Title 1 New debug/profile features in J2SE 6 Ivan Popov, May, 2006 Intel Corporation

Title 2 New features in J2SE 6 (JSR-270, core/debug) Access to heap contents (JDI, JDWP) rewritten JVMTI functions and callbacks for heap iteration new JDI and JDWP functions for finding objects in heap Attach-on-demand (JVMTI, java.lang.instrument) new entry points for dynamically loaded JVMTI and Java agents no spec for dynamic loading mechanism (implementation dependent) Multiple simultaneous agents (JVMTI, java.lang.instrument) defined algorithm of sequential classfile transformation introduced transformation capable/incapable agents new function RetransformClasses() in addition to RedefineClasses() support for instrumenting native calls by providing Java wrappers Several other changes in JVMTI, JDI, JDWP Getting monitor info for stack frames, access to constant pool, etc. JVMDI and JVMPI are removed

Title 3 Access to heap content JVMTI new set of heap iteration functions and callbacks similar functionality but new design old functions are still in JVMTI spec (marked version 1.0) JDI/JDWP Get all objects of a given class Get all objects which refer to a given object

Title 4 Attach-on-demand JVMTI: new entry point for dynamically loaded JVMTI agents Agent_OnAttach() vs. Agent_OnLoad() java.lang.instrument: new entry point for dynamically loaded Java agents agentmain() vs. premain() Problems: no spec for algorithm of dynamic agent loading – it is implementation specific no particular support for detach-on-demand

Title 5 Multiple simultaneous agents (bytecode instrumentation) JVMTI: described support for multiple classfile transformations introduced classfile retransformation algorithm for new transformation capable agents supports classfile redefinition algorithm for old transformation incapable agents clarified semantics of RedefineClasses(), RetransformClasses(), CLASS_FILE_LOAD_HOOK for agents of both kinds the whole algorithm is quite sophisticated java.lang.instrument: similar features for Java agents

Title 6 New features in J2SE 6 (JSR-270, core/debug) Access to heap contents (JDI, JDWP) rewritten JVMTI functions and callbacks for heap iteration new JDI and JDWP functions for finding objects in heap Attach-on-demand (JVMTI, java.lang.instrument) new entry points for dynamically loaded JVMTI and Java agents no spec for dynamic loading mechanism (implementation dependent) Multiple simultaneous agents (JVMTI, java.lang.instrument) defined algorithm of sequential classfile transformation introduced transformation capable/incapable agents new function RetransformClasses() in addition to RedefineClasses() support for instrumenting native calls by providing Java wrappers Several other changes in JVMTI, JDI, JDWP Getting monitor info for stack frames, access to constant pool, etc. JVMDI and JVMPI are removed

Title 7 Instrumenting native calls JVMTI: replacing native methods with Java wrappers adding prefixes for renaming original native methods managing prefixes for single and multiple agents clarified algorithm for binding native methods using prefixes the overall algorithm is quite sophisticated

Title 8 Other spec changes JVMTI, JDWP, JDI: Get locked monitors for frames new functions return association between frames and locked monitors support for monitor events on JDI/JDWP level Access to constant pool get classfile major/minor version get constant pool bytes Checking unmodifiable classes new function checks if class bytecode can be modified Force early method return new function to force method to return with given value new METHOD_EXIT_WITH_RETURN_VALUE event in JDI/JDWP

Title 9 Other spec changes (cont.) JVMTI: modification of class path for both bootstrap and system loaders: AddToSystemClassLoaderSearch vs. AddToBootstrapClassLoaderSearch JDI/JDWP: source file filter for CLASS_PREPARE events new JDI connector ProcessAttach uses PID for attaching to process eliminates knowing port number for attaching connection transport is determined dynamically and reported as local no details of the algorithm