linux-kernel - Re: x32 and width of blksize_t, suseconds

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Message-ID: <Pine.LNX.4.64.1203161435530.31619@digraph.polyomino.org.uk>
Date:	Fri, 16 Mar 2012 14:45:44 +0000 (UTC)
From:	"Joseph S. Myers" <joseph@...esourcery.com>
To:	"H. Peter Anvin" <hpa@...or.com>
cc:	Paul Eggert <eggert@...ucla.edu>, "H.J. Lu" <hjl.tools@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	GNU C Library <libc-alpha@...rceware.org>
Subject: Re: x32 and width of blksize_t, suseconds_t

On Fri, 16 Mar 2012, H. Peter Anvin wrote:

> On 03/16/2012 01:19 AM, Paul Eggert wrote:
> > Come to think of it, the proposed x32 patch may have issues
> > with blksize_t and suseconds_t as well.  POSIX says that an x32
> > implementation must support at least one programming environment
> > (presumably settable via a feature test macro) where blksize_t
> > and suseconds_t are no wider than 'long'; see
> > <http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/sys_types.h.html>.
> > But if I understand things correctly, x32 glibc would
> > define these to be 'long long'.  This issue affects system
> > calls such as 'stat' and 'select'.
> 
> That's just not going to happen, sorry.  Why on Earth is this a
> requirement?  It makes no sense whatsoever.

It's probably to support code written for C90.  Note that it's the 
POSIX-conforming system as a whole that is to support such an environment 
- but it might be an environment that uses the traditional 32-bit or 
64-bit ABIs, it needn't be one using the x32 ABI.  "getconf 
POSIX_V7_WIDTH_RESTRICTED_ENVS" must print the names of the environments 
meeting this requirement; if one is "POSIX_V7_ILP32_OFF32", for example, 
then "getconf POSIX_V7_ILP32_OFF32_CFLAGS" will print the flags (maybe 
-m32) and likewise for _LDFLAGS and _LIBS.  In glibc this means defining 
appropriate macros in bits/environment.h to give the right flags - and 
also probably changing posix/confstr.c which has comments saying 
"Currently this means all environment which the system allows." (the x32 
patch series may need to adjust this in some way).

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