On 08/08/16 17:30, Johannes Sixt wrote:
> Am 07.08.2016 um 22:34 schrieb Ramsay Jones:
>> On 05/08/16 23:26, Johannes Sixt wrote:
>> At this point 'enum iterator_selection' is an incomplete type and may
>> be used when the size of the object is not required. It is not needed,
>> for example, when a typedef name is being declared as a pointer to, or
>> as a function returning such a type. However, such a type must be
>> complete before such a function is called or defined.
> All you say is true when it is a struct type, of course. But I doubt that
> there exists such a thing called "incomplete enumeration type" in C. In fact,
> with these keywords I found
> https://gcc.gnu.org/onlinedocs/gcc/Incomplete-Enums.html which indicates that
> this is a GCC extension.
Ah, well spotted!
You prompted me to look at the C99 (and C11) standards, in particular
sections 184.108.40.206 (Enumeration specifiers) and 220.127.116.11 (Tags).
So, while (technically) enumeration types are incomplete prior to the
closing } in its definition, the constraint imposed in 18.104.22.168-2 states:
"A type specifier of the form
without an enumerator list shall only appear after
the type it specifies is complete"
which pretty much rules out its use here.
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