Permit impure expressions in __auto_type

src/frontc/cabs2cil.ml

@@ -5876,12 +5876,11 @@ and createAutoLocal ((((n, ndt, a, cloc) : A.name), (inite: A.init_expression))
   else
     match inite with
     | SINGLE_INIT exp ->
-      (match doPureExp exp with
-      | Some exp ->
+      (match doExp true exp (AExp None) with
+      | (_, exp, _) ->
         let t = Cil.typeOf exp in
         let specs = t,NoStorage,false,[] in
         createLocal specs name
-      | None -> E.s (error "__auto_type but init not pure")
       )
     | _ -> E.s (error "__auto_type but not SINGLE_INIT")
 (* Must catch the Static local variables. Make them global *)

test/small1/auto_type1.c

@@ -0,0 +1,14 @@
+struct dummmy {
+    char arr[0x0bad];
+};
+
+extern volatile struct dummmy side_effect1;
+struct dummmy side_effect2(struct dummmy);
+
+void *fn() {
+    __auto_type x = side_effect2(side_effect1);
+    static struct S1 {
+        int a : __builtin_choose_expr(sizeof(x) == 0x0bad, 1, -1);
+    } s1 = {0};
+    return &s1;
+}