2 % (c) The University of Glasgow 2006
3 % (c) The AQUA Project, Glasgow University, 1998
6 Desugaring foreign declarations (see also DsCCall).
9 module DsForeign ( dsForeigns ) where
11 #include "HsVersions.h"
12 import TcRnMonad -- temp
46 Desugaring of @foreign@ declarations is naturally split up into
47 parts, an @import@ and an @export@ part. A @foreign import@
50 foreign import cc nm f :: prim_args -> IO prim_res
54 f :: prim_args -> IO prim_res
55 f a1 ... an = _ccall_ nm cc a1 ... an
57 so we reuse the desugaring code in @DsCCall@ to deal with these.
60 type Binding = (Id, CoreExpr) -- No rec/nonrec structure;
61 -- the occurrence analyser will sort it all out
63 dsForeigns :: [LForeignDecl Id]
64 -> DsM (ForeignStubs, [Binding])
66 = returnDs (NoStubs, [])
69 fives <- mapM do_ldecl fos
71 (hs, cs, hdrs, idss, bindss) = unzip5 fives
73 fe_init_code = map foreignExportInitialiser fe_ids
77 (vcat cs $$ vcat fe_init_code)
81 do_ldecl (L loc decl) = putSrcSpanDs loc (do_decl decl)
83 do_decl (ForeignImport id _ spec)
84 = traceIf (text "fi start" <+> ppr id) `thenDs` \ _ ->
85 dsFImport (unLoc id) spec `thenDs` \ (bs, h, c, mbhd) ->
86 traceIf (text "fi end" <+> ppr id) `thenDs` \ _ ->
87 returnDs (h, c, maybeToList mbhd, [], bs)
89 do_decl (ForeignExport (L _ id) _ (CExport (CExportStatic ext_nm cconv)))
90 = dsFExport id (idType id)
91 ext_nm cconv False `thenDs` \(h, c, _, _) ->
92 returnDs (h, c, [], [id], [])
96 %************************************************************************
98 \subsection{Foreign import}
100 %************************************************************************
102 Desugaring foreign imports is just the matter of creating a binding
103 that on its RHS unboxes its arguments, performs the external call
104 (using the @CCallOp@ primop), before boxing the result up and returning it.
106 However, we create a worker/wrapper pair, thus:
108 foreign import f :: Int -> IO Int
110 f x = IO ( \s -> case x of { I# x# ->
111 case fw s x# of { (# s1, y# #) ->
114 fw s x# = ccall f s x#
116 The strictness/CPR analyser won't do this automatically because it doesn't look
117 inside returned tuples; but inlining this wrapper is a Really Good Idea
118 because it exposes the boxing to the call site.
123 -> DsM ([Binding], SDoc, SDoc, Maybe FastString)
124 dsFImport id (CImport cconv safety header lib spec)
125 = dsCImport id spec cconv safety no_hdrs `thenDs` \(ids, h, c) ->
126 returnDs (ids, h, c, if no_hdrs then Nothing else Just header)
128 no_hdrs = nullFS header
130 -- FIXME: the `lib' field is needed for .NET ILX generation when invoking
131 -- routines that are external to the .NET runtime, but GHC doesn't
132 -- support such calls yet; if `nullFastString lib', the value was not given
133 dsFImport id (DNImport spec)
134 = dsFCall id (DNCall spec) True {- No headers -} `thenDs` \(ids, h, c) ->
135 returnDs (ids, h, c, Nothing)
141 -> Bool -- True <=> no headers in the f.i decl
142 -> DsM ([Binding], SDoc, SDoc)
143 dsCImport id (CLabel cid) _ _ no_hdrs
144 = resultWrapper (idType id) `thenDs` \ (resTy, foRhs) ->
145 ASSERT(fromJust resTy `coreEqType` addrPrimTy) -- typechecker ensures this
146 let rhs = foRhs (mkLit (MachLabel cid Nothing)) in
147 returnDs ([(setImpInline no_hdrs id, rhs)], empty, empty)
148 dsCImport id (CFunction target) cconv safety no_hdrs
149 = dsFCall id (CCall (CCallSpec target cconv safety)) no_hdrs
150 dsCImport id CWrapper cconv _ _
151 = dsFExportDynamic id cconv
153 setImpInline :: Bool -- True <=> No #include headers
154 -- in the foreign import declaration
156 -- If there is a #include header in the foreign import
157 -- we make the worker non-inlinable, because we currently
158 -- don't keep the #include stuff in the CCallId, and hence
159 -- it won't be visible in the importing module, which can be
161 -- (The #include stuff is just collected from the foreign import
162 -- decls in a module.)
163 -- If you want to do cross-module inlining of the c-calls themselves,
164 -- put the #include stuff in the package spec, not the foreign
166 setImpInline True id = id
167 setImpInline False id = id `setInlinePragma` NeverActive
171 %************************************************************************
173 \subsection{Foreign calls}
175 %************************************************************************
178 dsFCall fn_id fcall no_hdrs
181 (tvs, fun_ty) = tcSplitForAllTys ty
182 (arg_tys, io_res_ty) = tcSplitFunTys fun_ty
183 -- Must use tcSplit* functions because we want to
184 -- see that (IO t) in the corner
186 newSysLocalsDs arg_tys `thenDs` \ args ->
187 mapAndUnzipDs unboxArg (map Var args) `thenDs` \ (val_args, arg_wrappers) ->
190 work_arg_ids = [v | Var v <- val_args] -- All guaranteed to be vars
199 dsLookupGlobalId checkDotnetResName `thenDs` \ check_id ->
200 return (Just check_id)
201 | otherwise = return Nothing
205 newSysLocalDs addrPrimTy `thenDs` \ err_res ->
206 returnDs (\ (mb_res_ty, resWrap) ->
208 Nothing -> (Just (mkTyConApp (tupleTyCon Unboxed 1)
211 Just x -> (Just (mkTyConApp (tupleTyCon Unboxed 2)
214 | otherwise = returnDs id
216 augmentResultDs `thenDs` \ augment ->
217 topConDs `thenDs` \ topCon ->
218 boxResult augment topCon io_res_ty `thenDs` \ (ccall_result_ty, res_wrapper) ->
220 newUnique `thenDs` \ ccall_uniq ->
221 newUnique `thenDs` \ work_uniq ->
224 worker_ty = mkForAllTys tvs (mkFunTys (map idType work_arg_ids) ccall_result_ty)
225 the_ccall_app = mkFCall ccall_uniq fcall val_args ccall_result_ty
226 work_rhs = mkLams tvs (mkLams work_arg_ids the_ccall_app)
227 work_id = setImpInline no_hdrs $ -- See comments with setImpInline
228 mkSysLocal FSLIT("$wccall") work_uniq worker_ty
231 work_app = mkApps (mkVarApps (Var work_id) tvs) val_args
232 wrapper_body = foldr ($) (res_wrapper work_app) arg_wrappers
233 wrap_rhs = mkInlineMe (mkLams (tvs ++ args) wrapper_body)
235 returnDs ([(work_id, work_rhs), (fn_id, wrap_rhs)], empty, empty)
239 %************************************************************************
241 \subsection{Foreign export}
243 %************************************************************************
245 The function that does most of the work for `@foreign export@' declarations.
246 (see below for the boilerplate code a `@foreign export@' declaration expands
249 For each `@foreign export foo@' in a module M we generate:
251 \item a C function `@foo@', which calls
252 \item a Haskell stub `@M.$ffoo@', which calls
254 the user-written Haskell function `@M.foo@'.
257 dsFExport :: Id -- Either the exported Id,
258 -- or the foreign-export-dynamic constructor
259 -> Type -- The type of the thing callable from C
260 -> CLabelString -- The name to export to C land
262 -> Bool -- True => foreign export dynamic
263 -- so invoke IO action that's hanging off
264 -- the first argument's stable pointer
265 -> DsM ( SDoc -- contents of Module_stub.h
266 , SDoc -- contents of Module_stub.c
267 , [MachRep] -- primitive arguments expected by stub function
268 , Int -- size of args to stub function
271 dsFExport fn_id ty ext_name cconv isDyn
274 (_tvs,sans_foralls) = tcSplitForAllTys ty
275 (fe_arg_tys', orig_res_ty) = tcSplitFunTys sans_foralls
276 -- We must use tcSplits here, because we want to see
277 -- the (IO t) in the corner of the type!
278 fe_arg_tys | isDyn = tail fe_arg_tys'
279 | otherwise = fe_arg_tys'
281 -- Look at the result type of the exported function, orig_res_ty
282 -- If it's IO t, return (t, True)
283 -- If it's plain t, return (t, False)
284 (case tcSplitIOType_maybe orig_res_ty of
285 Just (ioTyCon, res_ty, co) -> returnDs (res_ty, True)
286 -- The function already returns IO t
287 -- ToDo: what about the coercion?
288 Nothing -> returnDs (orig_res_ty, False)
289 -- The function returns t
290 ) `thenDs` \ (res_ty, -- t
291 is_IO_res_ty) -> -- Bool
293 mkFExportCBits ext_name
294 (if isDyn then Nothing else Just fn_id)
295 fe_arg_tys res_ty is_IO_res_ty cconv
298 @foreign import "wrapper"@ (previously "foreign export dynamic") lets
299 you dress up Haskell IO actions of some fixed type behind an
300 externally callable interface (i.e., as a C function pointer). Useful
301 for callbacks and stuff.
304 type Fun = Bool -> Int -> IO Int
305 foreign import "wrapper" f :: Fun -> IO (FunPtr Fun)
307 -- Haskell-visible constructor, which is generated from the above:
308 -- SUP: No check for NULL from createAdjustor anymore???
310 f :: Fun -> IO (FunPtr Fun)
312 bindIO (newStablePtr cback)
313 (\StablePtr sp# -> IO (\s1# ->
314 case _ccall_ createAdjustor cconv sp# ``f_helper'' <arg info> s1# of
315 (# s2#, a# #) -> (# s2#, A# a# #)))
317 foreign import "&f_helper" f_helper :: FunPtr (StablePtr Fun -> Fun)
319 -- and the helper in C:
321 f_helper(StablePtr s, HsBool b, HsInt i)
323 rts_evalIO(rts_apply(rts_apply(deRefStablePtr(s),
324 rts_mkBool(b)), rts_mkInt(i)));
329 dsFExportDynamic :: Id
331 -> DsM ([Binding], SDoc, SDoc)
332 dsFExportDynamic id cconv
333 = newSysLocalDs ty `thenDs` \ fe_id ->
334 getModuleDs `thenDs` \ mod ->
336 -- hack: need to get at the name of the C stub we're about to generate.
337 fe_nm = mkFastString (unpackFS (zEncodeFS (moduleNameFS (moduleName mod))) ++ "_" ++ toCName fe_id)
339 newSysLocalDs arg_ty `thenDs` \ cback ->
340 dsLookupGlobalId newStablePtrName `thenDs` \ newStablePtrId ->
341 dsLookupTyCon stablePtrTyConName `thenDs` \ stable_ptr_tycon ->
343 stable_ptr_ty = mkTyConApp stable_ptr_tycon [arg_ty]
344 export_ty = mkFunTy stable_ptr_ty arg_ty
346 dsLookupGlobalId bindIOName `thenDs` \ bindIOId ->
347 newSysLocalDs stable_ptr_ty `thenDs` \ stbl_value ->
348 dsFExport id export_ty fe_nm cconv True
349 `thenDs` \ (h_code, c_code, arg_reps, args_size) ->
352 The arguments to the external function which will
353 create a little bit of (template) code on the fly
354 for allowing the (stable pointed) Haskell closure
355 to be entered using an external calling convention
358 adj_args = [ mkIntLitInt (ccallConvToInt cconv)
360 , mkLit (MachLabel fe_nm mb_sz_args)
361 , mkLit (mkStringLit arg_type_info)
363 -- name of external entry point providing these services.
364 -- (probably in the RTS.)
365 adjustor = FSLIT("createAdjustor")
367 arg_type_info = map repCharCode arg_reps
368 repCharCode F32 = 'f'
369 repCharCode F64 = 'd'
370 repCharCode I64 = 'l'
373 -- Determine the number of bytes of arguments to the stub function,
374 -- so that we can attach the '@N' suffix to its label if it is a
375 -- stdcall on Windows.
376 mb_sz_args = case cconv of
377 StdCallConv -> Just args_size
381 dsCCall adjustor adj_args PlayRisky (mkTyConApp io_tc [res_ty]) `thenDs` \ ccall_adj ->
382 -- PlayRisky: the adjustor doesn't allocate in the Haskell heap or do a callback
384 let io_app = mkLams tvs $
386 mkCoerceI (mkSymCoI co) $
387 mkApps (Var bindIOId)
390 , mkApps (Var newStablePtrId) [ Type arg_ty, Var cback ]
391 , Lam stbl_value ccall_adj
394 fed = (id `setInlinePragma` NeverActive, io_app)
395 -- Never inline the f.e.d. function, because the litlit
396 -- might not be in scope in other modules.
398 returnDs ([fed], h_code, c_code)
402 (tvs,sans_foralls) = tcSplitForAllTys ty
403 ([arg_ty], fn_res_ty) = tcSplitFunTys sans_foralls
404 Just (io_tc, res_ty, co) = tcSplitIOType_maybe fn_res_ty
405 -- Must have an IO type; hence Just
406 -- co : fn_res_ty ~ IO res_ty
408 toCName :: Id -> String
409 toCName i = showSDoc (pprCode CStyle (ppr (idName i)))
414 \subsection{Generating @foreign export@ stubs}
418 For each @foreign export@ function, a C stub function is generated.
419 The C stub constructs the application of the exported Haskell function
420 using the hugs/ghc rts invocation API.
423 mkFExportCBits :: FastString
424 -> Maybe Id -- Just==static, Nothing==dynamic
427 -> Bool -- True <=> returns an IO type
431 [MachRep], -- the argument reps
432 Int -- total size of arguments
434 mkFExportCBits c_nm maybe_target arg_htys res_hty is_IO_res_ty cc
435 = (header_bits, c_bits,
436 [rep | (_,_,_,rep) <- arg_info], -- just the real args
437 sum [ machRepByteWidth rep | (_,_,_,rep) <- aug_arg_info] -- all the args
440 -- list the arguments to the C function
441 arg_info :: [(SDoc, -- arg name
443 Type, -- Haskell type
444 MachRep)] -- the MachRep
445 arg_info = [ (text ('a':show n), showStgType ty, ty,
446 typeMachRep (getPrimTyOf ty))
447 | (ty,n) <- zip arg_htys [1::Int ..] ]
449 -- add some auxiliary args; the stable ptr in the wrapper case, and
450 -- a slot for the dummy return address in the wrapper + ccall case
452 | isNothing maybe_target = stable_ptr_arg : insertRetAddr cc arg_info
453 | otherwise = arg_info
456 (text "the_stableptr", text "StgStablePtr", undefined,
457 typeMachRep (mkStablePtrPrimTy alphaTy))
459 -- stuff to do with the return type of the C function
460 res_hty_is_unit = res_hty `coreEqType` unitTy -- Look through any newtypes
462 cResType | res_hty_is_unit = text "void"
463 | otherwise = showStgType res_hty
465 -- Now we can cook up the prototype for the exported function.
466 pprCconv = case cc of
468 StdCallConv -> text (ccallConvAttribute cc)
470 header_bits = ptext SLIT("extern") <+> fun_proto <> semi
472 fun_proto = cResType <+> pprCconv <+> ftext c_nm <>
473 parens (hsep (punctuate comma (map (\(nm,ty,_,_) -> ty <+> nm)
476 -- the target which will form the root of what we ask rts_evalIO to run
478 = case maybe_target of
479 Nothing -> text "(StgClosure*)deRefStablePtr(the_stableptr)"
480 Just hs_fn -> char '&' <> ppr hs_fn <> text "_closure"
482 cap = text "cap" <> comma
484 -- the expression we give to rts_evalIO
486 = foldl appArg the_cfun arg_info -- NOT aug_arg_info
488 appArg acc (arg_cname, _, arg_hty, _)
490 <> parens (cap <> acc <> comma <> mkHObj arg_hty <> parens (cap <> arg_cname))
492 -- various other bits for inside the fn
493 declareResult = text "HaskellObj ret;"
494 declareCResult | res_hty_is_unit = empty
495 | otherwise = cResType <+> text "cret;"
497 assignCResult | res_hty_is_unit = empty
499 text "cret=" <> unpackHObj res_hty <> parens (text "ret") <> semi
501 -- an extern decl for the fn being called
503 = case maybe_target of
505 Just hs_fn -> text "extern StgClosure " <> ppr hs_fn <> text "_closure" <> semi
508 -- finally, the whole darn thing
515 , text "Capability *cap;"
518 , text "cap = rts_lock();"
519 -- create the application + perform it.
520 , text "cap=rts_evalIO" <> parens (
522 text "rts_apply" <> parens (
525 <> text (if is_IO_res_ty
527 else "runNonIO_closure")
533 , text "rts_checkSchedStatus" <> parens (doubleQuotes (ftext c_nm)
534 <> comma <> text "cap") <> semi
536 , text "rts_unlock(cap);"
537 , if res_hty_is_unit then empty
538 else text "return cret;"
543 foreignExportInitialiser :: Id -> SDoc
544 foreignExportInitialiser hs_fn =
545 -- Initialise foreign exports by registering a stable pointer from an
546 -- __attribute__((constructor)) function.
547 -- The alternative is to do this from stginit functions generated in
548 -- codeGen/CodeGen.lhs; however, stginit functions have a negative impact
549 -- on binary sizes and link times because the static linker will think that
550 -- all modules that are imported directly or indirectly are actually used by
552 -- (this is bad for big umbrella modules like Graphics.Rendering.OpenGL)
554 [ text "static void stginit_export_" <> ppr hs_fn
555 <> text "() __attribute__((constructor));"
556 , text "static void stginit_export_" <> ppr hs_fn <> text "()"
557 , braces (text "getStablePtr"
558 <> parens (text "(StgPtr) &" <> ppr hs_fn <> text "_closure")
563 -- NB. the calculation here isn't strictly speaking correct.
564 -- We have a primitive Haskell type (eg. Int#, Double#), and
565 -- we want to know the size, when passed on the C stack, of
566 -- the associated C type (eg. HsInt, HsDouble). We don't have
567 -- this information to hand, but we know what GHC's conventions
568 -- are for passing around the primitive Haskell types, so we
569 -- use that instead. I hope the two coincide --SDM
570 typeMachRep ty = argMachRep (typeCgRep ty)
572 mkHObj :: Type -> SDoc
573 mkHObj t = text "rts_mk" <> text (showFFIType t)
575 unpackHObj :: Type -> SDoc
576 unpackHObj t = text "rts_get" <> text (showFFIType t)
578 showStgType :: Type -> SDoc
579 showStgType t = text "Hs" <> text (showFFIType t)
581 showFFIType :: Type -> String
582 showFFIType t = getOccString (getName tc)
584 tc = case tcSplitTyConApp_maybe (repType t) of
586 Nothing -> pprPanic "showFFIType" (ppr t)
588 #if !defined(x86_64_TARGET_ARCH)
589 insertRetAddr CCallConv args = ret_addr_arg : args
590 insertRetAddr _ args = args
592 -- On x86_64 we insert the return address after the 6th
593 -- integer argument, because this is the point at which we
594 -- need to flush a register argument to the stack (See rts/Adjustor.c for
596 insertRetAddr CCallConv args = go 0 args
597 where go 6 args = ret_addr_arg : args
598 go n (arg@(_,_,_,rep):args)
599 | I64 <- rep = arg : go (n+1) args
600 | otherwise = arg : go n args
602 insertRetAddr _ args = args
605 ret_addr_arg = (text "original_return_addr", text "void*", undefined,
606 typeMachRep addrPrimTy)
608 -- This function returns the primitive type associated with the boxed
609 -- type argument to a foreign export (eg. Int ==> Int#).
610 getPrimTyOf :: Type -> Type
612 | isBoolTy rep_ty = intPrimTy
613 -- Except for Bool, the types we are interested in have a single constructor
614 -- with a single primitive-typed argument (see TcType.legalFEArgTyCon).
616 case splitProductType_maybe rep_ty of
617 Just (_, _, data_con, [prim_ty]) ->
618 ASSERT(dataConSourceArity data_con == 1)
619 ASSERT2(isUnLiftedType prim_ty, ppr prim_ty)
621 _other -> pprPanic "DsForeign.getPrimTyOf" (ppr ty)