From: Walter Alejandro Iglesias <wai@roquesor.com>
Subject: Re: Blender crashes when rendering animation to ffmpeg video
To: ports@openbsd.org
Date: Sat, 8 Nov 2025 14:31:55 +0100

On Sat, Nov 08, 2025 at 11:04:55AM +0000, Stuart Henderson wrote:
> > > It is IBT machine.
> > 
> > Sorry, what does IBT stands for?
> 
> indirect branch tracking, part of the control-flow enforcement features
> on 11th gen/newer intel cpus. apple M2 has similar. if program code makes
> an indirect jump, it will trap on SIGILL unless the jump target has a
> specific opcode stored at that location.
> 
> our compilers in base add this automatically, but asm code needs manual
> changes if it doesn't already handle this.
> 
> something changed in the FFmpeg 8 update that is triggering this in the
> libraries; previously /usr/local/bin/ffmpeg was tripping it but we
> didn't have such a problem with the libraries.
> 
> if you hit SIGILL on amd64 with IBT in the dmesg cpu attach line, run
> the program under ktrace, then kdump | grep SIGILL, look for a line like
> 
>   1020 xfreerdp PSIG  SIGILL caught handler=0x3f8c2682be0 mask=0<> code=ILL_BTCFI addr=0x3f87e823d20 trapno=21
> 
> if it has that ILL_BTCFI then that is the cause.
> 
> > > May I ask you to try this guess?
> > 
> > I got the gdb backtrace using the debug-blender package.  I'll download
> > the ports, compile blender and tell you if your diff helps.
> 
> it is very likely to help.
> 
> 

I noticed this:
 
  https://marc.info/?l=openbsd-ports-cvs&m=176260589723789&w=2

I figured the problem was related to the ffmpeg8, but oddly enough,
ffmpeg8 didn't give me any problems.  Before applying Kirills's diff,
from a images sequence generated with blender I made a video using
ffmpeg from command line.


-- 
Walter