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From: Junio C Hamano <gitster@pobox.com>
To: Jeff King <peff@peff.net>
Cc: Koakuma <koachan@protonmail.com>,
	 "git@vger.kernel.org" <git@vger.kernel.org>
Subject: Re: [PATCH 1/3] packfile: factor out --pack_header argument parsing
Date: Fri, 17 Jan 2025 14:45:04 -0800	[thread overview]
Message-ID: <xmqqo705hxfz.fsf@gitster.g> (raw)
In-Reply-To: <20250117125459.GA2893666@coredump.intra.peff.net> (Jeff King's message of "Fri, 17 Jan 2025 07:54:59 -0500")

Jeff King <peff@peff.net> writes:

>  			} else if (starts_with(arg, "--pack_header=")) {
> -				struct pack_header *hdr;
> -				char *c;
> -
> -				hdr = (struct pack_header *)input_buffer;
> -				hdr->hdr_signature = htonl(PACK_SIGNATURE);
> -				hdr->hdr_version = htonl(strtoul(arg + 14, &c, 10));

Interesting.  So the file-scope static input_buffer[] sits in the
BSS and happens to be well aligned not to cause the problem, but ...

> @@ -645,18 +646,9 @@ int cmd_unpack_objects(int argc,
>  				continue;
>  			}
>  			if (starts_with(arg, "--pack_header=")) {
> -				struct pack_header *hdr;
> -				char *c;
> -
> -				hdr = (struct pack_header *)buffer;
> -				hdr->hdr_signature = htonl(PACK_SIGNATURE);
> -				hdr->hdr_version = htonl(strtoul(arg + 14, &c, 10));

... the same file-scope static buffer[] that also sits in the BSS
was not well aligned by chance?

Otherwise these should be identical code.  Very interesting.

And of course the fix in the [2/3] is absolutely the right thing to
do.

Thanks.


  reply	other threads:[~2025-01-17 22:45 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-01-17  3:30 [BUG] git crashes with a SIGBUS on sparc64 during pull Koakuma
2025-01-17 12:11 ` Jeff King
2025-01-17 12:52   ` Jeff King
2025-01-17 12:54     ` [PATCH 1/3] packfile: factor out --pack_header argument parsing Jeff King
2025-01-17 22:45       ` Junio C Hamano [this message]
2025-01-18  9:23         ` Jeff King
2025-01-18 16:57           ` Koakuma
2025-01-17 12:55     ` [PATCH 2/3] parse_pack_header_option(): avoid unaligned memory writes Jeff King
2025-01-18  1:27       ` Junio C Hamano
2025-01-18  9:36         ` Jeff King
2025-01-17 12:56     ` [PATCH 3/3] index-pack, unpack-objects: use skip_prefix to avoid magic number Jeff King
2025-01-17 15:55     ` [BUG] git crashes with a SIGBUS on sparc64 during pull Koakuma
2025-01-18  9:20       ` Jeff King
2025-01-18 16:50         ` Koakuma
2025-01-19 13:12       ` [PATCH v2 0/5] " Jeff King
2025-01-19 13:23         ` [PATCH v2 1/5] bswap.h: squelch potential sparse -Wcast-truncate warnings Jeff King
2025-01-19 13:23         ` [PATCH v2 2/5] packfile: factor out --pack_header argument parsing Jeff King
2025-01-19 13:23         ` [PATCH v2 3/5] parse_pack_header_option(): avoid unaligned memory writes Jeff King
2025-01-19 13:25         ` [PATCH v2 4/5] index-pack, unpack-objects: use get_be32() for reading pack header Jeff King
2025-01-19 13:25         ` [PATCH v2 5/5] index-pack, unpack-objects: use skip_prefix to avoid magic number Jeff King
2025-01-20 15:20         ` [PATCH v2 0/5] git crashes with a SIGBUS on sparc64 during pull Koakuma
2025-01-21 16:37           ` Junio C Hamano

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