From: Ramsay Jones <ramsay@ramsayjones.plus.com>
To: Johannes Sixt <j6t@kdbg.org>, Michael Haggerty <mhagger@alum.mit.edu>
Cc: Git Mailing List <git@vger.kernel.org>
Subject: Re: Forward declaration of enum iterator_selection?
Date: Sun, 7 Aug 2016 21:34:12 +0100 [thread overview]
Message-ID: <0604cf0a-2b94-93b3-3a01-213ea5b9849b@ramsayjones.plus.com> (raw)
In-Reply-To: <933f540f-7752-cfce-5785-b67728fea987@kdbg.org>
On 05/08/16 23:26, Johannes Sixt wrote:
> When refs.c is being compiled, the only mention of enum iterator_selection is in this piece of code pulled in from refs-internal.h (have a look at the preprocessed code):
>
> typedef enum iterator_selection ref_iterator_select_fn(
> struct ref_iterator *iter0, struct ref_iterator *iter1,
> void *cb_data);
>
> This looks like a forward declarations of an enumeration type name, something that I thought is illegal in C. Am I wrong? (That may well be the case, my C-foo is quite rusty.)
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.
> My compiler does not complain (it's gcc 4.8), but I thought I mention it before someone with a pickier compiler stumbles over it...
So, I think this is correct.
Having said that, I would rather the 'enum iterator_selection' be defined
before this declaration. One solution could be to #include "iterator.h"
prior to _all_ #include "refs/refs-internal.h" in all compilation units
(Note it is in the opposite order in refs/iterator.c). Alternatively, you
could put the #include "../iterator.h" into refs/refs-internal.h directly
(some people would object to this).
ATB,
Ramsay Jones
next prev parent reply other threads:[~2016-08-07 20:34 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-05 22:26 Forward declaration of enum iterator_selection? Johannes Sixt
2016-08-07 20:34 ` Ramsay Jones [this message]
2016-08-08 16:30 ` Johannes Sixt
2016-08-08 18:28 ` Ramsay Jones
2016-08-08 18:52 ` Ramsay Jones
2016-08-10 22:46 ` Michael Haggerty
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