Also prevent overflows in constFold for unop

Author: michael-schwarz

src/cil.ml

@@ -2181,6 +2181,18 @@ let rec getInteger (e:exp) : cilint option =
     end
   | _ -> None
 
+(** Return the (wrapped) constant i if it fits into ik without any signed overflow,
+    otherwise return fallback  *)
+let const_if_not_overflow fallback ik i =
+  if not (isSigned ik) then
+    kintegerCilint ik i
+  else
+    let i', trunc = truncateCilint ik i in
+    if trunc = NoTruncation then
+      kintegerCilint ik i
+    else
+      fallback
+
 let isZero (e: exp) : bool =
   match getInteger e with
   | Some n -> is_zero_cilint n
@@ -2518,16 +2530,16 @@ and constFold (machdep: bool) (e: exp) : exp =
       try
         let tk =
           match unrollType tres with
-            TInt(ik, _) -> ik
+          | TInt(ik, _) -> ik
           | TEnum (ei, _) -> ei.ekind
           | _ -> raise Not_found (* probably a float *)
         in
         match constFold machdep e1 with
-          Const(CInt(i,ik,_)) -> begin
-	    let ic = mkCilintIk ik i in
+        |  Const(CInt(i,ik,s)) -> begin
+	         let ic = mkCilintIk ik i in
             match unop with
-              Neg -> kintegerCilint tk (neg_cilint ic)
-            | BNot -> kintegerCilint tk (lognot_cilint ic)
+              Neg -> const_if_not_overflow (UnOp(Neg,Const(CInt(i,ik,s)),tres)) tk (neg_cilint ic)
+            | BNot -> const_if_not_overflow (UnOp(BNot,Const(CInt(i,ik,s)),tres)) tk (lognot_cilint ic)
             | LNot -> if is_zero_cilint ic then one else zero
             end
         | e1c -> UnOp(unop, e1c, tres)
@@ -2600,16 +2612,6 @@ and constFoldLval machdep (host,offset) =
 and constFoldBinOp (machdep: bool) bop e1 e2 tres =
   let e1' = constFold machdep e1 in
   let e2' = constFold machdep e2 in
-  let if_not_overflow fallback ik i =
-    if not (isSigned ik) then
-      kintegerCilint ik i
-    else
-      let i', trunc = truncateCilint ik i in
-      if trunc = NoTruncation then
-        kintegerCilint ik i
-      else
-        fallback
-  in
   if isIntegralType tres then begin
     let newe =
       let tk =
@@ -2632,7 +2634,7 @@ and constFoldBinOp (machdep: bool) bop e1 e2 tres =
           with SizeOfError _ -> false
         else false
       in
-      let no_ov = if_not_overflow (BinOp(bop, e1', e2', tres)) tk in
+      let no_ov = const_if_not_overflow (BinOp(bop, e1', e2', tres)) tk in
       (* Assume that the necessary promotions have been done *)
       match bop, getInteger e1', getInteger e2' with
       | PlusA, Some i1, Some i2 -> no_ov (add_cilint i1 i2)