Java^TM Virtual Machine Debug Interface Reference

Object Information

Object Hash Code

jvmdiError
GetObjectHashCode(jobject object, jint *hashCodePtr) 

Parameters:

object

the object to query

hashCodePtr

on return, points to the object's hash code

This function returns either a universal error or one of the following errors:

JVMDI_ERROR_NULL_POINTER

Invalid pointer.

JVMDI_ERROR_INVALID_OBJECT

Invalid object.

Get Monitor Info

typedef struct {
    jthread owner;
    jint entry_count;
    jint waiter_count;
    jthread *waiters;
} JVMDI_monitor_info;

jvmdiError
GetMonitorInfo(jobject object, JVMDI_monitor_info *infoPtr)

Get information about the the object's monitor The fields of the JVMDI_owned_monitor_info structure are filled in with details of the monitor. Each thread that might affect the monitor state must either be suspended or must be the current thread.

This is an optional feature which may not be implemented for all virtual machines. Use GetCapabilities to determine whether this and other features are supported in a particular virtual machine.

Parameters:

object

the object to query

infoPtr

on return, filled with monitor information for the specified object. Returned objects (owner, array of waiters) are global references and must be explicitly freed with the JNI function DeleteGlobalRef. The returned waiter array buffer should be freed with Deallocate

This function returns either a universal error or one of the following errors:

JVMDI_ERROR_INVALID_OBJECT

thread was invalid.

JVMDI_ERROR_NULL_POINTER

Invalid pointer.

JVMDI_ERROR_THREAD_NOT_SUSPENDED

thread must be suspended before calling.

JVMDI_ERROR_NOT_IMPLEMENTED

Optional feature not present in this VM.

Field Information

Field Name and Signature

jvmdiError
GetFieldName(jclass clazz, jfieldID field, 
                   char **namePtr, char **signaturePtr)

Parameters:

clazz

the class to query

field

the field to query

namePtr

on return, refers to a pointer to the UTF-8 field name. The string should be freed with Deallocate

signaturePtr

on return, refers to a pointer to the UTF-8 field signature. The string should be freed with Deallocate

This function returns either a universal error or one of the following errors:

JVMDI_ERROR_NULL_POINTER

Invalid pointer.

JVMDI_ERROR_INVALID_FIELDID

Invalid field.

JVMDI_ERROR_INVALID_CLASS

Invalid clazz.

Field Declaring Class

jvmdiError
GetFieldDeclaringClass(jclass clazz, jfieldID field, jclass *declaringClassPtr)

Parameters:

clazz

the class to query

field

the field to query

declaringClassPtr

on return, points to the declaring class The returned class is a JNI global reference and must be explicitly freed with freed with the JNI function DeleteGlobalRef.

This function returns either a universal error or one of the following errors:

JVMDI_ERROR_NULL_POINTER

Invalid pointer.

JVMDI_ERROR_INVALID_FIELDID

Invalid field.

JVMDI_ERROR_INVALID_CLASS

Invalid clazz.

Field Modifier Flags

jvmdiError
GetFieldModifiers(jclass clazz, jfieldID field, jint *modifiersPtr)

Parameters:

clazz

the class to query

field

the field to query

modifiersPtr

on return, points to the access flags.

This function returns either a universal error or one of the following errors:

JVMDI_ERROR_NULL_POINTER

Invalid pointer.

JVMDI_ERROR_INVALID_FIELDID

Invalid method.

JVMDI_ERROR_INVALID_CLASS

Invalid clazz.

Is Field Synthetic

jvmdiError
IsFieldSynthetic(jclass clazz, jfieldID field, jboolean *isSyntheticPtr)

For the field indicated by clazz and field, return a value indicating whether the field is synthetic via isSyntheticPtr Synthetic fields are generated by the compiler but not present in the original source code.

This is an optional feature which may not be implemented for all virtual machines. Use GetCapabilities to determine whether this and other features are supported in a particular virtual machine.

Parameters:

clazz

the class to query

field

the field to query

isSyntheticPtr

on return, points to the boolean result of this function.

This function returns either a universal error or one of the following errors:

JVMDI_ERROR_NULL_POINTER

Invalid pointer.

JVMDI_ERROR_INVALID_FIELDID

Invalid field.

JVMDI_ERROR_INVALID_CLASS

Invalid clazz.

JVMDI_ERROR_NOT_IMPLEMENTED

Optional feature not present in this VM.

Method Information

Method Name and Signature

jvmdiError
GetMethodName(jclass clazz, jmethodID method, 
                    char **namePtr, char **signaturePtr)

For the method indicated by clazz and method, return the method name via namePtr and method signature via signaturePtr. The signature is a JNI signature also called a method descriptor in the Java Virtual Machine Specification; note this is different then method signature as defined in the Java Language Specification.

Parameters:

clazz

the class to query

method

the method to query

namePtr

on return, refers to a pointer to the UTF-8 method name. The string should be freed with Deallocate

signaturePtr

on return, refers to a pointer to the UTF-8 method signature. The string should be freed with Deallocate

This function returns either a universal error or one of the following errors:

JVMDI_ERROR_NULL_POINTER

Invalid pointer.

JVMDI_ERROR_INVALID_METHODID

Invalid method.

JVMDI_ERROR_INVALID_CLASS

Invalid clazz.

Method Declaring Class

jvmdiError
GetMethodDeclaringClass(jclass clazz, jmethodID method,
                                 jclass *declaringClassPtr)

Parameters:

clazz

the class to query

method

the method to query

declaringClassPtr

on return, points to the declaring class The returned class is a JNI global reference and must be explicitly freed with freed with the JNI function DeleteGlobalRef.

This function returns either a universal error or one of the following errors:

JVMDI_ERROR_NULL_POINTER

Invalid pointer.

JVMDI_ERROR_INVALID_METHODID

Invalid method.

JVMDI_ERROR_INVALID_CLASS

Invalid clazz.

Method Modifier Flags

jvmdiError
GetMethodModifiers(jclass clazz, jmethodID method,
                         jint *modifiersPtr)

Parameters:

clazz

the class to query

method

the method to query

modifiersPtr

on return, points to the access flags.

This function returns either a universal error or one of the following errors:

JVMDI_ERROR_NULL_POINTER

Invalid pointer.

JVMDI_ERROR_INVALID_METHODID

Invalid method.

JVMDI_ERROR_INVALID_CLASS

Invalid clazz.

Maximum Stack

jvmdiError
GetMaxStack(jclass clazz, jmethodID method, jint *maxPtr)

Parameters:

clazz

the class to query

method

the method to query

maxPtr

on return, points to the maximum number of stack words

This function returns either a universal error or one of the following errors:

JVMDI_ERROR_NULL_POINTER

Invalid pointer.

JVMDI_ERROR_INVALID_METHODID

Invalid method.

JVMDI_ERROR_INVALID_CLASS

Invalid clazz.

Locals Slots

jvmdiError
GetMaxLocals(jclass clazz, jmethodID method,
                  jint *maxPtr);

Parameters:

clazz

the class to query

method

the method to query

maxPtr

on return, points to the maximum number of local slots

This function returns either a universal error or one of the following errors:

JVMDI_ERROR_NULL_POINTER

Invalid pointer.

JVMDI_ERROR_INVALID_METHODID

Invalid method.

JVMDI_ERROR_INVALID_CLASS

Invalid clazz.

Argument Slots

jvmdiError
GetArgumentsSize(jclass clazz, jmethodID method, jint *sizePtr)

Parameters:

clazz

the class to query

method

the method to query

sizePtr

on return, points to the number of argument slots

This function returns either a universal error or one of the following errors:

JVMDI_ERROR_NULL_POINTER

Invalid pointer.

JVMDI_ERROR_INVALID_METHODID

Invalid method.

JVMDI_ERROR_INVALID_CLASS

Invalid clazz.

Source Line Numbers

jvmdiError
GetLineNumberTable(jclass clazz, jmethodID method,
 			 jint *entryCountPtr, 
             JVMDI_line_number_entry **tablePtr)

typedef struct {
    jlocation start_location;
    jint line_number;
} JVMDI_line_number_entry;

Parameters:

clazz

the class to query

method

the method to query

entryCountPtr

on return, points to the number of entries in the table

tablePtr

on return, points to the line number table pointer. The JVMDI allocator provides space for the table. You must deallocate the table using Deallocate().

This function returns either a universal error or one of the following errors:

JVMDI_ERROR_NONE

No error.

JVMDI_ERROR_NULL_POINTER

Invalid pointer.

JVMDI_ERROR_INVALID_METHODID

Invalid method.

JVMDI_ERROR_INVALID_CLASS

Invalid clazz.

JVMDI_ERROR_ABSENT_INFORMATION

Class information does not include line numbers.

Method Location

jvmdiError
GetMethodLocation(jclass clazz, jmethodID method,
                        jlocation *startLocationPtr, 
                        jlocation *endLocationPtr)

Parameters:

clazz

the class to query

method

the method to query

startLocationPtr

on return, points to the first location, or -1 if location information is not available.

endLocationPtr

on return, points to the last location, or -1 if location information is not available.

This function returns either a universal error or one of the following errors:

JVMDI_ERROR_NULL_POINTER

Invalid pointer.

JVMDI_ERROR_INVALID_METHODID

Invalid method.

JVMDI_ERROR_INVALID_CLASS

Invalid clazz.

JVMDI_ERROR_ABSENT_INFORMATION

Class information does not include method sizes.

Local Variables

jvmdiError
GetLocalVariableTable(jclass clazz, jmethodID method,
                            jint *entryCountPtr, 
                            JVMDI_local_variable_entry **tablePtr)

typedef struct {
    jlocation start_location;   /* variable valid start_location */
    jint length;                /* up to start_location+length */ 
    char *name;                 /* name in UTF-8 */
    char *signature;            /* type signature in UTF-8 */
    jint slot;                  /* variable slot, see JVMDI_GetLocal*()  */
} JVMDI_local_variable_entry;

Parameters:

clazz

the class to query

method

the method to query

entryCountPtr

on return, points to the number of entries in the table

tablePtr

on return, points to the local variable table pointer. The JVMDI allocator provides space for the table. In addition, each name and signature string in the table is allocated with the JVMDI allocator. You must deallocate these buffers using Deallocate.

This function returns either a universal error or one of the following errors:

JVMDI_ERROR_NULL_POINTER

Invalid pointer.

JVMDI_ERROR_INVALID_METHODID

Invalid method.

JVMDI_ERROR_INVALID_CLASS

Invalid clazz.

JVMDI_ERROR_ABSENT_INFORMATION

Class information does not include local variable information.

Exception Handlers

jvmdiError
GetExceptionHandlerTable(jclass clazz, jmethodID method,
                               jint *entryCountPtr, 
                               JVMDI_exception_handler_entry **tablePtr)

typedef struct {
    jlocation start_location;
    jlocation end_location;
    jlocation handler_location;
    jclass exception;           /* if null, all exceptions */
} JVMDI_exception_handler_entry;

A call to this function may trigger class loading for the thrown exception classes that have not yet been loaded. It should not be called while threads are suspended.

Parameters:

clazz

the class to query

method

the method to query

entryCountPtr

on return, points to the number of entries in the table

tablePtr

on return, points to the exception handler table pointer. The JVMDI allocator provides space for the table. You must deallocate the table using Deallocate(). The classes returned in the "exception" field of JVMDI_exception_handler_entry are global references and must be explicitly freed with the JNI function Deallocate

This function returns either a universal error or one of the following errors:

JVMDI_ERROR_NULL_POINTER

Invalid pointer.

JVMDI_ERROR_INVALID_METHODID

Invalid method.

JVMDI_ERROR_INVALID_CLASS

Invalid clazz.

Thrown Exceptions

jvmdiError
GetThrownExceptions(jclass clazz, jmethodID method,
                          jint *exceptionCountPtr, jclass **exceptionsPtr)

A call to this function may trigger class loading for the thrown exception classes that have not yet been loaded. It should not be called while threads are suspended.

Parameters:

clazz

the class to query

method

the method to query

exceptionCountPtr

on return, points to the number of running threads.

exceptionsPtr

on return, points to an array of references, one for each thrown exception. Exception classes in the array are JNI global references and must be explicitly freed with the JNI function DeleteGlobalRef. The returned exception array should be freed with Deallocate.

This function returns either a universal error or one of the following errors:

JVMDI_ERROR_NULL_POINTER

Invalid pointer.

JVMDI_ERROR_INVALID_METHODID

Invalid method.

JVMDI_ERROR_INVALID_CLASS

Invalid class.

Get Bytecodes

jvmdiError
GetBytecodes(jclass clazz, jmethodID method, jint *bytecodeCountPtr,
                         jbyte **bytecodesPtr)

This is an optional feature which may not be implemented for all virtual machines. Use GetCapabilities to determine whether this and other features are supported in a particular virtual machine.

Parameters:

clazz

the class to query

method

the method to query

bytecodeCountPtr

on return, points to the length of the byte code array

bytecodesPtr

on return, points to the pointer to the byte code array The JVMDI memory allocator provides memory for the byte code array. You must deallocate the table using Deallocate().

This function returns either a universal error or one of the following errors:

JVMDI_ERROR_NULL_POINTER

Invalid pointer.

JVMDI_ERROR_INVALID_CLASS

Invalid clazz.

JVMDI_ERROR_INVALID_METHODID

Invalid method.

JVMDI_ERROR_NOT_IMPLEMENTED

Optional feature not present in this VM.

Is Method Native

jvmdiError
IsMethodNative(jclass clazz, jmethodID method, jboolean *isNativePtr)

For the method indicated by clazz and method, return a value indicating whether the method is native via isNativePtr

Parameters:

clazz

the class to query

method

the method to query

isNativePtr

on return, points to the boolean result of this function.

This function returns either a universal error or one of the following errors:

JVMDI_ERROR_NULL_POINTER

Invalid pointer.

JVMDI_ERROR_INVALID_METHODID

Invalid method.

JVMDI_ERROR_INVALID_CLASS

Invalid clazz.

Is Method Synthetic

jvmdiError
IsMethodSynthetic(jclass clazz, jmethodID method, jboolean *isSyntheticPtr)

For the method indicated by clazz and method, return a value indicating whether the method is synthetic via isSyntheticPtr. Synthetic methods are generated by the compiler but not present in the original source code.

This is an optional feature which may not be implemented for all virtual machines. Use GetCapabilities to determine whether this and other features are supported in a particular virtual machine.

Parameters:

clazz

the class to query

method

the method to query

isSyntheticPtr

on return, points to the boolean result of this function.

This function returns either a universal error or one of the following errors:

JVMDI_ERROR_NULL_POINTER

Invalid pointer.

JVMDI_ERROR_INVALID_METHODID

Invalid method.

JVMDI_ERROR_INVALID_CLASS

Invalid clazz.

JVMDI_ERROR_NOT_IMPLEMENTED

Optional feature not present in this VM.

Raw Monitor Support

Create Raw Monitor

jvmdiError
CreateRawMonitor(char *name, JVMDI_RawMonitor *monitorPtr)

Parameters:

name

a name in UTF-8 to identify the monitor

monitorPtr

on return, points to the created monitor.

This function returns either a universal error or one of the following errors:

JVMDI_ERROR_NULL_POINTER

Invalid pointer.

Destroy Raw Monitor

jvmdiError
DestroyRawMonitor(JVMDI_RawMonitor monitor)

Parameters:

monitor

the monitor

This function returns either a universal error or one of the following errors:

JVMDI_ERROR_INVALID_MONITOR

Invalid monitor.

Raw Monitor Enter

jvmdiError
RawMonitorEnter(JVMDI_RawMonitor monitor)

Parameters:

monitor

the monitor

This function returns either a universal error or one of the following errors:

JVMDI_ERROR_INVALID_MONITOR

Invalid monitor.

Raw Monitor Exit

jvmdiError
RawMonitorExit(JVMDI_RawMonitor monitor)

Parameters:

monitor

the monitor

This function returns either a universal error or one of the following errors:

JVMDI_ERROR_INVALID_MONITOR

Invalid monitor.

JVMDI_ERROR_NOT_MONITOR_OWNER

Raw Monitor Wait

jvmdiError
RawMonitorWait(JVMDI_RawMonitor monitor, jlong millis)

Parameters:

monitor

the monitor

millis

the timeout, in milliseconds

This function returns either a universal error or one of the following errors:

JVMDI_ERROR_INVALID_MONITOR

Invalid monitor.

JVMDI_ERROR_NOT_MONITOR_OWNER

JVMDI_ERROR_INTERRUPT

Raw Monitor Notify

jvmdiError
RawMonitorNotify(JVMDI_RawMonitor monitor)

Parameters:

monitor

the monitor

This function returns either a universal error or one of the following errors:

JVMDI_ERROR_INVALID_MONITOR

Invalid monitor.

JVMDI_ERROR_NOT_MONITOR_OWNER

Raw Monitor Notify All

jvmdiError
RawMonitorNotifyAll(JVMDI_RawMonitor monitor)

Parameters:

monitor

the monitor

This function returns either a universal error or one of the following errors:

JVMDI_ERROR_INVALID_MONITOR

Invalid monitor.

JVMDI_ERROR_NOT_MONITOR_OWNER

Set Event Hook

typedef void (*JVMDI_EventHook)(JNIEnv *env , JVMDI_Event *event);

jvmdiError
SetEventHook(JVMDI_EventHook hook)

Parameters:

hook

the new event hook, or NULL to remove the existing hook.

This function returns a universal error on error.

Enable/Disable Events

jvmdiError
SetEventNotificationMode(jint mode, jint eventType, jthread thread, ...)

Global and per-thread enabling of events is independent. For example, if MethodEntry is initially disabled both globally and on each thread, MethodEntry is still disabled per-thread when it is enabled globally. When an executing thread encounters a potential event condition, an event will be sent if either that event is globally enabled OR that event is enabled for the executing thread. Thus globally enabling an event applies to threads created after the call as well.

See below for information on specific events.

The following events cannot be controlled (enabled or disabled) at the thread level through this function.

• JVMDI_EVENT_VM_INIT
• JVMDI_EVENT_VM_DEATH
• JVMDI_EVENT_THREAD_START
• JVMDI_EVENT_CLASS_UNLOAD

The following event cannot be controlled (enabled or disabled) at the global level through this function.

• JVMDI_EVENT_SINGLE_STEP

Initially, no events are enabled at the thread level. All events except the following are enabled at the global level.

• JVMDI_EVENT_SINGLE_STEP
• JVMDI_EVENT_EXCEPTION_CATCH
• JVMDI_EVENT_METHOD_ENTRY
• JVMDI_EVENT_METHOD_EXIT

Parameters:

mode

JVMDI_ENABLE or JVMDI_DISABLE

eventType

the event to control

thread

the thread to control, or NULL for all threads

This function returns either a universal error or one of the following errors:

JVMDI_ERROR_INVALID_THREAD

If thread is invalid or the thread has not run.

JVMDI_ERROR_INVALID_EVENT_TYPE

If eventType is invalid value.

JVMDI_ERROR_ILLEGAL_ARGUMENT

If thread argument is specified with one of the following events:

• JVMDI_EVENT_VM_INIT
• JVMDI_EVENT_VM_DEATH
• JVMDI_EVENT_THREAD_START
• JVMDI_EVENT_CLASS_UNLOAD

Miscellaneous Functions

Get Loaded Classes

jvmdiError
GetLoadedClasses(jint *classCountPtr, jclass **classesPtr)

Return an array of all classes loaded in the virtual machine. The number of classes in the array is returned via classCountPtr, and the array itself via classesPtr. You must deallocate the array using Deallocate().

Array classes of all types (including arrays of primitive types) are included in the returned list. Primitive classes (for example, java.lang.Integer.TYPE) are not included in this list.

Parameters:

classCountPtr

on return, points to the number of classes.

classesPtr

on return, points to an array of references, one for each class. Classes in the array are JNI global references and must be explicitly freed with the JNI function DeleteGlobalRef. The returned class array should be freed with Deallocate.

This function returns either a universal error or one of the following errors:

JVMDI_ERROR_NULL_POINTER

Invalid pointer.

Get Classloader Classes

jvmdiError
GetClassLoaderClasses(jobject initiatingLoader, jint *classCountPtr, jclass **classesPtr)

Returns an array of all classes for which this class loader has been recorded as the initiating loader. Each class in the returned array was created by this class loader, either by defining it directly or by delegation to another class loader.

For JDK 1.1 implementations which don't recognize the distinction between initiating and defining classloaders, this function should return all classes loaded in the virtual machine. The number of classes in the array is returned via classCountPtr, and the array itself via classesPtr. You must deallocate the array using Deallocate().

The initiatingLoader argument must not be null. The set of classes initiated by the system class loader is identical to the set of classes defined by that loader. This set can be determined by calling GetLoadedClasses and selecting those classes with a null class loader.

Parameters:

initiatingLoader

the initiating class loader.

classCountPtr

on return, points to the number of classes.

classesPtr

on return, points to an array of references, one for each class. Classes in the array are JNI global references and must be explicitly freed with the JNI function DeleteGlobalRef. The returned class array should be freed with Deallocate.

This function returns either a universal error or one of the following errors:

JVMDI_ERROR_NULL_POINTER

Invalid pointer.

Redefine Classes

typedef struct {
    jclass clazz;              /* Class to be redefined */
    jint class_byte_count;     /* number of bytes defining class (below) */
    jbyte *class_bytes;        /* bytes defining class */
                               /* (in Class File Format of JVM spec) */
} JVMDI_class_definition;

jvmdiError
RedefineClasses(jint classCount, JVMDI_class_definition *classDefs)

All classes given are redefined according to the definitions supplied. If any redefined methods have active stack frames, those active frames continue to run the bytecodes of the original method. The redefined methods will be used on new invokes. Any JVMDI function or event which returns a jmethodID, will return OBSOLETE_METHOD_ID when referring to the original method (for example, when examining a stack frame where the original method is still executing) unless it is equivalent to the redefined method (see below). The original method ID refers to the redefined method. Care should be taken thoughout a JVMDI client to handle OBSOLETE_METHOD_ID. If reseting of stack frames is desired, use PopFrame to pop frames with OBSOLETE_METHOD_IDs.

An original and a redefined method should be considered equivalent if:

• their bytecodes are the same except for indicies into the constant pool and
• the referenced constants are equal.

This function does not cause any initialization except that which would occur under the customary JVM semantics. In other words, redefining a class does not cause its initializers to be run. The values of preexisting static variables will remain as they were prior to the call. However, completely uninitialized (new) static variables will be assigned their default value.

If a redefined class has instances then all those instances will have the fields defined by the redefined class at the completion of the call. Preexisting fields will retain their previous values. Any new fields will have their default values; no instance initializers or constructors are run.

Threads need not be suspended.

All breakpoints in the class are cleared.

All attributes are updated.

No JVMDI events are generated by this function.

This is an optional feature which may not be implemented for all virtual machines. Examine can_redefine_classes, can_add_method and can_unrestrictedly_redefine_classes of GetCapabilities to determine whether this feature is supported in a particular virtual machine.

Parameters:

classCount

the number of classes specified in classDefs

classDefs

the array of new class definitions

JVMDI_ERROR_NULL_POINTER

Invalid pointer: classDefs or one of class_bytes is NULL.

JVMDI_ERROR_INVALID_CLASS

An element of classDefs is not a valid class.

JVMDI_ERROR_UNSUPPORTED_VERSION

A new class file has a version number not supported by this VM.

JVMDI_ERROR_INVALID_CLASS_FORMAT

A new class file is malformed (The VM would return a ClassFormatError).

JVMDI_ERROR_CIRCULAR_CLASS_DEFINITION

The new class file definitions would lead to a circular definition (the VM would return a ClassCircularityError).

JVMDI_ERROR_FAILS_VERIFICATION

The class bytes fail verification.

JVMDI_ERROR_NAMES_DONT_MATCH

The class name defined in the new class file is different from the name in the old class object.

JVMDI_ERROR_NOT_IMPLEMENTED

No aspect of this functionality is implemented (can_redefine_classes capability is false).

JVMDI_ERROR_ADD_METHOD_NOT_IMPLEMENTED

A new class file would require adding a method, (and can_add_method capability is false).

JVMDI_ERROR_SCHEMA_CHANGE_NOT_IMPLEMENTED

The new class version changes fields (and can_unrestrictedly_redefine_classes is false).

JVMDI_ERROR_HIERARCHY_CHANGE_NOT_IMPLEMENTED

A direct superclass is different for the new class version, or the set of directly implemented interfaces is different (and can_unrestrictedly_redefine_classes is false).

JVMDI_ERROR_DELETE_METHOD_NOT_IMPLEMENTED

The new class version does not declare a method declared in the old class version. (and can_unrestrictedly_redefine_classes is false).

JVMDI_ERROR_CLASS_MODIFIERS_CHANGE_NOT_IMPLEMENTED

The new version of a class has different class modifiers (public, abstract, final, ...) then the old version (and can_unrestrictedly_redefine_classes is false).

JVMDI_ERROR_METHOD_MODIFIERS_CHANGE_NOT_IMPLEMENTED

The new version of a class has a different method modifier (public, abstract, synchronized, ...) then the old version (and can_unrestrictedly_redefine_classes is false).

Get Version Number

jvmdiError
GetVersionNumber(jint *versionPtr)

Parameters:

versionPtr

on return, points to the JVMDI version.

This function returns either a universal error or one of the following errors:

JVMDI_ERROR_NULL_POINTER

Invalid pointer.

Get Capabilities

typedef struct {
    unsigned int can_watch_field_modification        : 1;
    unsigned int can_watch_field_access              : 1;
    unsigned int can_get_bytecodes                   : 1;
    unsigned int can_get_synthetic_attribute         : 1;
    unsigned int can_get_owned_monitor_info          : 1;
    unsigned int can_get_current_contended_monitor   : 1;
    unsigned int can_get_monitor_info                : 1;
    unsigned int reserved1                           : 1;
    unsigned int reserved2                           : 1;
    unsigned int reserved3                           : 1;
    unsigned int can_pop_frame                       : 1;
    unsigned int reserved4                           : 1;
    unsigned int can_redefine_classes                : 1; 
    unsigned int can_add_method                      : 1;
    unsigned int can_unrestrictedly_redefine_classes : 1;
    unsigned int reserved5                           : 1;
} JVMDI_capabilities;

jvmdiError
GetCapabilities(JVMDI_capabilities *capabilitiesPtr)

Parameters:

capabilitiesPtr

on return, points to the JVMDI capabilities.

This function returns either a universal error or one of the following errors:

JVMDI_ERROR_NULL_POINTER

Invalid pointer.

Every JVMDI function returns a jvmdiError error code.

Universal Errors

JVMDI_ERROR_NONE

No error has occurred. This is the error code that is returned on successful completion of the function.

JVMDI_ERROR_OUT_OF_MEMORY

The function needed to allocate memory and no more memory was available for allocation.

JVMDI_ERROR_ACCESS_DENIED

Debugging has not been enabled in this virtual machine. JVMDI cannot be used.

JVMDI_ERROR_UNATTACHED_THREAD

The thread being used to call this function is not attached to the virtual machine. Calls must be made from attached threads. See AttachCurrentThread() in the JNI invocation API.

JVMDI_ERROR_VM_DEAD

The virtual machine is not running.

JVMDI_ERROR_INTERNAL

An unexpected internal error has occurred.

Function Specific Errors

JVMDI_ERROR_INVALID_THREAD

passed thread is NULL, is not a valid thread or has exited

JVMDI_ERROR_INVALID_FIELDID

invalid field

JVMDI_ERROR_INVALID_METHODID

invalid method

JVMDI_ERROR_INVALID_LOCATION

invalid location

JVMDI_ERROR_INVALID_FRAMEID

invalid jframeID

JVMDI_ERROR_NO_MORE_FRAMES

There are no more Java programming language or JNI frames on the call stack.

JVMDI_ERROR_OPAQUE_FRAME

information about the frame is not available (e.g. for native frames)

JVMDI_ERROR_NOT_CURRENT_FRAME

operation can only be performed on current frame

JVMDI_ERROR_TYPE_MISMATCH

the variable is not an appropriate type for the function used

JVMDI_ERROR_INVALID_SLOT

invalid slot

JVMDI_ERROR_DUPLICATE

item already set

JVMDI_ERROR_THREAD_NOT_SUSPENDED

thread was not suspended

JVMDI_ERROR_THREAD_SUSPENDED

thread already suspended

JVMDI_ERROR_INVALID_OBJECT

invalid object

JVMDI_ERROR_INVALID_CLASS

invalid class

JVMDI_ERROR_CLASS_NOT_PREPARED

class has been loaded but not yet prepared

JVMDI_ERROR_NULL_POINTER

invalid pointer

JVMDI_ERROR_ABSENT_INFORMATION

The requested information is not available.

JVMDI_ERROR_INVALID_EVENT_TYPE

The specified event type id is not recognized.

JVMDI_ERROR_NOT_IMPLEMENTED

The functionality is not implemented in this virtual machine

JVMDI_ERROR_INVALID_THREAD_GROUP

thread group invalid

JVMDI_ERROR_INVALID_PRIORITY

invalid priority

JVMDI_ERROR_NOT_FOUND

Desired element (e.g. field or breakpoint) not found

JVMDI_ERROR_INVALID_MONITOR

invalid monitor

JVMDI_ERROR_ILLEGAL_ARGUMENT

illegal argument

JVMDI_ERROR_NOT_MONITOR_OWNER

This thread doesn't own the monitor.

JVMDI_ERROR_ABSENT_INFORMATION

Desired information is not available.

JVMDI_ERROR_INTERRUPT

The call has been interrupted before completion.

JVMDI_ERROR_INVALID_TYPESTATE

The state of the thread has been modified, and is now inconsistent.

JVMDI_ERROR_UNSUPPORTED_VERSION

A new class file has a version number not supported by this VM.

JVMDI_ERROR_INVALID_CLASS_FORMAT

A new class file is malformed (The VM would return a ClassFormatError).

JVMDI_ERROR_CIRCULAR_CLASS_DEFINITION

The new class file definitions would lead to a circular definition (the VM would return a ClassCircularityError).

JVMDI_ERROR_ADD_METHOD_NOT_IMPLEMENTED

A new class file would require adding a method, and can_add_method is false.

JVMDI_ERROR_SCHEMA_CHANGE_NOT_IMPLEMENTED

A new class file would require a schema change, and can_unrestrictedly_redefine_classes is false.

JVMDI_ERROR_FAILS_VERIFICATION

The class bytes fail verification.

JVMDI_ERROR_HIERARCHY_CHANGE_NOT_IMPLEMENTED

A direct superclass is different for the new class version, or the set of directly implemented interfaces is different and can_unrestrictedly_redefine_classes is false.

JVMDI_ERROR_DELETE_METHOD_NOT_IMPLEMENTED

The new class version does not declare a method declared in the old class version and can_unrestrictedly_redefine_classes is false.

JVMDI_ERROR_NAMES_DONT_MATCH

The class name defined in the new class file is different from the name in the old class object.

JVMDI_ERROR_CLASS_MODIFIERS_CHANGE_NOT_IMPLEMENTED

The new version of a class has different class modifiers (public, abstract, final, ...) then the old version (and can_unrestrictedly_redefine_classes is false).

JVMDI_ERROR_METHOD_MODIFIERS_CHANGE_NOT_IMPLEMENTED

The new version of a class has a different method modifier (public, abstract, synchronized, ...) then the old version (and can_unrestrictedly_redefine_classes is false).

• Introduction
• Single Step Event
  • JVMDI_EVENT_SINGLE_STEP
• Breakpoint Event
  • JVMDI_EVENT_BREAKPOINT
• Field Events
  • JVMDI_EVENT_FIELD_ACCESS
  • JVMDI_EVENT_FIELD_MODIFICATION
• Frame Events
  • JVMDI_EVENT_FRAME_POP
  • JVMDI_EVENT_METHOD_ENTRY
  • JVMDI_EVENT_METHOD_EXIT
• Exception Event
  • JVMDI_EVENT_EXCEPTION
• Exception Catch Event
  • JVMDI_EVENT_EXCEPTION_CATCH
• User Defined Event
  • JVMDI_EVENT_USER_DEFINED
• Thread Events
  • JVMDI_EVENT_THREAD_END
  • JVMDI_EVENT_THREAD_START
• Class Events
  • JVMDI_EVENT_CLASS_LOAD
  • JVMDI_EVENT_CLASS_UNLOAD
  • JVMDI_EVENT_CLASS_PREPARE
• VM Initialization Event
  • JVMDI_EVENT_VM_INIT
• VM Death Event
  • JVMDI_EVENT_VM_DEATH

JVMDI clients can be informed of many events that occur in application programs.

To handle Events, designate a hook function with SetEventHook. For each event the hook function will be called with a JVMDI_Event argument describing the event type and, depending on the event, additional information. The hook function is usually called from within application threads and the JVMDI implementation does not queue events in any way. This means that event hook functions must be written carefully. Here are some general guidelines. See the individual event descriptions for further suggestions.

• Any exception thrown during the execution of an event hook can overwrite any current pending exception in the current application thread. Care must be taken to preserve a pending exception when an event hook makes a JNI call that might generate an exception.
• Event hook functions must be re-entrant. The JVMDI implementation does not queue events. If a JVMDI client needs to process events one at a time, it can use a raw monitor inside the event hook function to serialize event processing.

Some JVMDI events identify objects with JNI references. All such references are passed to the event hook function via the JVMDI_Event argument. All references in JVMDI events are JNI local references and will become invalid after the event hook returns. The JVMDI_Event data structure is allocated locally and deallocated when the event hook function returns.

Events can be enabled and disabled with the function SetEventNotificationMode. Some events are enabled at application startup; others are not. Refer to the documentation for this function for details.

A thread that generates an event does not change its execution status. If an event should cause a thread to be suspended, then the event hook function is responsible for explicitly suspending the thread with SuspendThread.

The JVMDI_Event contains the event kind and a union of event-specific structures containing more information.

typedef struct {
    jint kind;		/* the discriminant */

    union {
	/* kind = JVMDI_EVENT_SINGLE_STEP */
        JVMDI_single_step_event_data single_step;
			
        /* kind = JVMDI_EVENT_BREAKPOINT */
        JVMDI_breakpoint_event_data breakpoint;

        /* kind = JVMDI_EVENT_FRAME_POP */
        /* kind = JVMDI_EVENT_METHOD_ENTRY */
        /* kind = JVMDI_EVENT_METHOD_EXIT */
        JVMDI_frame_event_data frame;

        /* kind = JVMDI_EVENT_FIELD_ACCESS */
        JVMDI_field_access_event_data field_access;

        /* kind = JVMDI_EVENT_FIELD_MODIFICATION */
        JVMDI_field_modification_event_data field_modification;

        /* kind = JVMDI_EVENT_EXCEPTION */
        JVMDI_exception_event_data exception;

        /* kind = JVMDI_EVENT_EXCEPTION_CATCH */
        JVMDI_exception_catch_event_data exception_catch;

        /* kind = JVMDI_EVENT_USER_DEFINED */
        JVMDI_user_event_data user;
			
        /* kind = JVMDI_EVENT_THREAD_END or */
        /* JVMDI_EVENT_THREAD_START */
        JVMDI_thread_change_event_data thread_change;
			
        /* kind = JVMDI_EVENT_CLASS_LOAD, */
        /* JVMDI_EVENT_CLASS_UNLOAD, or */
        /* JVMDI_EVENT_CLASS_PREPARE */
        JVMDI_class_event_data class_event;
			
        /* kind = JVMDI_EVENT_VM_DEATH, JVMDI_EVENT_VM_INIT */
        /* no additional fields */		
    } u;
} JVMDI_Event;

More information on specific events is given in the sections below.

Single Step Events (JVMDI_EVENT_SINGLE_STEP)

    typedef struct { 
        jthread thread;
        jclass clazz;
        jmethodID method;
        jlocation location;
    } JVMDI_single_step_event_data;

Single step events allow the JVMDI client to trace thread execution at the finest granularity allowed by the VM. A single step event is generated whenever a thread reaches a new location. Typically, single step events represent the completion of one VM instruction as defined the VM Specification; however, some implementations may define location differently. In any case the clazz, method, and location fields of the event structure uniquely identify the current location and allow the mapping to source file and line number when that information is available.

No single step events are generated from within native methods.

Single step events are disabled by default and can be enabled for a thread by calling SetEventNotificationMode

Breakpoint Events (JVMDI_EVENT_BREAKPOINT)

    typedef struct { 
        jthread thread;
        jclass clazz;
        jmethodID method;
        jlocation location;
    } JVMDI_breakpoint_event_data;

Breakpoint Events are generated whenever a thread reaches a location designated as a breakpoint with SetBreakpoint. The clazz, method, and location fields of the event structure uniquely identify the current location and allow the mapping to source file and line number when that information is available.

Breakpoint reporting, in general, can be enabled or disabled by calling SetEventNotificationMode and are enabled by default. If they are disabled, set breakpoints are ignored.

Field Events (JVMDI_EVENT_FIELD_ACCESS, JVMDI_EVENT_FIELD_MODIFICATION)

    /* kind = JVMDI_EVENT_FIELD_ACCESS */
    typedef struct { 
        jthread thread;
        jclass clazz;
        jmethodID method;
        jlocation location;
        jclass field_clazz;
        jobject object;
        jfieldID field;
    } JVMDI_field_access_event_data;
    
    /* kind = JVMDI_EVENT_FIELD_MODIFICATION */
    typedef struct { 
        jthread thread;
        jclass clazz;
        jmethodID method;
        jlocation location;
        jclass field_clazz;
        jobject object;
        jfieldID field;
        char signature_type;
        jvalue new_value;
    } JVMDI_field_modification_event_data;

Field Events are generated whenever a thread accesses or modifies a field designated as a watchpoint with SetFieldAccessWatch or with SetFieldModificationWatch. The clazz, method, and location fields of the event structures uniquely identify the current location and allow the mapping to source file and line number when that information is available. The field_clazz and field fields uniquely identify the field which is being accessed or modified. The object identifies the containing object if the field is an instance field. It is NULL otherwise.

Field watchpoint reporting, in general, can be enabled or disabled by calling SetEventNotificationMode and are enabled by default. If they are disabled, set watches are ignored.

Frame Events (JVMDI_EVENT_FRAME_POP, JVMDI_EVENT_METHOD_ENTRY, JVMDI_EVENT_METHOD_EXIT)

    typedef struct { 
        jthread thread;
        jclass clazz;
        jmethodID method;
        jframeID frame;
    } JVMDI_frame_event_data;

Method entry events are generated upon entry of Java programming language or native methods. Method exit events are generated upon exit from a Java programming language or native methods. Frame pop events are generated upon exit from a single method in a single frame as specified in a call to NotifyFramePop. If a method terminates by throwing an exception to its caller, neither a method exit event nor a frame pop event will be generated. JVMDI clients can check for this occurrence by monitoring exception catch events

The clazz and method fields uniquely identify the method being entered or exited. The frame field provides access to the stack frame for the method. On method entry, the location reported by GetFrameLocation identifies the initial executable location in the method. On method exit or frame pop, the location reported by GetFrameLocation identifies the executable location in the returning method, immediately prior to the return.

Method entry and exit are disabled by default and can be enabled by calling SetEventNotificationMode. Frame pop events are enabled by default and can be disabled similarly.

Exception Events (JVMDI_EVENT_EXCEPTION)

    typedef struct { 
        jthread thread;
        jclass clazz;
        jmethodID method;
        jlocation location;
        jobject exception;
        jclass catch_clazz;
        jmethodID catch_method;
        jlocation catch_location;
    } JVMDI_exception_event_data;

Exception events are generated whenever an exception is first detected in a Java programming language method. The exception may have been thrown by a Java programming language or native method, but in the case of native methods, the event is not generated until the exception is first seen by a Java programming language method. If an exception is set and cleared in a native method (and thus is never visible to Java programming language code), no exception event is generated.

The clazz, method, and location fields of the event structure uniquely identify the current location (where the exception was detected) and allow the mapping to source file and line number when that information is available. The exception field identifies the thrown exception object. The catch_clazz, catch_method, and catch_location identify the location of the catch clause, if any, that handles thrown exception. If there is no such catch clause, each field is set to 0. There is no guarantee that the thread will ever reach this catch clause. If there are native methods on the call stack between the throw location and the catch clause, the exception may be reset by one of those native methods. JVMDI clients can check for this occurrence by monitoring exception catch events

Exception events are enabled by default and can be disabled by calling SetEventNotificationMode.

Exception Catch Events (JVMDI_EVENT_EXCEPTION_CATCH)

    typedef struct { 
        jthread thread;
        jclass clazz;
        jmethodID method;
        jlocation location;
        jobject exception;
    } JVMDI_exception_catch_event_data;

Exception catch events are generated whenever a thrown exception is caught. If the exception is caught in a Java programming language method, the event is generated when the catch clause is reached. If the exception is caught in a native method, the event is generated as soon as control is returned to a Java programming language method. Exception catch events are generated for any exception for which a throw was detected in a Java programming language method.

The clazz, method, and location fields of the event structure uniquely identify the current location and allow the mapping to source file and line number when that information is available. For exceptions caught in a Java programming language method, the exception object identifies the exception object. Exceptions caught in native methods are not necessarily available by the time the exception catch is reported, so the exception field is set to NULL.

Exception catch events are disabled by default and can be enabled by calling SetEventNotificationMode.

User Defined Events (JVMDI_EVENT_USER_DEFINED)

    typedef struct { 
        jobject object;
        jint key;
    } JVMDI_user_event_data;

The meaning of user defined events and the fields in the user event data structure are defined by particular JVMDI implementations.

Thread Events (JVMDI_EVENT_THREAD_END, JVMDI_EVENT_THREAD_START)

    typedef struct { 
        jthread thread;
    } JVMDI_thread_change_event_data;

Thread start events are generated by a new thread before its initial method executes. Thread end events are generated by a terminating thread after its initial method has finished execution. A thread may be listed in the array returned by GetAllThreads before its thread start event is generated and after its thread end event is generated. It is possible for other events to be generated for a thread before its thread start event, but no events are generated after its thread end event.

Thread events are enabled by default and can be disabled by calling SetEventNotificationMode.

Class Events (JVMDI_EVENT_CLASS_LOAD, JVMDI_EVENT_CLASS_UNLOAD, JVMDI_EVENT_CLASS_PREPARE)

    typedef struct { 
        jthread thread;
        jclass clazz;
    } JVMDI_class_event_data;

Class events signal a change in status for a particular class.

A class load event is generated when a class is first loaded. The order of class load events are generated by a particular thread are guaranteed to match the order of class loading within that thread. Arrays of non-primitive types have class load events. Arrays of primitive types do not have class load events (they are considered loaded at the time of VM initialization). Primitive classes (for example, java.lang.Integer.TYPE) do not have class load events.

A class prepare event is generated when class preparation is complete. At this point, class fields, methods, and implemented interfaces are available, and no code from the class has been executed. Since array classes never have fields or methods, class prepare events are not generated for them. Class prepare events are not generated for primitive classes (for example, java.lang.Integer.TYPE).

A class unload event is generated when the class is about to be unloaded. Class unload events take place during garbage collection and must be handled extremely carefully. The garbage collector holds many locks and has suspended all other threads, so the event handler cannot depend on the ability to acquire any locks. The class unload event handler should do as little as possible, perhaps by queueing information to be processed later.

Class events are enabled by default and can be disabled by calling SetEventNotificationMode.

VM Initialization Event (JVMDI_EVENT_VM_INIT)

The VM initialization event signals the completion of VM initialization. Once this event is generated, the JVMDI client is free to call any JNI or JVMDI function. The VM initialization event can be preceded by or can be concurrent with other events, but the preceding events should be handled carefully, if at all because the VM has not completed its initialization. The thread start event for the main application thread is guaranteed not to occur until after the handler for the VM initialization event returns.

VM Death Event (JVMDI_EVENT_VM_DEATH)

If the current location is at the entry point of a method, the JVMDI_EVENT_METHOD_ENTRY event is reported before any other event at the current location in the same thread.

If an exception catch has been detected at the current location, (either because it is the beginning of a catch clause or a native method which cleared a pending exception has returned), the JVMDI_EVENT_EXCEPTION_CATCH event is reported before any other event at the current location in the same thread.

If a JVMDI_EVENT_SINGLE_STEP event or JVMDI_EVENT_BREAKPOINT event is triggered at the current location, the event is defined to occur immediately before the code at the current location is executed. These events are reported before any events which are triggered by the execution of code at the current location in the same thread (specifically, JVMDI_EVENT_EXCEPTION, JVMDI_EVENT_FIELD_ACCESS, and JVMDI_EVENT_FIELD_MODIFICATION). If both a step and breakpoint event are triggered for the same thread and location, the step event is reported before the breakpoint event.

If the current location is the exit point of a method (that is, the last location before returning to the caller), the JVMDI_EVENT_METHOD_EXIT event and the JVMDI_EVENT_FRAME_POP event (if requested) are reported after all other events at the current location in the same thread. There is no specified ordering of these two events with respect to each other.

Co-located events can be triggered during the processing of some other event by the JVMDI client at the same location in the same thread. If such an event, of type y, is triggered during the processing of an event of type x, and if x precedes y in the ordering specified above, then the co-located event y is reported for the current thread and location. If x does not precede y, then y is not reported for the current thread and location. For example, if a breakpoint is set at the current location during the processing of JVMDI_EVENT_SINGLE_STEP, that breakpoint will be reported before the thread moves off the current location.

The following events are never considered to be co-located with other events.

• JVMDI_EVENT_USER_DEFINED
• JVMDI_EVENT_VM_INIT
• JVMDI_EVENT_VM_DEATH
• JVMDI_EVENT_THREAD_START
• JVMDI_EVENT_THREAD_END
• JVMDI_EVENT_CLASS_LOAD
• JVMDI_EVENT_CLASS_UNLOAD
• JVMDI_EVENT_CLASS_PREPARE

The initial loading of a JVMDI client at VM startup can vary from VM to VM. The following description applies to the Sun J2SE 1.2 classic VM for Windows and Solaris.

The following command-line arguments are required on VM startup to properly load and run JVMDI clients.

-Xdebug

Enables debugging

-Xnoagent

Prevents the default debug agent (used with jdb) from running.

-Djava.compiler=NONE

Disables the JIT. The classic VM does not support debugging with the JIT enabled.

-Xrun:

Identifies the library containing the JVMDI client as well as an options string to be passed in at startup. The library must export a startup function with the following prototype.

JNIEXPORT jint JNICALL 
JVM_OnLoad(JavaVM *vm, char *options, void *reserved) 

This function will be called at startup by the VM. For example, if the option -Xrunfoo:opt1,opt2 is specified, the VM will attempt to load the shared library foo.dll under Windows or libfoo.so under Solaris. It will then attempt to find JVM_OnLoad and call it with "opt1,opt2" as the second argument. Since the VM is not initialized at the time of this call, there is very little that can be done safely inside JVM_OnLoad. It can safely process the options and set an event hook with SetEventHook. Once that event hook is called for the VM initialization event, the JVMDI client can complete its initialization.

Copyright © 1996-2004 Sun Microsystems, Inc. All Rights Reserved. Send questions or comments to: java-debugger@sun.com.