Re: modular-xorg-server now segfaults with both Clang and GCC

[maya%netbsd.org@localhost]

On Wed, Sep 19, 2018 at 10:04:22AM -0500, Cág wrote:
> Hi,
> 
> A couple of days ago I did a bulk build on NetBSD with pkgsrc-current
> and lang/clang as the compiler. I forgot that clang-compiled xorg
> produces segfaults and first wondered why Xorg wouldn't start -- it
> told about a segmentation fault but didn't dump a core. I think there
> was a thread about it a couple of years ago. Anyway, at first I thought
> it was Mesa, and rebuilt it. After no luck, I used Mesa from wip, with
> no luck again (thanks for the update btw! Maya, was that you?). At the 
> end of the day, I tried rebuilding modular-xorg-server with gcc, and
> it would still segfault, leaving the only option to use 1.19 instead
> of -current's 1.20.
> 
> Anybody got a clue, why this segfault happens? Maybe somebody got a
> patch? Does it happen to anyone else at all?
> 
> Thank you very much in advance!

I only touched libdrm on pkgsrc (not including wip). it's possible those
changes misbehave on older netbsd.
For diagnosing problems, there are two options:
- Run ktruss -i -o out startx
  kdump -x out and look what the last ioctl before SIGSEGV (not
  establishing the handler, but the actual crash)

This was pretty good for finding problems.

Xorg has an option for NoTrapSignals, where it will do a coredump, which
should tell where the backtrace is (I'm not very good at writing
functional xorg configuration files, though).

It's also interesting to know which NetBSD version you are running, and
which hardware (maybe show /var/log/Xorg.0.log)

David Shao did much of the work for MesaLib, Riastradh and I completed
it for NetBSD :-)