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Date:      Sat, 7 Jun 2014 10:29:46 -0600
From:      Warner Losh <imp@bsdimp.com>
To:        Adrian Chadd <adrian@freebsd.org>
Cc:        "freebsd-arm@freebsd.org" <freebsd-arm@freebsd.org>, Ian Lepore <ian@freebsd.org>, Olavi Kumpulainen <olavi.m.kumpulainen@gmail.com>
Subject:   Re: C++ exceptions in freebsd-arm doesn't seem to work
Message-ID:  <0567DA73-DE37-48F0-BD18-F6498D6083A6@bsdimp.com>
In-Reply-To: <CAJ-Vmo=7VSZQH8NGBvYN015cV7WGcA=S2ELdpnmk798y98ydSQ@mail.gmail.com>
References:  <BEAC4CFB-EC4F-456D-8173-2E34CCE3A2C1@gmail.com> <1402156516.20883.154.camel@revolution.hippie.lan> <CAJ-VmomsNogAzk8j6ob8aA%2BmJeiO5TEF=FQnq=mNzsVPyt23xw@mail.gmail.com> <EEBA06F7-0CF1-4712-BA61-5951323B541B@bsdimp.com> <CAJ-Vmo=7VSZQH8NGBvYN015cV7WGcA=S2ELdpnmk798y98ydSQ@mail.gmail.com>

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On Jun 7, 2014, at 10:24 AM, Adrian Chadd <adrian@freebsd.org> wrote:

> On 7 June 2014 12:14, Warner Losh <imp@bsdimp.com> wrote:
>>=20
>> On Jun 7, 2014, at 10:07 AM, Adrian Chadd <adrian@FreeBSD.org> wrote:
>>=20
>>>> Sadly, all I can do is confirm what you say:  C++ exceptions don't =
work
>>>> on ARM EABI, not with clang and not with gcc.  The only combo that =
works
>>>> is gcc and OABI, but with that combo you lose hardware floating =
point.
>>>>=20
>>>> There are rumours that this may be fixed in clang 3.5, but we =
apparently
>>>> can't import 3.5 because it can't be bootstrapped using gcc 4.2.  I
>>>> haven't had time yet to learn how to build clang 3.5 out-of-tree to
>>>> confirm that exceptions work there.
>>>>=20
>>>=20
>>> If only we had a way to tell our build system to build the =
in-src-tree
>>> compiler suite using an external compiler toolchain. That'd make =
those
>>> problems go away.
>>=20
>> We do. It isn=92t perfect, and you=92d have to bootstrap either a new =
gcc or a 3.4 clang first to do it though. The automation of the =
bootstrapping isn=92t present, and is what I=92m working on=85
>=20
> Cool! The last time I wrangled this, I could only get it to build the
> whole system with the compiler I fed in. It wouldn't build the
> in-source-tree compiler with the external compiler I gave it - using
> the external compiler seemed to totally just negate building the
> toolchain. I'm glad this isn't the case.

It does take many hand-stands to doit...

>> Of course, it doesn=92t solve all the problems, just means we have =
more tools to deploy.
>>=20
>> 3.5 is also quite experimental as well.
>>=20
>> But there=92s been no real talk about the right path forward: just =
FUD and hand wringing on the lists. We do need to have a real discussion =
about this. Not the lame pot-shots that have happened to date: what =
versions do we support upgrading from, what configurations, etc. If we =
had that discussion, then we wouldn=92t even need what Adrian suggests. =
We=92d just say you have to have FreeBSD 9.2 or newer with clang 3.3 (or =
is it clang  3.4) to bootstrap, and if you want to use other tools, you =
are on your own. This would break updating from 8.x, but that=92s likely =
OK. Be we need to have this discussion.
>=20
> I'd personally like to rehash the "build from under Linux" discussion.
> I keep bumping into cases like this where a lot of the work being done
> to make this stuff happen is in line with what we need to be able to
> build FreeBSD under a non-FreeBSD operating system. I'd really like
> _that_ to happen - it'll help migrations _to_ freebsd from other
> projects.

No. Have that as a separate discussion.  That=92s a big bike shed of =
wonder and requires functionality not present in the tree (e.g. actual =
work). My discussion is =93we currently allow X to work, I want to =
change that to X+Y so we can import Z.=94 which is much smaller. So go =
ahead and have your linux discussion, but don=92t hijack mine.

Warner

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