From: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
To: Junio C Hamano <gitster@pobox.com>
Cc: git@vger.kernel.org, Han-Wen Nienhuys <hanwen@google.com>,
Bagas Sanjaya <bagasdotme@gmail.com>
Subject: Re: [PATCH v3 1/3] refs API: use "failure_errno", not "errno"
Date: Thu, 13 Jan 2022 13:14:59 +0100 [thread overview]
Message-ID: <220113.86pmovvnis.gmgdl@evledraar.gmail.com> (raw)
In-Reply-To: <xmqqh7a8u3my.fsf@gitster.g>
On Wed, Jan 12 2022, Junio C Hamano wrote:
> Ævar Arnfjörð Bjarmason <avarab@gmail.com> writes:
>
>> @@ -1722,8 +1722,6 @@ const char *refs_resolve_ref_unsafe(struct ref_store *refs,
>> if (refs_read_raw_ref(refs, refname, oid, &sb_refname,
>> &read_flags, failure_errno)) {
>> *flags |= read_flags;
>> - if (errno)
>> - *failure_errno = errno;
>
> Looks good.
>
> The whole point of passing failure_errno down to refs_read_raw_ref()
> is that we capture the reason of the failure there without having to
> rely on errno at this point in the flow. Removal of this assignment
> makes perfect sense.
>
> But ...
>
>> diff --git a/refs/files-backend.c b/refs/files-backend.c
>> index b529fdf237e..43a3b882d7c 100644
>> --- a/refs/files-backend.c
>> +++ b/refs/files-backend.c
>> @@ -382,7 +382,6 @@ static int files_read_raw_ref(struct ref_store *ref_store, const char *refname,
>> if (lstat(path, &st) < 0) {
>> int ignore_errno;
>> myerr = errno;
>> - errno = 0;
>> if (myerr != ENOENT)
>> goto out;
>> if (refs_read_raw_ref(refs->packed_ref_store, refname, oid,
>> @@ -399,7 +398,6 @@ static int files_read_raw_ref(struct ref_store *ref_store, const char *refname,
>> strbuf_reset(&sb_contents);
>> if (strbuf_readlink(&sb_contents, path, st.st_size) < 0) {
>> myerr = errno;
>> - errno = 0;
>> if (myerr == ENOENT || myerr == EINVAL)
>> /* inconsistent with lstat; retry */
>> goto stat_ref;
>> @@ -469,6 +467,7 @@ static int files_read_raw_ref(struct ref_store *ref_store, const char *refname,
>>
>> strbuf_release(&sb_path);
>> strbuf_release(&sb_contents);
>> + errno = 0;
>> return ret;
>> }
>
> ... it is not clear to me if this part makes sense. If everybody
> above the callstack uses failure_errno as the source of truth,
> clearing errno here in this function should not be necessary and is
> misleading to readers of the code, no?
It's consistent with various other existing refs* code as we made this
transition, see:
git grep -W 'errno = 0' -- 'refs*'
I.e. we'd like to not only transition existing users away from errno,
but to ensure that the file backend errno semantics don't inadvertently
leak outside the API.
Doing so is a bit pedantic for sure, but ensures that we won't need to
deal with any subtle bugs in that are with the reftable backend.
next prev parent reply other threads:[~2022-01-13 12:16 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-08 11:38 errno oversight Han-Wen Nienhuys
2021-12-08 12:47 ` Ævar Arnfjörð Bjarmason
2021-12-08 13:00 ` Ævar Arnfjörð Bjarmason
2021-12-08 19:02 ` Junio C Hamano
2021-12-09 5:02 ` [PATCH 0/3] refs: ab/refs-errno-cleanup fixup + remove "failure_errno" Ævar Arnfjörð Bjarmason
2021-12-09 5:02 ` [PATCH 1/3] refs API: use "failure_errno", not "errno" Ævar Arnfjörð Bjarmason
2021-12-09 5:02 ` [PATCH 2/3] sequencer: don't use die_errno() on refs_resolve_ref_unsafe() failure Ævar Arnfjörð Bjarmason
2021-12-09 5:02 ` [PATCH 3/3] refs API: remove "failure_errno" from refs_resolve_ref_unsafe() Ævar Arnfjörð Bjarmason
2021-12-12 19:53 ` [PATCH v2 0/3] refs: ab/refs-errno-cleanup fixup + remove "failure_errno" Ævar Arnfjörð Bjarmason
2021-12-12 19:53 ` [PATCH v2 1/3] refs API: use "failure_errno", not "errno" Ævar Arnfjörð Bjarmason
2021-12-12 19:53 ` [PATCH v2 2/3] sequencer: don't use die_errno() on refs_resolve_ref_unsafe() failure Ævar Arnfjörð Bjarmason
2021-12-12 19:53 ` [PATCH v2 3/3] refs API: remove "failure_errno" from refs_resolve_ref_unsafe() Ævar Arnfjörð Bjarmason
2022-01-12 12:36 ` [PATCH v3 0/3] For v2.35.0: refs: ab/refs-errno-cleanup fixup + remove "failure_errno" Ævar Arnfjörð Bjarmason
2022-01-12 12:36 ` [PATCH v3 1/3] refs API: use "failure_errno", not "errno" Ævar Arnfjörð Bjarmason
2022-01-12 19:59 ` Junio C Hamano
2022-01-13 12:14 ` Ævar Arnfjörð Bjarmason [this message]
2022-01-12 12:36 ` [PATCH v3 2/3] sequencer: don't use die_errno() on refs_resolve_ref_unsafe() failure Ævar Arnfjörð Bjarmason
2022-01-12 20:02 ` Junio C Hamano
2022-01-12 12:36 ` [PATCH v3 3/3] refs API: remove "failure_errno" from refs_resolve_ref_unsafe() Ævar Arnfjörð Bjarmason
2022-01-12 19:34 ` [PATCH v3 0/3] For v2.35.0: refs: ab/refs-errno-cleanup fixup + remove "failure_errno" Junio C Hamano
2022-01-13 12:22 ` Ævar Arnfjörð Bjarmason
2022-01-13 18:54 ` Junio C Hamano
2022-01-14 12:21 ` Ævar Arnfjörð Bjarmason
2022-01-26 14:36 ` [PATCH v4 0/2] refs: remove the last use of "errno" from the public API Ævar Arnfjörð Bjarmason
2022-01-26 14:37 ` [PATCH v4 1/2] sequencer: don't use die_errno() on refs_resolve_ref_unsafe() failure Ævar Arnfjörð Bjarmason
2022-01-26 23:57 ` Junio C Hamano
2022-01-26 14:37 ` [PATCH v4 2/2] refs API: remove "failure_errno" from refs_resolve_ref_unsafe() Ævar Arnfjörð Bjarmason
2021-12-08 13:05 ` errno oversight Han-Wen Nienhuys
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