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, OrdList Binding)
70 = return (NoStubs, nilOL)
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),
81 foldr (appOL . toOL) nilOL bindss)
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], [])
97 %************************************************************************
99 \subsection{Foreign import}
101 %************************************************************************
103 Desugaring foreign imports is just the matter of creating a binding
104 that on its RHS unboxes its arguments, performs the external call
105 (using the @CCallOp@ primop), before boxing the result up and returning it.
107 However, we create a worker/wrapper pair, thus:
109 foreign import f :: Int -> IO Int
111 f x = IO ( \s -> case x of { I# x# ->
112 case fw s x# of { (# s1, y# #) ->
115 fw s x# = ccall f s x#
117 The strictness/CPR analyser won't do this automatically because it doesn't look
118 inside returned tuples; but inlining this wrapper is a Really Good Idea
119 because it exposes the boxing to the call site.
124 -> DsM ([Binding], SDoc, SDoc)
125 dsFImport id (CImport cconv safety _ spec) = do
126 (ids, h, c) <- dsCImport id spec cconv safety
133 -> DsM ([Binding], SDoc, SDoc)
134 dsCImport id (CLabel cid) cconv _ = do
136 fod = case splitTyConApp_maybe (repType ty) of
138 | tyConUnique tycon == funPtrTyConKey ->
141 (resTy, foRhs) <- resultWrapper ty
142 ASSERT(fromJust resTy `eqType` addrPrimTy) -- typechecker ensures this
144 rhs = foRhs (Lit (MachLabel cid stdcall_info fod))
145 stdcall_info = fun_type_arg_stdcall_info cconv ty
147 return ([(id, rhs)], empty, empty)
149 dsCImport id (CFunction target) cconv@PrimCallConv safety
150 = dsPrimCall id (CCall (CCallSpec target cconv safety))
151 dsCImport id (CFunction target) cconv safety
152 = dsFCall id (CCall (CCallSpec target cconv safety))
153 dsCImport id CWrapper cconv _
154 = dsFExportDynamic id cconv
156 -- For stdcall labels, if the type was a FunPtr or newtype thereof,
157 -- then we need to calculate the size of the arguments in order to add
158 -- the @n suffix to the label.
159 fun_type_arg_stdcall_info :: CCallConv -> Type -> Maybe Int
160 fun_type_arg_stdcall_info StdCallConv ty
161 | Just (tc,[arg_ty]) <- splitTyConApp_maybe (repType ty),
162 tyConUnique tc == funPtrTyConKey
164 (_tvs,sans_foralls) = tcSplitForAllTys arg_ty
165 (fe_arg_tys, _orig_res_ty) = tcSplitFunTys sans_foralls
166 in Just $ sum (map (widthInBytes . typeWidth . typeCmmType . getPrimTyOf) fe_arg_tys)
167 fun_type_arg_stdcall_info _other_conv _
172 %************************************************************************
174 \subsection{Foreign calls}
176 %************************************************************************
179 dsFCall :: Id -> ForeignCall -> DsM ([(Id, Expr TyVar)], SDoc, SDoc)
180 dsFCall fn_id fcall = do
183 (tvs, fun_ty) = tcSplitForAllTys ty
184 (arg_tys, io_res_ty) = tcSplitFunTys fun_ty
185 -- Must use tcSplit* functions because we want to
186 -- see that (IO t) in the corner
188 args <- newSysLocalsDs arg_tys
189 (val_args, arg_wrappers) <- mapAndUnzipM unboxArg (map Var args)
192 work_arg_ids = [v | Var v <- val_args] -- All guaranteed to be vars
194 (ccall_result_ty, res_wrapper) <- boxResult io_res_ty
196 ccall_uniq <- newUnique
197 work_uniq <- newUnique
200 worker_ty = mkForAllTys tvs (mkFunTys (map idType work_arg_ids) ccall_result_ty)
201 the_ccall_app = mkFCall ccall_uniq fcall val_args ccall_result_ty
202 work_rhs = mkLams tvs (mkLams work_arg_ids the_ccall_app)
203 work_id = mkSysLocal (fsLit "$wccall") work_uniq worker_ty
206 work_app = mkApps (mkVarApps (Var work_id) tvs) val_args
207 wrapper_body = foldr ($) (res_wrapper work_app) arg_wrappers
208 wrap_rhs = mkLams (tvs ++ args) wrapper_body
209 fn_id_w_inl = fn_id `setIdUnfolding` mkInlineUnfolding (Just (length args)) wrap_rhs
211 return ([(work_id, work_rhs), (fn_id_w_inl, wrap_rhs)], empty, empty)
215 %************************************************************************
217 \subsection{Primitive calls}
219 %************************************************************************
221 This is for `@foreign import prim@' declarations.
223 Currently, at the core level we pretend that these primitive calls are
224 foreign calls. It may make more sense in future to have them as a distinct
225 kind of Id, or perhaps to bundle them with PrimOps since semantically and
226 for calling convention they are really prim ops.
229 dsPrimCall :: Id -> ForeignCall -> DsM ([(Id, Expr TyVar)], SDoc, SDoc)
230 dsPrimCall fn_id fcall = do
233 (tvs, fun_ty) = tcSplitForAllTys ty
234 (arg_tys, io_res_ty) = tcSplitFunTys fun_ty
235 -- Must use tcSplit* functions because we want to
236 -- see that (IO t) in the corner
238 args <- newSysLocalsDs arg_tys
240 ccall_uniq <- newUnique
242 call_app = mkFCall ccall_uniq fcall (map Var args) io_res_ty
243 rhs = mkLams tvs (mkLams args call_app)
244 return ([(fn_id, rhs)], empty, empty)
248 %************************************************************************
250 \subsection{Foreign export}
252 %************************************************************************
254 The function that does most of the work for `@foreign export@' declarations.
255 (see below for the boilerplate code a `@foreign export@' declaration expands
258 For each `@foreign export foo@' in a module M we generate:
260 \item a C function `@foo@', which calls
261 \item a Haskell stub `@M.\$ffoo@', which calls
263 the user-written Haskell function `@M.foo@'.
266 dsFExport :: Id -- Either the exported Id,
267 -- or the foreign-export-dynamic constructor
268 -> Type -- The type of the thing callable from C
269 -> CLabelString -- The name to export to C land
271 -> Bool -- True => foreign export dynamic
272 -- so invoke IO action that's hanging off
273 -- the first argument's stable pointer
274 -> DsM ( SDoc -- contents of Module_stub.h
275 , SDoc -- contents of Module_stub.c
276 , String -- string describing type to pass to createAdj.
277 , Int -- size of args to stub function
280 dsFExport fn_id ty ext_name cconv isDyn= do
282 (_tvs,sans_foralls) = tcSplitForAllTys ty
283 (fe_arg_tys', orig_res_ty) = tcSplitFunTys sans_foralls
284 -- We must use tcSplits here, because we want to see
285 -- the (IO t) in the corner of the type!
286 fe_arg_tys | isDyn = tail fe_arg_tys'
287 | otherwise = fe_arg_tys'
289 -- Look at the result type of the exported function, orig_res_ty
290 -- If it's IO t, return (t, True)
291 -- If it's plain t, return (t, False)
293 is_IO_res_ty) <- -- Bool
294 case tcSplitIOType_maybe orig_res_ty of
295 Just (_ioTyCon, res_ty, _co) -> return (res_ty, True)
296 -- The function already returns IO t
297 -- ToDo: what about the coercion?
298 Nothing -> return (orig_res_ty, False)
299 -- The function returns t
302 mkFExportCBits ext_name
303 (if isDyn then Nothing else Just fn_id)
304 fe_arg_tys res_ty is_IO_res_ty cconv
307 @foreign import "wrapper"@ (previously "foreign export dynamic") lets
308 you dress up Haskell IO actions of some fixed type behind an
309 externally callable interface (i.e., as a C function pointer). Useful
310 for callbacks and stuff.
313 type Fun = Bool -> Int -> IO Int
314 foreign import "wrapper" f :: Fun -> IO (FunPtr Fun)
316 -- Haskell-visible constructor, which is generated from the above:
317 -- SUP: No check for NULL from createAdjustor anymore???
319 f :: Fun -> IO (FunPtr Fun)
321 bindIO (newStablePtr cback)
322 (\StablePtr sp# -> IO (\s1# ->
323 case _ccall_ createAdjustor cconv sp# ``f_helper'' <arg info> s1# of
324 (# s2#, a# #) -> (# s2#, A# a# #)))
326 foreign import "&f_helper" f_helper :: FunPtr (StablePtr Fun -> Fun)
328 -- and the helper in C:
330 f_helper(StablePtr s, HsBool b, HsInt i)
332 rts_evalIO(rts_apply(rts_apply(deRefStablePtr(s),
333 rts_mkBool(b)), rts_mkInt(i)));
338 dsFExportDynamic :: Id
340 -> DsM ([Binding], SDoc, SDoc)
341 dsFExportDynamic id cconv = do
342 fe_id <- newSysLocalDs ty
345 -- hack: need to get at the name of the C stub we're about to generate.
346 fe_nm = mkFastString (unpackFS (zEncodeFS (moduleNameFS (moduleName mod))) ++ "_" ++ toCName fe_id)
348 cback <- newSysLocalDs arg_ty
349 newStablePtrId <- dsLookupGlobalId newStablePtrName
350 stable_ptr_tycon <- dsLookupTyCon stablePtrTyConName
352 stable_ptr_ty = mkTyConApp stable_ptr_tycon [arg_ty]
353 export_ty = mkFunTy stable_ptr_ty arg_ty
354 bindIOId <- dsLookupGlobalId bindIOName
355 stbl_value <- newSysLocalDs stable_ptr_ty
356 (h_code, c_code, typestring, args_size) <- dsFExport id export_ty fe_nm cconv True
359 The arguments to the external function which will
360 create a little bit of (template) code on the fly
361 for allowing the (stable pointed) Haskell closure
362 to be entered using an external calling convention
365 adj_args = [ mkIntLitInt (ccallConvToInt cconv)
367 , Lit (MachLabel fe_nm mb_sz_args IsFunction)
368 , Lit (mkMachString typestring)
370 -- name of external entry point providing these services.
371 -- (probably in the RTS.)
372 adjustor = fsLit "createAdjustor"
374 -- Determine the number of bytes of arguments to the stub function,
375 -- so that we can attach the '@N' suffix to its label if it is a
376 -- stdcall on Windows.
377 mb_sz_args = case cconv of
378 StdCallConv -> Just args_size
381 ccall_adj <- dsCCall adjustor adj_args PlayRisky (mkTyConApp io_tc [res_ty])
382 -- PlayRisky: the adjustor doesn't allocate in the Haskell heap or do a callback
384 let io_app = mkLams tvs $
386 mkCoerce (mkSymCo co) $
387 mkApps (Var bindIOId)
390 , mkApps (Var newStablePtrId) [ Type arg_ty, Var cback ]
391 , Lam stbl_value ccall_adj
394 fed = (id `setInlineActivation` NeverActive, io_app)
395 -- Never inline the f.e.d. function, because the litlit
396 -- might not be in scope in other modules.
398 return ([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 String, -- 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, type_string,
436 sum [ widthInBytes (typeWidth rep) | (_,_,_,rep) <- aug_arg_info] -- all the args
437 -- NB. the calculation here isn't strictly speaking correct.
438 -- We have a primitive Haskell type (eg. Int#, Double#), and
439 -- we want to know the size, when passed on the C stack, of
440 -- the associated C type (eg. HsInt, HsDouble). We don't have
441 -- this information to hand, but we know what GHC's conventions
442 -- are for passing around the primitive Haskell types, so we
443 -- use that instead. I hope the two coincide --SDM
446 -- list the arguments to the C function
447 arg_info :: [(SDoc, -- arg name
449 Type, -- Haskell type
450 CmmType)] -- the CmmType
451 arg_info = [ let stg_type = showStgType ty in
452 (arg_cname n stg_type,
455 typeCmmType (getPrimTyOf ty))
456 | (ty,n) <- zip arg_htys [1::Int ..] ]
459 | libffi = char '*' <> parens (stg_ty <> char '*') <>
460 ptext (sLit "args") <> brackets (int (n-1))
461 | otherwise = text ('a':show n)
463 -- generate a libffi-style stub if this is a "wrapper" and libffi is enabled
464 libffi = cLibFFI && isNothing maybe_target
467 -- libffi needs to know the result type too:
468 | libffi = primTyDescChar res_hty : arg_type_string
469 | otherwise = arg_type_string
471 arg_type_string = [primTyDescChar ty | (_,_,ty,_) <- arg_info]
472 -- just the real args
474 -- add some auxiliary args; the stable ptr in the wrapper case, and
475 -- a slot for the dummy return address in the wrapper + ccall case
477 | isNothing maybe_target = stable_ptr_arg : insertRetAddr cc arg_info
478 | otherwise = arg_info
481 (text "the_stableptr", text "StgStablePtr", undefined,
482 typeCmmType (mkStablePtrPrimTy alphaTy))
484 -- stuff to do with the return type of the C function
485 res_hty_is_unit = res_hty `eqType` unitTy -- Look through any newtypes
487 cResType | res_hty_is_unit = text "void"
488 | otherwise = showStgType res_hty
490 -- when the return type is integral and word-sized or smaller, it
491 -- must be assigned as type ffi_arg (#3516). To see what type
492 -- libffi is expecting here, take a look in its own testsuite, e.g.
493 -- libffi/testsuite/libffi.call/cls_align_ulonglong.c
495 | is_ffi_arg_type = text "ffi_arg"
496 | otherwise = cResType
498 res_ty_key = getUnique (getName (typeTyCon res_hty))
499 is_ffi_arg_type = res_ty_key `notElem`
500 [floatTyConKey, doubleTyConKey,
501 int64TyConKey, word64TyConKey]
503 -- Now we can cook up the prototype for the exported function.
504 pprCconv = case cc of
506 StdCallConv -> text (ccallConvAttribute cc)
507 _ -> panic ("mkFExportCBits/pprCconv " ++ showPpr cc)
509 header_bits = ptext (sLit "extern") <+> fun_proto <> semi
512 | null aug_arg_info = text "void"
513 | otherwise = hsep $ punctuate comma
514 $ map (\(nm,ty,_,_) -> ty <+> nm) aug_arg_info
518 = ptext (sLit "void") <+> ftext c_nm <>
519 parens (ptext (sLit "void *cif STG_UNUSED, void* resp, void** args, void* the_stableptr"))
521 = cResType <+> pprCconv <+> ftext c_nm <> parens fun_args
523 -- the target which will form the root of what we ask rts_evalIO to run
525 = case maybe_target of
526 Nothing -> text "(StgClosure*)deRefStablePtr(the_stableptr)"
527 Just hs_fn -> char '&' <> ppr hs_fn <> text "_closure"
529 cap = text "cap" <> comma
531 -- the expression we give to rts_evalIO
533 = foldl appArg the_cfun arg_info -- NOT aug_arg_info
535 appArg acc (arg_cname, _, arg_hty, _)
537 <> parens (cap <> acc <> comma <> mkHObj arg_hty <> parens (cap <> arg_cname))
539 -- various other bits for inside the fn
540 declareResult = text "HaskellObj ret;"
541 declareCResult | res_hty_is_unit = empty
542 | otherwise = cResType <+> text "cret;"
544 assignCResult | res_hty_is_unit = empty
546 text "cret=" <> unpackHObj res_hty <> parens (text "ret") <> semi
548 -- an extern decl for the fn being called
550 = case maybe_target of
552 Just hs_fn -> text "extern StgClosure " <> ppr hs_fn <> text "_closure" <> semi
555 -- finally, the whole darn thing
562 , ptext (sLit "Capability *cap;")
565 , text "cap = rts_lock();"
566 -- create the application + perform it.
567 , ptext (sLit "cap=rts_evalIO") <> parens (
569 ptext (sLit "rts_apply") <> parens (
572 <> ptext (if is_IO_res_ty
573 then (sLit "runIO_closure")
574 else (sLit "runNonIO_closure"))
580 , ptext (sLit "rts_checkSchedStatus") <> parens (doubleQuotes (ftext c_nm)
581 <> comma <> text "cap") <> semi
583 , ptext (sLit "rts_unlock(cap);")
584 , ppUnless res_hty_is_unit $
586 then char '*' <> parens (ffi_cResType <> char '*') <>
587 ptext (sLit "resp = cret;")
588 else ptext (sLit "return cret;")
593 foreignExportInitialiser :: Id -> SDoc
594 foreignExportInitialiser hs_fn =
595 -- Initialise foreign exports by registering a stable pointer from an
596 -- __attribute__((constructor)) function.
597 -- The alternative is to do this from stginit functions generated in
598 -- codeGen/CodeGen.lhs; however, stginit functions have a negative impact
599 -- on binary sizes and link times because the static linker will think that
600 -- all modules that are imported directly or indirectly are actually used by
602 -- (this is bad for big umbrella modules like Graphics.Rendering.OpenGL)
604 [ text "static void stginit_export_" <> ppr hs_fn
605 <> text "() __attribute__((constructor));"
606 , text "static void stginit_export_" <> ppr hs_fn <> text "()"
607 , braces (text "getStablePtr"
608 <> parens (text "(StgPtr) &" <> ppr hs_fn <> text "_closure")
613 mkHObj :: Type -> SDoc
614 mkHObj t = text "rts_mk" <> text (showFFIType t)
616 unpackHObj :: Type -> SDoc
617 unpackHObj t = text "rts_get" <> text (showFFIType t)
619 showStgType :: Type -> SDoc
620 showStgType t = text "Hs" <> text (showFFIType t)
622 showFFIType :: Type -> String
623 showFFIType t = getOccString (getName (typeTyCon t))
625 typeTyCon :: Type -> TyCon
626 typeTyCon ty = case tcSplitTyConApp_maybe (repType ty) of
628 Nothing -> pprPanic "DsForeign.typeTyCon" (ppr ty)
630 insertRetAddr :: CCallConv -> [(SDoc, SDoc, Type, CmmType)]
631 -> [(SDoc, SDoc, Type, CmmType)]
632 #if !defined(x86_64_TARGET_ARCH)
633 insertRetAddr CCallConv args = ret_addr_arg : args
634 insertRetAddr _ args = args
636 -- On x86_64 we insert the return address after the 6th
637 -- integer argument, because this is the point at which we
638 -- need to flush a register argument to the stack (See rts/Adjustor.c for
640 insertRetAddr CCallConv args = go 0 args
641 where go :: Int -> [(SDoc, SDoc, Type, CmmType)]
642 -> [(SDoc, SDoc, Type, CmmType)]
643 go 6 args = ret_addr_arg : args
644 go n (arg@(_,_,_,rep):args)
645 | cmmEqType_ignoring_ptrhood rep b64 = arg : go (n+1) args
646 | otherwise = arg : go n args
648 insertRetAddr _ args = args
651 ret_addr_arg :: (SDoc, SDoc, Type, CmmType)
652 ret_addr_arg = (text "original_return_addr", text "void*", undefined,
653 typeCmmType addrPrimTy)
655 -- This function returns the primitive type associated with the boxed
656 -- type argument to a foreign export (eg. Int ==> Int#).
657 getPrimTyOf :: Type -> Type
659 | isBoolTy rep_ty = intPrimTy
660 -- Except for Bool, the types we are interested in have a single constructor
661 -- with a single primitive-typed argument (see TcType.legalFEArgTyCon).
663 case splitProductType_maybe rep_ty of
664 Just (_, _, data_con, [prim_ty]) ->
665 ASSERT(dataConSourceArity data_con == 1)
666 ASSERT2(isUnLiftedType prim_ty, ppr prim_ty)
668 _other -> pprPanic "DsForeign.getPrimTyOf" (ppr ty)
672 -- represent a primitive type as a Char, for building a string that
673 -- described the foreign function type. The types are size-dependent,
674 -- e.g. 'W' is a signed 32-bit integer.
675 primTyDescChar :: Type -> Char
677 | ty `eqType` unitTy = 'v'
679 = case typePrimRep (getPrimTyOf ty) of
680 IntRep -> signed_word
681 WordRep -> unsigned_word
687 _ -> pprPanic "primTyDescChar" (ppr ty)
689 (signed_word, unsigned_word)
690 | wORD_SIZE == 4 = ('W','w')
691 | wORD_SIZE == 8 = ('L','l')
692 | otherwise = panic "primTyDescChar"