2 % (c) The University of Glasgow 2006
3 % (c) The AQUA Project, Glasgow University, 1998
5 \section[TcForeign]{Typechecking \tr{foreign} declarations}
7 A foreign declaration is used to either give an externally
8 implemented function a Haskell type (and calling interface) or
9 give a Haskell function an external calling interface. Either way,
10 the range of argument and result types these functions can accommodate
11 is restricted to what the outside world understands (read C), and this
12 module checks to see if a foreign declaration has got a legal type.
21 #include "HsVersions.h"
48 isForeignImport :: LForeignDecl name -> Bool
49 isForeignImport (L _ (ForeignImport _ _ _)) = True
50 isForeignImport _ = False
53 isForeignExport :: LForeignDecl name -> Bool
54 isForeignExport (L _ (ForeignExport _ _ _)) = True
55 isForeignExport _ = False
58 %************************************************************************
62 %************************************************************************
65 tcForeignImports :: [LForeignDecl Name] -> TcM ([Id], [LForeignDecl Id])
66 tcForeignImports decls
67 = mapAndUnzipM (wrapLocSndM tcFImport) (filter isForeignImport decls)
69 tcFImport :: ForeignDecl Name -> TcM (Id, ForeignDecl Id)
70 tcFImport fo@(ForeignImport (L loc nm) hs_ty imp_decl)
71 = addErrCtxt (foreignDeclCtxt fo) $
72 do { sig_ty <- tcHsSigType (ForSigCtxt nm) hs_ty
74 -- Drop the foralls before inspecting the
75 -- structure of the foreign type.
76 (_, t_ty) = tcSplitForAllTys sig_ty
77 (arg_tys, res_ty) = tcSplitFunTys t_ty
78 id = mkLocalId nm sig_ty
79 -- Use a LocalId to obey the invariant that locally-defined
80 -- things are LocalIds. However, it does not need zonking,
81 -- (so TcHsSyn.zonkForeignExports ignores it).
83 ; imp_decl' <- tcCheckFIType sig_ty arg_tys res_ty imp_decl
84 -- Can't use sig_ty here because sig_ty :: Type and
85 -- we need HsType Id hence the undefined
86 ; return (id, ForeignImport (L loc id) undefined imp_decl') }
87 tcFImport d = pprPanic "tcFImport" (ppr d)
91 ------------ Checking types for foreign import ----------------------
93 tcCheckFIType :: Type -> [Type] -> Type -> ForeignImport -> TcM ForeignImport
95 tcCheckFIType sig_ty arg_tys res_ty idecl@(CImport _ safety _ (CLabel _))
96 = ASSERT( null arg_tys )
97 do { checkCg checkCOrAsmOrInterp
99 ; check (isFFILabelTy res_ty) (illegalForeignTyErr empty sig_ty)
100 ; return idecl } -- NB check res_ty not sig_ty!
101 -- In case sig_ty is (forall a. ForeignPtr a)
103 tcCheckFIType sig_ty arg_tys res_ty idecl@(CImport cconv safety _ CWrapper) = do
104 -- Foreign wrapper (former f.e.d.)
105 -- The type must be of the form ft -> IO (FunPtr ft), where ft is a
106 -- valid foreign type. For legacy reasons ft -> IO (Ptr ft) as well
107 -- as ft -> IO Addr is accepted, too. The use of the latter two forms
108 -- is DEPRECATED, though.
109 checkCg checkCOrAsmOrInterp
113 [arg1_ty] -> do checkForeignArgs isFFIExternalTy arg1_tys
114 checkForeignRes nonIOok isFFIExportResultTy res1_ty
115 checkForeignRes mustBeIO isFFIDynResultTy res_ty
116 checkFEDArgs arg1_tys
118 (arg1_tys, res1_ty) = tcSplitFunTys arg1_ty
119 _ -> addErrTc (illegalForeignTyErr empty sig_ty)
122 tcCheckFIType sig_ty arg_tys res_ty idecl@(CImport cconv safety _ (CFunction target))
123 | isDynamicTarget target = do -- Foreign import dynamic
124 checkCg checkCOrAsmOrInterp
127 case arg_tys of -- The first arg must be Ptr, FunPtr, or Addr
129 check False (illegalForeignTyErr empty sig_ty)
131 (arg1_ty:arg_tys) -> do
133 check (isFFIDynArgumentTy arg1_ty)
134 (illegalForeignTyErr argument arg1_ty)
135 checkForeignArgs (isFFIArgumentTy dflags safety) arg_tys
136 checkForeignRes nonIOok (isFFIImportResultTy dflags) res_ty
138 | cconv == PrimCallConv = do
140 check (dopt Opt_GHCForeignImportPrim dflags)
141 (text "Use -XGHCForeignImportPrim to allow `foreign import prim'.")
142 checkCg (checkCOrAsmOrDotNetOrInterp)
144 check (playSafe safety)
145 (text "The safe/unsafe annotation should not be used with `foreign import prim'.")
146 checkForeignArgs (isFFIPrimArgumentTy dflags) arg_tys
147 -- prim import result is more liberal, allows (#,,#)
148 checkForeignRes nonIOok (isFFIPrimResultTy dflags) res_ty
150 | otherwise = do -- Normal foreign import
151 checkCg (checkCOrAsmOrDotNetOrInterp)
156 checkForeignArgs (isFFIArgumentTy dflags safety) arg_tys
157 checkForeignRes nonIOok (isFFIImportResultTy dflags) res_ty
158 checkMissingAmpersand dflags arg_tys res_ty
162 -- This makes a convenient place to check
163 -- that the C identifier is valid for C
164 checkCTarget :: CCallTarget -> TcM ()
165 checkCTarget (StaticTarget str _) = do
166 checkCg checkCOrAsmOrDotNetOrInterp
167 check (isCLabelString str) (badCName str)
169 checkCTarget DynamicTarget = panic "checkCTarget DynamicTarget"
172 checkMissingAmpersand :: DynFlags -> [Type] -> Type -> TcM ()
173 checkMissingAmpersand dflags arg_tys res_ty
174 | null arg_tys && isFunPtrTy res_ty &&
175 dopt Opt_WarnDodgyForeignImports dflags
176 = addWarn (ptext (sLit "possible missing & in foreign import of FunPtr"))
181 On an Alpha, with foreign export dynamic, due to a giant hack when
182 building adjustor thunks, we only allow 4 integer arguments with
183 foreign export dynamic (i.e., 32 bytes of arguments after padding each
184 argument to a quadword, excluding floating-point arguments).
186 The check is needed for both via-C and native-code routes
189 #include "nativeGen/NCG.h"
191 checkFEDArgs :: [Type] -> TcM ()
192 #if alpha_TARGET_ARCH
194 = check (integral_args <= 32) err
196 integral_args = sum [ (widthInBytes . argMachRep . primRepToCgRep) prim_rep
197 | prim_rep <- map typePrimRep arg_tys,
198 primRepHint prim_rep /= FloatHint ]
199 err = ptext (sLit "On Alpha, I can only handle 32 bytes of non-floating-point arguments to foreign export dynamic")
201 checkFEDArgs _ = return ()
206 %************************************************************************
210 %************************************************************************
213 tcForeignExports :: [LForeignDecl Name]
214 -> TcM (LHsBinds TcId, [LForeignDecl TcId])
215 tcForeignExports decls
216 = foldlM combine (emptyLHsBinds, []) (filter isForeignExport decls)
218 combine (binds, fs) fe = do
219 (b, f) <- wrapLocSndM tcFExport fe
220 return (b `consBag` binds, f:fs)
222 tcFExport :: ForeignDecl Name -> TcM (LHsBind Id, ForeignDecl Id)
223 tcFExport fo@(ForeignExport (L loc nm) hs_ty spec) =
224 addErrCtxt (foreignDeclCtxt fo) $ do
226 sig_ty <- tcHsSigType (ForSigCtxt nm) hs_ty
227 rhs <- tcPolyExpr (nlHsVar nm) sig_ty
229 tcCheckFEType sig_ty spec
231 -- we're exporting a function, but at a type possibly more
232 -- constrained than its declared/inferred type. Hence the need
233 -- to create a local binding which will call the exported function
234 -- at a particular type (and, maybe, overloading).
237 -- We need to give a name to the new top-level binding that
238 -- is *stable* (i.e. the compiler won't change it later),
239 -- because this name will be referred to by the C code stub.
240 id <- mkStableIdFromName nm sig_ty loc mkForeignExportOcc
241 return (mkVarBind id rhs, ForeignExport (L loc id) undefined spec)
242 tcFExport d = pprPanic "tcFExport" (ppr d)
245 ------------ Checking argument types for foreign export ----------------------
248 tcCheckFEType :: Type -> ForeignExport -> TcM ()
249 tcCheckFEType sig_ty (CExport (CExportStatic str cconv)) = do
251 check (isCLabelString str) (badCName str)
253 checkForeignArgs isFFIExternalTy arg_tys
254 checkForeignRes nonIOok isFFIExportResultTy res_ty
256 -- Drop the foralls before inspecting n
257 -- the structure of the foreign type.
258 (_, t_ty) = tcSplitForAllTys sig_ty
259 (arg_tys, res_ty) = tcSplitFunTys t_ty
264 %************************************************************************
266 \subsection{Miscellaneous}
268 %************************************************************************
271 ------------ Checking argument types for foreign import ----------------------
272 checkForeignArgs :: (Type -> Bool) -> [Type] -> TcM ()
273 checkForeignArgs pred tys
276 go ty = check (pred ty) (illegalForeignTyErr argument ty)
278 ------------ Checking result types for foreign calls ----------------------
279 -- Check that the type has the form
280 -- (IO t) or (t) , and that t satisfies the given predicate.
282 checkForeignRes :: Bool -> (Type -> Bool) -> Type -> TcM ()
284 nonIOok, mustBeIO :: Bool
288 checkForeignRes non_io_result_ok pred_res_ty ty
289 -- (IO t) is ok, and so is any newtype wrapping thereof
290 | Just (_, res_ty, _) <- tcSplitIOType_maybe ty,
295 = check (non_io_result_ok && pred_res_ty ty)
296 (illegalForeignTyErr result ty)
300 checkCOrAsm :: HscTarget -> Maybe SDoc
301 checkCOrAsm HscC = Nothing
302 checkCOrAsm HscAsm = Nothing
304 = Just (text "requires via-C or native code generation (-fvia-C)")
306 checkCOrAsmOrInterp :: HscTarget -> Maybe SDoc
307 checkCOrAsmOrInterp HscC = Nothing
308 checkCOrAsmOrInterp HscAsm = Nothing
309 checkCOrAsmOrInterp HscInterpreted = Nothing
310 checkCOrAsmOrInterp _
311 = Just (text "requires interpreted, C or native code generation")
313 checkCOrAsmOrDotNetOrInterp :: HscTarget -> Maybe SDoc
314 checkCOrAsmOrDotNetOrInterp HscC = Nothing
315 checkCOrAsmOrDotNetOrInterp HscAsm = Nothing
316 checkCOrAsmOrDotNetOrInterp HscInterpreted = Nothing
317 checkCOrAsmOrDotNetOrInterp _
318 = Just (text "requires interpreted, C or native code generation")
320 checkCg :: (HscTarget -> Maybe SDoc) -> TcM ()
323 let target = hscTarget dflags
325 HscNothing -> return ()
329 Just err -> addErrTc (text "Illegal foreign declaration:" <+> err)
335 checkCConv :: CCallConv -> TcM ()
336 checkCConv CCallConv = return ()
338 checkCConv StdCallConv = return ()
340 checkCConv StdCallConv = addErrTc (text "calling convention not supported on this platform: stdcall")
342 checkCConv PrimCallConv = addErrTc (text "The `prim' calling convention can only be used with `foreign import'")
343 checkCConv CmmCallConv = panic "checkCConv CmmCallConv"
346 Deprecated "threadsafe" calls
349 checkSafety :: Safety -> TcM ()
350 checkSafety (PlaySafe True) = addWarn (text "The `threadsafe' foreign import style is deprecated. Use `safe' instead.")
351 checkSafety _ = return ()
357 check :: Bool -> Message -> TcM ()
358 check True _ = return ()
359 check _ the_err = addErrTc the_err
361 illegalForeignTyErr :: SDoc -> Type -> SDoc
362 illegalForeignTyErr arg_or_res ty
363 = hang (hsep [ptext (sLit "Unacceptable"), arg_or_res,
364 ptext (sLit "type in foreign declaration:")])
367 -- Used for 'arg_or_res' argument to illegalForeignTyErr
368 argument, result :: SDoc
369 argument = text "argument"
370 result = text "result"
372 badCName :: CLabelString -> Message
374 = sep [quotes (ppr target) <+> ptext (sLit "is not a valid C identifier")]
376 foreignDeclCtxt :: ForeignDecl Name -> SDoc
378 = hang (ptext (sLit "When checking declaration:"))