Handle missing stack traces in ExtendedThreadInformation

Fix ArrayIndexOutOfBoundsException on invocation of Message.getFormattedMessage() when any thread has no stack trace, which occurs on some JVM implementations.

Author: PAX523

log4j-core-test/src/test/java/org/apache/logging/log4j/core/message/ExtendedThreadInformationTest.java

@@ -16,10 +16,17 @@
  */
 package org.apache.logging.log4j.core.message;
 
+import static org.hamcrest.CoreMatchers.containsString;
+import static org.hamcrest.MatcherAssert.assertThat;
 import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
 
+import java.lang.management.ThreadInfo;
 import org.apache.logging.log4j.message.ThreadDumpMessage;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.EnumSource;
 
 /**
  * Tests that ThreadDumpMessage uses ExtendedThreadInformation when available.
@@ -33,4 +40,42 @@ void testMessage() {
         // System.out.print(message);
         assertTrue(message.contains(" Id="), "No header");
     }
+
+    @ParameterizedTest
+    @EnumSource(Thread.State.class)
+    void testMessageWithNullStackTrace(final Thread.State state) {
+        obtainMessageWithMissingStackTrace(state, null);
+    }
+
+    @ParameterizedTest
+    @EnumSource(Thread.State.class)
+    void testMessageWithEmptyStackTrace(final Thread.State state) {
+        obtainMessageWithMissingStackTrace(state, new StackTraceElement[0]);
+    }
+
+    private void obtainMessageWithMissingStackTrace(final Thread.State state, final StackTraceElement[] stackTrace) {
+        // setup
+        final String threadName = "the thread name";
+        final long threadId = 23523L;
+
+        final ThreadInfo threadInfo = mock(ThreadInfo.class);
+        when(threadInfo.getStackTrace()).thenReturn(stackTrace);
+        when(threadInfo.getThreadName()).thenReturn(threadName);
+        when(threadInfo.getThreadId()).thenReturn(threadId);
+        when(threadInfo.isSuspended()).thenReturn(true);
+        when(threadInfo.isInNative()).thenReturn(true);
+        when(threadInfo.getThreadState()).thenReturn(state);
+
+        // given
+        final ExtendedThreadInformation sut = new ExtendedThreadInformation(threadInfo);
+
+        // when
+        final StringBuilder result = new StringBuilder();
+        sut.printThreadInfo(result);
+
+        // then
+        assertThat(result.toString(), containsString(threadName));
+        assertThat(result.toString(), containsString(state.name()));
+        assertThat(result.toString(), containsString(String.valueOf(threadId)));
+    }
 }

log4j-core/src/main/java/org/apache/logging/log4j/core/message/ExtendedThreadInformation.java

@@ -119,7 +119,7 @@ private void formatState(final StringBuilder sb, final ThreadInfo info) {
                 break;
             }
             case WAITING: {
-                final StackTraceElement element = info.getStackTrace()[0];
+                final StackTraceElement element = getStackTraceElement(info);
                 final String className = element.getClassName();
                 final String method = element.getMethodName();
                 if (className.equals("java.lang.Object") && method.equals("wait")) {
@@ -144,7 +144,7 @@ private void formatState(final StringBuilder sb, final ThreadInfo info) {
                 break;
             }
             case TIMED_WAITING: {
-                final StackTraceElement element = info.getStackTrace()[0];
+                final StackTraceElement element = getStackTraceElement(info);
                 final String className = element.getClassName();
                 final String method = element.getMethodName();
                 if (className.equals("java.lang.Object") && method.equals("wait")) {
@@ -174,4 +174,14 @@ private void formatState(final StringBuilder sb, final ThreadInfo info) {
                 break;
         }
     }
+
+    private static StackTraceElement getStackTraceElement(final ThreadInfo info) {
+        final StackTraceElement[] stackTrace = info.getStackTrace();
+        if (stackTrace == null || stackTrace.length < 1) {
+            final String textualInfo = "Unknown";
+            return new StackTraceElement(textualInfo, textualInfo, textualInfo, -1);
+        }
+
+        return stackTrace[0];
+    }
 }