Subject: Re: Building for Sparc32



On 01/01/2017 11:23 PM, eddie_cottongim eddie_cottongim wrote:
> I realize this is probably a bad idea for many reasons, and likely a dead end
> at some point, as low level support has been dropped at some point in the
> kernel
> and it appears to have problems in gcc. But maybe a leap forward of 5-10
> years is possible.

One problem with SPARCv8 (which this machine type uses) is that it does not
support the compare-and-swap
instruction (CAS) which means that lock-free atomics are not possible on these
machines. However, lock-free
atomics are required for proper C++11 support. Thus, when you compile gcc on
SPARC with anything older than v9,
you will not be able to use std::future which also a problem Debian's armel
port is facing and which is
one of the reasons why the port is most likely going to be removed from Debian
10 (Codename: Buster) [1].

There are ways to emulate these atomics with helper functions in the kernel
[2], however, I don't know
how much effort it is and you probably need more than one active porter to
achieve this.

Adrian

> [1] https://lists.debian.org/debian-devel/2016/12/msg00141.html
> [2] https://stuff.mit.edu/afs/sipb/contrib/linux/Documentation/atomic_ops.txt

--
.''`. John Paul Adrian Glaubitz
: :' : Debian Developer - [email protected]
`. `' Freie Universitaet Berlin - [email protected]
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