8381567: ProcessHandle.descendants fails with ArrayIndexOutOfBoundException for process 0

src/java.base/share/classes/java/lang/ProcessHandleImpl.java

@@ -458,7 +458,10 @@ public Stream<ProcessHandle> descendants() {
                     next++;
                 }
             }
-            ppid = pids[++count];   // pick up the next pid to scan for
+            if (++count >= size) {
+                break;
+            }
+            ppid = pids[count];   // pick up the next pid to scan for
             ppStart = starttimes[count];    // and its start time
         } while (count < next);
 

test/jdk/java/lang/ProcessHandle/PidZero.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2026, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+import org.junit.jupiter.api.Test;
+
+/*
+ * @test
+ * @summary ProcessHandle.descendants fails with AIOOE for process 0
+ * @requires os.family == "mac"
+ * @library /test/lib
+ * @run junit PidZero
+ */
+public class PidZero {
+    /**
+     * Test of ProcessHandle.descendants for pid 0
+     * Only Macos allows a ProcessHandle to be instantiated for pid 0
+     * which includes all processes on the system, but the implementation
+     * throws ArrayIndexOutOfBoundException without this fix.
+     */
+    @Test
+    public void test() {
+         int num = ProcessHandle.of(0).orElseThrow().descendants().toList().size();
+    }
+}