From: Junio C Hamano <gitster@pobox.com>
To: Jeff King <peff@peff.net>
Cc: "Todd Zullinger" <tmz@pobox.com>, "René Scharfe" <l.s.r@web.de>,
"Randall S. Becker" <rsbecker@nexbridge.com>,
"Christian Couder" <chriscool@tuxfamily.org>,
"SZEDER Gábor" <szeder.dev@gmail.com>,
git@vger.kernel.org, git-packagers@googlegroups.com
Subject: Re: [ANNOUNCE] Git v2.23.0-rc0 - Initial test failures on NonStop
Date: Tue, 30 Jul 2019 13:39:48 -0700 [thread overview]
Message-ID: <xmqqpnlrs1d7.fsf@gitster-ct.c.googlers.com> (raw)
In-Reply-To: <20190730200203.GA4882@sigill.intra.peff.net> (Jeff King's message of "Tue, 30 Jul 2019 16:02:03 -0400")
Jeff King <peff@peff.net> writes:
> @@ -116,19 +116,11 @@ unsigned int memihash_cont(unsigned int hash_seed, const void *buf, size_t len);
> * Converts a cryptographic hash (e.g. SHA-1) into an int-sized hash code
> * for use in hash tables. Cryptographic hashes are supposed to have
> * uniform distribution, so in contrast to `memhash()`, this just copies
> - * the first `sizeof(int)` bytes without shuffling any bits. Note that
> - * the results will be different on big-endian and little-endian
> - * platforms, so they should not be stored or transferred over the net.
;-)
> + * the first `sizeof(int)` bytes without shuffling any bits.
> */
> static inline unsigned int oidhash(const struct object_id *oid)
> {
> - /*
> - * Equivalent to 'return *(unsigned int *)oid->hash;', but safe on
> - * platforms that don't support unaligned reads.
> - */
> - unsigned int hash;
> - memcpy(&hash, oid->hash, sizeof(hash));
> - return hash;
> + return get_be32(oid->hash);
> }
>
> /*
> diff --git a/t/t0016-oidmap.sh b/t/t0016-oidmap.sh
> index bbe719e950..6656db9d69 100755
> --- a/t/t0016-oidmap.sh
> +++ b/t/t0016-oidmap.sh
> @@ -93,9 +93,9 @@ put three 3
> iterate" "NULL
> NULL
> NULL
> +$(git rev-parse three) 3
> $(git rev-parse two) 2
> -$(git rev-parse one) 1
> -$(git rev-parse three) 3"
> +$(git rev-parse one) 1"
>
> '
>
> which not only fixes this test but any other hash-based oddities. I
> wonder if it's appreciably less efficient. I'll bet I could nerd-snipe
> René into doing a bunch of measurements and explorations of the
> disassembled code. ;)
I'd rather see us go in the direction of discouraging people from
relying on the hash order.
next prev parent reply other threads:[~2019-07-30 20:39 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-30 17:08 [ANNOUNCE] Git v2.23.0-rc0 - Initial test failures on NonStop Randall S. Becker
2019-07-30 17:31 ` Junio C Hamano
2019-07-30 18:09 ` Matheus Tavares Bernardino
2019-07-30 18:10 ` Randall S. Becker
2019-07-30 18:35 ` Junio C Hamano
2019-07-30 19:45 ` Jeff King
2019-07-30 20:25 ` Randall S. Becker
2019-07-30 19:49 ` Todd Zullinger
2019-07-30 20:02 ` Jeff King
2019-07-30 20:39 ` Junio C Hamano [this message]
2019-07-30 20:56 ` SZEDER Gábor
2019-07-31 0:59 ` Jeff King
2019-07-31 1:23 ` Jeff King
2019-07-31 1:27 ` Jeff King
2019-07-31 1:59 ` Todd Zullinger
2019-07-31 3:27 ` Jeff King
2019-07-31 3:53 ` Jeff King
2019-07-31 17:17 ` Junio C Hamano
2019-07-31 21:22 ` non-cryptographic hash algorithms in git Jeff King
2019-07-31 4:06 ` [ANNOUNCE] Git v2.23.0-rc0 - Initial test failures on NonStop René Scharfe
2019-07-31 4:30 ` Jeff King
2019-07-31 6:04 ` Todd Zullinger
2019-07-31 16:57 ` Junio C Hamano
2019-07-30 20:27 ` Randall S. Becker
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