From: "znz (Kazuhiro NISHIYAMA) via ruby-core" <ruby-core@...>
Date: 2026-10-09T04:23:14+00:00
Subject: [ruby-core:127023] [Ruby Bug#22421] `RubyVM::YJIT.max_compile_time_ns=` aborts the process when YJIT is not enabled

Issue #22421 has been reported by znz (Kazuhiro NISHIYAMA).

----------------------------------------
Bug #22421: `RubyVM::YJIT.max_compile_time_ns=` aborts the process when YJIT is not enabled
https://bugs.ruby-lang.org/issues/22421

* Author: znz (Kazuhiro NISHIYAMA)
* Status: Open
* Assignee: jit
* ruby -v: ruby 4.1.0dev (2026-10-09T00:54:42Z master 21f68cfec7) +PRISM [x86_64-linux]
* Backport: 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN
----------------------------------------
Calling `RubyVM::YJIT.max_compile_time_ns=` (added by [Feature #22236]) before YJIT is enabled aborts the process with a Rust panic.

```
$ ruby -v
ruby 4.1.0dev (2026-10-09T00:54:42Z master 21f68cfec7) +PRISM [x86_64-linux]

$ ruby -e 'RubyVM::YJIT.max_compile_time_ns = 10'

thread '<unnamed>' (10) panicked at /usr/src/ruby/yjit/src/codegen.rs:11313:43:
called `Option::unwrap()` on a `None` value
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

thread '<unnamed>' (10) panicked at .../library/core/src/panicking.rs:225:5:
panic in a function that cannot unwind
Aborted (core dumped)
```

The same happens with `ruby --yjit-disable -e 'RubyVM::YJIT.max_compile_time_ns = 10'`.
It works as expected once YJIT is enabled, either with `--yjit` or after `RubyVM::YJIT.enable`:

```
$ ruby --yjit -e 'RubyVM::YJIT.max_compile_time_ns = 10; p RubyVM::YJIT.max_compile_time_ns'
10
$ ruby -e 'RubyVM::YJIT.enable; RubyVM::YJIT.max_compile_time_ns = 10; p RubyVM::YJIT.max_compile_time_ns'
10
```

The reader side does not crash (`RubyVM::YJIT.max_compile_time_ns` and `RubyVM::YJIT.total_compile_time_ns` return 0 when YJIT is not enabled).

The panic is the `unwrap()` in `CodegenGlobals::get_instance()` (yjit/src/codegen.rs), which is `None` until YJIT is initialized. Other YJIT methods that touch the globals (for example `reset_stats!` or `enable`) check `CodegenGlobals::has_instance()` or the enabled state first.

Expected behavior: either store the value so that it takes effect when YJIT is enabled later (useful for the warmup-budget use case in [Feature #22236], where the budget may be set early in a boot script), or raise a Ruby exception, but not abort the process.

Reproduced in the `ghcr.io/ruby/ruby:master` Docker image (x86_64-linux).




-- 
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