Re: [PATCH v3 0/2] check-attr: add support to work with revisions

From: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
To: Karthik Nayak <karthik.188@gmail.com>
Cc: git@vger.kernel.org, toon@iotcl.com
Subject: Re: [PATCH v3 0/2] check-attr: add support to work with revisions
Date: Mon, 19 Dec 2022 10:45:10 +0100	[thread overview]
Message-ID: <221219.86359b20bc.gmgdl@evledraar.gmail.com> (raw)
In-Reply-To: <20221216093552.3171319-1-karthik.188@gmail.com>

On Fri, Dec 16 2022, Karthik Nayak wrote:

> v1: https://lore.kernel.org/git/20221206103736.53909-1-karthik.188@gmail.com/
> v2: https://lore.kernel.org/git/CAOLa=ZSsFGBw3ta1jWN8cmUch2ca=zTEjp1xMA6Linafx9W53g@mail.gmail.com/T/#t
>
> Given a pathname, git-check-attr(1) will list the attributes which apply to that
> pathname by reading all relevant gitattributes files. Currently there is no way
> to specify a revision to read the gitattributes from.
>
> This is specifically useful in bare repositories wherein the gitattributes are
> only present in the git working tree but not available directly on the
> filesystem.
>
> This series aims to add a new flag `-r|--revisions` to git-check-attr(1) which
> allows us to read gitattributes from the specified revision.
>
> Changes since version 2:
> - Changes to the commit message [1/2] to use more specific terms and to
>   be more descriptive.
> - Moved the flag's position in the documentation to be before the unbound
>   list of non-options.

Aside from the UX concerns with this series, this segfaults with it, but
not on "master":

	./git check-attr diff git-send-email.perl foo.perl git-send-email.perl
	AddressSanitizer:DEADLYSIGNAL
	=================================================================
	==1828755==ERROR: AddressSanitizer: SEGV on unknown address (pc 0x0000008ee4a8 bp 0x7fffe4cef820 sp 0x7fffe4cef800 T0)
	==1828755==The signal is caused by a READ memory access.
	==1828755==Hint: this fault was caused by a dereference of a high value address (see register values below).  Disassemble the provided pc to learn which register was used.
	    #0 0x8ee4a8 in hasheq_algop hash.h:236
	    #1 0x8ee632 in oideq hash.h:253
	    #2 0x8ee657 in is_null_oid hash.h:258
	    #3 0x8f79e2 in do_oid_object_info_extended object-file.c:1550
	    #4 0x8f8206 in oid_object_info_extended object-file.c:1640
	    #5 0x8f860c in read_object object-file.c:1672
	    #6 0x8f8a8a in read_object_file_extended object-file.c:1715
	    #7 0x8f01ef in repo_read_object_file object-store.h:253
	    #8 0x8f8e37 in read_object_with_reference object-file.c:1756
	    #9 0xafb411 in get_tree_entry tree-walk.c:612
	    #10 0x6d1975 in read_attr_from_blob attr.c:776
	    #11 0x6d1b80 in read_attr attr.c:826
	    #12 0x6d1f35 in bootstrap_attr_stack attr.c:912
	    #13 0x6d2173 in prepare_attr_stack attr.c:948
	    #14 0x6d3285 in collect_some_attrs attr.c:1143
	    #15 0x6d33e1 in git_check_attr attr.c:1157
	    #16 0x453581 in check_attr builtin/check-attr.c:72
	    #17 0x453f1f in cmd_check_attr builtin/check-attr.c:190
	    #18 0x40b63d in run_builtin git.c:466
	    #19 0x40bf7f in handle_builtin git.c:721
	    #20 0x40c686 in run_argv git.c:788
	    #21 0x40d42f in cmd_main git.c:926
	    #22 0x6885b5 in main common-main.c:57
	    #23 0x7f96725a8189 in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58
	    #24 0x7f96725a8244 in __libc_start_main_impl ../csu/libc-start.c:381
	    #25 0x407230 in _start (git+0x407230)

	AddressSanitizer can not provide additional info.
	SUMMARY: AddressSanitizer: SEGV hash.h:236 in hasheq_algop
	==1828755==ABORTING
	Aborted

If the tests are still passing for you (I didn't check) then we probably
have a bad test blind spot with kthat we should start by addressing
before adding the new feature.