From: Michael Felt <aixtools@felt.demon.nl>
To: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Cc: "brian m. carlson" <sandals@crustytoothpaste.net>,
git@vger.kernel.org, Dan Shumow <shumow@gmail.com>,
Junio C Hamano <gitster@pobox.com>, Jeff King <peff@peff.net>
Subject: Re: Is detecting endianness at compile-time unworkable?
Date: Tue, 31 Jul 2018 16:01:03 +0200 [thread overview]
Message-ID: <287cdba8-19c1-2fe8-4aff-d0385b38e92c@felt.demon.nl> (raw)
In-Reply-To: <87wotdt649.fsf@evledraar.gmail.com>
I hope a I have a "leap forward"
On 7/30/2018 11:39 AM, Ævar Arnfjörð Bjarmason wrote:
> Perhaps it's worth taking a step back here and thinking about whether
> this whole thing is unworkable. It was hard enough to get this to work
> on the combination of Linux, *BSD and Solaris, but I suspect we'll run
> into increasingly obscure platforms where this is hard or impossible
> (AIX, HP/UX etc.)
While I still cannot say for HP/UX it does seem there is a potential
solution based on the status for _LITTLE_ENDIAN and _BIG_ENDIAN. At
least, gcc on POWER and xlc on POWER provides one or the other - and my
hope is that gcc on other platforms also provides them.
For "other" compilers that do not provide them - a modification to
CFLAGS to define one or the other should make "make" work.
Details (note - I am not a programmer, so by definition at least one of
my "macros" will be wrong :)
AIX and xlc
root@x066:[/]xlc -qshowmacros -E /dev/null | grep -i endi
1506-297 (S) Unable to open input file null. A file or directory in the
path name does not exist..
#define __HHW_BIG_ENDIAN__ 1
#define __BIG_ENDIAN__ 1
#define __THW_BIG_ENDIAN__ 1
#define _BIG_ENDIAN 1
On SLES12 (le) and xlc
suse12test:~/images/littleEndian/sles # xlc -qshowmacros -dM -E x.c |
grep -i endi
#define _LITTLE_ENDIAN 1
#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__
#define __FLOAT_WORD_ORDER__ __ORDER_LITTLE_ENDIAN__
#define __LITTLE_ENDIAN__ 1
#define __ORDER_BIG_ENDIAN__ 4321
#define __ORDER_LITTLE_ENDIAN__ 1234
#define __ORDER_PDP_ENDIAN__ 3412
#define __VEC_ELEMENT_REG_ORDER__ __ORDER_LITTLE_ENDIAN__
Based on what I can see on gcc on POWER and xlc on POWER I think an
approach (simplified) can be:
#if undefined(_BIG_ENDIAN) && undef(_LITTLE_ENDIAN)
#error "one of _BIG_ENDIAN or _LITTLE_ENDIAN must be defined. Try adding
the correct value to CFLAGS"
#else defined(_BIG_ENDIAN) && defined(_LITTLE_ENDIAN)
#error "Only one of _BIG_ENDIAN and _LITTLE_ENDIAN may be defined, not both"
#endif
And then logic based on the value set.
This should also make cross-compile possible by unsetting an incorrect
default and setting the correct value.
p.s. Is there a setting I need to set somewhere so I receive a copy of
the email sent after it is received by the list. I could send myself a
copy, but I much prefer it comes from the maillist - as verification it
was received.
next prev parent reply other threads:[~2018-07-31 14:01 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-29 16:44 git broken for AIX somewhere between 2.13.2 and 2.13.3 Michael
2018-07-29 18:10 ` brian m. carlson
2018-07-29 19:46 ` Michael
2018-07-29 20:05 ` Ævar Arnfjörð Bjarmason
2018-07-29 21:40 ` Andreas Schwab
2018-07-30 6:22 ` Michael
[not found] ` <2309fa7f-c2d8-ee57-aff5-b9e32d2da609@felt.demon.nl>
[not found] ` <20180729192753.GD945730@genre.crustytoothpaste.net>
2018-07-29 19:48 ` Michael
2018-07-29 20:06 ` brian m. carlson
2018-07-29 20:50 ` Michael
2018-07-30 9:39 ` Is detecting endianness at compile-time unworkable? Ævar Arnfjörð Bjarmason
2018-07-30 14:54 ` Junio C Hamano
2018-07-30 18:32 ` Junio C Hamano
2018-07-30 18:39 ` Daniel Shumow
2018-07-31 10:06 ` Michael Felt
2018-08-01 1:35 ` Eric Wong
2018-08-01 7:16 ` Ævar Arnfjörð Bjarmason
2018-07-31 10:39 ` Michael Felt
2018-08-01 7:31 ` Ævar Arnfjörð Bjarmason
2018-08-02 20:50 ` [PATCH] sha1dc: update from upstream Ævar Arnfjörð Bjarmason
2018-08-02 21:29 ` Michael Felt (aixtools)
2018-08-02 21:32 ` Stefan Beller
2018-07-31 12:32 ` Is detecting endianness at compile-time unworkable? Michael Felt
2018-07-31 14:01 ` Michael Felt [this message]
2018-07-31 14:25 ` Ævar Arnfjörð Bjarmason
2018-07-31 20:06 ` Michael
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