[sane-devel] [janitorial] sanei_thread "fixes" and Fedora 26 CI builds

[Olaf Meeuwissen]

Hi all,

I've put my leading whitespaces proposal on hold for a few days and
started fixing compiler warnings from the Alpine 3.6 musl builds.

Alpine uses the musl C library and that means stuff is sometimes a bit
different.  Which is a Good Thing!  Its pthread "idiosyncracies" led to
a pile of [-Wint-conversion] warnings that hilighted some preconceived
notions in the sanei_thread.c code and a large number of backends using
that.

The backends have been fixed up now and the sanei_thread.c code patched
up to a point where it should work with all integer type based pthread_t
implementations.  The configure script now checks for this and disables
pthread support if it doesn't find an integer pthread_t.

So for folks using musl, which uses a struct __pthread *, that means
your "multi-threading" support will fall back to multi-processing.
Patches to sanei_thread.c are welcome :-)

@Rolf> Can you take a look at 73861ea, please?  It affects the pixma
       backend.  I think it's fine but I'd like an extra pair of eyes
       on that.

On a different front, Fedora 26 was released[1] on 2017-07-11 so I've
added a CI builder for that as well.  The Fedora 25 build will stay
around for a bit longer yet, but probably not that long.

 [1]: https://fedoramagazine.org/fedora-26-is-here/

Hope this helps,
--
Olaf Meeuwissen, LPIC-2            FSF Associate Member since 2004-01-27
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