src: don't kill own process group on failed spawn

[lazerg]

libuv only assigns a pid to the process handle once uv_spawn() succeeds, so a child that never started keeps pid 0. Calling kill() on that child still reached uv_process_kill(), which ended up in kill(0, signal) and signalled every process in the caller's own process group, Node included. The handle is now reported as ESRCH when there is no pid, so child.kill() just returns false. The pid is also zeroed in the constructor so the check never reads an unassigned value.

Reproducing it on its own needs no prototype tampering:

const { spawn } = require('child_process');
const child = spawn('foo123');
child.on('error', () => {});
child.kill();  // terminates the whole process group

In the report the spawn failed for a different reason: overriding Array.prototype[Symbol.iterator] makes normalizeSpawnArguments() build an empty env, so the command was no longer found through PATH. The dead handle is what took the parent down.

Behavior change

kill() on a child that failed to spawn used to return true on POSIX. It now returns false.

Windows was never affected by the process-group problem, since uv_process_kill() bails out with EINVAL when the handle has no process handle. It reached the throw new ErrnoException(err, 'kill') branch instead, so there kill() goes from throwing EINVAL to returning false. Both platforms now agree.

subprocess.killed is also left alone in this case, which matches what the docs already say about it being set only when a signal is sent successfully.

Fixes: #65052

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/76096/

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.99%. Comparing base (728ae35) to head (2eeec11).
⚠️ Report is 143 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #65054      +/-   ##
==========================================
- Coverage   90.01%   89.99%   -0.02%     
==========================================
  Files         757      757              
  Lines      257739   257740       +1     
  Branches    48882    48890       +8     
==========================================
- Hits       232001   231956      -45     
- Misses      16844    16865      +21     
- Partials     8894     8919      +25     

Files with missing lines	Coverage Δ
src/process_wrap.cc	75.11% <100.00%> (+0.11%)	⬆️

... and 40 files with indirect coverage changes

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[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/76155/

[lazerg]

Thanks, rebased. The branch now sits on top of 728ae35678, which includes 02f4630, so doc/node.1 is back in sync. make tools/.manpagelintstamp passes locally.

New head: 2eeec115f5. There were no conflicts, and the fix itself is unchanged: src/process_wrap.cc plus the test and its fixture.

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/77181/

[nodejs-github-bot]

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- Loading data for nodejs/node/pull/65054
✔  Done loading data for nodejs/node/pull/65054
----------------------------------- PR info ------------------------------------
Title      src: don't kill own process group on failed spawn (#65054)
Author     Lazizbek Ergashev <lazerg2@gmail.com> (@lazerg)
Branch     lazerg:fix/issue-65052-kill-unspawned-process -> nodejs:main
Labels     child_process, c++, needs-ci, commit-queue
Commits    3
 - src: don't kill own process group on failed spawn
 - test: drop redundant Refs comment from kill-spawn-error test
 - test: move inline kill-spawn-error script to a fixture
Committers 1
 - Lazizbek Ergashev <lazerg2@gmail.com>
PR-URL: https://github.com/nodejs/node/pull/65054
Fixes: https://github.com/nodejs/node/issues/65052
Reviewed-By: Aviv Keller <me@aviv.sh>
Reviewed-By: Robert Nagy <ronagy@icloud.com>
------------------------------ Generated metadata ------------------------------
PR-URL: https://github.com/nodejs/node/pull/65054
Fixes: https://github.com/nodejs/node/issues/65052
Reviewed-By: Aviv Keller <me@aviv.sh>
Reviewed-By: Robert Nagy <ronagy@icloud.com>
--------------------------------------------------------------------------------
   ℹ  This PR was created on Wed, 05 Aug 2026 16:34:50 GMT
   ✔  Approvals: 2
   ✔  - Aviv Keller (@avivkeller): https://github.com/nodejs/node/pull/65054#pullrequestreview-4867699604
   ✔  - Robert Nagy (@ronag) (TSC): https://github.com/nodejs/node/pull/65054#pullrequestreview-5138143552
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   ℹ  Last Full PR CI on 2026-09-08T06:36:20Z: https://ci.nodejs.org/job/node-test-pull-request/77181/
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