Date: Fri, 18 Nov 2016 20:23:28 +0000
From: Brooks Davis <brooks@freebsd.org>
To: Paul Eggert <eggert@cs.ucla.edu>
Cc: Ashish SHUKLA <ashish.is@lostca.se>, freebsd-hackers@freebsd.org, 24892@debbugs.gnu.org
Subject: Re: bug#24892: {s, }brk removed from FreeBSD 11.x and later, arm64 architecture
Message-ID: <20161118202328.GA79070@spindle.one-eyed-alien.net>
In-Reply-To: <5ec481c4-41e1-c7dd-433d-f533653b132f@cs.ucla.edu>
References: <c9396165-da2e-3c41-ec2b-070ce9c885bb@cs.ucla.edu> <mvmtwbfachr.fsf@hawking.suse.de> <40f8df50-b431-1ebd-221c-df2aa453aa81@cs.ucla.edu> <mvmfumz8e2u.fsf@hawking.suse.de> <06ee71fd-1a64-d32b-862e-c725807aef4e@cs.ucla.edu> <mvm60nv8cky.fsf@hawking.suse.de> <876cf047-82fb-f08c-bbb3-024206f6fabd@cs.ucla.edu> <83twb6dnkm.fsf@gnu.org> <8637ipm0nb.fsf@lostca.se> <5ec481c4-41e1-c7dd-433d-f533653b132f@cs.ucla.edu>
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--envbJBWh7q8WU6mo Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Nov 18, 2016 at 08:21:04AM -0800, Paul Eggert wrote: > Ashish SHUKLA wrote: >=20 > > One of the FreeBSD developer has > > pointed me to this ongoing discussion[1] on freebsd-hackers@ list. > > > > References: > > [1] https://lists.freebsd.org/pipermail/freebsd-hackers/2016-November/= 050144.html >=20 > OK, thanks, I'll CC: freebsd-hackers. FreeBSD hackers: this is following = up on=20 > this serious Emacs bug report, which says that Emacs no longer works on F= reeBSD=20 > 11.x arm64: >=20 > https://bugs.gnu.org/24892 >=20 > The referenced FreeBSD discussion appears to be under the misapprehension= that=20 > sbrk is useful only to estimate how much memory is in use, and since this= use=20 > has long been wrong sbrk should be unceremoniously removed. Unfortunately= , this=20 > assumption is incorrect for Emacs, as (bleeding-edge) Emacs uses its own= =20 > allocator during its build process, and reverts to malloc only during use= r=20 > operation. (The build-time Emacs makes a copy of itself in a new executab= le, and=20 > relies on sbrk during the build.) Obviously this is dicey and we are plan= ning to=20 > change Emacs to make it more portable; however, this will require nontriv= ial=20 > reengineering on our part. >=20 > In the meantime we respectfully request that sbrk functionality be kept i= n=20 > FreeBSD 11.x arm64 for a while. It is fine to mark it as deprecated or ob= solete,=20 > or even rename it, but please do not remove the functionality entirely. Under FreeBSD's stability rules if we shipped ANY release for a platforms (e.g. arm64, riscv) with a system call, we must support it for the life of the architecture (approximately FOREVER). As such, if any other solution is viable, we'd prefer that. What does emacs actually need from sbrk()? Could it get by with something with the same interface allocating from .bss or does it need its allocations to be at the end of .bss? I'm happy to put some time into a userspace workaround if one is viable. -- Brooks --envbJBWh7q8WU6mo Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEcBAEBAgAGBQJYL2M/AAoJEKzQXbSebgfAIWkH/1lRbnad9HgqjZzmWERuV9hn NqlZjygWmyALFvLnmTQPlEYK0MIWoVKlyRkozd7Okd4CEN5gvgOA/NilDLGktkuF 5Cttp5x9CxhXKOHJS0bABs1jEqXXgCz3B9GnWoDQ2u7JxLdv4UTretvFTBAlgY4G rljgv3B2NGa2+PrvON1cKmmMPJnn/lGkrNr2bOkOYmQFuMgI0XcqpszbxQYfeR2R /zCibyTIAYELxu2fBFJxf5WO5VE7yUkP+hzeTL0DVSGalQgQ4pkTTVUsJaV8uSr+ ++TjPzDqUONgQmr+WKxqwg89Yd/JUdL2OARbpnywqlZeahKxJTXy1w9RfnO1pxI= =IA5Z -----END PGP SIGNATURE----- --envbJBWh7q8WU6mo--
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