From: Joseph Myers <joseph@codesourcery.com>
To: Steve Ellcey <sellcey@cavium.com>
Cc: Martin Sebor <msebor@gmail.com>,
Gcc Patch List <gcc-patches@gcc.gnu.org>,
Jonathan Wakely <jwakely@redhat.com>,
libstdc++ <libstdc++@gcc.gnu.org>
Subject: Re: [PATCH] detect incompatible aliases (PR c/81854)
Date: Wed, 20 Sep 2017 18:14:00 -0000 [thread overview]
Message-ID: <alpine.DEB.2.20.1709201809200.18346@digraph.polyomino.org.uk> (raw)
In-Reply-To: <1505930878.2286.117.camel@cavium.com>
[-- Attachment #1: Type: text/plain, Size: 1493 bytes --]
On Wed, 20 Sep 2017, Steve Ellcey wrote:
> On Wed, 2017-09-20 at 18:01 +0000, Joseph Myers wrote:
> >Â
> > (It may nevertheless be a good idea to setÂ
> > default_gnu_indirect_function=yes for AArch64 configurations in GCC
> > thatÂ
> > use glibc.)
> >
>
> I have submitted a patch for that.
>
> https://gcc.gnu.org/ml/gcc-patches/2017-09/msg00285.html
I'm not entirely convinced the architecture conditions make sense there.
The problem case is: binutils gains support for IFUNCs for an architecture
that didn't previously have them. glibc detects the support, but cannot
use IFUNC attributes with any existing GCC version for that architecture
because GCC didn't know that binutils would gain that support. That means
existing GCC versions unnecessarily cannot build glibc with new binutils
for that architecture. (You could make the multi-arch support test check
for IFUNC attribute support so multi-arch just gets disabled in that case,
but it would be better to be able to build with existing GCC versions.)
I.e. what I think would be better is: compiler support depends on the
target OS, and make sure the linker gives a clear error (even better, that
the assembler does so) if you try to build something with IFUNCs on an
architecture without support. (If the linker / assembler don't already
give such errors you could choose to keep architecture conditionals when
building GCC with older binutils versions.)
--
Joseph S. Myers
joseph@codesourcery.com
next prev parent reply other threads:[~2017-09-20 18:14 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-18 8:10 Martin Sebor
2017-08-18 13:10 ` Joseph Myers
2017-08-18 13:57 ` Jonathan Wakely
2017-08-18 18:22 ` Martin Sebor
2017-08-18 18:37 ` Jonathan Wakely
2017-08-18 21:02 ` Martin Sebor
2017-09-02 22:50 ` [PING] " Martin Sebor
2017-09-12 16:17 ` Joseph Myers
2017-09-18 21:21 ` Martin Sebor
2017-09-18 21:44 ` Joseph Myers
2017-09-19 15:16 ` Martin Sebor
2017-09-20 15:37 ` Steve Ellcey
2017-09-20 16:17 ` Martin Sebor
2017-09-20 16:38 ` Steve Ellcey
2017-09-20 17:23 ` Steve Ellcey
2017-09-20 17:32 ` Martin Sebor
2017-09-20 17:45 ` Steve Ellcey
2017-09-20 18:05 ` Joseph Myers
2017-09-20 18:01 ` Joseph Myers
2017-09-20 18:08 ` Steve Ellcey
2017-09-20 18:14 ` Joseph Myers [this message]
2017-09-20 21:01 ` Joseph Myers
2017-09-20 21:32 ` Martin Sebor
2017-09-20 21:45 ` Joseph Myers
2017-10-02 19:49 ` Steve Ellcey
2017-10-02 19:53 ` Joseph Myers
2017-10-02 20:17 ` Martin Sebor
2017-10-03 21:41 ` Andreas Schwab
2017-10-03 23:43 ` Martin Sebor
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