feat: Add -Wmemcpy, checking compatibility of dst and src.

Also works on `memcmp`.

src/Tokstyle/C/Linter.hs

@@ -18,6 +18,7 @@ import qualified Tokstyle.C.Linter.BoolConversion as BoolConversion
 import qualified Tokstyle.C.Linter.CallbackParams as CallbackParams
 import qualified Tokstyle.C.Linter.Cast           as Cast
 import qualified Tokstyle.C.Linter.Conversion     as Conversion
+import qualified Tokstyle.C.Linter.Memcpy         as Memcpy
 import qualified Tokstyle.C.Linter.Memset         as Memset
 import qualified Tokstyle.C.Linter.SizeArg        as SizeArg
 import qualified Tokstyle.C.Linter.Sizeof         as Sizeof
@@ -30,6 +31,7 @@ linters =
     , ("callback-params"    , CallbackParams.analyse   )
     , ("cast"               , Cast.analyse             )
     , ("conversion"         , Conversion.analyse       )
+    , ("memcpy"             , Memcpy.analyse           )
     , ("memset"             , Memset.analyse           )
     , ("size-arg"           , SizeArg.analyse          )
     , ("sizeof"             , Sizeof.analyse           )

src/Tokstyle/C/Linter/Memcpy.hs

@@ -0,0 +1,87 @@
+{-# OPTIONS_GHC -Wwarn #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE Strict            #-}
+module Tokstyle.C.Linter.Memcpy (analyse) where
+
+import           Control.Monad                   (unless)
+import           Data.Functor.Identity           (Identity)
+import           Language.C.Analysis.AstAnalysis (ExprSide (..), tExpr)
+import           Language.C.Analysis.SemError    (typeMismatch)
+import           Language.C.Analysis.SemRep      (CompTypeRef (CompTypeRef),
+                                                  GlobalDecls,
+                                                  IntType (TyUChar), Type (..),
+                                                  TypeName (TyComp, TyIntegral, TyVoid))
+import           Language.C.Analysis.TravMonad   (Trav, TravT, recordError)
+import           Language.C.Analysis.TypeUtils   (canonicalType)
+import           Language.C.Data.Ident           (Ident (..))
+import           Language.C.Pretty               (pretty)
+import           Language.C.Syntax.AST           (CExpr, CExpression (..),
+                                                  annotation)
+import           Tokstyle.C.Env                  (Env)
+import           Tokstyle.C.TraverseAst          (AstActions (..), astActions,
+                                                  traverseAst)
+
+compatibleType :: Type -> Type -> Bool
+compatibleType (PtrType    a _ _  ) (PtrType    b _ _  ) = compatibleType a b
+compatibleType (ArrayType  a _ _ _) (PtrType    b _ _  ) = compatibleType a b
+compatibleType (PtrType    a _ _  ) (ArrayType  b _ _ _) = compatibleType a b
+compatibleType (ArrayType  a _ _ _) (ArrayType  b _ _ _) = compatibleType a b
+compatibleType (DirectType a _ _  ) (DirectType b _ _  ) = compatibleTypeName a b
+compatibleType _ _                                       = False
+
+compatibleTypeName :: TypeName -> TypeName -> Bool
+-- `uint8_t*` can can be memcpy'd to and from any integral type.
+compatibleTypeName (TyIntegral TyUChar) TyIntegral{} = True
+compatibleTypeName TyIntegral{} (TyIntegral TyUChar) = True
+-- Integral types can only be memcpy'd to the same integral type.
+compatibleTypeName (TyIntegral a) (TyIntegral b) = a == b
+-- Structs can only be memcpy'd to the exact same struct.
+compatibleTypeName (TyComp (CompTypeRef a _ _)) (TyComp (CompTypeRef b _ _)) = a == b
+-- Everything else is disallowed.
+compatibleTypeName _ TyComp{} = False
+compatibleTypeName TyComp{} _ = False
+-- Void pointers are disallowed.
+compatibleTypeName TyVoid _ = False
+compatibleTypeName _ TyVoid = False
+-- Error here for now, to discover more cases.
+compatibleTypeName a b = error (show a ++ "\n" ++ show b)
+
+validMemType :: Type -> Bool
+validMemType (PtrType   DirectType{} _ _  ) = True
+validMemType (ArrayType DirectType{} _ _ _) = True
+validMemType _                              = False
+
+checkMemType :: String -> CExpr -> Type -> Trav Env ()
+checkMemType fname expr ty =
+    unless (validMemType (canonicalType ty)) $
+        let annot = (annotation expr, ty) in
+        recordError $ typeMismatch
+            ("`" <> fname <> "` argument type `" <> show (pretty ty)
+            <> "` is not a valid memory type (pointers to arrays are not allowed)")
+            annot annot
+
+checkCompatibility :: String -> CExpr -> CExpr -> Trav Env ()
+checkCompatibility fname dst src = do
+    dstTy <- tExpr [] RValue dst
+    srcTy <- tExpr [] RValue src
+    checkMemType fname dst dstTy
+    checkMemType fname src srcTy
+    unless (compatibleType (canonicalType dstTy) (canonicalType srcTy)) $
+        recordError $ typeMismatch
+            ("`" <> fname <> "` first argument type `" <> show (pretty dstTy)
+            <> "` is not compatible with second argument type `"
+            <> show (pretty srcTy) <> "`")
+            (annotation dst, dstTy) (annotation src, srcTy)
+
+linter :: AstActions (TravT Env Identity)
+linter = astActions
+    { doExpr = \node act -> case node of
+        CCall (CVar (Ident fname _ _) _) [dst, src, _] _ | fname `elem` ["memcpy", "memcmp"] -> do
+            checkCompatibility fname dst src
+            act
+
+        _ -> act
+    }
+
+analyse :: GlobalDecls -> Trav Env ()
+analyse = traverseAst linter

tokstyle.cabal

@@ -24,6 +24,7 @@ library
     Tokstyle.C.Linter.CallbackParams
     Tokstyle.C.Linter.Cast
     Tokstyle.C.Linter.Conversion
+    Tokstyle.C.Linter.Memcpy
     Tokstyle.C.Linter.Memset
     Tokstyle.C.Linter.SizeArg
     Tokstyle.C.Linter.Sizeof