coding_style: Add case for enum as switch variable

diff --git a/doc/coding-style.txt b/doc/coding-style.txt
index 9e5a811..6fa355e 100644 (file)
--- a/doc/coding-style.txt
+++ b/doc/coding-style.txt
@@ -173,6 +173,38 @@ enum animal_type {
        ANIMAL_TYPE_TWO_LEGS =          2,
 };
 
+M12: Enum as switch variable
+====================
+
+If the variable of a switch is an enum, you must not include a default in
+switch body. The reason for this is: If later on you modify the enum by adding
+a new type, and forget to change the switch accordingly, the compiler will
+complain the new added type hasn't been handled.
+
+Example:
+
+enum animal_type {
+       ANIMAL_TYPE_FOUR_LEGS =         4,
+       ANIMAL_TYPE_EIGHT_LEGS =        8,
+       ANIMAL_TYPE_TWO_LEGS =          2,
+};
+
+enum animal_type t;
+
+switch (t) {
+case ANIMAL_TYPE_FOUR_LEGS:
+       ...
+       break;
+case ANIMAL_TYPE_EIGHT_LEGS:
+       ...
+       break;
+case ANIMAL_TYPE_TWO_LEGS:
+       ...
+       break;
+default:  // wrong
+       break;
+}
+
 O1: Shorten the name
 ====================
 Better to use abbreviation, rather than full name, to name a variable,