[PATCH v2] configure.ac: use AC_HEADER_MAJOR to detect major()/minor()

[Emil Velikov]

On 12 December 2017 at 08:28, Pekka Paalanen <ppaalanen at gmail.com> wrote:
> On Mon, 11 Dec 2017 16:16:47 +0200
> Pekka Paalanen <ppaalanen at gmail.com> wrote:
>
>> On Wed, 31 May 2017 22:17:50 +0100
>> Sergei Trofimovich <slyfox at gentoo.org> wrote:
>>
>> > This change slightly updates c4d7f66c12853b9575366dd9f4a7960ec5694934
>> > which added <sys/sysmacros.h> inclusion.
>> >
>> > Autoconf has AC_HEADER_MAJOR to find out which header defines
>> > reqiured macros:
>> >     https://www.gnu.org/software/autoconf/manual/autoconf-2.69/html_node/Particular-Headers.html
>> >
>> > This change should increase portability across other libcs.
>> >
>> > Bug: https://bugs.gentoo.org/610652
>> > Signed-off-by: Sergei Trofimovich <slyfox at gentoo.org>
>> > ---
>> > Change since v1:
>> > - rebased on top of current master
>> > - dedented nested '#    include'
>> >  configure.ac                       | 1 +
>> >  libweston/launcher-direct.c        | 9 ++++++++-
>> >  libweston/launcher-logind.c        | 9 ++++++++-
>> >  libweston/launcher-weston-launch.c | 8 +++++++-
>> >  libweston/weston-launch.c          | 9 ++++++++-
>> >  5 files changed, 32 insertions(+), 4 deletions(-)
>>
>> Hi,
>>
>> I'm on Gentoo with sys-libs/glibc-2.25-r9:2.2 and I am now getting a
>> bunch of warnings like this:
>>
>> /home/pq/git/weston/libweston/weston-launch.c: In function ‘handle_open’:
>> /home/pq/git/weston/libweston/weston-launch.c:333:13: warning: In the GNU C Library, "major" is defined
>>  by <sys/sysmacros.h>. For historical compatibility, it is
>>  currently defined by <sys/types.h> as well, but we plan to
>>  remove this soon. To use "major", include <sys/sysmacros.h>
>>  directly. If you did not intend to use a system-defined macro
>>  "major", you should undefine it after including <sys/types.h>.
>>   if (major(s.st_rdev) != INPUT_MAJOR &&
>>
>>
>> Reverting this patch makes the warnings go away.
>>
>> What's the right fix here?
>>
>> In config.h I have:
>>
>> /* Define to 1 if `major', `minor', and `makedev' are declared in <mkdev.h>.
>>    */
>> /* #undef MAJOR_IN_MKDEV */
>>
>> /* Define to 1 if `major', `minor', and `makedev' are declared in
>>    <sysmacros.h>. */
>> /* #undef MAJOR_IN_SYSMACROS */
>>
>> I'm not sure what I needed to do get even that far, maybe wipe my
>> out-of-tree build dir. Even then, I cannot find any evidence of
>> configure actually running the tests. I always start a new build dir by
>> running autogen.sh.
>
> Hi,
>
> there is an email thread of the problem from a slightly different point
> of view:
> https://lists.gnu.org/archive/html/autoconf/2016-09/msg00000.html
>
> If we keep the code as is, the warning will not go away until glibc
> actually drops the things from sys/types.h and distros ship it.
> Apparently there is a workaround one could make with config.site:
> https://lists.gnu.org/archive/html/autoconf/2016-09/msg00013.html
>
> Or we could wait for a new autoconf release and require it, but the
> discussion happened in 2016 and at least Gentoo does not have a
> autoconf 2.70 yet. Or we could ship a fixed AC_HEADER_MAJOR.
>
> Or we could just revert this patch until something in the above changes
> or we have migrated to Meson.
>
I wish the glibc people were a bit more diligent about the deprecation :-(
Haven't looked at how Meson does it, but I would suspect it has a
workaround similar to this [1].

-Emil
[1] https://cgit.freedesktop.org/mesa/drm/commit/?id=7040fea0280bad527ed4b3d5eee7d7bfbf303efc