Where is the entry point of java calls

[Karen Kinnear]

Colin,

Let's start with reading the bytecodes. You have a .class file.
Run javap -c Main > Main.jasm to get the bytecodes from Main.class
    - now you can view the translated generated bytecodes using your
      favorite editor (read, not modify)

In the sample I looked at, in which there was a
    private native Class myNative(args)

in the bytecodes for the caller, there was the instruction:
    invokespecial #83; // Method myNative:(...signature for args)

#83 refers to the constant pool entry #83

See java.sun.com/docs/books/jvms/second_edition/html/VMSpecTOC.doc.html
Look in section 4.1 for details on the class file format.

2. Method invocation should use one of: invokevirtual/special/static/ 
interface
so find that bytecode in your generated code. You can put a breakpoint  
in
the interpreter you are debugging - for when it checks for a native  
method call.

good luck,
Karen

On Mar 4, 2009, at 1:36 PM, Colin(Du Li) wrote:

>
> Hi, Karen,
>
> Thanks for your prompt reply!
> What I wanna do is to trap all the java method call, and pick out  
> the native
> calls (JNI). I still have two questions.
> 1. How can I read the generated bytecodes. When I use Vi to open  
> a .class
> file, it's not very readable.
> 2. Does every method call for another java method can be trapped at
> invoke_virtual/special/static in bytecodeInterpreter.cpp?
>
> Thanks again.
>
> Colin.
>
> Karen Kinnear wrote:
>>
>> Colin,
>>
>> We don't use javaCalls for calls from one java method to another.
>> I believe you are writing an interpreter (or modifying the C++
>> interpreter)?
>> So you want to look at the code you generated - which will invoke
>> java methods directly. See the bytecodes for invoke_virtual/special/
>> interface.
>>
>> hope this helps,
>> Karen
>>
>> On Mar 4, 2009, at 12:53 PM, Colin(Du Li) wrote:
>>
>>>
>>> Hi, guys.
>>> Could anyone help me ? Or do I need express my question more  
>>> clearly?
>>> I really need help for this question.
>>> Thanks a lot!
>>>
>>> Colin
>>>
>>> Colin(Du Li) wrote:
>>>>
>>>> Hello,
>>>> My question is where is the entry point of java calls in hotspot.
>>>> If I have a simple application as follow:
>>>>
>>>> public class HelloWorld{
>>>>       public static void main(String[] args){
>>>>               hello2();
>>>>       }
>>>>       public static void hello2(){
>>>>               System.out.println("hello 2.");
>>>>       }
>>>> }
>>>>
>>>> If I observe at  javaCalls:call_helper(), I can only see method
>>>> HelloWorld.main(), I cannot see method  HelloWorld.hello2(). Why?
>>>> and How
>>>> can I find the entry point of method HelloWorld.hello2()?
>>>>
>>>> Thanks a lot!
>>>>
>>>> Colin
>>>>
>>>>
>>>
>>> -- 
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>>> Sent from the OpenJDK Hotspot Virtual Machine mailing list archive
>>> at Nabble.com.
>>>
>>
>>
>>
>
> -- 
> View this message in context: http://www.nabble.com/Where-is-the-entry-point-of-java-calls-tp22298233p22336385.html
> Sent from the OpenJDK Hotspot Virtual Machine mailing list archive  
> at Nabble.com.
>