Fix terminateHandler() on macOS

[edolstra]

Motivation

On macOS, calling std::set_terminate(nullptr) to restore the original terminate handler is ineffective, since std::terminate() calls the handler recorded in the exception. So we end up in an infinite recursion of terminateHandler() calls, which eventually overflows the stack, leading to an unhelpful crash report.

So instead, just call onTerminate() to print the stack trace and abort.

(On Linux / libstdc++, std::terminate() calls the global terminate handler so we don't have this issue.)

Also added some hackery to make the __cxa_throw interposer build with libc++ on Linux, and added an abort mode to nix __crash.

Context

Summary by CodeRabbit

• New Features

  • Added an abort option to the crash-testing command, allowing users to simulate process termination explicitly.

• Bug Fixes

  • Improved termination handling so unexpected failures consistently produce a crash report and log the active exception when available.
  • Improved crash diagnostics with clearer formatting in termination messages.

• Tests

  • Expanded crash-reporting coverage to include the new abort scenario alongside existing crash types.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 34d2639f-bef7-4fba-83ed-91312fbb2d27

📥 Commits

Reviewing files that changed from the base of the PR and between 1128ff5 and 96cc170.

📒 Files selected for processing (6)

• nix-meson-build-support/common/cxa-throw/is-logic-error.hh
• src/libutil/include/nix/util/error.hh
• src/nix/crash-handler.cc
• src/nix/crash.cc
• src/nix/main.cc
• tests/functional/sentry.sh

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📝 Walkthrough

Walkthrough

Crash termination handling now uses a shared onTerminate() path, adds portable logic-error termination support, exposes an abort crash scenario, and tests abort crash reporting through the Sentry functional test.

Changes

Crash termination handling

Layer / File(s)	Summary
Portable logic-error termination hook nix-meson-build-support/common/cxa-throw/is-logic-error.hh	Adds an overrideable CXA_THROW_ON_LOGIC_ERROR() hook defaulting to abort(), plus conditional Itanium ABI RTTI declarations.
Shared termination entry point src/libutil/include/nix/util/error.hh, src/nix/crash-handler.cc, src/nix/main.cc	Declares and defines nix::onTerminate(), and routes terminateHandler() through it after recording Sentry exception tags.
Abort crash scenario src/nix/crash.cc, tests/functional/sentry.sh	Adds the abort crash type and includes it in Sentry crash-dump coverage.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Sequence Diagram(s)

sequenceDiagram
  participant terminateHandler
  participant onTerminate
  participant logFatal
  terminateHandler->>onTerminate: delegate termination
  onTerminate->>logFatal: log current exception and crash message
  onTerminate->>onTerminate: call abort

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🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly matches the main change: fixing terminateHandler() behavior on macOS.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

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• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix-terminate

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