Signal handling: CRuby-compatible SignalException conversion + SIG_DFL re-raise

[sisshiki1969]

Summary

Implements CRuby's signal semantics. Previously only SIGINT converted to a Ruby exception, and an uncaught SignalException exited 1 — so Process.kill(:TERM, Process.pid) killed the process outright, and $?.signaled?/termsig never saw signal deaths.

Changes

1. Default-convert set = CRuby's (verified on 4.0.2): HUP, INT→Interrupt, QUIT, ALRM, TERM, USR1, USR2 are caught by the async stub and raised as rescuable SignalExceptions at the next poll point. (PIPE/CHLD/CONT/WINCH stay unconverted, as in CRuby.)

2. Uncaught SignalException re-raises with SIG_DFL — both top-level handle_error and the fork-child error path restore SIG_DFL, unblock, and kill(self, signo), so the parent sees a signal death ($?.signaled? / termsig), including raise SignalException, 'SIGKILL'. Reporting matches CRuby: Interrupt prints the report; plain SignalException dies silently.

3. Process.kill to self drains synchronously — a self-signal is delivered before kill(2) returns, so the exception raises inside the kill call (-> { Process.kill(...) }.should.raise(SignalException) passes).

4. Kernel#sleep is signal-interruptible — nanosleep + EINTR→poll instead of std::thread::sleep (which silently retries EINTR; a signaled sleeper dozed the full interval and converted at a later, racy poll). A trap handler resumes the remaining sleep; a conversion aborts it.

5. Pending-signal bitmap → process-global static — signals and sigaction are process-wide; per-Codegen JIT-data storage meant a second Codegen (another test thread) re-pointing the handlers at its bitmap silently lost signals recorded there while polls read another. Both arch stubs now OR into the global's absolute address. This was the root of the flaky fork tests.

6. Child-status observation fixes surfaced by the specs:

   • IO.popen(String) no longer interposes sh for plain commands — a wrapping shell reports a signal-killed child as normal exit 128+signo, destroying signaled? (this is what made mspec's ruby_exe exit-status assertions fail). POSIX shell builtins (exit, exec, …) still route through sh, matching CRuby's posix_sh_cmds.
   • Backticks now set $? (previously left nil).
   • SignalException.new(name, msg) raises ArgumentError; #signo derives from the message for runtime-materialized exceptions.

Results

Spec	Before	After
core/exception/signal_exception_spec	process death (tagged)	16/16 pass
core/exception/signm_spec / signo_spec	process death (tagged)	pass
core/exception/interrupt_spec	3 failures	1 failure (backtrace frame granularity — follow-up)
core/exception category	—	248 examples, 5 failures, 0 errors

• 3 spec/tags entries removed (10 → 7 files).
• All CI spec categories stay 0 failures / 0 errors; thread/process/io/kernel/socket categories complete with no hang.
• Full lib suite 1828 passed; new subprocess integration tests in tests/signal_handling.rs (8 tests — in-process self-signal tests would signal the shared cargo-test process).
• 7-point CRuby diff battery (rescue payloads, fork $?, SIGKILL raise, popen builtins, backtick $?): all MATCH.

Known limitation (documented)

A process blocked in a Rust EINTR-retrying read/write survives a single SIGTERM (the pending bit is set but the poll is never reached). Healthy execution converts promptly; when killing a genuinely hung monoruby, use timeout -k (KILL fallback). Follow-up: CRuby-style interruptible blocking I/O.

🤖 Generated with Claude Code

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Generated by Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 65.18519% with 47 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.49%. Comparing base (9406ad2) to head (7e768c0).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
monoruby/src/globals/error.rs	19.04%	17 Missing ⚠️
monoruby/src/builtins/kernel.rs	76.66%	14 Missing ⚠️
monoruby/src/executor.rs	7.69%	12 Missing ⚠️
monoruby/src/main.rs	33.33%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #910      +/-   ##
==========================================
- Coverage   90.50%   90.49%   -0.02%     
==========================================
  Files         189      189              
  Lines      123266   123474     +208     
==========================================
+ Hits       111562   111732     +170     
- Misses      11704    11742      +38     

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