Re: [patch+7.8?] Fix --with-babeltrace with gcc-4.9.1

[Doug Evans <dje@google.com>]

On Tue, Aug 12, 2014 at 12:22 PM, Jan Kratochvil
<jan.kratochvil@redhat.com> wrote:
> On Wed, 06 Aug 2014 03:00:04 +0200, Yao Qi wrote:
>> This patch fixes https://sourceware.org/bugzilla/show_bug.cgi?id=17104
>> Please mention it in ChangeLog entry.  I had a patch to this PR, but
>> didn't follow it up.  Yours is fine.
>
> I think the one of yours is better, posting it here for new approval.
>
> IMO it could go also for 7.8.1.
>
>
> My original reproducer is wrong, one also has to specify -Wall in CFLAGS:
>         CFLAGS=-Wall ./configure --with-babeltrace; make
>
>
> Thanks,
> Jan
>
> gdb/
> 2014-07-01  Yao Qi  <yao@codesourcery.com>
>
>         PR build/17104
>         * configure.ac: Use local variable 'pos'.
>         * configure: Regenerated.
>
> diff --git a/gdb/configure b/gdb/configure
> index a4c0a8c..7956aa7 100755
> --- a/gdb/configure
> +++ b/gdb/configure
> @@ -15234,6 +15234,7 @@ struct bt_iter_pos *pos = bt_iter_get_pos (bt_ctf_get_iter (NULL));
>                         struct bt_ctf_event *event = NULL;
>                         const struct bt_definition *scope;
>
> +                       bt_iter_set_pos (bt_ctf_get_iter (NULL), pos);
>                         scope = bt_ctf_get_top_level_scope (event,
>                                                            BT_STREAM_EVENT_HEADER);
>                         bt_ctf_get_uint64 (bt_ctf_get_field (event, scope, "id"));
> diff --git a/gdb/configure.ac b/gdb/configure.ac
> index a2ac15f..fc1d8bc 100644
> --- a/gdb/configure.ac
> +++ b/gdb/configure.ac
> @@ -2417,6 +2417,7 @@ else
>                         struct bt_ctf_event *event = NULL;
>                         const struct bt_definition *scope;
>
> +                       bt_iter_set_pos (bt_ctf_get_iter (NULL), pos);
>                         scope = bt_ctf_get_top_level_scope (event,
>                                                            BT_STREAM_EVENT_HEADER);
>                         bt_ctf_get_uint64 (bt_ctf_get_field (event, scope, "id"));
>

Hi.
This seems like an excessive amount of code just to test whether a
library exists.
Do we really need all of it?
E.g., can we just delete "pos" and the function call that initializes it?

struct bt_iter_pos *pos = bt_iter_get_pos (bt_ctf_get_iter (NULL));

Or, if for some reason we need to test whether bf_ctf_get_iter exists,
can we just
call it and discard the result?  [And similarly for the rest of the code.]
None of this code gets run anyways.