[matt-edmondson]

Fixes #219

What was wrong

On Linux, an instance that has exited but whose parent hasn't reaped it yet (a launcher, wrapper or supervisor that doesn't wait()) keeps its /proc/<pid> entry in state Z. For that process:

• HasExited is false
• the name still reads back
• the memory map is empty, so there is no main module

Since #215, a null main module falls back to the name check. The zombie passes that check, so every later launch reported "already running" until the parent went away. The legacy plain-PID path had the same blind spot.

Change

• New HasExited(Process) returns process.HasExited || IsLinuxZombie(pid). It's used in IsStoredProcessRunning, IsStoredProcessRunningByName and IsLegacyProcessRunning.
• IsLinuxZombie reads /proc/<pid>/stat and treats state Z or X as exited. It does nothing on other platforms. When the state can't be read, it doesn't change the result.
• ParseLinuxProcessState takes the state field from after the last ), because the command name in field 2 can itself contain spaces and parentheses.
• The On Linux, a second instance launches when the running one belongs to another user: MainModule is null there, not a Win32Exception, so the name-only fallback never runs #214 cross-user fallback is unchanged. A live process in another user's session is in state S/R, so it still falls back to the name and start-time check. The existing IsStoredProcessRunning_WhenMainModuleIsUnreadable_* tests still pass.

Test helpers and the CI runner image

The first CI run failed in an existing test, IsStoredProcessRunning_WhenMainModuleIsUnreadable_ShouldFallBackToNameAndStartTime, with "process has exited".

ubuntu-latest now ships uutils coreutils, a multi-call binary that picks the utility from its executable name. HelperProcess copied /bin/sleep under a test name, so the copy printed coreutils: unknown program 'StartTimeHelper' and exited at once. Every helper-based test then raced an exited process.

• On Linux the helper is now a copy of /bin/sh that runs sleep 120 as a child. The copy keeps the requested name and main module. Windows and macOS are unchanged.
• Disposing a helper kills its whole process tree, so no sleep outlives a test.

Tests

• IsAlreadyRunning_WhenStoredProcessIsAnUnreapedZombie_ShouldReturnFalse and IsAlreadyRunning_WithLegacyPidFile_WhenProcessIsAnUnreapedZombie_ShouldReturnFalse create a real zombie. A shell backgrounds a copied sh -c 'exit 0' that exits at once, then execs into sleep, which never reaps it. Disposing kills that parent, so init reaps the zombie. Each test writes the zombie into a JSON or legacy PID file and asserts IsAlreadyRunning() is false. On other platforms they are inconclusive.
• ParseLinuxProcessState data-row tests cover a command name like a) b (c) and input that can't be parsed.
• With IsLinuxZombie taken out of HasExited, both zombie tests fail and the other 65 pass.
• Full suite on Linux / .NET 10: 67 passed, 1 skipped. The skip was already there: the read-only-folder test is inconclusive when run as root. CI passes on Ubuntu, macOS and Windows.
• This branch merges cleanly with the open PR Recognise a running instance after the wall clock is stepped on Linux [patch] #216, which edits the same process-identity checks.

🤖 Generated with Claude Code

https://claude.ai/code/session_017vfJW3W1DsZmnUsfmWXu2k

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
90.9% Coverage on New Code
0.0% Duplication on New Code

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