Process management improvements (#881)

This PR improves process lifecycle handling and resilience across several areas:

- **Reclaim stale shared-memory entries instead of exiting** (`zenserver.cpp`): When a zenserver instance fails to attach as a sponsor to an existing process (e.g. because the PID was reused by an unrelated process), the server now clears the stale shared-memory entry and proceeds with normal startup instead of calling `std::exit(1)`.

- **Wait for child process exit in `Kill()` and `Terminate()` on Unix** (`process.cpp`): After sending `SIGTERM` in `Kill()`, the code now waits up to 5s for graceful shutdown (escalating to `SIGKILL` on timeout), matching the Windows behavior. `Terminate()` also waits after `SIGKILL` so the child is properly reaped and doesn't linger as a zombie clogging up the process table.

- **Fix sysctl buffer race in macOS `FindProcess`** (`process.cpp`): The macOS process enumeration now retries the `sysctl` call (up to 3 attempts with 25% buffer padding) to handle the race where the process list changes between the sizing call and the data-fetching call. Also flattens the nesting and fixes the guard/free scoping.

- **Terminate stale processes before integration tests** (`zenserver-test.cpp`, `test.lua`): The integration test runner now accepts a `--kill-stale-processes` flag (passed automatically by `test.lua`) that scans for and terminates any leftover `zenserver`, `zenserver-test`, and `zentest-appstub` processes from previous test runs, logging the executable name and PID of each. This addresses flaky test failures caused by stale processes from prior runs holding ports or other resources.

1 files changed, 24 insertions, 11 deletions

diff --git a/src/zenutil/zenserverprocess.cpp b/src/zenutil/zenserverprocess.cpp
index a2ab4c291..3993d6a32 100644
--- a/src/zenutil/zenserverprocess.cpp
+++ b/src/zenutil/zenserverprocess.cpp
@@ -1375,18 +1375,31 @@ ZenServerInstance::OnServerReady()
 
 	const ZenServerState::ZenServerEntry* Entry = nullptr;
 
-	if (m_BasePort)
+	// The child process signals its ready event after writing its state entry, but under
+	// heavy instrumentation (e.g. sanitizers) the shared memory writes may not be immediately
+	// visible to this process. Retry briefly before giving up.
+	for (int Attempt = 0; Attempt < 10; ++Attempt)
 	{
-		Entry = State.Lookup(m_BasePort);
-	}
-	else
-	{
-		State.Snapshot([&](const ZenServerState::ZenServerEntry& InEntry) {
-			if (InEntry.Pid == (uint32_t)m_Process.Pid())
-			{
-				Entry = &InEntry;
-			}
-		});
+		if (m_BasePort)
+		{
+			Entry = State.Lookup(m_BasePort);
+		}
+		else
+		{
+			State.Snapshot([&](const ZenServerState::ZenServerEntry& InEntry) {
+				if (InEntry.Pid == (uint32_t)m_Process.Pid())
+				{
+					Entry = &InEntry;
+				}
+			});
+		}
+
+		if (Entry)
+		{
+			break;
+		}
+
+		Sleep(100);
 	}
 
 	if (!Entry)