[LLVMdev] Exception handling question

[James Williams]

2010/1/22 Garrison Venn <gvenn.cfe.dev at gmail.com>

> Yes. The issue here, as you pointed out, is that your personality function
> is not called at all.
> Even if you did nothing in the personality function, associated with the
> setup caused by
> llvm.eh.selector, but returned _URC_CONTINUE_UNWIND (8), it should still be
> called.
> Your results are acting like either dwarf exception header info is not
> emitted (llvm::DwarfExceptionHandling = true;
> not executed could affect this), _Unwind_RaiseException(...) is not being
> called, or the default  or another personality
> function (_gcc_personality_v0(...)) is called instead by the
> unwind infrastructure. Although you implied you
> dumped the exception headers and found your personality function, I can if
> you wish instead given you breaks for
> gbd so you can see if lvm.eh.selector is correctly prepping your
> personality function for eventual dwarf emission.
>
> It looks like __gxx_personality_v0 is getting called at least once but I
might expect that to tear down the frame of the C++ test function calling
throw? It then disappears into std::terminate() and the aborts.

If there is some sane way I can debug this it would be really handy so if
you can tell me some good spots to set breakpoints I'd be grateful. As it is
I'm stepping through reams of unfamiliar assembly with little clue what's
going on.

-- James


> Garrison
>
> On Jan 22, 2010, at 8:06, James Williams wrote:
>
>
>
> 2010/1/22 Duncan Sands <baldrick at free.fr>
>
>> Hi Garrison,
>>
>>
>>  %7 = invoke i8* (...)* bitcast (i32 (%struct._Unwind_Exception*)*
>>> @_Unwind_RaiseException to i8* (...)*)(i64* %6)
>>>          to label %8 unwind label %.finally_pad  ; <i8*> [#uses=0]
>>>
>>> I am not sure this is going to work, at least from the way I've played
>>> with the system. In my examples the _Unwind_RaiseException(...) is called
>>> from a frame (function) called via
>>> the invoke instruction, not from a frame that contains the invoke
>>> instruction.
>>>
>>
>> I'm pretty sure this doesn't matter.  It seems to me more likely that the
>> exception object was not initialized properly.
>>
> Hmm. I've tried a bunch of different ways of creating the exception
> including calling a C++ function that then does a throw. If I understand
> right, the personality function should still be offered the foreign
> exception so it has a chance to call cleanups?
>
>
>> Ciao,
>>
>> Duncan.
>>
>>
>
>
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