New subject: [ruby-core:124123] [Ruby Bug#21772] ruby: YJIT has panicked StackOpnd(1) should be a heap object, but was ImmSymbol for VALUE(137647867319760)

10 Dec 2025

      Issue #21772 has been reported by gearoiddc (Gearoid de Cleir).

----------------------------------------
Bug #21772: ruby: YJIT has panicked StackOpnd(1) should be a heap object, but was ImmSymbol for VALUE(137647867319760)
https://bugs.ruby-lang.org/issues/21772

* Author: gearoiddc (Gearoid de Cleir)
* Status: Open
* ruby -v: 3.4.7
* Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN
----------------------------------------
I'm getting a YJIT has panicked crash in my rails app locally when a part of my application rapidly uses a gem I have "auto_session_timeout".

If I patch the gem by changing the symbol to a string the error goes away.

``` ruby
  module AutoSessionTimeout
    private

    def session_expired?(c)
      c.session[:auto_session_expires_at].<(Time.now)
    end
  end

```

to

``` ruby
  def session_expired?(c)
    c.session["auto_session_expires_at"].<(Time.now)
  end
```

I can consistently cause the crash but I can't find a way to reproduce the error in a snipped of code.

But it looks like YJIT is keeping the key as a sybmol even though it was converted to a string.

def [](key)
  load_for_read!
  key = key.to_s

  if key == "session_id" # <-- crash occurs here
    id&.public_id
  else
    @delegate[key]
  end
end

Didn't have the same issue on ruby 3.3 with YJIT.

System Configuration
Ruby Version: ruby 3.4.7 (2025-10-08 revision 7a5688e2a2) +YJIT +PRISM [x86_64-linux]

Environment:  Ubuntu 22.04.5 LTS (x86_64)

Backtrace & Logs

```
ruby: YJIT has panicked. More info to follow...

thread '<unnamed>' panicked at ./yjit/src/codegen.rs:5018:9:
StackOpnd(1) should be a heap object, but was ImmSymbol for VALUE(137647867319760)
stack backtrace:
   0: __rustc::rust_begin_unwind
             at /rustc/1159e78c4747b02ef996e55082b704c09b970588/library/std/src/panicking.rs:697:5
   1: core::panicking::panic_fmt
             at /rustc/1159e78c4747b02ef996e55082b704c09b970588/library/core/src/panicking.rs:75:14
   2: yjit::codegen::jit_guard_known_klass
             at /home/travis/.rvm/src/ruby-3.4.7/yjit/src/codegen.rs:5018:9
   3: yjit::codegen::gen_equality_specialized
             at /home/travis/.rvm/src/ruby-3.4.7/yjit/src/codegen.rs:3690:9
   4: yjit::codegen::gen_opt_eq
             at /home/travis/.rvm/src/ruby-3.4.7/yjit/src/codegen.rs:3753:29
   5: yjit::codegen::gen_single_block
             at /home/travis/.rvm/src/ruby-3.4.7/yjit/src/codegen.rs:1382:22
   6: yjit::core::gen_block_series_body
             at /home/travis/.rvm/src/ruby-3.4.7/yjit/src/core.rs:3088:23
   7: yjit::core::gen_block_series
             at /home/travis/.rvm/src/ruby-3.4.7/yjit/src/core.rs:3066:18
   8: yjit::core::branch_stub_hit_body
             at /home/travis/.rvm/src/ruby-3.4.7/yjit/src/core.rs:3604:17
   9: yjit::core::branch_stub_hit::{{closure}}::{{closure}}
             at /home/travis/.rvm/src/ruby-3.4.7/yjit/src/core.rs:3493:36
  10: yjit::stats::with_compile_time
             at /home/travis/.rvm/src/ruby-3.4.7/yjit/src/stats.rs:1084:15
  11: yjit::core::branch_stub_hit::{{closure}}
             at /home/travis/.rvm/src/ruby-3.4.7/yjit/src/core.rs:3493:13
  12: std::panicking::catch_unwind::do_call
             at /rustc/1159e78c4747b02ef996e55082b704c09b970588/library/std/src/panicking.rs:589:40
  13: std::panicking::catch_unwind
             at /rustc/1159e78c4747b02ef996e55082b704c09b970588/library/std/src/panicking.rs:552:19
  14: std::panic::catch_unwind
             at /rustc/1159e78c4747b02ef996e55082b704c09b970588/library/std/src/panic.rs:359:14
  15: yjit::cruby::with_vm_lock
             at /home/travis/.rvm/src/ruby-3.4.7/yjit/src/cruby.rs:688:21
  16: yjit::core::branch_stub_hit
             at /home/travis/.rvm/src/ruby-3.4.7/yjit/src/core.rs:3492:9
  17: <unknown>
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
/home/gearoid/.rvm/gems/ruby-3.4.7@7.2.3/gems/actionpack-7.2.3/lib/action_dispatch/request/session.rb:118: [BUG] YJIT: panicked at ./yjit/src/codegen.rs:5018:9:
StackOpnd(1) should be a heap object, but was ImmSymbol for VALUE(137647867319760)
ruby 3.4.7 (2025-10-08 revision 7a5688e2a2) +YJIT +PRISM [x86_64-linux]

```

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

[ruby-core:124121] [Ruby Bug#21772] ruby: YJIT has panicked StackOpnd(1) should be a heap object, but was ImmSymbol for VALUE(137647867319760)

gearoiddc (Gearoid de Cleir)

k0kubun (Takashi Kokubun)

gearoiddc (Gearoid de Cleir)

alanwu (Alan Wu)

gearoiddc (Gearoid de Cleir)

alanwu (Alan Wu)

k0kubun (Takashi Kokubun)

tags

participants (3)