Date: Wed, 20 Aug 2014 13:19:52 -0600 From: Ian Lepore <ian@FreeBSD.org> To: Olavi Kumpulainen <olavi.m.kumpulainen@gmail.com> Cc: freebsd-arm@freebsd.org Subject: Re: C++ exceptions in freebsd-arm doesn't seem to work Message-ID: <1408562392.1150.4.camel@revolution.hippie.lan> In-Reply-To: <F4EE79A6-9D99-4EE1-9452-2C7ECF963646@gmail.com> References: <BEAC4CFB-EC4F-456D-8173-2E34CCE3A2C1@gmail.com> <1405809318.85788.35.camel@revolution.hippie.lan> <1406063473.71975.8.camel@revolution.hippie.lan> <53D2CFBE.3040207@fgznet.ch> <834BA562-84ED-425C-9D61-0A235A28A94A@gmail.com> <1408472517.56408.659.camel@revolution.hippie.lan> <F4EE79A6-9D99-4EE1-9452-2C7ECF963646@gmail.com>
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On Wed, 2014-08-20 at 19:19 +0200, Olavi Kumpulainen wrote: > On 19 Aug 2014, at 20:21 , Ian Lepore <ian@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@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 -- Ianhelp
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