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digitalmars.D.ldc - Win64 exception handling

reply "Johan Engelen" <j j.nl> writes:
Hi all,
   I have been trying to work on exception handling on Windows x64 
(with LLVM 3.6), but for a long time now, I am stuck on something 
perhaps very simple.

My test case is this program:
int main() {
     try {
         throw new Exception("johan");
     } catch (Exception jow) {
     }
     return 0;
}

This crashes, and Visual Studio's debugger tells me it's because 
of an unhandled exception. As far as I understand it, we call 
RtlRaiseException() from _d_throw_exception() and that should 
call the personality function _d_eh_personality(). However, 
_d_eh_personality() is never entered. Instead, 
RtlRaiseException() returns and the program crashes. I am stuck 
on how to continue from here. I have tried many different things, 
but I cannot get the OS to call _d_eh_personality().

One thing that strikes me is that the exception code 
STATUS_LDC_D_EXCEPTION is passed to RtlRaiseException(), but is 
not used anywhere else in our source.
Does LLVM not correctly register _d_eh_personality() with the OS? 
Or is there some filtering done on the exception code?

I'd appreciate any help.

-Johan
Mar 23 2015
parent reply "Kai Nacke" <kai redstar.de> writes:
On Monday, 23 March 2015 at 22:55:18 UTC, Johan Engelen wrote:
 Hi all,
   I have been trying to work on exception handling on Windows 
 x64 (with LLVM 3.6), but for a long time now, I am stuck on 
 something perhaps very simple.

 My test case is this program:
 int main() {
     try {
         throw new Exception("johan");
     } catch (Exception jow) {
     }
     return 0;
 }

 This crashes, and Visual Studio's debugger tells me it's 
 because of an unhandled exception. As far as I understand it, 
 we call RtlRaiseException() from _d_throw_exception() and that 
 should call the personality function _d_eh_personality(). 
 However, _d_eh_personality() is never entered. Instead, 
 RtlRaiseException() returns and the program crashes. I am stuck 
 on how to continue from here. I have tried many different 
 things, but I cannot get the OS to call _d_eh_personality().

 One thing that strikes me is that the exception code 
 STATUS_LDC_D_EXCEPTION is passed to RtlRaiseException(), but is 
 not used anywhere else in our source.
 Does LLVM not correctly register _d_eh_personality() with the 
 OS? Or is there some filtering done on the exception code?

 I'd appreciate any help.

 -Johan
Hi Johan! A quick check revealed: it works with current LLVM trunk but not with 3.6. I hvae no clue why. The connection between RtlRaiseException() and _d_eh_personality() is the unwind information. You can "disassemble" the unwind information with llvm-objdump -u. If the code range is wrong or some other data is corrupt then the personality function is not called. You should also disassemble the object file and check .xdata and .pdata sections. (The unwind information from LLVM 3.6 has no flag set. I believe that at least UNW_ExceptionHandler must be set.) Regards, Kai
Mar 24 2015
parent reply "kink" <noone nowhere.com> writes:
Also see 
https://github.com/ldc-developers/ldc/issues/758#issuecomment-76863220 
(I've used LLVM master, i.e., 3.7 at the time). It appears as if 
the broken EH accounts for nearly all Phobos failures on Win64 
and seriously corrupts the stack.

I've given up for the time being. I think it would be wiser to 
wait until LLVM supports MSVC exceptions, which is currently 
active work in progress, e.g., see 
http://reviews.llvm.org/rL232003 and 
http://www.llvm.org/docs/ExceptionHandling.html. We could then 
probably use MSVCRT's personality function __CxxFrameHandler3 or 
__C_specific_handler.
Mar 24 2015
parent reply "Johan Engelen" <j j.nl> writes:
On Tuesday, 24 March 2015 at 15:55:38 UTC, kink wrote:
 Also see 
 https://github.com/ldc-developers/ldc/issues/758#issuecomment-76863220 
 (I've used LLVM master, i.e., 3.7 at the time). It appears as 
 if the broken EH accounts for nearly all Phobos failures on 
 Win64 and seriously corrupts the stack.
Yep I had seen it. I was wondering how you got that far, and thought perhaps it had something to do with my build. (well, it _has_ something to do with my build using LLVM 3.6 :) Thanks for your hints Kai and kink. It gave me some new pointers. I'll bang my head against my monitor some more, and move to some other thing if that doesn't work. :) Johan
Mar 24 2015
parent reply "Kai Nacke" <kai redstar.de> writes:
On Tuesday, 24 March 2015 at 21:05:31 UTC, Johan Engelen wrote:
 Thanks for your hints Kai and kink. It gave me some new 
 pointers. I'll bang my head against my monitor some more, and 
 move to some other thing if that doesn't work.
Hi Johan, if you like to learn more about ldc then checkout the merge-2.067 branch and have have a look at issue #868. :-) Regards, Kai
Mar 24 2015
parent reply "Johan Engelen" <j j.nl> writes:
On Wednesday, 25 March 2015 at 05:46:07 UTC, Kai Nacke wrote:
 On Tuesday, 24 March 2015 at 21:05:31 UTC, Johan Engelen wrote:
 Thanks for your hints Kai and kink. It gave me some new 
 pointers. I'll bang my head against my monitor some more, and 
 move to some other thing if that doesn't work.
Hi Johan, if you like to learn more about ldc then checkout the merge-2.067 branch and have have a look at issue #868. :-)
Hi Kai, I've been working on something else :-) https://github.com/JohanEngelen/ldc/tree/coverage -Johan
Mar 29 2015
parent "Kai Nacke" <kai redstar.de> writes:
On Sunday, 29 March 2015 at 16:30:16 UTC, Johan Engelen wrote:
 On Wednesday, 25 March 2015 at 05:46:07 UTC, Kai Nacke wrote:
 On Tuesday, 24 March 2015 at 21:05:31 UTC, Johan Engelen wrote:
 Thanks for your hints Kai and kink. It gave me some new 
 pointers. I'll bang my head against my monitor some more, and 
 move to some other thing if that doesn't work.
Hi Johan, if you like to learn more about ldc then checkout the merge-2.067 branch and have have a look at issue #868. :-)
Hi Kai, I've been working on something else :-) https://github.com/JohanEngelen/ldc/tree/coverage -Johan
Hi Johan! Looks really nice! Looking forward to your pull request. :-) Regards, Kai
Mar 29 2015