C++ exceptions in freebsd-arm doesn't seem to work

[Olavi Kumpulainen]

On 20 Aug 2014, at 21:19 , Ian Lepore <ian at FreeBSD.org> wrote:

> On Wed, 2014-08-20 at 19:19 +0200, Olavi Kumpulainen wrote:
>> On 19 Aug 2014, at 20:21 , Ian Lepore <ian at FreeBSD.org> wrote:
>> 
>>> On Tue, 2014-08-19 at 19:40 +0200, Olavi Kumpulainen wrote:
>>>> On 25 Jul 2014, at 23:44 , Andreas Tobler <andreast-list at fgznet.ch> wrote:
>>>> 
>>>>> On 22.07.14 23:11, Ian Lepore wrote:
>>>>>> On Sat, 2014-07-19 at 16:35 -0600, Ian Lepore wrote:
>>>>>>> On Sat, 2014-06-07 at 14:12 +0200, Olavi Kumpulainen wrote:
>>>>>>>> [c++ exceptions don't work and related discussion]
>>>>>>> 
>>>>>>> I checked in a partial fix for c++ exception handling in r268893.  It
>>>>>>> fixes the specific problem you detailed above, which was essentially
>>>>>>> that the __gnu_Unwind_Find_exidx() function was not available in any
>>>>>>> shared library, making the unwinder fall back to using the __exidx_start
>>>>>>> and end symbols, which are only valid in a statically-linked app.
>>>>>>> 
>>>>>>> With the new function in place, exceptions are closer to working with
>>>>>>> gcc 4.2.1, but still don't work with clang.  With gcc, some things work
>>>>>>> and some things don't.  For example if you throw an exception and in the
>>>>>>> same function have a catch with the right specific type it segfaults,
>>>>>>> but a catch(...) will catch it without problems.  But you can catch an
>>>>>>> exception by type if the catch is in a function higher up the call chain
>>>>>>> from the place it was thrown.
>>>>>>> 
>>>>>>> We're continuing to debug this at $work, and welcome any input if anyone
>>>>>>> else makes progress with it.  Right now we still don't know whether the
>>>>>>> segfaults are because of bad unwinder library code or bad unwind data
>>>>>>> emitted by gcc.  (I sure hope it's the library, because that's easier to
>>>>>>> fix.)
>>>>>>> 
>>>>>>> On the clang front, it has been said that c++ exceptions work in clang
>>>>>>> 3.5, so we tried the clang-devel port, and it didn't just work.  But it
>>>>>>> turns out that port hasn't been updated for quite a while, so we may not
>>>>>>> have tested the code that's supposed to work right.  While trying that I
>>>>>>> discovered that clang 3.5 isn't scheduled for release for about another
>>>>>>> year, so that really isn't a viable solution for anyone with near-term
>>>>>>> needs, unless the required changes can be cherry-picked and brought into
>>>>>>> our version of 3.4.
>>>>>>> 
>>>>>>> -- Ian
>>>>>> 
>>>>>> Another update to this... today I committed r268993 and r268994, and now
>>>>>> I believe arm eabi c++ exceptions are fully working with gcc.  I haven't
>>>>>> run an extensive test suite, but all the test cases we've been using at
>>>>>> $work to debug this now work correctly.
>>>>> 
>>>>> Thank you! Confirmed. My test cases which are working with gcc-4.10 are now also working with the system gcc, 4.2.1.
>>>>> I totally forgot about this change. I have it in my local gcc tree since a while but I forgot about.....
>>>>> 
>>>>> Andreas
>>>>> 
>>>>> 
>>>> 
>>>> Please excuse my late reply. I’ve been away from keyboard for a while.
>>>> 
>>>> I back-ported r268893,  r268993 and r268994 to stable/10 for beaglebone. C++ exceptions works for static builds, but not for binaries linked to shared libs.
>>>> 
>>>> Since this seems to work ok in HEAD, I’m obviously missing something. Do any of you guys have any ideas?
>>>> 
>>>> Cheers
>>>> 
>>> 
>>> I'm not sure what you mean by "backported to stable/10", I merged all
>>> the necessary changes to stable-10 as r269792 on Aug 10.  Are you
>>> working with a checkout from earlier than that?  If so, just updating
>>> should fix it for you.
>>> 
>>> -- Ian
>>> 
>>> 
>> 
>> 
>> Updating to stable-10 as of today didn’t help. I’m running a clean checkout except for a couple of drivers in the kernel.
>> This makes me think I have a bad src.conf - How shall I configure the build for this to work?
>> 
>> /Olavi
>> 
>> 
>> 
>> 
> 
> You need to use GCC, not clang, as the compiler.  Exceptions are just
> broken on clang 3.4, so we're waiting for 3.5 (should be released any
> time now I think).
> 
> To compile with gcc, put this in your /etc/make.conf:
> 
> WITH_GCC=yes
> WITH_GNUCXX=yes
> WITH_GCC_BOOTSTRAP=yes
> WITHOUT_CLANG=yes
> WITHOUT_CLANG_IS_CC=yes
> WITHOUT_CLANG_BOOTSTRAP=yes
> 
> -- Ian
> 
> 


Thank you. It turned out that I already used these with the exception of WITHOUT_CLANG_BOOTSTRAP.

However, c++ exceptions in stable/10 is still defunct when I build it. 

So instead I pulled master, built and installed that instead. And voila - Exceptions do work! 

Therefore it seems my build method, flags and environment is ok after all. I glanced the commit logs in master but didn’t find anything obvious, but still; something related seems missing in stable/10 if you ask me.

/Olavi