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From Gregory Shimansky <gshiman...@gmail.com>
Subject Re: [classlib][launcher] Signal handler disabling
Date Fri, 09 Feb 2007 12:25:10 GMT
Mark Hindess wrote:
> I think we should go for the record of resurrecting a thread the most
> times ;-)
> The current solution still compiles the hysig code.  However, I've
> got a patch (windows and Linux but only tested on Linux) that adds a
> flag to give the option to avoid the compilation of the hysig library
> completely.  The default is to compile it but I'd actually like to
> reverse that after some wider testing.
> Does this seem reasonable?
> I want to use this option because it means I can avoid porting the
> signalling code to new architectures and platforms until we decide if we
> are going to keep it.  At the moment, I think we probably should get rid
> of it and let the VM handle signals.
> Gregory, why did you want it to be optional?  Do you use this option?

The reason is quite simple. When VM crashes it is much easier to debug 
it right at the spot of the crash. On Windows it is done with Just In 
Time debugging facility, on Linux core dump is useful. DRLVM with can 
and does detect the condition when crash happens inside of VM and when 
it is ran with -XDassert_dialog=true (default) does not try to do 
anything intelligent like printing stack. This allows debugging at the 
spot of the crash.

When launcher installs its own handler it catches the crash. Even though 
it can print registers and maybe some stack symbols, it is not as good 
as using full fledged debugger to analyze the problem.

> On 10 January 2007 at 21:07, Gregory Shimansky <gshimansky@gmail.com> wrote:
>> Tim Ellison wrote:
>>> I'm going for the record of resurrecting the oldest thread ;-)
>>> Having this additional signal handler in the launcher is causing me pain
>>> too, so unless there are objections now I'm going to go ahead and
>>> disable it by default, and have an option to enable it for those that want.
>> +1
>> Let's have it optional.
>>> Ivan Volosyuk wrote:
>>>> It seems that in cmain.c in function genericSignalHandler() just
>>>> removing abort() statement will cause default system handler to
>>>> execute pointing the exact place of fault right after printing all
>>>> this useless crash info. I have no idea how to obtain property value
>>>> in this place to make the abort() conditional. Anyway, I think it
>>>> would be much beneficial for developers to have crash by default.
>>>> -- 
>>>> Ivan
>>>> On 9/22/06, Geir Magnusson Jr. <geir@pobox.com> wrote:
>>>>> This can't be that hard.  Maybe a simple command-line flag
>>>>>    -launcher:something
>>>>> Give it a wack and see what happens...
>>>>> geir
>>>>> On Sep 22, 2006, at 1:29 PM, Ivan Volosyuk wrote:
>>>>>> Exactly. I would like to have a way to disable the crash handler
>>>>>> invoked in the call.
>>>>>> It is quite painful to locate crashing place when the crash handler
>>>>>> enabled. Even setting breakpoint in the handler doesn't help - stack
>>>>>> at this place has number of system frames without debug information
>>>>>> which hide the actual problematic point.
>>>>>> --
>>>>>> Ivan
>>>>>> On 9/22/06, Geir Magnusson Jr. <geir@pobox.com> wrote:
>>>>>>> Do you mean sig_protect in cmain.c?
>>>>>>> geir
>>>>>>> On Sep 22, 2006, at 12:22 PM, Ivan Volosyuk wrote:
>>>>>>>> Hi,
>>>>>>>> While working on windows on DRLVM I introduced some crash
>>>>>>> situation. I
>>>>>>>> found out that there are two active crash handlers. One in
>>>>>>> DRLVM, the
>>>>>>>> other in launcher/classlib.
>>>>>>>> I can disable DRLVM's one: -Dvm.assert_dialog=1
>>>>>>>> But the launcher's crash handler still prevent me to use
>>>>>>> debugger to
>>>>>>>> locate exact place of access violation in VM code. Is it
>>>>>>> possible to
>>>>>>>> disable it somehow?
>>>> ---------------------------------------------------------------------
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>> -- 
>> Gregory


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