[ruby-core:123206] [Ruby Bug#21565] YJIT has panicked in rails

10 Sep 2025

      Issue #21565 has been updated by eiskrenkov (Egor Iskrenkov).

File ruby-2025-09-09-184849.ips added

k0kubun (Takashi Kokubun) wrote in #note-3:
...
We've modified the assertion failure message https://github.com/ruby/ruby/pull/14480 to debug this further. I'll release Ruby 3.4.6 early next week with that patch, so it'd be nice to see an updated error report once you encounter that with the new Ruby version.
Hello, Takashi! Thank you so much for that commit, I built Ruby from the repo, taking v3.4.5 tag as a base, adding your commit on top and removing `fn gen_opt_new` function from codegen.rs. I started my rails app again and got more verbose error report this time thanks to your work!

```
Started GET "/api/admin/app_data" for ::1 at 2025-09-09 18:47:05 +0200
Processing by Api::Admin::AppDataController#show as JSON
  Parameters: {"app_datum" => {}}
ruby: YJIT has panicked. More info to follow...

thread '<unnamed>' panicked at ../yjit/src/codegen.rs:5086:9:
StackOpnd(1) should be a heap object, but was ImmSymbol for VALUE(4928731040)
stack backtrace:
   0: rust_begin_unwind
             at /rustc/4eb161250e340c8f48f66e2b929ef4a5bed7c181/library/std/src/panicking.rs:692:5
   1: core::panicking::panic_fmt
             at /rustc/4eb161250e340c8f48f66e2b929ef4a5bed7c181/library/core/src/panicking.rs:75:14
   2: yjit::codegen::jit_guard_known_klass
             at /Users/eiskrenkov/dev/ruby/build/../yjit/src/codegen.rs:5086:9
   3: yjit::codegen::gen_equality_specialized
             at /Users/eiskrenkov/dev/ruby/build/../yjit/src/codegen.rs:3695:9
   4: yjit::codegen::gen_opt_eq
             at /Users/eiskrenkov/dev/ruby/build/../yjit/src/codegen.rs:3758:29
   5: yjit::codegen::gen_single_block
             at /Users/eiskrenkov/dev/ruby/build/../yjit/src/codegen.rs:1387:22
   6: yjit::core::gen_block_series_body
             at /Users/eiskrenkov/dev/ruby/build/../yjit/src/core.rs:3088:23
   7: yjit::core::gen_block_series
             at /Users/eiskrenkov/dev/ruby/build/../yjit/src/core.rs:3066:18
   8: yjit::core::branch_stub_hit_body
             at /Users/eiskrenkov/dev/ruby/build/../yjit/src/core.rs:3604:17
   9: yjit::core::branch_stub_hit::{{closure}}::{{closure}}
             at /Users/eiskrenkov/dev/ruby/build/../yjit/src/core.rs:3493:36
  10: yjit::stats::with_compile_time
             at /Users/eiskrenkov/dev/ruby/build/../yjit/src/stats.rs:1084:15
  11: yjit::core::branch_stub_hit::{{closure}}
             at /Users/eiskrenkov/dev/ruby/build/../yjit/src/core.rs:3493:13
  12: std::panicking::try::do_call
             at /Users/eiskrenkov/.rustup/toolchains/1.85.1-aarch64-apple-darwin/lib/rustlib/src/rust/library/std/src/panicking.rs:584:40
  13: std::panicking::try
             at /Users/eiskrenkov/.rustup/toolchains/1.85.1-aarch64-apple-darwin/lib/rustlib/src/rust/library/std/src/panicking.rs:547:19
  14: std::panic::catch_unwind
             at /Users/eiskrenkov/.rustup/toolchains/1.85.1-aarch64-apple-darwin/lib/rustlib/src/rust/library/std/src/panic.rs:358:14
  15: yjit::cruby::with_vm_lock
             at /Users/eiskrenkov/dev/ruby/build/../yjit/src/cruby.rs:688:21
  16: yjit::core::branch_stub_hit
             at /Users/eiskrenkov/dev/ruby/build/../yjit/src/core.rs:3492:9
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
/Users/eiskrenkov/.rubies/ruby-master/lib/ruby/gems/3.4.0/gems/actionpack-8.0.2.1/lib/action_dispatch/request/session.rb:118: [BUG] YJIT: panicked at ../yjit/src/codegen.rs:5086:9:
StackOpnd(1) should be a heap object, but was ImmSymbol for VALUE(4928731040)
ruby 3.4.5 (2025-09-09 revision cd7c672545) +YJIT +PRISM [arm64-darwin24]
```

Please, let me know if I can provide any more information necessary for debugging or I can be of any more help. Thank you so much!

----------------------------------------
Bug #21565: YJIT has panicked in rails
https://bugs.ruby-lang.org/issues/21565#change-114537

* Author: eiskrenkov (Egor Iskrenkov)
* Status: Assigned
* Assignee: jit
* ruby -v: ruby 3.4.5 (2025-07-16 revision 20cda200d3) +PRISM [arm64-darwin24]
* Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN
----------------------------------------
I've got YJIT has panicked crash in rails app locally on my M1 Pro Mac Book pro for 2 times for last 2 weeks

```
Started GET "/api/admin/environments/13/edit" for ::1 at 2025-09-08 18:32:17 +0200
Processing by Api::Admin::EnvironmentsController#edit as JSON
  Parameters: {"id" => "13", "environment" => {}}
ruby: YJIT has panicked. More info to follow...

thread '<unnamed>' panicked at ./yjit/src/codegen.rs:5031:9:
assertion failed: !val_type.is_imm()
stack backtrace:
   0: _rust_begin_unwind
   1: core::panicking::panic_fmt
   2: core::panicking::panic
   3: yjit::codegen::jit_guard_known_klass
   4: yjit::codegen::gen_equality_specialized
   5: yjit::codegen::gen_opt_eq
   6: yjit::codegen::gen_single_block
   7: yjit::core::gen_block_series
   8: yjit::core::branch_stub_hit_body
   9: yjit::stats::with_compile_time
  10: yjit::cruby::with_vm_lock
  11: yjit::core::branch_stub_hit
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
/Users/eiskrenkov/.local/share/mise/installs/ruby/3.4.5/lib/ruby/gems/3.4.0/gems/actionpack-8.0.2.1/lib/action_dispatch/request/session.rb:118: [BUG] YJIT: panicked at ./yjit/src/codegen.rs:5031:9:
assertion failed: !val_type.is_imm()
ruby 3.4.5 (2025-07-16 revision 20cda200d3) +YJIT +PRISM [arm64-darwin24]
```

It happens randomly, I couldn't find reproduction steps sadly

---Files--------------------------------
ruby-2025-09-08-183231.ips (45.3 KB)
ruby-2025-09-09-184849.ips (71.7 KB)

-- 
https://bugs.ruby-lang.org/