[PROF-12743] Runtime stack collection callback registration

[gyuheon0h]

What does this PR do?
We want to collect runtime frames for the crashtracker. This approach follows how we access the call stack for profiling.

Motivation:

Change log entry

Additional Notes:

How to test the change?

"Ruby and C method runtime stack capture" RSpec test

Run a ruby program with the crashtracker initialized. Runtime stacks should be visible in the experimental section of the crash report. Stacktrace emitted from an example script I wrote to test

{
  "format": "Datadog Runtime Callback 1.0",
  "frames": [
    {
      "file": "<Fiddle (C extension)>",
      "function": "free"
    },
    {
      "file": "debug_runtime_callback.rb",
      "function": "final_crash_point",
      "line": 244
    },
    {
      "file": "<Integer (C extension)>",
      "function": "times"
    },
    {
      "file": "debug_runtime_callback.rb",
      "function": "final_crash_point",
      "line": 243
    },
   .....
    {
      "file": "debug_runtime_callback.rb",
      "function": "main_crash_test",
      "line": 251
    },
    {
      "file": "debug_runtime_callback.rb",
      "function": "<main>",
      "line": 276
    },
    {
      "file": "<Kernel (C extension)>",
      "function": "fork"
    }
  ]
}

[github-actions]

👋 Hey @DataDog/ruby-guild, please fill "Change log entry" section in the pull request description.

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^{Visited at: 2025-11-18 21:06:17 UTC}

[github-actions]

Typing analysis

Ignored files

This PR introduces 1 ignored file. It decreases the percentage of typed files from 38.32% to 38.21% (-0.11%).

Ignored files (+1-0)

❌ Introduced:

lib/datadog/core/crashtracking/component.rb

Note: Ignored files are excluded from the next sections.

Untyped other declarations

This PR clears 1 untyped other declaration. It decreases the percentage of typed other declarations from 68.02% to 67.96% (-0.06%).

Untyped other declarations (+0-1)

✅ Cleared:

sig/datadog/core/crashtracking/component.rbs:33
└── attr_reader logger: untyped

[datadog-datadog-prod-us1]

✅ Tests

🎉 All green!

❄️ No new flaky tests detected
🧪 All tests passed

🎯 Code Coverage
• Patch Coverage: 85.14%
• Total Coverage: 98.51% (+0.03%)

View detailed report

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: df60ca0 | Docs | Datadog PR Page | Was this helpful? Give us feedback!}

[gyuheon0h]

• [PROF-12743] Runtime stack collection callback registration #4984 👈 (View in Graphite)
• master

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[gyuheon0h]

Paper trail

[ ] Checking unreasonable string sizes
[ ] Checking that string pointers point to valid strings
[ ] Checking that control frames are valid
[ ] Checking that iseq is valid, and the instruction size is not unreasonable
[ ] Validating that pointers are readable using mincore
[ ] Checking for recursive frames
[ ] Strings can have different representations, take that into account
[ ] Ruby apps commonly have very deep stacks. We default in the profiler to collecting 400 and we've seen GitHub go close to 600, handle this
[ ] Pay attention to structure keeping the bytecode-to-line mapping

[gyuheon0h]

Taken from ext/datadog_profiling_native_extension/extconf.rb, so that we can access private Ruby headers

[gyuheon0h]

Will be removed when this repo is updated to use libdatadog v24; just for lower friction when local dev rn

[gyuheon0h]

Taken from ext/datadog_profiling_native_extension/private_vm_api_access.c so that we can access internal Ruby structures

[chatgpt-codex-connector]

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