[LLVMdev] Exception handling question

Garrison Venn gvenn.cfe.dev at gmail.com
Fri Jan 22 05:25:37 PST 2010

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.

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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