On 08/08/16 19:28, Ramsay Jones wrote:
> 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:
> [snip]
>>> 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 (Enumeration specifiers) and (Tags).
> So, while (technically) enumeration types are incomplete prior to the
> closing } in its definition, the constraint imposed in states:
>       "A type specifier of the form
>               enum identifier
>       without an enumerator list shall only appear after
>       the type it specifies is complete"
> which pretty much rules out its use here.

BTW, you can make gcc be that 'pickier compiler' you mentioned, thus:

$ rm refs.o
$ make CFLAGS='-g -O2 -Wall -std=c99 -pedantic' refs.o
    * new build flags
    CC refs.o
In file included from refs.c:8:0:
refs/refs-internal.h:363:14: warning: ISO C forbids forward references to 
‘enum’ types [-Wpedantic]
 typedef enum iterator_selection ref_iterator_select_fn(


Ramsay Jones

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