vm,repl: (add ability to) break on sigint/ctrl+c

[addaleax]

Checklist

• tests and code linting passes
• a test and/or benchmark is included
• documentation is changed or added
• the commit message follows commit guidelines

Affected core subsystem(s)

vm, repl

Description of change

vm:

• Adds the breakEvalOnSigint option to vm.runIn(This)Context. This uses a watchdog thread to wait for SIGINT and generally works just like the existing timeout option.
• Adds a method to the existing timer-based watchdog to check if it stopped regularly or by running into the timeout. This is used to tell a SIGINT abort from a timer-based one.
• Adds (internal) process._{start,stop}SigintWatchdog methods to start/stop the watchdog thread used by the above option manually. This will be used in the REPL to set up SIGINT handling before entering terminal raw mode, so that there is no time window in which Ctrl+C fully aborts the process.

readline:

• Return the previous raw mode setting from the internal _setRawMode so that is easier to reset it to its original state later.

repl: Use all that stuff to fix #6612. This probably does not work on Windows as-is.

Current CI: https://ci.nodejs.org/job/node-test-commit/3222/

[mscdex]

I think the string here should not reference something platform-specific (pthreads is a POSIX thing).

[addaleax]

Current CI is looking good for everything except Windows, but even there at least it compiles.

[bnoordhuis]

Not strictly necessary, value->BooleanValue() == false when value->IsUndefined() == true (and you can shorten return value->Booleanvalue() to return value->IsTrue().)

[addaleax]

Updated based on @bnoordhuis’ suggestions. Thanks!

[bnoordhuis]

Just curious, shouldn't this clear has_pending_signal_?

[bnoordhuis]

The tests are failing on Windows, but I suppose that isn't too surprising:

not ok 176 test-process-sigint-watchdog.js
  ---
  duration_ms: 0.132
  ...
not ok 190 test-repl-sigint-nested-eval.js
# TIMEOUT
# process.kill(+process.env.REPL_TEST_PPID, "SIGUSR2");vm.runInThisContext("while(true){}", { breakOnSigint: true });
# > Error: Unknown signal: SIGUSR2
#     at process.kill (internal/process.js:167:15)
#     at repl:1:9
#     at REPLServer.defaultEval (repl.js:295:29)
#     at bound (domain.js:280:14)
#     at REPLServer.runBound [as eval] (domain.js:293:12)
#     at REPLServer.<anonymous> (repl.js:481:10)
#     at emitOne (events.js:96:13)
#     at REPLServer.emit (events.js:188:7)
#     at REPLServer.Interface._onLine (readline.js:222:10)
#     at REPLServer.<anonymous> (readline.js:355:12)
# > 
  ---
  duration_ms: 60.173
  ...
not ok 255 test-vm-sigint.js
# 
# assert.js:90
#   throw new assert.AssertionError({
#   ^
# AssertionError: 'Unknown signal: SIGUSR2' === 'Script execution interrupted.'
#     at ChildProcess.<anonymous> (C:\workspace\node-test-binary-windows\RUN_SUBSET\1\VS_VERSION\vcbt2015\label\win10\test\parallel\test-vm-sigint.js:42:10)
#     at emitTwo (events.js:106:13)
#     at ChildProcess.emit (events.js:191:7)
#     at maybeClose (internal/child_process.js:850:16)
#     at Process.ChildProcess._handle.onexit (internal/child_process.js:215:5)
  ---
  duration_ms: 0.265
  ...
not ok 190 test-repl-sigint.js
# TIMEOUT
# a = 1001;process.kill(+process.env.REPL_TEST_PPID, "SIGUSR2");while(true){}
# > Error: Unknown signal: SIGUSR2
#     at process.kill (internal/process.js:167:15)
#     at repl:1:18
#     at REPLServer.defaultEval (repl.js:295:29)
#     at bound (domain.js:280:14)
#     at REPLServer.runBound [as eval] (domain.js:293:12)
#     at REPLServer.<anonymous> (repl.js:481:10)
#     at emitOne (events.js:96:13)
#     at REPLServer.emit (events.js:188:7)
#     at REPLServer.Interface._onLine (readline.js:222:10)
#     at REPLServer.<anonymous> (readline.js:355:12)
# > 
  ---
  duration_ms: 60.139
  ...
not ok 256 test-vm-timeout.js
# vm.js:18
#   return this.runInContext(context, options);
#               ^
# Error: Script execution interrupted.
#     at Error (native)
#     at ContextifyScript.Script.runInNewContext (vm.js:18:15)
#     at Object.exports.runInNewContext (vm.js:49:17)
#     at context.runInVM (C:\workspace\node-test-binary-windows\RUN_SUBSET\2\VS_VERSION\vcbt2015\label\win10\test\parallel\test-vm-timeout.js:29:10)
#     at evalmachine.<anonymous>:1:1
#     at ContextifyScript.Script.runInNewContext (vm.js:18:15)
#     at Object.exports.runInNewContext (vm.js:49:17)
#     at C:\workspace\node-test-binary-windows\RUN_SUBSET\2\VS_VERSION\vcbt2015\label\win10\test\parallel\test-vm-timeout.js:32:6
#     at _tryBlock (assert.js:318:5)
#     at _throws (assert.js:337:12)
  ---
  duration_ms: 0.416

The centos5-64 failure looks like a flake, or at least unrelated to this PR.

[addaleax]

Updated again.

@bnoordhuis Yeah, I don’t have access to a Windows machine for developing right now. If someone comes along in the next days to check that this works on Windows and/or writes tests for that platform (or I find the opportunity myself), great, but otherwise I’ll disable this feature on Windows for now.

And yep, the centos5-64 failure is a known flaky test.

[bnoordhuis]

LGTM (apart from the Windows issues) with an outstanding question on whether or not to clear has_pending_signal_.

[addaleax]

@bnoordhuis Oh, yeah, sorry, forgot to answer that one. In the last update, I included that, but a few lines below your comments so it doesn’t need to be duplicated.