fossilize_replay dumped core

I've lately seen this for the first time:

# dmesg
[101136.441571] fossilize_repla[540674]: segfault at 10 ip 000055cfc73cdd74 sp 00007ffeb8737bb0 error 4 cpu 7 in fossilize_replay[55cfc73a1000+169000]
[101136.441580] Code: 00 48 c7 44 24 58 00 00 00 00 48 8d 8c c8 30 08 00 00 48 8b 80 b0 08 00 00 48 c7 44 24 60 00 00 00 00 c7 44 24 40 11 00 00 00 <48> 8b 78 10 48 8d 05 31 d0 16 00 ff 10 e9 0f ff ff ff 89 c7 e8 93

I'm not sure how to decode this, I'm also seeing a similar dmesg output for Electron apps sometimes. The coredump isn't very helpful either because debug info seems missing:

# sudo coredumpctl info 540674
           PID: 540674 (fossilize_repla)
           UID: 500 (kakra)
           GID: 500 (kakra)
        Signal: 11 (SEGV)
     Timestamp: Sun 2020-12-20 23:32:05 CET (2 days ago)
  Command Line: /home/kakra/.local/share/Steam/ubuntu12_32/../ubuntu12_64/fossilize_replay /home/kakra/.local/share/Steam/steamapps/shadercache/489830/fozpipelinesv4/steamapp_pipeline_cache.foz /home/kakra/.local/share/Steam/steamapps/shadercache/489830/fozpipelinesv4/steam_pipeline_cache.foz --master-process --quiet-slave --shmem-fd 82 --spirv-val --num-threads 2 --on-disk-validation-whitelist /home/kakra/.local/share/Steam/steamapps/shadercache/489830/fozpipelinesv4/steam_pipeline_cache_whitelist --device-index 0 --timeout-seconds 10 --implicit-whitelist 0
    Executable: /home/kakra/.local/share/Steam/ubuntu12_64/fossilize_replay
 Control Group: /user.slice/user-500.slice/user@500.service/app.slice/app-steam-2cad372f130f4fb1b9d86232268f33c5.scope
          Unit: user@500.service
     User Unit: app-steam-2cad372f130f4fb1b9d86232268f33c5.scope
         Slice: user-500.slice
     Owner UID: 500 (kakra)
       Boot ID: 25c3b6c46f9341b4b5d0d292e264aec4
    Machine ID: 121b87ca633e8ac0016656680000001b
      Hostname: jupiter
       Storage: /var/lib/systemd/coredump/core.fossilize_repla.500.25c3b6c46f9341b4b5d0d292e264aec4.540674.1608503525000000.zst
       Message: Process 540674 (fossilize_repla) of user 500 dumped core.

Error 4 probably means user-space was faulting for a non-existing page (PF_USER).

I copied the 489830 cache to my local build and try to reproduce now with this command:

./fossilize-replay 489830/fozpipelinesv4/steamapp_pipeline_cache.foz 489830/fozpipelinesv4/steam_pipeline_cache.foz --spirv-val --on-disk-validation-whitelist 489830/fozpipelinesv4/steam_pipeline_cache_whitelist --device-index 0 --timeout-seconds 10 --implicit-whitelist 0

It resulted in the following log: https://gist.github.com/kakra/0272aa4ca003836750c18e687d6e1bf3

Retry with a debug build?

Start with the copied 489830 cache and run the provided fossilize-replay command to reproduce the crash, then compare the result with the linked dmesg output and gist log. Use the core dump or a debug build to identify where fossilize_replay faults; done means the reproduction is explained and the crash is fixed or narrowed to a documented cause.