We need a libunwind expert to figure out a good approach for handling exceptions thrown by C++ code into D.

Is anyone fluent with libunwind?


Andrei

On Tuesday, 23 September 2014 at 17:37:42 UTC, Andrei Alexandrescu wrote:
> We need a libunwind expert to figure out a good approach for handling exceptions thrown by C++ code into D.
>
> Is anyone fluent with libunwind?

More or less.

What exactly are your goals? I thought the options we have are fairly clear, as discussed a few days ago. At least, Amaury and I seemed to agree (both of us worked on EH recently). The main question to decide is whether you want to go down the catch-C++-exceptions-in-D rabbit hole.

David

On Tuesday, 23 September 2014 at 18:03:18 UTC, David Nadlinger wrote:
> On Tuesday, 23 September 2014 at 17:37:42 UTC, Andrei Alexandrescu wrote:
>> We need a libunwind expert to figure out a good approach for handling exceptions thrown by C++ code into D.
>>
>> Is anyone fluent with libunwind?
> […]
> The main  question to decide is whether you want to go
> down the catch-C++-exceptions-in-D rabbit hole.

Let me also note that if you do, it's no longer a question of just libunwind, but also of C++ runtime internals. I assume your primary target is g++ on Linux x86/x86_64?

David

On 9/23/14, 11:03 AM, David Nadlinger wrote:
> On Tuesday, 23 September 2014 at 17:37:42 UTC, Andrei Alexandrescu wrote:
>> We need a libunwind expert to figure out a good approach for handling
>> exceptions thrown by C++ code into D.
>>
>> Is anyone fluent with libunwind?
>
> More or less.
>
> What exactly are your goals? I thought the options we have are fairly
> clear, as discussed a few days ago. At least, Amaury and I seemed to
> agree (both of us worked on EH recently). The main question to decide is
> whether you want to go down the catch-C++-exceptions-in-D rabbit hole.

I think we should explore that rabbit hole. In the interim, a simpler solution may work: a C++ exception can only be caught from within C++ code. If no handler, the program terminates reliably. -- Andrei

On 9/23/14, 11:06 AM, David Nadlinger wrote:
> On Tuesday, 23 September 2014 at 18:03:18 UTC, David Nadlinger wrote:
>> On Tuesday, 23 September 2014 at 17:37:42 UTC, Andrei Alexandrescu wrote:
>>> We need a libunwind expert to figure out a good approach for handling
>>> exceptions thrown by C++ code into D.
>>>
>>> Is anyone fluent with libunwind?
>> […]
>> The main  question to decide is whether you want to go
>> down the catch-C++-exceptions-in-D rabbit hole.
>
> Let me also note that if you do, it's no longer a question of just
> libunwind, but also of C++ runtime internals. I assume your primary
> target is g++ on Linux x86/x86_64?

Yes. -- Andrei

On 9/23/2014 11:03 AM, David Nadlinger wrote:
> On Tuesday, 23 September 2014 at 17:37:42 UTC, Andrei Alexandrescu wrote:
>> We need a libunwind expert to figure out a good approach for handling
>> exceptions thrown by C++ code into D.
>>
>> Is anyone fluent with libunwind?
>
> More or less.
>
> What exactly are your goals? I thought the options we have are fairly clear, as
> discussed a few days ago. At least, Amaury and I seemed to agree (both of us
> worked on EH recently). The main question to decide is whether you want to go
> down the catch-C++-exceptions-in-D rabbit hole.

One goal is to have dmd use the g++ exception handling mechanism. But googling how that works, I find dead links, specs that are 15 years old accompanied by vague comments about it being "extended" and "look at the g++ source code", etc.

Are there any actual docs about how it works for x86? Or is it the usual "take apart the output of g++ and figure it out" that I usually wind up doing :-( ?

I believe pretty much anything *ix on 64-bit(at least) x86 (32-bit gets a
bit murkier due to historical issues) is using the same exception handling
ABI (which itself was based off the Itanic ABI):

http://www.x86-64.org/documentation/abi.pdf



On Tue, Sep 23, 2014 at 1:31 PM, Walter Bright via Digitalmars-d < digitalmars-d@puremagic.com> wrote:

> On 9/23/2014 11:03 AM, David Nadlinger wrote:
>
>> On Tuesday, 23 September 2014 at 17:37:42 UTC, Andrei Alexandrescu wrote:
>>
>>> We need a libunwind expert to figure out a good approach for handling exceptions thrown by C++ code into D.
>>>
>>> Is anyone fluent with libunwind?
>>>
>>
>> More or less.
>>
>> What exactly are your goals? I thought the options we have are fairly
>> clear, as
>> discussed a few days ago. At least, Amaury and I seemed to agree (both of
>> us
>> worked on EH recently). The main question to decide is whether you want
>> to go
>> down the catch-C++-exceptions-in-D rabbit hole.
>>
>
> One goal is to have dmd use the g++ exception handling mechanism. But googling how that works, I find dead links, specs that are 15 years old accompanied by vague comments about it being "extended" and "look at the g++ source code", etc.
>
> Are there any actual docs about how it works for x86? Or is it the usual "take apart the output of g++ and figure it out" that I usually wind up doing :-( ?
>
>

On 9/23/2014 11:58 AM, Jason King via Digitalmars-d wrote:
> I believe pretty much anything *ix on 64-bit(at least) x86 (32-bit gets a bit
> murkier due to historical issues) is using the same exception handling ABI
> (which itself was based off the Itanic ABI):
>
> http://www.x86-64.org/documentation/abi.pdf

Thanks, this contains part of the info.

On 2014-09-23 20:31, Walter Bright wrote:

> One goal is to have dmd use the g++ exception handling mechanism.

That would be cool. It's useful for Objective-C on x86-64 as well.

> But googling how that works, I find dead links, specs that are 15 years old
> accompanied by vague comments about it being "extended" and "look at the
> g++ source code", etc.
>
> Are there any actual docs about how it works for x86? Or is it the usual
> "take apart the output of g++ and figure it out" that I usually wind up
> doing :-( ?

From the LLVM docs [1]:

A more complete description of the Itanium ABI exception handling runtime support of can be found at Itanium C++ ABI: Exception Handling [2]. A description of the exception frame format can be found at Exception Frames [3], with details of the DWARF 4 specification at DWARF 4 Standard [4]. A description for the C++ exception table formats can be found at Exception Handling Tables [5].

[1] http://llvm.org/docs/ExceptionHandling.html#itanium-abi-zero-cost-exception-handling

[2] http://mentorembedded.github.com/cxx-abi/abi-eh.html

[3] http://refspecs.linuxfoundation.org/LSB_3.0.0/LSB-Core-generic/LSB-Core-generic/ehframechpt.html

[4] http://dwarfstd.org/Dwarf4Std.php

[5] http://mentorembedded.github.com/cxx-abi/exceptions.pdf

-- 
/Jacob Carlborg

On 9/23/2014 12:57 PM, Jacob Carlborg wrote:
>  From the LLVM docs [1]:

Thank you. This is helpful.