Segfault with Ruby 3.4.9 and mini_racer 0.21.1

[ekzobrain]

Hi. I have updated my project to Ruby 3.4.9 (from 3.3.8) and started getting a segfault on startup inside docker deployment. I am using docker.io/library/ruby:3.4.9-slim base image. From the C level backtrace information it seems like this segfault is related to mini_racer extension. See segfault.txt attached.

segfault.txt

[SamSaffron]

Any chance you can post a dockerfile reproducing this?

[ekzobrain]

Hi. I attached a demo project that reproduces this issue. It is just a basic rails project sceleton, but with Gemfile from my actual project. So this seems to be a dependency conflict issue. Just run docker build and you'll see a segfault during build process (on RUN SECRET_KEY_BASE_DUMMY=1 ./bin/rails assets:precompile line). If you remove this line from Dockerfile - build will success, but you'll get segfault on container start (docker run -it -e RAILS_ENV=development test_mini_racer).
This issue does not occur if I build image with arg RUBY_VERSION=3.3.8, so the only difference is base Ruby image

store.zip

[tisba]

jFYI: From the initially posted segfault.txt it looks like this is on x86

[ekzobrain]

Hi. Need help identifying the exact gem (and/or it's deps) that's causing a crash?

[ashsystems]

No info at the moment on the cause or solution, but I ran into a similar issue with ruby 3.4.9 and mini_racer 0.21.4 when packaging discourse 2026.7.0 in nixpkgs. Interestingly, the official discourse docker file uses the same version of mini_racer and ruby, but to my knowledge does not have this issue.

Excerpt of the segfault error.txt
The WIP patched version of nixpkgs where I encountered this error (while running discourse.tests)

[ashsystems]

The segfault appears to be fixed by disabling the :single_threaded option in mini_racer, at least in my case.