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
161 -- This makes a convenient place to check
162 -- that the C identifier is valid for C
163 checkCTarget :: CCallTarget -> TcM ()
164 checkCTarget (StaticTarget str) = do
165 checkCg checkCOrAsmOrDotNetOrInterp
166 check (isCLabelString str) (badCName str)
167 checkCTarget DynamicTarget = panic "checkCTarget DynamicTarget"
169 checkMissingAmpersand :: DynFlags -> [Type] -> Type -> TcM ()
170 checkMissingAmpersand dflags arg_tys res_ty
171 | null arg_tys && isFunPtrTy res_ty &&
172 dopt Opt_WarnDodgyForeignImports dflags
173 = addWarn (ptext (sLit "possible missing & in foreign import of FunPtr"))
178 On an Alpha, with foreign export dynamic, due to a giant hack when
179 building adjustor thunks, we only allow 4 integer arguments with
180 foreign export dynamic (i.e., 32 bytes of arguments after padding each
181 argument to a quadword, excluding floating-point arguments).
183 The check is needed for both via-C and native-code routes
186 #include "nativeGen/NCG.h"
188 checkFEDArgs :: [Type] -> TcM ()
189 #if alpha_TARGET_ARCH
191 = check (integral_args <= 32) err
193 integral_args = sum [ (widthInBytes . argMachRep . primRepToCgRep) prim_rep
194 | prim_rep <- map typePrimRep arg_tys,
195 primRepHint prim_rep /= FloatHint ]
196 err = ptext (sLit "On Alpha, I can only handle 32 bytes of non-floating-point arguments to foreign export dynamic")
198 checkFEDArgs _ = return ()
203 %************************************************************************
207 %************************************************************************
210 tcForeignExports :: [LForeignDecl Name]
211 -> TcM (LHsBinds TcId, [LForeignDecl TcId])
212 tcForeignExports decls
213 = foldlM combine (emptyLHsBinds, []) (filter isForeignExport decls)
215 combine (binds, fs) fe = do
216 (b, f) <- wrapLocSndM tcFExport fe
217 return (b `consBag` binds, f:fs)
219 tcFExport :: ForeignDecl Name -> TcM (LHsBind Id, ForeignDecl Id)
220 tcFExport fo@(ForeignExport (L loc nm) hs_ty spec) =
221 addErrCtxt (foreignDeclCtxt fo) $ do
223 sig_ty <- tcHsSigType (ForSigCtxt nm) hs_ty
224 rhs <- tcPolyExpr (nlHsVar nm) sig_ty
226 tcCheckFEType sig_ty spec
228 -- we're exporting a function, but at a type possibly more
229 -- constrained than its declared/inferred type. Hence the need
230 -- to create a local binding which will call the exported function
231 -- at a particular type (and, maybe, overloading).
234 -- We need to give a name to the new top-level binding that
235 -- is *stable* (i.e. the compiler won't change it later),
236 -- because this name will be referred to by the C code stub.
237 id <- mkStableIdFromName nm sig_ty loc mkForeignExportOcc
238 return (mkVarBind id rhs, ForeignExport (L loc id) undefined spec)
239 tcFExport d = pprPanic "tcFExport" (ppr d)
242 ------------ Checking argument types for foreign export ----------------------
245 tcCheckFEType :: Type -> ForeignExport -> TcM ()
246 tcCheckFEType sig_ty (CExport (CExportStatic str cconv)) = do
248 check (isCLabelString str) (badCName str)
250 checkForeignArgs isFFIExternalTy arg_tys
251 checkForeignRes nonIOok isFFIExportResultTy res_ty
253 -- Drop the foralls before inspecting n
254 -- the structure of the foreign type.
255 (_, t_ty) = tcSplitForAllTys sig_ty
256 (arg_tys, res_ty) = tcSplitFunTys t_ty
261 %************************************************************************
263 \subsection{Miscellaneous}
265 %************************************************************************
268 ------------ Checking argument types for foreign import ----------------------
269 checkForeignArgs :: (Type -> Bool) -> [Type] -> TcM ()
270 checkForeignArgs pred tys
273 go ty = check (pred ty) (illegalForeignTyErr argument ty)
275 ------------ Checking result types for foreign calls ----------------------
276 -- Check that the type has the form
277 -- (IO t) or (t) , and that t satisfies the given predicate.
279 checkForeignRes :: Bool -> (Type -> Bool) -> Type -> TcM ()
281 nonIOok, mustBeIO :: Bool
285 checkForeignRes non_io_result_ok pred_res_ty ty
286 -- (IO t) is ok, and so is any newtype wrapping thereof
287 | Just (_, res_ty, _) <- tcSplitIOType_maybe ty,
292 = check (non_io_result_ok && pred_res_ty ty)
293 (illegalForeignTyErr result ty)
297 checkCOrAsm :: HscTarget -> Maybe SDoc
298 checkCOrAsm HscC = Nothing
299 checkCOrAsm HscAsm = Nothing
301 = Just (text "requires via-C or native code generation (-fvia-C)")
303 checkCOrAsmOrInterp :: HscTarget -> Maybe SDoc
304 checkCOrAsmOrInterp HscC = Nothing
305 checkCOrAsmOrInterp HscAsm = Nothing
306 checkCOrAsmOrInterp HscInterpreted = Nothing
307 checkCOrAsmOrInterp _
308 = Just (text "requires interpreted, C or native code generation")
310 checkCOrAsmOrDotNetOrInterp :: HscTarget -> Maybe SDoc
311 checkCOrAsmOrDotNetOrInterp HscC = Nothing
312 checkCOrAsmOrDotNetOrInterp HscAsm = Nothing
313 checkCOrAsmOrDotNetOrInterp HscInterpreted = Nothing
314 checkCOrAsmOrDotNetOrInterp _
315 = Just (text "requires interpreted, C or native code generation")
317 checkCg :: (HscTarget -> Maybe SDoc) -> TcM ()
320 let target = hscTarget dflags
322 HscNothing -> return ()
326 Just err -> addErrTc (text "Illegal foreign declaration:" <+> err)
332 checkCConv :: CCallConv -> TcM ()
333 checkCConv CCallConv = return ()
335 checkCConv StdCallConv = return ()
337 checkCConv StdCallConv = addErrTc (text "calling convention not supported on this platform: stdcall")
339 checkCConv PrimCallConv = addErrTc (text "The `prim' calling convention can only be used with `foreign import'")
340 checkCConv CmmCallConv = panic "checkCConv CmmCallConv"
343 Deprecated "threadsafe" calls
346 checkSafety :: Safety -> TcM ()
347 checkSafety (PlaySafe True) = addWarn (text "The `threadsafe' foreign import style is deprecated. Use `safe' instead.")
348 checkSafety _ = return ()
354 check :: Bool -> Message -> TcM ()
355 check True _ = return ()
356 check _ the_err = addErrTc the_err
358 illegalForeignTyErr :: SDoc -> Type -> SDoc
359 illegalForeignTyErr arg_or_res ty
360 = hang (hsep [ptext (sLit "Unacceptable"), arg_or_res,
361 ptext (sLit "type in foreign declaration:")])
364 -- Used for 'arg_or_res' argument to illegalForeignTyErr
365 argument, result :: SDoc
366 argument = text "argument"
367 result = text "result"
369 badCName :: CLabelString -> Message
371 = sep [quotes (ppr target) <+> ptext (sLit "is not a valid C identifier")]
373 foreignDeclCtxt :: ForeignDecl Name -> SDoc
375 = hang (ptext (sLit "When checking declaration:"))