Re: [patch] Fix oddity in personality routine

[Andrew Haley <aph at redhat dot com>]

Jack Howarth wrote:
> On Fri, Nov 27, 2009 at 10:40:17AM +0000, Andrew Haley wrote:
>> borlum wrote:
>>>
>>> Jack Howarth-3 wrote:
>>>> On Tue, Nov 17, 2009 at 05:13:31PM +0000, Andrew Haley wrote:
>>>>> Sometimes it doesn't work, so you have to be inventive.  Try
>>>>> setting a breakpoint on Unwind_RaiseException, or step a single
>>>>> instruction at a time when you get to a call.
>>>>>
>>>>>> I assume that gcc trunk's
>>>>>> debug code is still compatible with Apple's gdb. If not, I do have
>>>>>> a build of gdb 7.0 on Intel darwin that I can use instead. Thanks
>>>>>> in advance for any hints on this issue.
>>>>>>               Jack
>>>>>> ps I do notice that gdb can't find the object files from
>>>>> /sw/src/fink.build/gcc45-4.4.999-20091116/darwin_objdir/x86_64-apple-darwin9.8.0/libjava/.libs/libgcj.lax
>>>>> so it might have problems with debugging within libgcj. If I recall
>>>>> correctly this .lax issue is known...
>>>>>> http://gcc.gnu.org/ml/gcc/2008-10/msg00083.html
>>>>> Ouch.  That will cause gdb breakage, for sure.
>>>> Andrew,
>>>>    Re-reading Peter's comments in
>>>> http://gcc.gnu.org/ml/gcc/2008-10/msg00083.html, I think I
>>>> may be able to work around the lax issue with the proper setting of
>>>> LD_LIBRARY to point to 
>>>> the shared library in the build directory. I'll see if I can puzzle that
>>>> one out.
>>>>                  Jack
>>>>> Andrew.
>>> Hey Andrew,
>>>
>>> Did you ever solve the problem? I'm having the same rather frustrating
>>> error.
>> Not me, no.  I don't have a Darwin system.

>     Now that we have a set of patches to fix the breakage in current gcc
> trunk to dsymutil, I have uploaded a much more complete walk under x86_64-apple-darwin10.
> I haven't managed to walk into _Unwind_Exception() yet but I do see that the 
> crash occurs on continuing from the 39th instance of the _Unwind_Exception() breakpoint.

That's probably just the end of the stack.  If you do a stack trace
in gdb you'll probably find it's something like 39 deep.

> Is there some way I can get the unwinder data from inside of libgcj itself before
> the call to _Unwind_Exception()? If the bad unwind information is being generated in
> libjava wouldn't it be just as easy to see that from outside of libgcc (before the call
> to _Unwind_Exception()?

You mean decoding the unwinder data by hand?  It's not impossible, but
it'd be a hell of a job.

Andrew.