will think that
530 -- all modules that are imported directly or indirectly are actually used by
532 -- (this is bad for big umbrella modules like Graphics.Rendering.OpenGL)
535 = case maybe_target of
539 [ text "static void stginit_export_" <> ppr hs_fn
540 <> text "() __attribute__((constructor));"
541 , text "static void stginit_export_" <> ppr hs_fn <> text "()"
542 , braces (text "getStablePtr"
543 <> parens (text "(StgPtr) &" <> ppr hs_fn <> text "_closure")
547 -- finally, the whole darn thing
554 , text "Capability *cap;"
557 , text "cap = rts_lock();"
558 -- create the application + perform it.
559 , text "cap=rts_evalIO" <> parens (
561 text "rts_apply" <> parens (
564 <> text (if is_IO_res_ty
566 else "runNonIO_closure")
572 , text "rts_checkSchedStatus" <> parens (doubleQuotes (ftext c_nm)
573 <> comma <> text "cap") <> semi
575 , text "rts_unlock(cap);"
576 , if res_hty_is_unit then empty
577 else text "return cret;"
582 -- NB. the calculation here isn't strictly speaking correct.
583 -- We have a primitive Haskell type (eg. Int#, Double#), and
584 -- we want to know the size, when passed on the C stack, of
585 -- the associated C type (eg. HsInt, HsDouble). We don't have
586 -- this information to hand, but we know what GHC's conventions
587 -- are for passing around the primitive Haskell types, so we
588 -- use that instead. I hope the two coincide --SDM
589 typeMachRep ty = argMachRep (typeCgRep ty)
591 mkHObj :: Type -> SDoc
592 mkHObj t = text "rts_mk" <> text (showFFIType t)
594 unpackHObj :: Type -> SDoc
595 unpackHObj t = text "rts_get" <> text (showFFIType t)
597 showStgType :: Type -> SDoc
598 showStgType t = text "Hs" <> text (showFFIType t)
600 showFFIType :: Type -> String
601 showFFIType t = getOccString (getName tc)
603 tc = case tcSplitTyConApp_maybe (repType t) of
605 Nothing -> pprPanic "showFFIType" (ppr t)
607 #if !defined(x86_64_TARGET_ARCH)
608 insertRetAddr CCallConv args = ret_addr_arg : args
609 insertRetAddr _ args = args
611 -- On x86_64 we insert the return address after the 6th
612 -- integer argument, because this is the point at which we
613 -- need to flush a register argument to the stack (See rts/Adjustor.c for
615 insertRetAddr CCallConv args = go 0 args
616 where go 6 args = ret_addr_arg : args
617 go n (arg@(_,_,_,rep):args)
618 | I64 <- rep = arg : go (n+1) args
619 | otherwise = arg : go n args
621 insertRetAddr _ args = args
624 ret_addr_arg = (text "original_return_addr", text "void*", undefined,
625 typeMachRep addrPrimTy)
627 -- This function returns the primitive type associated with the boxed
628 -- type argument to a foreign export (eg. Int ==> Int#).
629 getPrimTyOf :: Type -> Type
631 | isBoolTy rep_ty = intPrimTy
632 -- Except for Bool, the types we are interested in have a single constructor
633 -- with a single primitive-typed argument (see TcType.legalFEArgTyCon).
635 case splitProductType_maybe rep_ty of
636 Just (_, _, data_con, [prim_ty]) ->
637 ASSERT(dataConSourceArity data_con == 1)
638 ASSERT2(isUnLiftedType prim_ty, ppr prim_ty)
640 _other -> pprPanic "DsForeign.getPrimTyOf" (ppr ty)