forked from unom/punktfunk
enricobuehler
5a14d2b3f4
`Child::kill` is one `TerminateProcess`: it ends exactly the process we launched. On Unix
that is the whole story here — `kscreen-doctor`, `systemctl`, `pw-dump` are single processes
we exec directly. On Windows there is no direct exec, so every helper is reached through a
shell (`cmd /c …`, `powershell -Command "… | pnputil …"`) and the process that actually
hangs is a GRANDCHILD. Killing the shell left it running, holding the stdio handles and the
working directory it inherited from us, which means the budget bounded nothing.
Not theoretical: it is why a fully green `cargo test -p pf-vdisplay` still failed its CI job
on `33a31427`. The suite's own hung-helper case orphaned a 60-second `ping.exe`; it kept the
build step's stdout pipe open past the runner's 10 s WaitDelay ("exec: WaitDelay expired
before I/O complete") and pinned `crates\pf-vdisplay` so the workspace could not be cleaned
up. The tests reported `55 passed; 0 failed` in the same log.
Spawned children are now enrolled in a Job object. Job membership is inherited across
`CreateProcess`, so one `TerminateJobObject` ends every descendant, and
`JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE` makes that hold on paths that never reach the explicit
call — an early `?`, a panic — because closing the last handle is then itself the kill.
Best-effort: a box that cannot make a job object degrades to the single-process kill it did
before rather than failing the query, the same stance as the already-ignored `Child::kill`.
`output_within` ends the tree BEFORE `wait_with_output`. That read runs to EOF, and a
grandchild outliving the helper holds the write end — the one way this "bounded" helper
could still hang forever.
The new test is the permanent lever, and it is not vacuous: it asserts the grandchild
reached its first marker before asserting it never reached its second. Verified on .173
(Win11 26200): 56 pass, `clippy -p punktfunk-host -p pf-vdisplay --all-targets` clean, no
`ping.exe` survivors. A/B with the job disabled: the test fails with "a grandchild outlived
the budget" and one orphan survives. On the CI runner .133 the job APIs were also checked
directly, as Administrator (already inside a job — nesting works) and as SYSTEM: both kill
the tree.
Trap for anyone editing that test: a .cmd file is read in the OEM code page, so an absolute
path baked into it is mangled the moment the temp dir holds a non-ASCII character
(`C:\Users\Enrico Bühler\…` arrives as `B?hler`) and every redirect fails with "path not
found". It uses `%~dp0` instead, so the file stays pure ASCII.