% % (c) The University of Glasgow 2006 % (c) The AQUA Project, Glasgow University, 1998 % \section[TcForeign]{Typechecking \tr{foreign} declarations} A foreign declaration is used to either give an externally implemented function a Haskell type (and calling interface) or give a Haskell function an external calling interface. Either way, the range of argument and result types these functions can accommodate is restricted to what the outside world understands (read C), and this module checks to see if a foreign declaration has got a legal type. \begin{code} module TcForeign ( tcForeignImports , tcForeignExports ) where #include "HsVersions.h" import HsSyn import TcRnMonad import TcHsType import TcExpr import TcEnv import ForeignCall import ErrUtils import Id #if alpha_TARGET_ARCH import Type import SMRep #endif import Name import TcType import DynFlags import Outputable import SrcLoc import Bag import FastString \end{code} \begin{code} -- Defines a binding isForeignImport :: LForeignDecl name -> Bool isForeignImport (L _ (ForeignImport _ _ _)) = True isForeignImport _ = False -- Exports a binding isForeignExport :: LForeignDecl name -> Bool isForeignExport (L _ (ForeignExport _ _ _)) = True isForeignExport _ = False \end{code} %************************************************************************ %* * \subsection{Imports} %* * %************************************************************************ \begin{code} tcForeignImports :: [LForeignDecl Name] -> TcM ([Id], [LForeignDecl Id]) tcForeignImports decls = mapAndUnzipM (wrapLocSndM tcFImport) (filter isForeignImport decls) tcFImport :: ForeignDecl Name -> TcM (Id, ForeignDecl Id) tcFImport fo@(ForeignImport (L loc nm) hs_ty imp_decl) = addErrCtxt (foreignDeclCtxt fo) $ do { sig_ty <- tcHsSigType (ForSigCtxt nm) hs_ty ; let -- Drop the foralls before inspecting the -- structure of the foreign type. (_, t_ty) = tcSplitForAllTys sig_ty (arg_tys, res_ty) = tcSplitFunTys t_ty id = mkLocalId nm sig_ty -- Use a LocalId to obey the invariant that locally-defined -- things are LocalIds. However, it does not need zonking, -- (so TcHsSyn.zonkForeignExports ignores it). ; imp_decl' <- tcCheckFIType sig_ty arg_tys res_ty imp_decl -- Can't use sig_ty here because sig_ty :: Type and -- we need HsType Id hence the undefined ; return (id, ForeignImport (L loc id) undefined imp_decl') } tcFImport d = pprPanic "tcFImport" (ppr d) \end{code} ------------ Checking types for foreign import ---------------------- \begin{code} tcCheckFIType :: Type -> [Type] -> Type -> ForeignImport -> TcM ForeignImport tcCheckFIType sig_ty arg_tys res_ty idecl@(CImport _ safety _ (CLabel _)) = ASSERT( null arg_tys ) do { checkCg checkCOrAsmOrInterp ; checkSafety safety ; check (isFFILabelTy res_ty) (illegalForeignTyErr empty sig_ty) ; return idecl } -- NB check res_ty not sig_ty! -- In case sig_ty is (forall a. ForeignPtr a) tcCheckFIType sig_ty arg_tys res_ty idecl@(CImport cconv safety _ CWrapper) = do -- Foreign wrapper (former f.e.d.) -- The type must be of the form ft -> IO (FunPtr ft), where ft is a -- valid foreign type. For legacy reasons ft -> IO (Ptr ft) as well -- as ft -> IO Addr is accepted, too. The use of the latter two forms -- is DEPRECATED, though. checkCg checkCOrAsmOrInterp checkCConv cconv checkSafety safety case arg_tys of [arg1_ty] -> do checkForeignArgs isFFIExternalTy arg1_tys checkForeignRes nonIOok isFFIExportResultTy res1_ty checkForeignRes mustBeIO isFFIDynResultTy res_ty checkFEDArgs arg1_tys where (arg1_tys, res1_ty) = tcSplitFunTys arg1_ty _ -> addErrTc (illegalForeignTyErr empty sig_ty) return idecl tcCheckFIType sig_ty arg_tys res_ty idecl@(CImport cconv safety _ (CFunction target)) | isDynamicTarget target = do -- Foreign import dynamic checkCg checkCOrAsmOrInterp checkCConv cconv checkSafety safety case arg_tys of -- The first arg must be Ptr, FunPtr, or Addr [] -> do check False (illegalForeignTyErr empty sig_ty) return idecl (arg1_ty:arg_tys) -> do dflags <- getDOpts check (isFFIDynArgumentTy arg1_ty) (illegalForeignTyErr argument arg1_ty) checkForeignArgs (isFFIArgumentTy dflags safety) arg_tys checkForeignRes nonIOok (isFFIImportResultTy dflags) res_ty return idecl | cconv == PrimCallConv = do dflags <- getDOpts check (dopt Opt_GHCForeignImportPrim dflags) (text "Use -XGHCForeignImportPrim to allow `foreign import prim'.") checkCg (checkCOrAsmOrDotNetOrInterp) checkCTarget target check (playSafe safety) (text "The safe/unsafe annotation should not be used with `foreign import prim'.") checkForeignArgs (isFFIPrimArgumentTy dflags) arg_tys -- prim import result is more liberal, allows (#,,#) checkForeignRes nonIOok (isFFIPrimResultTy dflags) res_ty return idecl | otherwise = do -- Normal foreign import checkCg (checkCOrAsmOrDotNetOrInterp) checkCConv cconv checkSafety safety checkCTarget target dflags <- getDOpts checkForeignArgs (isFFIArgumentTy dflags safety) arg_tys checkForeignRes nonIOok (isFFIImportResultTy dflags) res_ty checkMissingAmpersand dflags arg_tys res_ty return idecl -- This makes a convenient place to check -- that the C identifier is valid for C checkCTarget :: CCallTarget -> TcM () checkCTarget (StaticTarget str) = do checkCg checkCOrAsmOrDotNetOrInterp check (isCLabelString str) (badCName str) checkCTarget DynamicTarget = panic "checkCTarget DynamicTarget" checkMissingAmpersand :: DynFlags -> [Type] -> Type -> TcM () checkMissingAmpersand dflags arg_tys res_ty | null arg_tys && isFunPtrTy res_ty && dopt Opt_WarnDodgyForeignImports dflags = addWarn (ptext (sLit "possible missing & in foreign import of FunPtr")) | otherwise = return () \end{code} On an Alpha, with foreign export dynamic, due to a giant hack when building adjustor thunks, we only allow 4 integer arguments with foreign export dynamic (i.e., 32 bytes of arguments after padding each argument to a quadword, excluding floating-point arguments). The check is needed for both via-C and native-code routes \begin{code} #include "nativeGen/NCG.h" checkFEDArgs :: [Type] -> TcM () #if alpha_TARGET_ARCH checkFEDArgs arg_tys = check (integral_args <= 32) err where integral_args = sum [ (widthInBytes . argMachRep . primRepToCgRep) prim_rep | prim_rep <- map typePrimRep arg_tys, primRepHint prim_rep /= FloatHint ] err = ptext (sLit "On Alpha, I can only handle 32 bytes of non-floating-point arguments to foreign export dynamic") #else checkFEDArgs _ = return () #endif \end{code} %************************************************************************ %* * \subsection{Exports} %* * %************************************************************************ \begin{code} tcForeignExports :: [LForeignDecl Name] -> TcM (LHsBinds TcId, [LForeignDecl TcId]) tcForeignExports decls = foldlM combine (emptyLHsBinds, []) (filter isForeignExport decls) where combine (binds, fs) fe = do (b, f) <- wrapLocSndM tcFExport fe return (b `consBag` binds, f:fs) tcFExport :: ForeignDecl Name -> TcM (LHsBind Id, ForeignDecl Id) tcFExport fo@(ForeignExport (L loc nm) hs_ty spec) = addErrCtxt (foreignDeclCtxt fo) $ do sig_ty <- tcHsSigType (ForSigCtxt nm) hs_ty rhs <- tcPolyExpr (nlHsVar nm) sig_ty tcCheckFEType sig_ty spec -- we're exporting a function, but at a type possibly more -- constrained than its declared/inferred type. Hence the need -- to create a local binding which will call the exported function -- at a particular type (and, maybe, overloading). -- We need to give a name to the new top-level binding that -- is *stable* (i.e. the compiler won't change it later), -- because this name will be referred to by the C code stub. id <- mkStableIdFromName nm sig_ty loc mkForeignExportOcc return (L loc (VarBind id rhs), ForeignExport (L loc id) undefined spec) tcFExport d = pprPanic "tcFExport" (ppr d) \end{code} ------------ Checking argument types for foreign export ---------------------- \begin{code} tcCheckFEType :: Type -> ForeignExport -> TcM () tcCheckFEType sig_ty (CExport (CExportStatic str cconv)) = do checkCg checkCOrAsm check (isCLabelString str) (badCName str) checkCConv cconv checkForeignArgs isFFIExternalTy arg_tys checkForeignRes nonIOok isFFIExportResultTy res_ty where -- Drop the foralls before inspecting n -- the structure of the foreign type. (_, t_ty) = tcSplitForAllTys sig_ty (arg_tys, res_ty) = tcSplitFunTys t_ty \end{code} %************************************************************************ %* * \subsection{Miscellaneous} %* * %************************************************************************ \begin{code} ------------ Checking argument types for foreign import ---------------------- checkForeignArgs :: (Type -> Bool) -> [Type] -> TcM () checkForeignArgs pred tys = mapM_ go tys where go ty = check (pred ty) (illegalForeignTyErr argument ty) ------------ Checking result types for foreign calls ---------------------- -- Check that the type has the form -- (IO t) or (t) , and that t satisfies the given predicate. -- checkForeignRes :: Bool -> (Type -> Bool) -> Type -> TcM () nonIOok, mustBeIO :: Bool nonIOok = True mustBeIO = False checkForeignRes non_io_result_ok pred_res_ty ty -- (IO t) is ok, and so is any newtype wrapping thereof | Just (_, res_ty, _) <- tcSplitIOType_maybe ty, pred_res_ty res_ty = return () | otherwise = check (non_io_result_ok && pred_res_ty ty) (illegalForeignTyErr result ty) \end{code} \begin{code} checkCOrAsm :: HscTarget -> Maybe SDoc checkCOrAsm HscC = Nothing checkCOrAsm HscAsm = Nothing checkCOrAsm _ = Just (text "requires via-C or native code generation (-fvia-C)") checkCOrAsmOrInterp :: HscTarget -> Maybe SDoc checkCOrAsmOrInterp HscC = Nothing checkCOrAsmOrInterp HscAsm = Nothing checkCOrAsmOrInterp HscInterpreted = Nothing checkCOrAsmOrInterp _ = Just (text "requires interpreted, C or native code generation") checkCOrAsmOrDotNetOrInterp :: HscTarget -> Maybe SDoc checkCOrAsmOrDotNetOrInterp HscC = Nothing checkCOrAsmOrDotNetOrInterp HscAsm = Nothing checkCOrAsmOrDotNetOrInterp HscInterpreted = Nothing checkCOrAsmOrDotNetOrInterp _ = Just (text "requires interpreted, C or native code generation") checkCg :: (HscTarget -> Maybe SDoc) -> TcM () checkCg check = do dflags <- getDOpts let target = hscTarget dflags case target of HscNothing -> return () _ -> case check target of Nothing -> return () Just err -> addErrTc (text "Illegal foreign declaration:" <+> err) \end{code} Calling conventions \begin{code} checkCConv :: CCallConv -> TcM () checkCConv CCallConv = return () #if i386_TARGET_ARCH checkCConv StdCallConv = return () #else checkCConv StdCallConv = addErrTc (text "calling convention not supported on this platform: stdcall") #endif checkCConv PrimCallConv = addErrTc (text "The `prim' calling convention can only be used with `foreign import'") checkCConv CmmCallConv = panic "checkCConv CmmCallConv" \end{code} Deprecated "threadsafe" calls \begin{code} checkSafety :: Safety -> TcM () checkSafety (PlaySafe True) = addWarn (text "The `threadsafe' foreign import style is deprecated. Use `safe' instead.") checkSafety _ = return () \end{code} Warnings \begin{code} check :: Bool -> Message -> TcM () check True _ = return () check _ the_err = addErrTc the_err illegalForeignTyErr :: SDoc -> Type -> SDoc illegalForeignTyErr arg_or_res ty = hang (hsep [ptext (sLit "Unacceptable"), arg_or_res, ptext (sLit "type in foreign declaration:")]) 4 (hsep [ppr ty]) -- Used for 'arg_or_res' argument to illegalForeignTyErr argument, result :: SDoc argument = text "argument" result = text "result" badCName :: CLabelString -> Message badCName target = sep [quotes (ppr target) <+> ptext (sLit "is not a valid C identifier")] foreignDeclCtxt :: ForeignDecl Name -> SDoc foreignDeclCtxt fo = hang (ptext (sLit "When checking declaration:")) 4 (ppr fo) \end{code}