Reproducer for a JBR bug where -XX:+AllowEnhancedClassRedefinition causes a JVM crash (SIGSEGV) when Mockito/ByteBuddy retransforms a class whose bytecode was previously modified by a ClassFileTransformer using javassist.

The crash occurs in VM_EnhancedRedefineClasses::find_class_bytes() → JvmtiClassFileReconstituter::write_method_infos().

This reproduces what happens when HotswapAgent's Vaadin plugin transforms VaadinServlet's constructor via javassist, and then Mockito creates a mock of VaadinServlet using ByteBuddy's inline mock maker.

• JetBrains Runtime (JBR) with -XX:+AllowEnhancedClassRedefinition support
• Maven 3.x

Build:

mvn package -DskipTests

Test 1 — baseline (no agent, should pass):

java -XX:+EnableDynamicAgentLoading \
  -cp "target/jbr-crash-reproducer-1.0-SNAPSHOT.jar:target/lib/*" \
  test.NestAccessTest

Test 2 — agent without the flag (should pass):

java -XX:+EnableDynamicAgentLoading \
  -javaagent:target/jbr-crash-reproducer-1.0-SNAPSHOT.jar \
  -cp "target/jbr-crash-reproducer-1.0-SNAPSHOT.jar:target/lib/*" \
  test.NestAccessTest

Test 3 — agent with the flag (crashes on affected JBR versions):

java -XX:+EnableDynamicAgentLoading \
  -XX:+AllowEnhancedClassRedefinition \
  -javaagent:target/jbr-crash-reproducer-1.0-SNAPSHOT.jar \
  -cp "target/jbr-crash-reproducer-1.0-SNAPSHOT.jar:target/lib/*" \
  test.NestAccessTest

1. A java agent (agent.NoOpAgent) uses javassist to transform BaseServlet's constructor, injecting a call to PluginClass.onServletInit(this)
2. PluginClass.onServletInit() references PluginClass.Command, a package-private inner class
3. Mockito.mock(BaseServlet.class) triggers ByteBuddy's inline mock maker, which calls Instrumentation.retransformClasses(BaseServlet.class)
4. With -XX:+AllowEnhancedClassRedefinition enabled, the JVM enters VM_EnhancedRedefineClasses::find_class_bytes() and crashes in JvmtiClassFileReconstituter::write_method_infos() with a SIGSEGV

V  [libjvm.so]  JvmtiClassFileReconstituter::write_method_infos()
V  [libjvm.so]  JvmtiClassFileReconstituter::write_class_file_format()
V  [libjvm.so]  VM_EnhancedRedefineClasses::find_class_bytes()
V  [libjvm.so]  VM_EnhancedRedefineClasses::load_new_class_versions()
V  [libjvm.so]  VM_EnhancedRedefineClasses::doit()
V  [libjvm.so]  VM_Operation::evaluate()
V  [libjvm.so]  VMThread::evaluate_operation()

• JBR-25.0.1+8-268.52-nomod (OpenJDK 25, aarch64)