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
50 Desugaring of @foreign@ declarations is naturally split up into
51 parts, an @import@ and an @export@ part. A @foreign import@
54 foreign import cc nm f :: prim_args -> IO prim_res
58 f :: prim_args -> IO prim_res
59 f a1 ... an = _ccall_ nm cc a1 ... an
61 so we reuse the desugaring code in @DsCCall@ to deal with these.
64 type Binding = (Id, CoreExpr) -- No rec/nonrec structure;
65 -- the occurrence analyser will sort it all out
67 dsForeigns :: [LForeignDecl Id]
68 -> DsM (ForeignStubs, [Binding])
70 = return (NoStubs, [])
72 fives <- mapM do_ldecl fos
74 (hs, cs, idss, bindss) = unzip4 fives
76 fe_init_code = map foreignExportInitialiser fe_ids
80 (vcat cs $$ vcat fe_init_code),
83 do_ldecl (L loc decl) = putSrcSpanDs loc (do_decl decl)
85 do_decl (ForeignImport id _ spec) = do
86 traceIf (text "fi start" <+> ppr id)
87 (bs, h, c) <- dsFImport (unLoc id) spec
88 traceIf (text "fi end" <+> ppr id)
91 do_decl (ForeignExport (L _ id) _ (CExport (CExportStatic ext_nm cconv))) = do
92 (h, c, _, _) <- dsFExport id (idType id) ext_nm cconv False
93 return (h, c, [id], [])
95 do_decl d = pprPanic "dsForeigns/do_decl" (ppr d)
99 %************************************************************************
101 \subsection{Foreign import}
103 %************************************************************************
105 Desugaring foreign imports is just the matter of creating a binding
106 that on its RHS unboxes its arguments, performs the external call
107 (using the @CCallOp@ primop), before boxing the result up and returning it.
109 However, we create a worker/wrapper pair, thus:
111 foreign import f :: Int -> IO Int
113 f x = IO ( \s -> case x of { I# x# ->
114 case fw s x# of { (# s1, y# #) ->
117 fw s x# = ccall f s x#
119 The strictness/CPR analyser won't do this automatically because it doesn't look
120 inside returned tuples; but inlining this wrapper is a Really Good Idea
121 because it exposes the boxing to the call site.
126 -> DsM ([Binding], SDoc, SDoc)
127 dsFImport id (CImport cconv safety _ _ spec) = do
128 (ids, h, c) <- dsCImport id spec cconv safety
131 -- FIXME: the `lib' field is needed for .NET ILX generation when invoking
132 -- routines that are external to the .NET runtime, but GHC doesn't
133 -- support such calls yet; if `nullFastString lib', the value was not given
134 dsFImport id (DNImport spec) = do
135 (ids, h, c) <- dsFCall id (DNCall spec)
142 -> DsM ([Binding], SDoc, SDoc)
143 dsCImport id (CLabel cid) cconv _ = do
145 (resTy, foRhs) <- resultWrapper ty
146 ASSERT(fromJust resTy `coreEqType` addrPrimTy) -- typechecker ensures this
148 rhs = foRhs (Lit (MachLabel cid stdcall_info))
149 stdcall_info = fun_type_arg_stdcall_info cconv ty
151 return ([(id, rhs)], empty, empty)
153 dsCImport id (CFunction target) cconv safety
154 = dsFCall id (CCall (CCallSpec target cconv safety))
155 dsCImport id CWrapper cconv _
156 = dsFExportDynamic id cconv
158 -- For stdcall labels, if the type was a FunPtr or newtype thereof,
159 -- then we need to calculate the size of the arguments in order to add
160 -- the @n suffix to the label.
161 fun_type_arg_stdcall_info :: CCallConv -> Type -> Maybe Int
162 fun_type_arg_stdcall_info StdCallConv ty
163 | Just (tc,[arg_ty]) <- splitTyConApp_maybe (repType ty),
164 tyConUnique tc == funPtrTyConKey
166 (_tvs,sans_foralls) = tcSplitForAllTys arg_ty
167 (fe_arg_tys, _orig_res_ty) = tcSplitFunTys sans_foralls
168 in Just $ sum (map (widthInBytes . typeWidth . typeCmmType . getPrimTyOf) fe_arg_tys)
169 fun_type_arg_stdcall_info _other_conv _
174 %************************************************************************
176 \subsection{Foreign calls}
178 %************************************************************************
181 dsFCall :: Id -> ForeignCall -> DsM ([(Id, Expr TyVar)], SDoc, SDoc)
182 dsFCall fn_id fcall = do
185 (tvs, fun_ty) = tcSplitForAllTys ty
186 (arg_tys, io_res_ty) = tcSplitFunTys fun_ty
187 -- Must use tcSplit* functions because we want to
188 -- see that (IO t) in the corner
190 args <- newSysLocalsDs arg_tys
191 (val_args, arg_wrappers) <- mapAndUnzipM unboxArg (map Var args)
194 work_arg_ids = [v | Var v <- val_args] -- All guaranteed to be vars
202 | forDotnet = Just <$> dsLookupGlobalId checkDotnetResName
203 | otherwise = return Nothing
207 return (\ (mb_res_ty, resWrap) ->
209 Nothing -> (Just (mkTyConApp (tupleTyCon Unboxed 1)
212 Just x -> (Just (mkTyConApp (tupleTyCon Unboxed 2)
215 | otherwise = return id
217 augment <- augmentResultDs
219 (ccall_result_ty, res_wrapper) <- boxResult augment topCon io_res_ty
221 ccall_uniq <- newUnique
222 work_uniq <- newUnique
225 worker_ty = mkForAllTys tvs (mkFunTys (map idType work_arg_ids) ccall_result_ty)
226 the_ccall_app = mkFCall ccall_uniq fcall val_args ccall_result_ty
227 work_rhs = mkLams tvs (mkLams work_arg_ids the_ccall_app)
228 work_id = mkSysLocal (fsLit "$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 return ([(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 , String -- string describing type to pass to createAdj.
268 , Int -- size of args to stub function
271 dsFExport fn_id ty ext_name cconv isDyn= do
273 (_tvs,sans_foralls) = tcSplitForAllTys ty
274 (fe_arg_tys', orig_res_ty) = tcSplitFunTys sans_foralls
275 -- We must use tcSplits here, because we want to see
276 -- the (IO t) in the corner of the type!
277 fe_arg_tys | isDyn = tail fe_arg_tys'
278 | otherwise = fe_arg_tys'
280 -- Look at the result type of the exported function, orig_res_ty
281 -- If it's IO t, return (t, True)
282 -- If it's plain t, return (t, False)
284 is_IO_res_ty) <- -- Bool
285 case tcSplitIOType_maybe orig_res_ty of
286 Just (_ioTyCon, res_ty, _co) -> return (res_ty, True)
287 -- The function already returns IO t
288 -- ToDo: what about the coercion?
289 Nothing -> return (orig_res_ty, False)
290 -- The function returns t
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 = do
333 fe_id <- newSysLocalDs ty
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 cback <- newSysLocalDs arg_ty
340 newStablePtrId <- dsLookupGlobalId newStablePtrName
341 stable_ptr_tycon <- dsLookupTyCon stablePtrTyConName
343 stable_ptr_ty = mkTyConApp stable_ptr_tycon [arg_ty]
344 export_ty = mkFunTy stable_ptr_ty arg_ty
345 bindIOId <- dsLookupGlobalId bindIOName
346 stbl_value <- newSysLocalDs stable_ptr_ty
347 (h_code, c_code, typestring, args_size) <- dsFExport id export_ty fe_nm cconv True
350 The arguments to the external function which will
351 create a little bit of (template) code on the fly
352 for allowing the (stable pointed) Haskell closure
353 to be entered using an external calling convention
356 adj_args = [ mkIntLitInt (ccallConvToInt cconv)
358 , Lit (MachLabel fe_nm mb_sz_args)
359 , Lit (mkMachString typestring)
361 -- name of external entry point providing these services.
362 -- (probably in the RTS.)
363 adjustor = fsLit "createAdjustor"
365 -- Determine the number of bytes of arguments to the stub function,
366 -- so that we can attach the '@N' suffix to its label if it is a
367 -- stdcall on Windows.
368 mb_sz_args = case cconv of
369 StdCallConv -> Just args_size
372 ccall_adj <- dsCCall adjustor adj_args PlayRisky (mkTyConApp io_tc [res_ty])
373 -- PlayRisky: the adjustor doesn't allocate in the Haskell heap or do a callback
375 let io_app = mkLams tvs $
377 mkCoerceI (mkSymCoI co) $
378 mkApps (Var bindIOId)
381 , mkApps (Var newStablePtrId) [ Type arg_ty, Var cback ]
382 , Lam stbl_value ccall_adj
385 fed = (id `setInlinePragma` NeverActive, io_app)
386 -- Never inline the f.e.d. function, because the litlit
387 -- might not be in scope in other modules.
389 return ([fed], h_code, c_code)
393 (tvs,sans_foralls) = tcSplitForAllTys ty
394 ([arg_ty], fn_res_ty) = tcSplitFunTys sans_foralls
395 Just (io_tc, res_ty, co) = tcSplitIOType_maybe fn_res_ty
396 -- Must have an IO type; hence Just
397 -- co : fn_res_ty ~ IO res_ty
399 toCName :: Id -> String
400 toCName i = showSDoc (pprCode CStyle (ppr (idName i)))
405 \subsection{Generating @foreign export@ stubs}
409 For each @foreign export@ function, a C stub function is generated.
410 The C stub constructs the application of the exported Haskell function
411 using the hugs/ghc rts invocation API.
414 mkFExportCBits :: FastString
415 -> Maybe Id -- Just==static, Nothing==dynamic
418 -> Bool -- True <=> returns an IO type
422 String, -- the argument reps
423 Int -- total size of arguments
425 mkFExportCBits c_nm maybe_target arg_htys res_hty is_IO_res_ty cc
426 = (header_bits, c_bits, type_string,
427 sum [ widthInBytes (typeWidth rep) | (_,_,_,rep) <- aug_arg_info] -- all the args
428 -- NB. the calculation here isn't strictly speaking correct.
429 -- We have a primitive Haskell type (eg. Int#, Double#), and
430 -- we want to know the size, when passed on the C stack, of
431 -- the associated C type (eg. HsInt, HsDouble). We don't have
432 -- this information to hand, but we know what GHC's conventions
433 -- are for passing around the primitive Haskell types, so we
434 -- use that instead. I hope the two coincide --SDM
437 -- list the arguments to the C function
438 arg_info :: [(SDoc, -- arg name
440 Type, -- Haskell type
441 CmmType)] -- the CmmType
442 arg_info = [ let stg_type = showStgType ty in
443 (arg_cname n stg_type,
446 typeCmmType (getPrimTyOf ty))
447 | (ty,n) <- zip arg_htys [1::Int ..] ]
450 | libffi = char '*' <> parens (stg_ty <> char '*') <>
451 ptext (sLit "args") <> brackets (int (n-1))
452 | otherwise = text ('a':show n)
454 -- generate a libffi-style stub if this is a "wrapper" and libffi is enabled
455 libffi = cLibFFI && isNothing maybe_target
458 -- libffi needs to know the result type too:
459 | libffi = primTyDescChar res_hty : arg_type_string
460 | otherwise = arg_type_string
462 arg_type_string = [primTyDescChar ty | (_,_,ty,_) <- arg_info]
463 -- just the real args
465 -- add some auxiliary args; the stable ptr in the wrapper case, and
466 -- a slot for the dummy return address in the wrapper + ccall case
468 | isNothing maybe_target = stable_ptr_arg : insertRetAddr cc arg_info
469 | otherwise = arg_info
472 (text "the_stableptr", text "StgStablePtr", undefined,
473 typeCmmType (mkStablePtrPrimTy alphaTy))
475 -- stuff to do with the return type of the C function
476 res_hty_is_unit = res_hty `coreEqType` unitTy -- Look through any newtypes
478 cResType | res_hty_is_unit = text "void"
479 | otherwise = showStgType res_hty
481 -- Now we can cook up the prototype for the exported function.
482 pprCconv = case cc of
484 StdCallConv -> text (ccallConvAttribute cc)
485 CmmCallConv -> panic "mkFExportCBits/pprCconv CmmCallConv"
487 header_bits = ptext (sLit "extern") <+> fun_proto <> semi
490 | null aug_arg_info = text "void"
491 | otherwise = hsep $ punctuate comma
492 $ map (\(nm,ty,_,_) -> ty <+> nm) aug_arg_info
496 = ptext (sLit "void") <+> ftext c_nm <>
497 parens (ptext (sLit "void *cif STG_UNUSED, void* resp, void** args, void* the_stableptr"))
499 = cResType <+> pprCconv <+> ftext c_nm <> parens fun_args
501 -- the target which will form the root of what we ask rts_evalIO to run
503 = case maybe_target of
504 Nothing -> text "(StgClosure*)deRefStablePtr(the_stableptr)"
505 Just hs_fn -> char '&' <> ppr hs_fn <> text "_closure"
507 cap = text "cap" <> comma
509 -- the expression we give to rts_evalIO
511 = foldl appArg the_cfun arg_info -- NOT aug_arg_info
513 appArg acc (arg_cname, _, arg_hty, _)
515 <> parens (cap <> acc <> comma <> mkHObj arg_hty <> parens (cap <> arg_cname))
517 -- various other bits for inside the fn
518 declareResult = text "HaskellObj ret;"
519 declareCResult | res_hty_is_unit = empty
520 | otherwise = cResType <+> text "cret;"
522 assignCResult | res_hty_is_unit = empty
524 text "cret=" <> unpackHObj res_hty <> parens (text "ret") <> semi
526 -- an extern decl for the fn being called
528 = case maybe_target of
530 Just hs_fn -> text "extern StgClosure " <> ppr hs_fn <> text "_closure" <> semi
533 -- finally, the whole darn thing
540 , ptext (sLit "Capability *cap;")
543 , text "cap = rts_lock();"
544 -- create the application + perform it.
545 , ptext (sLit "cap=rts_evalIO") <> parens (
547 ptext (sLit "rts_apply") <> parens (
550 <> ptext (if is_IO_res_ty
551 then (sLit "runIO_closure")
552 else (sLit "runNonIO_closure"))
558 , ptext (sLit "rts_checkSchedStatus") <> parens (doubleQuotes (ftext c_nm)
559 <> comma <> text "cap") <> semi
561 , ptext (sLit "rts_unlock(cap);")
562 , if res_hty_is_unit then empty
564 then char '*' <> parens (cResType <> char '*') <>
565 ptext (sLit "resp = cret;")
566 else ptext (sLit "return cret;")
571 foreignExportInitialiser :: Id -> SDoc
572 foreignExportInitialiser hs_fn =
573 -- Initialise foreign exports by registering a stable pointer from an
574 -- __attribute__((constructor)) function.
575 -- The alternative is to do this from stginit functions generated in
576 -- codeGen/CodeGen.lhs; however, stginit functions have a negative impact
577 -- on binary sizes and link times because the static linker will think that
578 -- all modules that are imported directly or indirectly are actually used by
580 -- (this is bad for big umbrella modules like Graphics.Rendering.OpenGL)
582 [ text "static void stginit_export_" <> ppr hs_fn
583 <> text "() __attribute__((constructor));"
584 , text "static void stginit_export_" <> ppr hs_fn <> text "()"
585 , braces (text "getStablePtr"
586 <> parens (text "(StgPtr) &" <> ppr hs_fn <> text "_closure")
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 insertRetAddr :: CCallConv -> [(SDoc, SDoc, Type, CmmType)]
608 -> [(SDoc, SDoc, Type, CmmType)]
609 #if !defined(x86_64_TARGET_ARCH)
610 insertRetAddr CCallConv args = ret_addr_arg : args
611 insertRetAddr _ args = args
613 -- On x86_64 we insert the return address after the 6th
614 -- integer argument, because this is the point at which we
615 -- need to flush a register argument to the stack (See rts/Adjustor.c for
617 insertRetAddr CCallConv args = go 0 args
618 where go :: Int -> [(SDoc, SDoc, Type, CmmType)]
619 -> [(SDoc, SDoc, Type, CmmType)]
620 go 6 args = ret_addr_arg : args
621 go n (arg@(_,_,_,rep):args)
622 | cmmEqType_ignoring_ptrhood rep b64 = arg : go (n+1) args
623 | otherwise = arg : go n args
625 insertRetAddr _ args = args
628 ret_addr_arg :: (SDoc, SDoc, Type, CmmType)
629 ret_addr_arg = (text "original_return_addr", text "void*", undefined,
630 typeCmmType addrPrimTy)
632 -- This function returns the primitive type associated with the boxed
633 -- type argument to a foreign export (eg. Int ==> Int#).
634 getPrimTyOf :: Type -> Type
636 | isBoolTy rep_ty = intPrimTy
637 -- Except for Bool, the types we are interested in have a single constructor
638 -- with a single primitive-typed argument (see TcType.legalFEArgTyCon).
640 case splitProductType_maybe rep_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)
649 -- represent a primitive type as a Char, for building a string that
650 -- described the foreign function type. The types are size-dependent,
651 -- e.g. 'W' is a signed 32-bit integer.
652 primTyDescChar :: Type -> Char
654 | ty `coreEqType` unitTy = 'v'
656 = case typePrimRep (getPrimTyOf ty) of
657 IntRep -> signed_word
658 WordRep -> unsigned_word
664 _ -> pprPanic "primTyDescChar" (ppr ty)
666 (signed_word, unsigned_word)
667 | wORD_SIZE == 4 = ('W','w')
668 | wORD_SIZE == 8 = ('L','l')
669 | otherwise = panic "primTyDescChar"