[Bug c/81845] const union's field doesn't interpret as const in switch/case

[alenuke at yandex dot ru]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81845

--- Comment #3 from Aleksandr Slobodeniuk <alenuke at yandex dot ru> ---
(In reply to Richard Biener from comment #1)
> it has to be a constant literal.

Sorry, I didn't really specify the standard (and mess c with c++).

C11 standard.
6.8.4.2 The switch statement.

> 3 The expression of each case label shall be an integer constant expression
> and no two of the case constant expressions in the same switch statement 
> shall have the same value after conversion.


So, by C11 standard case label shall be a constant expression.

Fields of const-qualified structs and unions, that were initialized with const
literals ARE *constant expressions*, isn't it?

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Yes, the standard also says that uninitialized part of union is undefined, but
that's not that case if we have fields with the same size.

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Sorry for wasting your time.