Is enum listing acceptable for another enum in [C]?

Question

I have two listings.

enum A { A1=1, A2=2 } enum B { B1=1, B2=2 } 

Is this really C standard?

 A a = A1; B b = a; 

(compiled with Clang, but I'm not sure if this is standard behavior or extension behavior)

Answer 1

It is valid by standard, but the C99 specification indicates that some implementations may generate a warning:

An implementation can generate warnings in many situations, none of which are indicated as part of this international standard. Below are some of the most common situations.

• A value is assigned to an object of an enumerated type, different from the assignment of an enumeration constant that is a member of this type, or an enumeration variable that has the same type, or a function value that returns the same type (6.7.2.2).

Answer 2

I believe that in C enumerations, mostly int with personality. (This contrasts with C ++, where they are full-fledged types.) Thus, assigning different enum effectively still works only with int s, so it is legal. However, I am not saying this is recommended :)

Answer 3

This is really C standard, but it is a bad idea. Please note that this is not valid with C ++.

Answer 4

valid - enumerations are language functions that are designed to help the developer. If you do not specify the values ​​of the enumeration element, their values ​​will be generated automatically. From another language .