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From "Ivan Popov (JIRA)" <j...@apache.org>
Subject [jira] Created: (HARMONY-3730) [drlvm][jvmti] SINGLE_STEP events are not reported in JIT mode
Date Mon, 23 Apr 2007 17:26:15 GMT
[drlvm][jvmti] SINGLE_STEP events are not reported in JIT mode
--------------------------------------------------------------

                 Key: HARMONY-3730
                 URL: https://issues.apache.org/jira/browse/HARMONY-3730
             Project: Harmony
          Issue Type: Bug
          Components: DRLVM
         Environment: Windows/x86, Linux/x86, harmony-jdk-r531438
            Reporter: Ivan Popov


'Step Return' sometime works incorrectly in Eclipse debugger when Harmony is launched in JIT
mode. To reproduce this use attached TestClass.java example:

1. Load TestClass.java into Eclipse
2. Set breakpoint to line 26
3. Launch this class under debugger (Run->Debug...) 
4. After stopped at breakpoint line click 'Step Return'

In -Xint mode the application will be stopped at line 19 (or in some system calls before this
line, if classlib is compiled with debug info). But in JIT mode this code is executed without
steps and application is stopped at Exception constructor in line 21 or even in system shutdown
code. This incorrect behavior causes problem with Eclipse Scrapbook functionality, details
are here: http://thread.gmane.org/gmane.comp.java.harmony.devel/26043/focus=26079.

The problem is that SINGLE_STEP events are not generated for the executed code in this case.
Below are details.

After the application is stopped at breakpoint the stack is the following:

Thread [main] (Suspended (breakpoint at line 26 in TestClass))	
	TestClass.hello() line: 26	
	VMReflection.invokeMethod(long, Object, Object[]) line: not available [native method]	
	Method.invoke(Object, Object[]) line: 381	
	TestClass.run() line: 17	
	TestClass.main(String[]) line: 7	

After user clicked 'Step Return', JDWP agent sets NotifyFramePop hook for the current frame
hello() and resumes VM. When current method hello() returns, agent receives FRAME_POP event.
Then it turns on SINGLE_STEP event and waits for step event is received for the next instruction
in the calling method. 

In -Xint mode it works well, I see the following JVMTI events are generated:

  EVENT: [RequestManager.cpp:1417] FRAME_POP event: class=LTestClass; method=hello loc=8 by_exception=0
  EVENT: [RequestManager.cpp:1344] STEP event: class=Ljava/lang/reflect/Method; method=invoke
location=77

Code of native method VMReflection.invokeMethod() is skipped and application is stopped in
Method.invoke().

But in JIT mode the following JVMTI events are generated:

  EVENT: [RequestManager.cpp:1417] FRAME_POP event: class=LTestClass; method=hello loc=8 by_exception=0
  EVENT: [RequestManager.cpp:1344] STEP event: class=Ljava/lang/Exception; method=<init>
location=0

In this case not only code of native method VMReflection.invokeMethod() is skipped, but also
all subsequent code until constructor of Exception is invoked.

I think this happens because SINGLE_STEP event is turned on while native method is on top
of the thread stack. This causes JVMTI not to generate step events even after returning from
native method.

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