Xorg crashes on startup with "Segmentation fault at address 0x0" [SOLVED]

[list at museum.rain.com]

On Sat, Mar 25, 2017 at 10:13:36AM +0000, Arthur Chance wrote:
> On 24/03/2017 19:20, list at museum.rain.com wrote:
> > I'm running FreeBSD 11-STABLE on a Dell 7010 with an AMD Radeon graphics
> > card.
> > 
> > I recently did a 'pkg upgrade' of kde4, xorg, and dependendents:
> > 
> > pkg upgrade -fR ....
> > 
> > I can no longer start an X server, due to a segmentation fault error on
> > X startup.  The Xorg.0.log is below.  At this point I am simply trying
> > to start the X server by running /usr/local/bin/X.  I am not yet to the
> > point of trying to use startx/startkde to bring up the KDE environment.
> > 
> > I'd like to find out why X is crashing.  I am not using an xorg.conf file.

[... snip ...]

> Use "pkg info -x llvm" to see if you have two versions of llvm present.
> If you do, delete the older one. Because of the way some X drivers are
> linked you can end up with two llvm runtime systems being used by X and
> one of them isn't initialised properly and crashes in calls to the
> pthread library, which seems to be what's happening here.
> 
> If it's not that, I'm afraid someone else will have to help.

Thank you, Arthur.  That was precisely correct.  'pkg info' reported three versions
of llvm installed:

jimsdesk : 09:43:41 /root# pkg info -x llvm
llvm35-3.5.2_2
llvm37-3.7.1_4
llvm39-3.9.1_2

Uninstalling llvm35 and llvm37 fixed the problem.

Thank you!

Jim