Re: [aspectj-users] Instrumenting System Classes from aspectj

["David Mohr" <dmohr@xxxxxxxxxx>]

On Wed, Jul 2, 2008 at 9:48 PM, 100ji <itz100ji@xxxxxxxxx> wrote:
> Hi,
>
> Thanks for the response. I have wrapped the constructor to the Thread
> class as follows:
>
> ------------------
>
> public aspect AddTaintVarToThread {
>    after() : execution(new(..)) && this(Thread) {
>        //throw new IllegalStateException("Should never be
> constructing a bad type");
>        System.out.println("Hurray! Thread advice works!");
>    }
> }
>
> --------------------------
>
> I compiled it using ajc as follows:
>
>
> ajc -1.5 -cp /u/suman/installs/aspectj1.6/lib/aspectjrt.jar
>     -inpath /usr/lib/jvm/java-1.5.0-sun/jre/lib/rt.jar
>     -Xmx1500M -XX:PermSize=640M -XX:MaxPermSize=1280M
>     -d ./build
>    -outjar rt.jar  src/*.aj src/*.java
>
> I think the wrapping worked because, the decompiled versions of the
> original thread class and the new thread class were different.
>
> The compile worked fine but, when I run my application I get the
> following error:
>
> ---------------------------------------------------------------------
> cd /home/suman/exercise/steve_rnr/ytrace/ytrace_examples/Examples/build ;
> java -Xbootclasspath/p:. -cp
> /u/suman/installs/aspectj1.6//lib/aspectjweaver.jar:. BankExample
>
> Error occurred during initialization of VM
> java.lang.NullPointerException
> make: *** [client] Error 1
>
> -------------------------------------------------------------------------
>
> I tried googling but found no pointers to why this happens. Am I
> missing something? Any pointers will be helpful.

I haven't tried this with aspectj, but I have instrumented system
classes by other means before. I was seeing similar errors because the
jvm was using the instrumented threads internally as part of its
initialization. At that point the i/o subsystem is probably not
initialized yet, so you get the exception when you try to use
System.out.println.

The workaround that I used, although clumsy, was to add a field
"jvm_init_done" to the thread class. I set it to be true first thing
in the main method. In my thread instrumentation, I don't execute my
custom code if that flag is not set, so that the jvm can initialize
without interference.

~David

> TIA,
> -S-
>
> PS: I made sure that I am loading the generated classes by switching
> on the verbose mode.
>
>
> On Thu, Jun 26, 2008 at 12:05 PM, Andrew Eisenberg <andrew@xxxxxxxxxxxx> wrote:
>> Have you placed rt.jar (windows) or classes.jar (mac) on your in path?
>>  Classes on the in path are fed to the weaver and rewoven with all
>> aspects in the project.  This should work.
>>
>> Since the jar is quite large, you may want to add extra heap space to
>> your compiler (ie- if running in eclipse then add the following vm
>> arguments to the command line to run eclipse:  -vmargs -Xmx764M
>> -XX:PermSize=64M -XX:MaxPermSize=128M)
>>
>> On Thu, Jun 26, 2008 at 8:42 AM, 100ji <itz100ji@xxxxxxxxx> wrote:
>>> Hi all,
>>>
>>> I am relatively new to aspectj. I tried writing an aspect to
>>> instrument java.lang.String, but the eclipse IDE tells me that the
>>> class is not exposed (even tried using privileged aspect). So, I want
>>> to know if there is a way to instrument system classes from aspectj? I
>>> want to instrument java.lang.String and other such classes. Any
>>> pointers will be helpful.
>>>
>>> Thanks for your time,
>>> -S-
>>> _______________________________________________
>>> aspectj-users mailing list
>>> aspectj-users@xxxxxxxxxxx
>>> https://dev.eclipse.org/mailman/listinfo/aspectj-users
>>>
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