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Date: Wed, 24 Jun 2015 14:10:06 +0000
From: Joseph Myers <joseph@...esourcery.com>
To: Rich Felker <dalias@...c.org>
CC: Rob Landley <rob@...dley.net>, <musl@...ts.openwall.com>,
	<libc-alpha@...rceware.org>, <linux-sh@...r.kernel.org>
Subject: Re: SH sigcontext ABI is broken

On Wed, 24 Jun 2015, Rich Felker wrote:

> Nominally SH3 support remains in both the kernel and glibc. If it can
> be established that multiple parties agree that there's really no one
> left who cares about the old no-FPU sigcontext ABI on SH3, I will be
> all for dropping it and unifying sigcontext.

Note that right now we have BE and LE versions of *three* ABIs for SH in 
glibc (SH3 soft-float, SH4 soft-float, SH4 hard-float) (and as noted in 
this discussion, right now each would only work properly on a kernel with 
the corresponding configuration).  See 
<https://sourceware.org/glibc/wiki/ABIList>.

We can, of course, choose to declare processor or ABI variants no longer 
supported in glibc, much like we desupported i386 in glibc (requiring i486 
or later - albeit the official desupporting happening several years after 
i386 would no longer build) or removed support for non-EABI ARM.  But 
since we don't have an SH maintainer at all in glibc at present, it's 
harder to make such a decision (whereas if an architecture maintainer 
decided some variants were no longer relevant, they could just remove 
support - make those variants give a configure-time error - in the absence 
of someone objecting and willing to take over maintaining support for 
those variants).

I think the next glibc change likely to require action from each 
architecture's maintainer to avoid breaking the build may be Adhemerval's 
cancellation changes - so if no-one comes forward as SH maintainer to at 
least update SH for those changes when they are ready to go in, the build 
for SH will be broken and that will indicate, as per 
<https://sourceware.org/ml/libc-alpha/2015-06/msg00424.html>, that it may 
be time to remove the port from glibc.

-- 
Joseph S. Myers
joseph@...esourcery.com

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