[Bug c/116892] forward declaration of enum followed by packed on the enum type causes an ICE in verify_type

[uecker at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116892

--- Comment #9 from uecker at gcc dot gnu.org ---
(In reply to Richard Earnshaw from comment #8)
> Forward declarations of enums in C requires c23, when you can use the size
> type specifier.  For earlier versions this isn't valid code.

Is is a GNU extension: 
https://gcc.gnu.org/onlinedocs/gcc/Enum-Extensions.html