fix: don't kill grandchildren of forked processes

frankenphp.c

@@ -178,6 +178,10 @@ static void *frankenphp_parent_death_watcher(void *arg) {
 #endif
 
 static void frankenphp_fork_child(void) {
+  // a fork of a fork (e.g. a daemonizer) must outlive its short-lived parent
+  if (is_forked_child) {
+    return;
+  }
   frankenphp_mark_fork_child();
 #if defined(__linux__)
   // if the parent process dies between fork() and this prctl()

frankenphp_test.go

@@ -508,6 +508,24 @@ func testPhpInfoForkChild(t *testing.T, opts *testOptions) {
 	}, opts)
 }
 
+func TestDoubleForkGrandchild_module(t *testing.T) { testDoubleForkGrandchild(t, nil) }
+func TestDoubleForkGrandchild_worker(t *testing.T) {
+	testDoubleForkGrandchild(t, &testOptions{workerScript: "double-fork.php"})
+}
+func testDoubleForkGrandchild(t *testing.T, opts *testOptions) {
+	if opts == nil {
+		opts = &testOptions{}
+	}
+	opts.nbParallelRequests = 1
+	runTest(t, func(handler func(http.ResponseWriter, *http.Request), _ *httptest.Server, _ int) {
+		body, _ := testGet("http://example.com/double-fork.php", handler, t)
+		if body == "pcntl-unavailable" {
+			t.Skip("pcntl/posix not fully loaded")
+		}
+		require.Equal(t, "grandchild-alive", body)
+	}, opts)
+}
+
 func TestPersistentObject_module(t *testing.T) { testPersistentObject(t, nil) }
 func TestPersistentObject_worker(t *testing.T) {
 	testPersistentObject(t, &testOptions{workerScript: "persistent-object.php"})

testdata/double-fork.php

@@ -0,0 +1,43 @@
+<?php
+
+require_once __DIR__.'/_executor.php';
+
+return function () {
+    foreach (['pcntl_fork', 'pcntl_exec', 'pcntl_waitpid', 'posix_kill', 'posix_getpid'] as $function) {
+        if (!function_exists($function)) {
+            echo "pcntl-unavailable";
+            return;
+        }
+    }
+
+    $marker = tempnam(sys_get_temp_dir(), 'frankenphp-double-fork-');
+    unlink($marker);
+
+    $pid = pcntl_fork();
+    if ($pid === -1) {
+        echo "fork-failed";
+        return;
+    }
+    if ($pid === 0) {
+        if (pcntl_fork() === 0) {
+            pcntl_exec('/bin/sh', ['-c', 'sleep 0.2; touch "$1"', 'sh', $marker]);
+        }
+        // exit without PHP or Go teardown, like a daemonizer's intermediate process
+        posix_kill(posix_getpid(), SIGKILL);
+    }
+
+    pcntl_waitpid($pid, $status);
+
+    $deadline = microtime(true) + 3;
+    do {
+        clearstatcache();
+        if (file_exists($marker)) {
+            unlink($marker);
+            echo "grandchild-alive";
+            return;
+        }
+        usleep(10000);
+    } while (microtime(true) < $deadline);
+
+    echo "grandchild-killed";
+};