From: "yokomaru (Yoko Suzuki) via ruby-core" <ruby-core@...>
Date: 2026-08-04T05:45:39+00:00
Subject: [ruby-core:126240] [Ruby Bug#22217] Segmentation fault when resuming execution with `Coverage.start` and ruby/debug

Issue #22217 has been updated by yokomaru (Yoko Suzuki).


Thank you so much for the quick fix and for preparing the backport!

----------------------------------------
Bug #22217: Segmentation fault when resuming execution with `Coverage.start` and ruby/debug
https://bugs.ruby-lang.org/issues/22217#change-118326

* Author: yokomaru (Yoko Suzuki)
* Status: Closed
* Assignee: luke-gru (Luke Gruber)
* Target version: 4.0
* ruby -v: ruby 4.1.0dev (2026-07-29T23:49:57Z master 94933bfebf) +PRISM [arm64-darwin25],ruby 4.1.0dev (2026-07-29T23:49:57Z master 94933bfebf) +PRISM [x86_64-linux],ruby 4.0.6 (2026-07-14 revision 03b6d3f889) +PRISM [arm64-darwin25],ruby 4.0.6 (2026-07-14 revision 03b6d3f889) +PRISM [x86_64-linux]
* Backport: 4.0: REQUIRED
----------------------------------------
Resuming execution from `ruby/debug` while coverage collection is enabled via `Coverage.start` can cause a segmentation fault and crash the Ruby process.

The crash is intermittent, but reproduces frequently using the same steps. I confirmed it on both macOS (arm64) and Linux (x86_64) using debug 1.11.1. It reproduced with Ruby 4.0.5, Ruby 4.0.6, and Ruby 4.1.0-dev, but did not reproduce in my limited testing with Ruby 3.4.10 or Ruby 3.3.12.

## Reproduction Code

`test.rb`

```ruby
require "coverage"

Coverage.start

require "debug"

debugger
```

## Steps to Reproduce

Run:

```console
$ ruby test.rb
```

At the debugger prompt, enter:

```text
continue
```

The same crash also occurs with `next`, `step`, and `finish`.

## Backtrace Excerpt

Both macOS and Linux crash around the Ruby VM event hooks.

On macOS (arm64), the C-level backtrace includes:

```text
libruby.4.1.dylib(exec_hooks_protected+0xb0)
libruby.4.1.dylib(rb_exec_event_hooks+0x7c)
libruby.4.1.dylib(vm_trace_hook+0x198)
libruby.4.1.dylib(vm_trace+0x24c)
```

On Linux (x86_64), it includes:

```text
libruby.so.4.1(exec_hooks_body+0x20) vm_trace.c:453
libruby.so.4.1(exec_hooks_protected+0x10b) vm_trace.c:515
libruby.so.4.1(rb_exec_event_hooks+0x83) vm_trace.c:562
libruby.so.4.1(vm_trace_hook+0x17c) vm_core.h:2376
libruby.so.4.1(vm_trace+0x344) vm_insnhelper.c:7373
```


I've attached the crash log from the latest version (4.1.0-dev).


---Files--------------------------------
test.rb (62 Bytes)
stderr-macos-4.1-dev.log (35.7 KB)
stderr-linux-4.1-dev.log (35.4 KB)
ruby-2026-07-30-112302.ips (15 KB)


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