From: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
To: Junio C Hamano <gitster@pobox.com>
Cc: git@vger.kernel.org, Jeff King <peff@peff.net>,
Michael Kebe <michael.kebe@gmail.com>,
"Liam R . Howlett" <Liam.Howlett@Oracle.com>,
Adam Dinwoodie <adam@dinwoodie.org>,
Stefan Beller <sbeller@google.com>
Subject: Re: [PATCH 1/3] sha1dc: update from my PR #36
Date: Tue, 27 Jun 2017 21:35:09 +0200 [thread overview]
Message-ID: <87r2y5jkb6.fsf@gmail.com> (raw)
In-Reply-To: <xmqq7ezx1c31.fsf@gitster.mtv.corp.google.com>
On Tue, Jun 27 2017, Junio C. Hamano jotted:
> Ævar Arnfjörð Bjarmason <avarab@gmail.com> writes:
>
>> Because in the current code is, abbreviated:
>>
>> #if (defined(_BYTE_ORDER) || defined(__BYTE_ORDER) || defined(__BYTE_ORDER__))
>> #if /* byte order is bendian */
>> #define SHA1DC_BIGENDIAN
>> #endif
>> #else
>> #if /*some processor tests/* || defined(__sparc))
>> #define SHA1DC_BIGENDIAN
>> #endif
>>
>> And since Solaris defines _BYTE_ORDER we never get to checking __sparc,
>> and in fact the "/* byte order is bendian */" test errors out.
>>
>> This is fixed by my patch, where we first check gcc settings, then
>> glibc, then processors, and finally _BYTE_ORDER (but as discussed that
>> last bit could be adjusted to sun && _BYTE_ORDER, if we can find what
>> "sun" is.
>
> Well, if Solaris defines _BYTE_ORDER, doesn't that mean they define
> two constants _BIG_ENDIAN and _LITTLE_ENDIAN to compare it with?
No, under gcc/clang & glibc you're expected to compare them. Under
Solaris it's just defined(_BIG_ENDIAN), but as explained in another
comment this whole thing actually turns out to be not needed, on Solaris
it's sufficient that we fall through and check __sparc.
> that is the case, I suspect that the change to make "comparison
> between __BYTE_ORDER and __BIG_ENDIAN for GCC only" is going in a
> wrong direction, as it wants to take the same approach as GCC, but
> just uses a slightly different symbol.
>
> I wonder if the approach like the following might be cleaner to
> extend as we find other oddball platforms.
>
> #undef __SHA1DC_BYTE_ORDER
> #if defined(_BYTE_ORDER)
> #define __SHA1DC_BYTE_ORDER _BYTE_ORDER
> #elif defined(__BYTE_ORDER)
> #define __SHA1DC_BYTE_ORDER __BYTE_ORDER
> #elif defined(__BYTE_ORDER__))
> #define __SHA1DC_BYTE_ORDER __BYTE_ORDER__
> #endif
>
> #ifdef __SHA1DC_BYTE_ORDER
> #undef __SHA1DC_BIG_ENDIAN
> /* do the same for variations of BIG_ENDIAN constant */
> #if defined(_BIG_ENDIAN)
> ...
> #endif
>
> #if __SHA1DC_BYTE_ORDER == __SHA1DC_BIG_ENDIAN
> #define SHA1DC_BIGENDIAN
> #endif
As explained above no, because some e.g. _BIG_ENDIAN don't have a value
at all.
But more generally we can't assume that we can just exhaustively search
for some ^_*BIG_ENDIAN_*$ macro and compare it with some
^_*BYTE_ORDER_*$ value and get an expected result.
> #else
> /*
> * as the platform does not use "compare BYTE-ORDER with
> * BIG_ENDIAN macro" strategy, defined-ness of BIG_ENDIAN
> * may be usable as a sign that it is a big-endian box.
> */
> #endif
next prev parent reply other threads:[~2017-06-27 19:35 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-26 7:32 Compile Error v2.13.2 on Solaris SPARC Michael Kebe
[not found] ` <87lgofcf7r.fsf@gmail.com>
2017-06-26 12:36 ` Michael Kebe
2017-06-26 12:47 ` Ævar Arnfjörð Bjarmason
2017-06-26 14:00 ` Michael Kebe
2017-06-26 18:31 ` Ævar Arnfjörð Bjarmason
2017-06-26 18:29 ` Liam R. Howlett
[not found] ` <87fuem7aw2.fsf@gmail.com>
2017-06-27 5:41 ` Michael Kebe
2017-06-27 6:28 ` Michael Kebe
2017-06-27 16:28 ` Liam R. Howlett
2017-06-27 17:38 ` Junio C Hamano
2017-06-27 18:29 ` Liam R. Howlett
2017-06-27 18:55 ` Ævar Arnfjörð Bjarmason
2017-06-27 17:59 ` Ævar Arnfjörð Bjarmason
2017-06-27 12:17 ` [PATCH 0/3] update sha1dc from PR #36 Ævar Arnfjörð Bjarmason
2017-06-27 18:37 ` Stefan Beller
2017-06-27 20:33 ` [PATCH v2 " Ævar Arnfjörð Bjarmason
2017-06-27 21:37 ` Junio C Hamano
2017-06-27 21:38 ` Junio C Hamano
2017-06-27 22:24 ` Ævar Arnfjörð Bjarmason
2017-06-28 21:42 ` Ævar Arnfjörð Bjarmason
2017-06-28 22:02 ` Junio C Hamano
2017-06-27 20:33 ` [PATCH v2 1/3] sha1dc: correct endian detection for Solaris (and others?) Ævar Arnfjörð Bjarmason
2017-06-27 20:33 ` [PATCH v2 2/3] sha1dc: optionally use sha1collisiondetection as a submodule Ævar Arnfjörð Bjarmason
2017-06-27 20:33 ` [PATCH v2 3/3] sha1collisiondetection: automatically enable when submodule is populated Ævar Arnfjörð Bjarmason
2017-07-01 22:05 ` [PATCH v3 0/3] Update sha1dc from upstream Ævar Arnfjörð Bjarmason
2017-07-01 22:05 ` [PATCH v3 1/3] sha1dc: update " Ævar Arnfjörð Bjarmason
2017-07-01 22:05 ` [PATCH v3 2/3] sha1dc: optionally use sha1collisiondetection as a submodule Ævar Arnfjörð Bjarmason
2017-07-03 17:11 ` Junio C Hamano
2017-07-03 20:29 ` Ævar Arnfjörð Bjarmason
2017-07-04 17:26 ` Junio C Hamano
2017-07-04 22:50 ` Ævar Arnfjörð Bjarmason
2017-07-05 0:36 ` Stefan Beller
2017-07-05 1:56 ` Junio C Hamano
2017-07-05 17:46 ` Stefan Beller
2017-07-05 18:03 ` Ævar Arnfjörð Bjarmason
2017-07-01 22:05 ` [PATCH v3 3/3] sha1collisiondetection: automatically enable when submodule is populated Ævar Arnfjörð Bjarmason
2017-06-27 12:17 ` [PATCH 1/3] sha1dc: update from my PR #36 Ævar Arnfjörð Bjarmason
2017-06-27 15:22 ` Junio C Hamano
2017-06-27 15:53 ` Junio C Hamano
2017-06-27 18:07 ` Ævar Arnfjörð Bjarmason
2017-06-27 15:55 ` Junio C Hamano
2017-06-27 16:31 ` Liam R. Howlett
2017-06-27 18:11 ` Ævar Arnfjörð Bjarmason
2017-06-27 19:10 ` Junio C Hamano
2017-06-27 19:33 ` Junio C Hamano
2017-06-27 19:35 ` Ævar Arnfjörð Bjarmason [this message]
2017-06-27 19:38 ` Junio C Hamano
2017-06-27 19:38 ` Liam R. Howlett
2017-06-27 19:48 ` Junio C Hamano
2017-06-27 18:06 ` Ævar Arnfjörð Bjarmason
2017-06-27 18:12 ` Junio C Hamano
2017-06-27 18:19 ` Ævar Arnfjörð Bjarmason
2017-06-27 20:17 ` Junio C Hamano
2017-06-27 18:23 ` Junio C Hamano
2017-06-27 18:52 ` Ævar Arnfjörð Bjarmason
2017-06-27 12:17 ` [PATCH 2/3] sha1dc: optionally use sha1collisiondetection as a submodule Ævar Arnfjörð Bjarmason
2017-06-27 18:46 ` Stefan Beller
2017-06-27 18:56 ` Ævar Arnfjörð Bjarmason
2017-06-27 12:17 ` [PATCH 3/3] sha1collisiondetection: automatically enable when submodule is populated Ævar Arnfjörð Bjarmason
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