Do not access JNI on Agent_OnLoad

Author: jbachorik

ddprof-lib/src/main/cpp/vmEntry.cpp

@@ -535,6 +535,9 @@ void JNICALL VM::VMInit(jvmtiEnv* jvmti, JNIEnv* jni, jthread thread) {
     ready(jvmti, jni);
     loadAllMethodIDs(jvmti, jni);
 
+    // initialize the heap usage tracking only after the VM is ready
+    ddprof::HeapUsage::initJMXUsage(VM::jni());
+
     // Delayed start of profiler if agent has been loaded at VM bootstrap
     Error error = Profiler::instance()->run(_agent_args);
     if (error) {

ddprof-lib/src/main/cpp/vmStructs_dd.cpp

@@ -44,7 +44,6 @@ namespace ddprof {
     initOffsets();
     initJvmFunctions();
     initUnsafeFunctions();
-    HeapUsage::initJMXUsage(VM::jni());
   }
 
   void VMStructs_::initOffsets() {