2 % (c) The University of Glasgow 2006
3 % (c) The AQUA Project, Glasgow University, 1998
6 Desugaring foreign declarations (see also DsCCall).
10 -- The above warning supression flag is a temporary kludge.
11 -- While working on this module you are encouraged to remove it and fix
12 -- any warnings in the module. See
13 -- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
16 module DsForeign ( dsForeigns ) where
18 #include "HsVersions.h"
19 import TcRnMonad -- temp
55 Desugaring of @foreign@ declarations is naturally split up into
56 parts, an @import@ and an @export@ part. A @foreign import@
59 foreign import cc nm f :: prim_args -> IO prim_res
63 f :: prim_args -> IO prim_res
64 f a1 ... an = _ccall_ nm cc a1 ... an
66 so we reuse the desugaring code in @DsCCall@ to deal with these.
69 type Binding = (Id, CoreExpr) -- No rec/nonrec structure;
70 -- the occurrence analyser will sort it all out
72 dsForeigns :: [LForeignDecl Id]
73 -> DsM (ForeignStubs, [Binding])
75 = return (NoStubs, [])
77 fives <- mapM do_ldecl fos
79 (hs, cs, hdrs, idss, bindss) = unzip5 fives
81 fe_init_code = map foreignExportInitialiser fe_ids
85 (vcat cs $$ vcat fe_init_code)
89 do_ldecl (L loc decl) = putSrcSpanDs loc (do_decl decl)
91 do_decl (ForeignImport id _ spec) = do
92 traceIf (text "fi start" <+> ppr id)
93 (bs, h, c, mbhd) <- dsFImport (unLoc id) spec
94 traceIf (text "fi end" <+> ppr id)
95 return (h, c, maybeToList mbhd, [], bs)
97 do_decl (ForeignExport (L _ id) _ (CExport (CExportStatic ext_nm cconv))) = do
98 (h, c, _, _) <- dsFExport id (idType id) ext_nm cconv False
99 return (h, c, [], [id], [])
103 %************************************************************************
105 \subsection{Foreign import}
107 %************************************************************************
109 Desugaring foreign imports is just the matter of creating a binding
110 that on its RHS unboxes its arguments, performs the external call
111 (using the @CCallOp@ primop), before boxing the result up and returning it.
113 However, we create a worker/wrapper pair, thus:
115 foreign import f :: Int -> IO Int
117 f x = IO ( \s -> case x of { I# x# ->
118 case fw s x# of { (# s1, y# #) ->
121 fw s x# = ccall f s x#
123 The strictness/CPR analyser won't do this automatically because it doesn't look
124 inside returned tuples; but inlining this wrapper is a Really Good Idea
125 because it exposes the boxing to the call site.
130 -> DsM ([Binding], SDoc, SDoc, Maybe FastString)
131 dsFImport id (CImport cconv safety header lib spec) = do
132 (ids, h, c) <- dsCImport id spec cconv safety no_hdrs
133 return (ids, h, c, if no_hdrs then Nothing else Just header)
135 no_hdrs = nullFS header
137 -- FIXME: the `lib' field is needed for .NET ILX generation when invoking
138 -- routines that are external to the .NET runtime, but GHC doesn't
139 -- support such calls yet; if `nullFastString lib', the value was not given
140 dsFImport id (DNImport spec) = do
141 (ids, h, c) <- dsFCall id (DNCall spec) True {- No headers -}
142 return (ids, h, c, Nothing)
148 -> Bool -- True <=> no headers in the f.i decl
149 -> DsM ([Binding], SDoc, SDoc)
150 dsCImport id (CLabel cid) _ _ no_hdrs = do
151 (resTy, foRhs) <- resultWrapper (idType id)
152 ASSERT(fromJust resTy `coreEqType` addrPrimTy) -- typechecker ensures this
153 let rhs = foRhs (mkLit (MachLabel cid Nothing)) in
154 return ([(setImpInline no_hdrs id, rhs)], empty, empty)
155 dsCImport id (CFunction target) cconv safety no_hdrs
156 = dsFCall id (CCall (CCallSpec target cconv safety)) no_hdrs
157 dsCImport id CWrapper cconv _ _
158 = dsFExportDynamic id cconv
160 setImpInline :: Bool -- True <=> No #include headers
161 -- in the foreign import declaration
163 -- If there is a #include header in the foreign import
164 -- we make the worker non-inlinable, because we currently
165 -- don't keep the #include stuff in the CCallId, and hence
166 -- it won't be visible in the importing module, which can be
168 -- (The #include stuff is just collected from the foreign import
169 -- decls in a module.)
170 -- If you want to do cross-module inlining of the c-calls themselves,
171 -- put the #include stuff in the package spec, not the foreign
173 setImpInline True id = id
174 setImpInline False id = id `setInlinePragma` NeverActive
178 %************************************************************************
180 \subsection{Foreign calls}
182 %************************************************************************
185 dsFCall fn_id fcall no_hdrs = do
188 (tvs, fun_ty) = tcSplitForAllTys ty
189 (arg_tys, io_res_ty) = tcSplitFunTys fun_ty
190 -- Must use tcSplit* functions because we want to
191 -- see that (IO t) in the corner
193 args <- newSysLocalsDs arg_tys
194 (val_args, arg_wrappers) <- mapAndUnzipM unboxArg (map Var args)
197 work_arg_ids = [v | Var v <- val_args] -- All guaranteed to be vars
205 | forDotnet = Just <$> dsLookupGlobalId checkDotnetResName
206 | otherwise = return Nothing
210 err_res <- newSysLocalDs addrPrimTy
211 return (\ (mb_res_ty, resWrap) ->
213 Nothing -> (Just (mkTyConApp (tupleTyCon Unboxed 1)
216 Just x -> (Just (mkTyConApp (tupleTyCon Unboxed 2)
219 | otherwise = return id
221 augment <- augmentResultDs
223 (ccall_result_ty, res_wrapper) <- boxResult augment topCon io_res_ty
225 ccall_uniq <- newUnique
226 work_uniq <- newUnique
229 worker_ty = mkForAllTys tvs (mkFunTys (map idType work_arg_ids) ccall_result_ty)
230 the_ccall_app = mkFCall ccall_uniq fcall val_args ccall_result_ty
231 work_rhs = mkLams tvs (mkLams work_arg_ids the_ccall_app)
232 work_id = setImpInline no_hdrs $ -- See comments with setImpInline
233 mkSysLocal FSLIT("$wccall") work_uniq worker_ty
236 work_app = mkApps (mkVarApps (Var work_id) tvs) val_args
237 wrapper_body = foldr ($) (res_wrapper work_app) arg_wrappers
238 wrap_rhs = mkInlineMe (mkLams (tvs ++ args) wrapper_body)
240 return ([(work_id, work_rhs), (fn_id, wrap_rhs)], empty, empty)
244 %************************************************************************
246 \subsection{Foreign export}
248 %************************************************************************
250 The function that does most of the work for `@foreign export@' declarations.
251 (see below for the boilerplate code a `@foreign export@' declaration expands
254 For each `@foreign export foo@' in a module M we generate:
256 \item a C function `@foo@', which calls
257 \item a Haskell stub `@M.$ffoo@', which calls
259 the user-written Haskell function `@M.foo@'.
262 dsFExport :: Id -- Either the exported Id,
263 -- or the foreign-export-dynamic constructor
264 -> Type -- The type of the thing callable from C
265 -> CLabelString -- The name to export to C land
267 -> Bool -- True => foreign export dynamic
268 -- so invoke IO action that's hanging off
269 -- the first argument's stable pointer
270 -> DsM ( SDoc -- contents of Module_stub.h
271 , SDoc -- contents of Module_stub.c
272 , String -- string describing type to pass to createAdj.
273 , Int -- size of args to stub function
276 dsFExport fn_id ty ext_name cconv isDyn= do
278 (_tvs,sans_foralls) = tcSplitForAllTys ty
279 (fe_arg_tys', orig_res_ty) = tcSplitFunTys sans_foralls
280 -- We must use tcSplits here, because we want to see
281 -- the (IO t) in the corner of the type!
282 fe_arg_tys | isDyn = tail fe_arg_tys'
283 | otherwise = fe_arg_tys'
285 -- Look at the result type of the exported function, orig_res_ty
286 -- If it's IO t, return (t, True)
287 -- If it's plain t, return (t, False)
289 is_IO_res_ty) <- -- Bool
290 case tcSplitIOType_maybe orig_res_ty of
291 Just (ioTyCon, res_ty, co) -> return (res_ty, True)
292 -- The function already returns IO t
293 -- ToDo: what about the coercion?
294 Nothing -> return (orig_res_ty, False)
295 -- The function returns t
298 mkFExportCBits ext_name
299 (if isDyn then Nothing else Just fn_id)
300 fe_arg_tys res_ty is_IO_res_ty cconv
303 @foreign import "wrapper"@ (previously "foreign export dynamic") lets
304 you dress up Haskell IO actions of some fixed type behind an
305 externally callable interface (i.e., as a C function pointer). Useful
306 for callbacks and stuff.
309 type Fun = Bool -> Int -> IO Int
310 foreign import "wrapper" f :: Fun -> IO (FunPtr Fun)
312 -- Haskell-visible constructor, which is generated from the above:
313 -- SUP: No check for NULL from createAdjustor anymore???
315 f :: Fun -> IO (FunPtr Fun)
317 bindIO (newStablePtr cback)
318 (\StablePtr sp# -> IO (\s1# ->
319 case _ccall_ createAdjustor cconv sp# ``f_helper'' <arg info> s1# of
320 (# s2#, a# #) -> (# s2#, A# a# #)))
322 foreign import "&f_helper" f_helper :: FunPtr (StablePtr Fun -> Fun)
324 -- and the helper in C:
326 f_helper(StablePtr s, HsBool b, HsInt i)
328 rts_evalIO(rts_apply(rts_apply(deRefStablePtr(s),
329 rts_mkBool(b)), rts_mkInt(i)));
334 dsFExportDynamic :: Id
336 -> DsM ([Binding], SDoc, SDoc)
337 dsFExportDynamic id cconv = do
338 fe_id <- newSysLocalDs ty
341 -- hack: need to get at the name of the C stub we're about to generate.
342 fe_nm = mkFastString (unpackFS (zEncodeFS (moduleNameFS (moduleName mod))) ++ "_" ++ toCName fe_id)
344 cback <- newSysLocalDs arg_ty
345 newStablePtrId <- dsLookupGlobalId newStablePtrName
346 stable_ptr_tycon <- dsLookupTyCon stablePtrTyConName
348 stable_ptr_ty = mkTyConApp stable_ptr_tycon [arg_ty]
349 export_ty = mkFunTy stable_ptr_ty arg_ty
350 bindIOId <- dsLookupGlobalId bindIOName
351 stbl_value <- newSysLocalDs stable_ptr_ty
352 (h_code, c_code, typestring, args_size) <- dsFExport id export_ty fe_nm cconv True
355 The arguments to the external function which will
356 create a little bit of (template) code on the fly
357 for allowing the (stable pointed) Haskell closure
358 to be entered using an external calling convention
361 adj_args = [ mkIntLitInt (ccallConvToInt cconv)
363 , mkLit (MachLabel fe_nm mb_sz_args)
364 , mkLit (mkStringLit typestring)
366 -- name of external entry point providing these services.
367 -- (probably in the RTS.)
368 adjustor = FSLIT("createAdjustor")
370 -- Determine the number of bytes of arguments to the stub function,
371 -- so that we can attach the '@N' suffix to its label if it is a
372 -- stdcall on Windows.
373 mb_sz_args = case cconv of
374 StdCallConv -> Just args_size
377 ccall_adj <- dsCCall adjustor adj_args PlayRisky (mkTyConApp io_tc [res_ty])
378 -- PlayRisky: the adjustor doesn't allocate in the Haskell heap or do a callback
380 let io_app = mkLams tvs $
382 mkCoerceI (mkSymCoI co) $
383 mkApps (Var bindIOId)
386 , mkApps (Var newStablePtrId) [ Type arg_ty, Var cback ]
387 , Lam stbl_value ccall_adj
390 fed = (id `setInlinePragma` NeverActive, io_app)
391 -- Never inline the f.e.d. function, because the litlit
392 -- might not be in scope in other modules.
394 return ([fed], h_code, c_code)
398 (tvs,sans_foralls) = tcSplitForAllTys ty
399 ([arg_ty], fn_res_ty) = tcSplitFunTys sans_foralls
400 Just (io_tc, res_ty, co) = tcSplitIOType_maybe fn_res_ty
401 -- Must have an IO type; hence Just
402 -- co : fn_res_ty ~ IO res_ty
404 toCName :: Id -> String
405 toCName i = showSDoc (pprCode CStyle (ppr (idName i)))
410 \subsection{Generating @foreign export@ stubs}
414 For each @foreign export@ function, a C stub function is generated.
415 The C stub constructs the application of the exported Haskell function
416 using the hugs/ghc rts invocation API.
419 mkFExportCBits :: FastString
420 -> Maybe Id -- Just==static, Nothing==dynamic
423 -> Bool -- True <=> returns an IO type
427 String, -- the argument reps
428 Int -- total size of arguments
430 mkFExportCBits c_nm maybe_target arg_htys res_hty is_IO_res_ty cc
431 = (header_bits, c_bits, type_string,
432 sum [ machRepByteWidth rep | (_,_,_,rep) <- aug_arg_info] -- all the args
435 -- list the arguments to the C function
436 arg_info :: [(SDoc, -- arg name
438 Type, -- Haskell type
439 MachRep)] -- the MachRep
440 arg_info = [ let stg_type = showStgType ty in
441 (arg_cname n stg_type,
444 typeMachRep (getPrimTyOf ty))
445 | (ty,n) <- zip arg_htys [1::Int ..] ]
448 | libffi = char '*' <> parens (stg_ty <> char '*') <>
449 ptext SLIT("args") <> brackets (int (n-1))
450 | otherwise = text ('a':show n)
452 -- generate a libffi-style stub if this is a "wrapper" and libffi is enabled
453 libffi = cLibFFI && isNothing maybe_target
456 -- libffi needs to know the result type too:
457 | libffi = primTyDescChar res_hty : arg_type_string
458 | otherwise = arg_type_string
460 arg_type_string = [primTyDescChar ty | (_,_,ty,_) <- arg_info]
461 -- just the real args
463 -- add some auxiliary args; the stable ptr in the wrapper case, and
464 -- a slot for the dummy return address in the wrapper + ccall case
466 | isNothing maybe_target = stable_ptr_arg : insertRetAddr cc arg_info
467 | otherwise = arg_info
470 (text "the_stableptr", text "StgStablePtr", undefined,
471 typeMachRep (mkStablePtrPrimTy alphaTy))
473 -- stuff to do with the return type of the C function
474 res_hty_is_unit = res_hty `coreEqType` unitTy -- Look through any newtypes
476 cResType | res_hty_is_unit = text "void"
477 | otherwise = showStgType res_hty
479 -- Now we can cook up the prototype for the exported function.
480 pprCconv = case cc of
482 StdCallConv -> text (ccallConvAttribute cc)
484 header_bits = ptext SLIT("extern") <+> fun_proto <> semi
488 = ptext SLIT("void") <+> ftext c_nm <>
489 parens (ptext SLIT("void *cif STG_UNUSED, void* resp, void** args, void* the_stableptr"))
491 = cResType <+> pprCconv <+> ftext c_nm <>
492 parens (hsep (punctuate comma (map (\(nm,ty,_,_) -> ty <+> nm)
495 -- the target which will form the root of what we ask rts_evalIO to run
497 = case maybe_target of
498 Nothing -> text "(StgClosure*)deRefStablePtr(the_stableptr)"
499 Just hs_fn -> char '&' <> ppr hs_fn <> text "_closure"
501 cap = text "cap" <> comma
503 -- the expression we give to rts_evalIO
505 = foldl appArg the_cfun arg_info -- NOT aug_arg_info
507 appArg acc (arg_cname, _, arg_hty, _)
509 <> parens (cap <> acc <> comma <> mkHObj arg_hty <> parens (cap <> arg_cname))
511 -- various other bits for inside the fn
512 declareResult = text "HaskellObj ret;"
513 declareCResult | res_hty_is_unit = empty
514 | otherwise = cResType <+> text "cret;"
516 assignCResult | res_hty_is_unit = empty
518 text "cret=" <> unpackHObj res_hty <> parens (text "ret") <> semi
520 -- an extern decl for the fn being called
522 = case maybe_target of
524 Just hs_fn -> text "extern StgClosure " <> ppr hs_fn <> text "_closure" <> semi
527 -- finally, the whole darn thing
534 , ptext SLIT("Capability *cap;")
537 , text "cap = rts_lock();"
538 -- create the application + perform it.
539 , ptext SLIT("cap=rts_evalIO") <> parens (
541 ptext SLIT("rts_apply") <> parens (
544 <> ptext (if is_IO_res_ty
545 then SLIT("runIO_closure")
546 else SLIT("runNonIO_closure"))
552 , ptext SLIT("rts_checkSchedStatus") <> parens (doubleQuotes (ftext c_nm)
553 <> comma <> text "cap") <> semi
555 , ptext SLIT("rts_unlock(cap);")
556 , if res_hty_is_unit then empty
558 then char '*' <> parens (cResType <> char '*') <>
559 ptext SLIT("resp = cret;")
560 else ptext SLIT("return cret;")
565 foreignExportInitialiser :: Id -> SDoc
566 foreignExportInitialiser hs_fn =
567 -- Initialise foreign exports by registering a stable pointer from an
568 -- __attribute__((constructor)) function.
569 -- The alternative is to do this from stginit functions generated in
570 -- codeGen/CodeGen.lhs; however, stginit functions have a negative impact
571 -- on binary sizes and link times because the static linker will think that
572 -- all modules that are imported directly or indirectly are actually used by
574 -- (this is bad for big umbrella modules like Graphics.Rendering.OpenGL)
576 [ text "static void stginit_export_" <> ppr hs_fn
577 <> text "() __attribute__((constructor));"
578 , text "static void stginit_export_" <> ppr hs_fn <> text "()"
579 , braces (text "getStablePtr"
580 <> parens (text "(StgPtr) &" <> ppr hs_fn <> text "_closure")
585 -- NB. the calculation here isn't strictly speaking correct.
586 -- We have a primitive Haskell type (eg. Int#, Double#), and
587 -- we want to know the size, when passed on the C stack, of
588 -- the associated C type (eg. HsInt, HsDouble). We don't have
589 -- this information to hand, but we know what GHC's conventions
590 -- are for passing around the primitive Haskell types, so we
591 -- use that instead. I hope the two coincide --SDM
592 typeMachRep ty = argMachRep (typeCgRep ty)
594 mkHObj :: Type -> SDoc
595 mkHObj t = text "rts_mk" <> text (showFFIType t)
597 unpackHObj :: Type -> SDoc
598 unpackHObj t = text "rts_get" <> text (showFFIType t)
600 showStgType :: Type -> SDoc
601 showStgType t = text "Hs" <> text (showFFIType t)
603 showFFIType :: Type -> String
604 showFFIType t = getOccString (getName tc)
606 tc = case tcSplitTyConApp_maybe (repType t) of
608 Nothing -> pprPanic "showFFIType" (ppr t)
610 #if !defined(x86_64_TARGET_ARCH)
611 insertRetAddr CCallConv args = ret_addr_arg : args
612 insertRetAddr _ args = args
614 -- On x86_64 we insert the return address after the 6th
615 -- integer argument, because this is the point at which we
616 -- need to flush a register argument to the stack (See rts/Adjustor.c for
618 insertRetAddr CCallConv args = go 0 args
619 where go 6 args = ret_addr_arg : args
620 go n (arg@(_,_,_,rep):args)
621 | I64 <- rep = arg : go (n+1) args
622 | otherwise = arg : go n args
624 insertRetAddr _ args = args
627 ret_addr_arg = (text "original_return_addr", text "void*", undefined,
628 typeMachRep addrPrimTy)
630 -- This function returns the primitive type associated with the boxed
631 -- type argument to a foreign export (eg. Int ==> Int#).
632 getPrimTyOf :: Type -> Type
634 | isBoolTy rep_ty = intPrimTy
635 -- Except for Bool, the types we are interested in have a single constructor
636 -- with a single primitive-typed argument (see TcType.legalFEArgTyCon).
638 case splitProductType_maybe rep_ty of
639 Just (_, _, data_con, [prim_ty]) ->
640 ASSERT(dataConSourceArity data_con == 1)
641 ASSERT2(isUnLiftedType prim_ty, ppr prim_ty)
643 _other -> pprPanic "DsForeign.getPrimTyOf" (ppr ty)
647 -- represent a primitive type as a Char, for building a string that
648 -- described the foreign function type. The types are size-dependent,
649 -- e.g. 'W' is a signed 32-bit integer.
650 primTyDescChar :: Type -> Char
652 | ty `coreEqType` unitTy = 'v'
654 = case typePrimRep (getPrimTyOf ty) of
655 IntRep -> signed_word
656 WordRep -> unsigned_word
662 _ -> pprPanic "primTyDescChar" (ppr ty)
664 (signed_word, unsigned_word)
665 | wORD_SIZE == 4 = ('W','w')
666 | wORD_SIZE == 8 = ('L','l')
667 | otherwise = panic "primTyDescChar"