www/firefox, UPDATING, and "This platform lacks a functioning sem_open implementation..."

[Jan Beich]

David Wolfskill <david at catwhisker.org> writes:

> In case it helps someone else, I had encountered the symptoms cited in
> UPDATING entry 20170411, but the UPDATING entry didn't exist at the
> time.
>
> So I poked around, and discovered that -- in my case -- the thing that
> was apparently causing the problem was that lang/python27 had been built
> with "SEM=off".
>
> So I re-built lang/python27 after enabling its SEM option; that
> done, www/firefox built without further incident.
>
> (Checking the svn log for lang/python27/Makefile, it seems that SEM
> had been changed to "default on" in r361735, 2014-07-14 00:20:40
> -0700.  I had no known reason to change the setting at that time....)

I've filed bug 218641 to avoid documenting the issue in UPDATING.
ac_cv_* usage implies users should not disable POSIX semaphores if the
platform provides those. r230031 described some limitations of the
previous implementation on FreeBSD 5.0-8.4. PTH was removed in r363790,
so the only way to make "multiprocessing" usable is via SEM.