You are viewing a plain text version of this content. The canonical link for it is here.
Posted to bcel-user@jakarta.apache.org by Marc Van Daele <ma...@zappware.com> on 2006/05/09 15:49:29 UTC
find out whether a method is called on this
Hello,
I'm (trying to) writing a deadlock detection tool.
This works now relatively fine but it generates way too many false
positives
since too many virtual functions are expanded.
To limit this, I want to find out whether a method is called on 'this'
since then I can limit the expansion.
Hence my question: Is there an easy way in BCEL to find out whether a
method is called on 'this' vs on another object?
I tried the following:
I know that ALOAD_0 pushes the this pointer to the stack.
So by using Instruction.consumeStack and Instruction.produceStack, I try
to model the stack and
derive whether the method-call got executed on 'this' or on another object.
However, this fails, at least in the following code fragment
drawObject2((b)?true:false);
which is translated in bytecode to
aload_0[42](1)
aload_0[42](1)
getfield[180](3) 70
ifeq[153](3) -> iconst_0
iconst_1[4](1)
goto[167](3) -> invokespecial 74
iconst_0[3](1)
invokespecial[183](3) 74
Since I only use consumeStack and produceStack (and don't bother with
branches), I put an object on the stack for both iconst instructions
and hence I incorrectly conclude that invokespecial is called on
iconst_1 which isn't this.
Input is appreciated,
Marc
---------------------------------------------------------------------
To unsubscribe, e-mail: bcel-user-unsubscribe@jakarta.apache.org
For additional commands, e-mail: bcel-user-help@jakarta.apache.org
Re: find out whether a method is called on this
Posted by Marc Van Daele <ma...@zappware.com>.
Dave Brosius wrote:
> Yes Trinaries are very annoying. They are the only place, afaik that
> the compiler maintains a non zero sized stack across a branch.
Hello Dave,
Thanks for your reply.
Do you know another way of knowing whether a function is called on the
'this' object?
Btw, I ran accross another construct that had the same problem
drawObject2(startNr == selectedNr && isFocused());
which result in the following bytecode
aload_0[42](1)
aload_0[42](1)
getfield[180](3) 55
aload_0[42](1)
getfield[180](3) 57
if_icmpne[160](3) -> iconst_0
aload_0[42](1)
invokespecial[183](3) 61
ifeq[153](3) -> iconst_0
iconst_1[4](1)
goto[167](3) -> invokespecial 74
iconst_0[3](1)
invokespecial[183](3) 74
return[177](1)
Is this also covered by the OpcodeStack?
Kind Regards,
Marc
>
> The findbugs.sourceforge.net class OpcodeStack attempts to merge
> stacks across trinaries. You might find that useful.
>
> cheers!
> dave
>
> ----- Original Message ----- From: "Marc Van Daele"
> <ma...@zappware.com>
> To: <bc...@jakarta.apache.org>
> Sent: Tuesday, May 09, 2006 9:49 AM
> Subject: find out whether a method is called on this
>
>
>> Hello,
>>
>> I'm (trying to) writing a deadlock detection tool.
>> This works now relatively fine but it generates way too many false
>> positives
>> since too many virtual functions are expanded.
>>
>> To limit this, I want to find out whether a method is called on 'this'
>> since then I can limit the expansion.
>>
>> Hence my question: Is there an easy way in BCEL to find out whether a
>> method is called on 'this' vs on another object?
>>
>> I tried the following:
>> I know that ALOAD_0 pushes the this pointer to the stack.
>> So by using Instruction.consumeStack and Instruction.produceStack, I
>> try to model the stack and
>> derive whether the method-call got executed on 'this' or on another
>> object.
>>
>> However, this fails, at least in the following code fragment
>> drawObject2((b)?true:false); which is translated in bytecode to
>> aload_0[42](1)
>> aload_0[42](1)
>> getfield[180](3) 70
>> ifeq[153](3) -> iconst_0
>> iconst_1[4](1)
>> goto[167](3) -> invokespecial 74
>> iconst_0[3](1)
>> invokespecial[183](3) 74
>> Since I only use consumeStack and produceStack (and don't bother with
>> branches), I put an object on the stack for both iconst instructions
>> and hence I incorrectly conclude that invokespecial is called on
>> iconst_1 which isn't this.
>>
>> Input is appreciated,
>>
>> Marc
>>
>>
>>
>> ---------------------------------------------------------------------
>> To unsubscribe, e-mail: bcel-user-unsubscribe@jakarta.apache.org
>> For additional commands, e-mail: bcel-user-help@jakarta.apache.org
>>
>>
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: bcel-user-unsubscribe@jakarta.apache.org
> For additional commands, e-mail: bcel-user-help@jakarta.apache.org
>
>
>
---------------------------------------------------------------------
To unsubscribe, e-mail: bcel-user-unsubscribe@jakarta.apache.org
For additional commands, e-mail: bcel-user-help@jakarta.apache.org
Re: find out whether a method is called on this
Posted by Dave Brosius <db...@apache.org>.
Yes Trinaries are very annoying. They are the only place, afaik that the
compiler maintains a non zero sized stack across a branch.
The findbugs.sourceforge.net class OpcodeStack attempts to merge stacks
across trinaries. You might find that useful.
cheers!
dave
----- Original Message -----
From: "Marc Van Daele" <ma...@zappware.com>
To: <bc...@jakarta.apache.org>
Sent: Tuesday, May 09, 2006 9:49 AM
Subject: find out whether a method is called on this
> Hello,
>
> I'm (trying to) writing a deadlock detection tool.
> This works now relatively fine but it generates way too many false
> positives
> since too many virtual functions are expanded.
>
> To limit this, I want to find out whether a method is called on 'this'
> since then I can limit the expansion.
>
> Hence my question: Is there an easy way in BCEL to find out whether a
> method is called on 'this' vs on another object?
>
> I tried the following:
> I know that ALOAD_0 pushes the this pointer to the stack.
> So by using Instruction.consumeStack and Instruction.produceStack, I try
> to model the stack and
> derive whether the method-call got executed on 'this' or on another
> object.
>
> However, this fails, at least in the following code fragment
> drawObject2((b)?true:false); which is translated in bytecode to
> aload_0[42](1)
> aload_0[42](1)
> getfield[180](3) 70
> ifeq[153](3) -> iconst_0
> iconst_1[4](1)
> goto[167](3) -> invokespecial 74
> iconst_0[3](1)
> invokespecial[183](3) 74
> Since I only use consumeStack and produceStack (and don't bother with
> branches), I put an object on the stack for both iconst instructions
> and hence I incorrectly conclude that invokespecial is called on iconst_1
> which isn't this.
>
> Input is appreciated,
>
> Marc
>
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: bcel-user-unsubscribe@jakarta.apache.org
> For additional commands, e-mail: bcel-user-help@jakarta.apache.org
>
>
---------------------------------------------------------------------
To unsubscribe, e-mail: bcel-user-unsubscribe@jakarta.apache.org
For additional commands, e-mail: bcel-user-help@jakarta.apache.org