Fix void main

specification.md

@@ -229,10 +229,11 @@ Modifications made to an array inside a function are visible outside the functio
         arr[2] = 42;
     }
 
-    void main() {
+    int main() {
         int[5] arr;
         foo(arr);
         print_int(arr[2]); // outputs 42
+        return 0;
     }
 
 While strings can be re-assigned (in contrast to arrays), this is not visible outside the function call.
@@ -241,11 +242,12 @@ While strings can be re-assigned (in contrast to arrays), this is not visible ou
         s = "foo";
     }
 
-    void main() {
+    int main() {
         string s;
         s = "bar";
         foo(s);
         print(s); // outputs bar
+        return 0;
     }
 
 #### Type Conversion