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Re: Systems that can't USE_LSB_TAG
From: |
Paul Eggert |
Subject: |
Re: Systems that can't USE_LSB_TAG |
Date: |
Tue, 15 Apr 2014 22:25:42 -0700 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 |
Stefan Monnier wrote:
Hmmm.. so with this patch we fail on all hosts where USE_LSB_TAG can't
be used, even those where DATA_SEG_BITS is not needed.
Yes, that's why I originally went for the wide-int fallback.
Which systems currently can't USE_LSB_TAG?
Only IRIX as far as I know. Specifically, the list includes:
1. Systems with pre-C11 compilers that are not in the following list:
GCC, HP, IBM, Intel, Sun/Oracle, Microsoft, plus any mimics of these
(such as clang). Fundamentally we need the equivalent of GCC's
attribute ((aligned (8))) and/or C11's _Alignas (8).
2. Systems where we must use the system malloc and it doesn't return a
multiple of 8.
The only category (1) system I know of is IRIX cc, which SGI stopped
supporting in December. I don't know of any category (2) systems.
I don't know all the Emacs porting targets and quite possibly I've
missed some. Perhaps other unusual systems are in category (1); most
likely we could port to them if we knew the right incantation to get an
_Alignas equivalent on their compiler, and if not we could fall back on
aligning the static C variables some other way. We could port to
category (2) systems (if any practical ones exist) by wrapping
malloc/free/etc. and losing at most 8 bytes per allocation. I hope we
needn't use either hack, though.
- Re: [Emacs-diffs] emacs-24 r116961: Port to IRIX 6.5., Stefan Monnier, 2014/04/14
- Re: [Emacs-diffs] emacs-24 r116961: Port to IRIX 6.5., Paul Eggert, 2014/04/14
- Re: [Emacs-diffs] emacs-24 r116961: Port to IRIX 6.5., Stefan Monnier, 2014/04/14
- Re: [Emacs-diffs] emacs-24 r116961: Port to IRIX 6.5., Paul Eggert, 2014/04/14
- Re: [Emacs-diffs] emacs-24 r116961: Port to IRIX 6.5., Stefan Monnier, 2014/04/15
- Re: [Emacs-diffs] emacs-24 r116961: Port to IRIX 6.5., Paul Eggert, 2014/04/15
- Re: [Emacs-diffs] emacs-24 r116961: Port to IRIX 6.5., Stefan Monnier, 2014/04/15
- Re: [Emacs-diffs] emacs-24 r116961: Port to IRIX 6.5., Paul Eggert, 2014/04/15
- Systems that can't USE_LSB_TAG, Stefan Monnier, 2014/04/15
- Re: Systems that can't USE_LSB_TAG,
Paul Eggert <=
- Re: Systems that can't USE_LSB_TAG, Stefan Monnier, 2014/04/16