From: Han-Wen Nienhuys <hanwen@google.com>
To: Junio C Hamano <gitster@pobox.com>
Cc: Han-Wen Nienhuys via GitGitGadget <gitgitgadget@gmail.com>,
git <git@vger.kernel.org>, Han-Wen Nienhuys <hanwenn@gmail.com>
Subject: Re: [PATCH 1/8] refs: remove EINVAL specification from the errno sideband in read_raw_ref_fn
Date: Wed, 19 May 2021 14:25:37 +0200 [thread overview]
Message-ID: <CAFQ2z_MCySh2p+fL0uL8tAQhkpbnkGF6e=NOYicpAxN582aqag@mail.gmail.com> (raw)
In-Reply-To: <xmqqk0okebtb.fsf@gitster.g>
On Fri, Apr 30, 2021 at 4:38 AM Junio C Hamano <gitster@pobox.com> wrote:
>
> "Han-Wen Nienhuys via GitGitGadget" <gitgitgadget@gmail.com> writes:
>
> > From: Han-Wen Nienhuys <hanwen@google.com>
> >
> > A grep for EINVAL */*c reveals that no code inspects EINVAL after reading
> > references.
>
> We often use a pattern (which is common) like this:
>
> if (some_func_in_ref_API(...) < 0) {
> if (errno == ENOENT || errno == EISDIR)
> ... it is OK for the file to be missing ...
> else
> ... error ...
> }
>
> If a piece of code currently sets EINVAL to errno manually when
> signalling a failure by returning a negative value to communicate
> with such a caller, we wouldn't see EINVAL mentioned, so such a grep
> alone would not help us guarantee the correctness of an update to
> stop assignment of EINVAL at all. The callers must be vetted more
> carefully than "we are happy that nobody explicitly mentions EINVAL".
Sure. I looked at the callers, and documented further what I looked
for. But how far should one go? It's a global variable, so
transitively, almost all of the code could be observing the EINVAL
value under very specific circumstances. But it would also be a
terrible, fragile coding style and use of undocumented behavior.
> > The files ref backend does use EINVAL so parse_loose_ref_contents() can
> > communicate to lock_raw_ref() about garbage following the hex SHA1, or a short
> > read in files_read_raw_ref(), but the files backend does not call into
> > refs_read_raw_ref(), so its EINVAL sideband error is unused.
>
> This paragraph is confusing. It says EINVAL is used to signal
> lock_raw_ref(), and it says EINVAL is not used by the same files
> backend. Which is correct? If one part of the backend uses it, and
> other parts don't, wouldn't the backend as a whole still use it?
I tried to clarify the message. files-backend.c makes assumptions
about the errno return for files_read_raw_ref, but it's not making
assumptions about the abstracted API in refs.h
> That is because there is a codeflow like this:
>
> if (files_read_raw_ref(...)) {
> if (errno == ENOENT) {
> ... do various things ...
> } else if (errno == EISDIR) {
> ... do different and various things ...
> } else if (errno == EINVAL && (*type & REF_ISBROKEN)) {
> ... deal with broken ref ...
> }
> ...
> }
as mentioned above, this isn't calling refs_read_raw_ref, so it's not
affected by this patch.
> > + * Return 0 on success. If the ref doesn't exist, set errno to ENOENT and return
> > + * -1. If the ref exists but is neither a symbolic ref nor an object ID, it is
> > + * broken; set REF_ISBROKEN in type, and return -1. If there is another error
> > + * reading the ref, set errno appropriately and return -1.
>
> So, this is not sufficient to let caller correctly and safely handle
> errors. "set REF_ISBROKEN in type, set errno to something other
> than ENOENT or EISDIR, and then return -1" is necessary, I would
> think.
I tweaked the comment. Note that the function has only a handful of
callers (and only one caller where this behavior is relevant), and
it's changed in a follow-on patch in this series. Is it worth the
effort to wordsmith this further?
--
Han-Wen Nienhuys - Google Munich
I work 80%. Don't expect answers from me on Fridays.
--
Google Germany GmbH, Erika-Mann-Strasse 33, 80636 Munich
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg
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next prev parent reply other threads:[~2021-05-19 12:25 UTC|newest]
Thread overview: 148+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-29 15:32 [PATCH 0/8] refs: cleanup errno sideband ref related functions Han-Wen Nienhuys via GitGitGadget
2021-04-29 15:32 ` [PATCH 1/8] refs: remove EINVAL specification from the errno sideband in read_raw_ref_fn Han-Wen Nienhuys via GitGitGadget
2021-04-30 2:38 ` Junio C Hamano
2021-05-19 12:25 ` Han-Wen Nienhuys [this message]
2021-06-03 2:19 ` Jonathan Tan
2021-06-09 11:28 ` Han-Wen Nienhuys
2021-04-29 15:32 ` [PATCH 2/8] refs/files-backend: stop setting errno from lock_ref_oid_basic Han-Wen Nienhuys via GitGitGadget
2021-04-30 3:10 ` Junio C Hamano
2021-05-19 12:29 ` Han-Wen Nienhuys
2021-06-03 2:33 ` Jonathan Tan
2021-06-10 10:02 ` Han-Wen Nienhuys
2021-04-29 15:32 ` [PATCH 3/8] refs: make errno output explicit for read_raw_ref_fn Han-Wen Nienhuys via GitGitGadget
2021-04-30 3:34 ` Junio C Hamano
2021-04-30 6:02 ` Junio C Hamano
2021-05-19 12:33 ` Han-Wen Nienhuys
2021-06-03 2:37 ` Jonathan Tan
2021-06-10 10:05 ` Han-Wen Nienhuys
2021-04-29 15:32 ` [PATCH 4/8] refs: make errno output explicit for refs_resolve_ref_unsafe Han-Wen Nienhuys via GitGitGadget
2021-06-03 2:51 ` Jonathan Tan
2021-06-10 11:27 ` Han-Wen Nienhuys
2021-04-29 15:32 ` [PATCH 5/8] refs: add failure_errno to refs_read_raw_ref() signature Han-Wen Nienhuys via GitGitGadget
2021-04-29 15:32 ` [PATCH 6/8] refs: clear errno return in refs_resolve_ref_unsafe() Han-Wen Nienhuys via GitGitGadget
2021-06-03 2:53 ` Jonathan Tan
2021-06-10 11:45 ` Han-Wen Nienhuys
2021-04-29 15:32 ` [PATCH 7/8] refs: stop setting EINVAL and ELOOP in symref resolution Han-Wen Nienhuys via GitGitGadget
2021-06-03 2:55 ` Jonathan Tan
2021-06-10 11:58 ` Han-Wen Nienhuys
2021-04-29 15:32 ` [PATCH 8/8] refs: explicitly propagate errno from refs_read_raw_ref Han-Wen Nienhuys via GitGitGadget
2021-06-03 2:13 ` [PATCH 0/8] refs: cleanup errno sideband ref related functions Jonathan Tan
2021-06-09 11:29 ` Han-Wen Nienhuys
2021-06-10 12:57 ` [PATCH v2 " Han-Wen Nienhuys via GitGitGadget
2021-06-10 12:57 ` [PATCH v2 1/8] refs: remove EINVAL errno output from specification of read_raw_ref_fn Han-Wen Nienhuys via GitGitGadget
2021-06-10 12:57 ` [PATCH v2 2/8] refs/files-backend: stop setting errno from lock_ref_oid_basic Han-Wen Nienhuys via GitGitGadget
2021-07-01 11:13 ` Ævar Arnfjörð Bjarmason
2021-07-05 14:16 ` Han-Wen Nienhuys
2021-06-10 12:57 ` [PATCH v2 3/8] refs: make errno output explicit for read_raw_ref_fn Han-Wen Nienhuys via GitGitGadget
2021-07-01 11:34 ` Ævar Arnfjörð Bjarmason
2021-07-05 14:34 ` Han-Wen Nienhuys
2021-06-10 12:57 ` [PATCH v2 4/8] refs: make errno output explicit for refs_resolve_ref_unsafe Han-Wen Nienhuys via GitGitGadget
2021-07-01 11:56 ` Ævar Arnfjörð Bjarmason
2021-06-10 12:57 ` [PATCH v2 5/8] refs: use refs_resolve_ref_unsafe_with_errno() where needed Han-Wen Nienhuys via GitGitGadget
2021-07-01 11:58 ` Ævar Arnfjörð Bjarmason
2021-06-10 12:57 ` [PATCH v2 6/8] refs: add failure_errno to refs_read_raw_ref() signature Han-Wen Nienhuys via GitGitGadget
2021-07-01 12:06 ` Ævar Arnfjörð Bjarmason
2021-06-10 12:57 ` [PATCH v2 7/8] refs: clear errno return in refs_resolve_ref_unsafe() Han-Wen Nienhuys via GitGitGadget
2021-07-01 12:19 ` Ævar Arnfjörð Bjarmason
2021-06-10 12:57 ` [PATCH v2 8/8] refs: explicitly propagate errno from refs_read_raw_ref Han-Wen Nienhuys via GitGitGadget
2021-07-01 12:26 ` Ævar Arnfjörð Bjarmason
2021-07-05 16:09 ` Han-Wen Nienhuys
2021-07-05 19:08 ` Ævar Arnfjörð Bjarmason
2021-07-05 19:39 ` Han-Wen Nienhuys
2021-06-14 10:10 ` [PATCH v2 0/8] refs: cleanup errno sideband ref related functions Han-Wen Nienhuys
2021-07-05 20:56 ` [PATCH v3 0/5] " Han-Wen Nienhuys via GitGitGadget
2021-07-05 20:56 ` [PATCH v3 1/5] refs: remove EINVAL errno output from specification of read_raw_ref_fn Han-Wen Nienhuys via GitGitGadget
2021-07-05 20:56 ` [PATCH v3 2/5] refs/files-backend: stop setting errno from lock_ref_oid_basic Han-Wen Nienhuys via GitGitGadget
2021-07-05 20:56 ` [PATCH v3 3/5] refs: make errno output explicit for read_raw_ref_fn Han-Wen Nienhuys via GitGitGadget
2021-07-05 20:56 ` [PATCH v3 4/5] refs: add failure_errno to refs_read_raw_ref() signature Han-Wen Nienhuys via GitGitGadget
2021-07-06 19:28 ` Junio C Hamano
2021-07-05 20:56 ` [PATCH v3 5/5] refs: make errno output explicit for refs_resolve_ref_unsafe Han-Wen Nienhuys via GitGitGadget
2021-07-06 0:38 ` [PATCH v3 0/5] refs: cleanup errno sideband ref related functions Ævar Arnfjörð Bjarmason
2021-07-06 9:53 ` Han-Wen Nienhuys
2021-07-06 14:27 ` Ævar Arnfjörð Bjarmason
2021-07-06 18:36 ` Han-Wen Nienhuys
2021-07-06 18:55 ` [PATCH v4 0/6] " Han-Wen Nienhuys via GitGitGadget
2021-07-06 18:55 ` [PATCH v4 1/6] refs: remove EINVAL errno output from specification of read_raw_ref_fn Han-Wen Nienhuys via GitGitGadget
2021-07-06 18:55 ` [PATCH v4 2/6] refs/files-backend: stop setting errno from lock_ref_oid_basic Han-Wen Nienhuys via GitGitGadget
2021-07-06 18:55 ` [PATCH v4 3/6] refs: make errno output explicit for read_raw_ref_fn Han-Wen Nienhuys via GitGitGadget
2021-07-06 18:55 ` [PATCH v4 4/6] refs: add failure_errno to refs_read_raw_ref() signature Han-Wen Nienhuys via GitGitGadget
2021-07-06 19:39 ` Junio C Hamano
2021-07-06 18:55 ` [PATCH v4 5/6] refs: explicitly return failure_errno from parse_loose_ref_contents Han-Wen Nienhuys via GitGitGadget
2021-07-06 19:37 ` Junio C Hamano
2021-07-07 8:20 ` Han-Wen Nienhuys
2021-07-06 18:55 ` [PATCH v4 6/6] refs: make errno output explicit for refs_resolve_ref_unsafe Han-Wen Nienhuys via GitGitGadget
2021-07-07 19:07 ` [PATCH v5 0/6] refs: cleanup errno sideband ref related functions Han-Wen Nienhuys via GitGitGadget
2021-07-07 19:07 ` [PATCH v5 1/6] refs: remove EINVAL errno output from specification of read_raw_ref_fn Han-Wen Nienhuys via GitGitGadget
2021-07-07 19:07 ` [PATCH v5 2/6] refs/files-backend: stop setting errno from lock_ref_oid_basic Han-Wen Nienhuys via GitGitGadget
2021-07-11 11:38 ` Ævar Arnfjörð Bjarmason
2021-07-13 8:00 ` Han-Wen Nienhuys
2021-07-07 19:07 ` [PATCH v5 3/6] refs: make errno output explicit for read_raw_ref_fn Han-Wen Nienhuys via GitGitGadget
2021-07-11 11:52 ` Ævar Arnfjörð Bjarmason
2021-07-07 19:07 ` [PATCH v5 4/6] refs: add failure_errno to refs_read_raw_ref() signature Han-Wen Nienhuys via GitGitGadget
2021-07-11 11:59 ` Ævar Arnfjörð Bjarmason
2021-07-13 8:02 ` Han-Wen Nienhuys
2021-07-07 19:07 ` [PATCH v5 5/6] refs: explicitly return failure_errno from parse_loose_ref_contents Han-Wen Nienhuys via GitGitGadget
2021-07-11 12:41 ` Ævar Arnfjörð Bjarmason
2021-07-07 19:07 ` [PATCH v5 6/6] refs: make errno output explicit for refs_resolve_ref_unsafe Han-Wen Nienhuys via GitGitGadget
2021-07-07 20:44 ` [PATCH v5 0/6] refs: cleanup errno sideband ref related functions Junio C Hamano
2021-07-11 16:30 ` [PATCH v6? 00/17] refs API: get rid of errno setting entirely Ævar Arnfjörð Bjarmason
2021-07-11 16:30 ` [PATCH v6? 01/17] refs: remove EINVAL errno output from specification of read_raw_ref_fn Ævar Arnfjörð Bjarmason
2021-07-11 16:30 ` [PATCH v6? 02/17] refs/files-backend: stop setting errno from lock_ref_oid_basic Ævar Arnfjörð Bjarmason
2021-07-11 16:30 ` [PATCH v6? 03/17] refs: make errno output explicit for read_raw_ref_fn Ævar Arnfjörð Bjarmason
2021-07-11 16:30 ` [PATCH v6? 04/17] refs: add failure_errno to refs_read_raw_ref() signature Ævar Arnfjörð Bjarmason
2021-07-11 16:30 ` [PATCH v6? 05/17] refs: explicitly return failure_errno from parse_loose_ref_contents Ævar Arnfjörð Bjarmason
2021-07-11 16:30 ` [PATCH v6? 06/17] refs: make errno output explicit for refs_resolve_ref_unsafe Ævar Arnfjörð Bjarmason
2021-07-11 16:30 ` [PATCH v6? 07/17] refs: make errno ignoring explicit in lock_ref_oid_basic() Ævar Arnfjörð Bjarmason
2021-07-11 16:30 ` [PATCH v6? 08/17] refs file-backend.c: stop setting "EBUSY" in verify_lock() Ævar Arnfjörð Bjarmason
2021-07-13 8:08 ` Han-Wen Nienhuys
2021-07-11 16:30 ` [PATCH v6? 09/17] refs file-backend.c: deal with errno directly " Ævar Arnfjörð Bjarmason
2021-07-11 16:30 ` [PATCH v6? 10/17] refs API: remove refs_read_ref_full() wrapper Ævar Arnfjörð Bjarmason
2021-07-11 16:30 ` [PATCH v6? 11/17] refs API: make resolve_gitlink_ref() not set errno Ævar Arnfjörð Bjarmason
2021-07-11 16:30 ` [PATCH v6? 12/17] refs API: make refs_resolve_ref_unsafe() static Ævar Arnfjörð Bjarmason
2021-07-11 16:30 ` [PATCH v6? 13/17] refs API: make refs_resolve_refdup() not set errno Ævar Arnfjörð Bjarmason
2021-07-11 16:30 ` [PATCH v6? 14/17] refs API: make refs_ref_exists() " Ævar Arnfjörð Bjarmason
2021-07-11 16:30 ` [PATCH v6? 15/17] refs API: make resolve_ref_unsafe() " Ævar Arnfjörð Bjarmason
2021-07-13 8:13 ` Han-Wen Nienhuys
2021-07-14 8:32 ` Ævar Arnfjörð Bjarmason
2021-07-11 16:30 ` [PATCH v6? 16/17] refs API: make expand_ref() and repo_dwim_log() " Ævar Arnfjörð Bjarmason
2021-07-11 16:30 ` [PATCH v6? 17/17] refs API: don't leak "errno" in run_transaction_hook() Ævar Arnfjörð Bjarmason
2021-07-13 8:28 ` [PATCH v6? 00/17] refs API: get rid of errno setting entirely Han-Wen Nienhuys
2021-07-13 18:26 ` Ævar Arnfjörð Bjarmason
2021-07-14 8:38 ` Ævar Arnfjörð Bjarmason
2021-07-14 8:43 ` Han-Wen Nienhuys
2021-07-14 11:43 ` [PATCH v7 0/6] refs: cleanup errno sideband ref related functions Ævar Arnfjörð Bjarmason
2021-07-14 11:43 ` [PATCH v7 1/6] refs: remove EINVAL errno output from specification of read_raw_ref_fn Ævar Arnfjörð Bjarmason
2021-07-14 11:43 ` [PATCH v7 2/6] refs/files-backend: stop setting errno from lock_ref_oid_basic Ævar Arnfjörð Bjarmason
2021-07-14 11:43 ` [PATCH v7 3/6] refs: make errno output explicit for read_raw_ref_fn Ævar Arnfjörð Bjarmason
2021-07-14 11:43 ` [PATCH v7 4/6] refs: add failure_errno to refs_read_raw_ref() signature Ævar Arnfjörð Bjarmason
2021-07-14 11:43 ` [PATCH v7 5/6] refs: explicitly return failure_errno from parse_loose_ref_contents Ævar Arnfjörð Bjarmason
2021-07-14 11:43 ` [PATCH v7 6/6] refs: make errno output explicit for refs_resolve_ref_unsafe Ævar Arnfjörð Bjarmason
2021-07-16 14:22 ` [PATCH v8 0/7] refs: cleanup errno sideband ref related functions Ævar Arnfjörð Bjarmason
2021-07-16 14:22 ` [PATCH v8 1/7] refs file backend: move raceproof_create_file() here Ævar Arnfjörð Bjarmason
2021-07-16 14:22 ` [PATCH v8 2/7] refs: remove EINVAL errno output from specification of read_raw_ref_fn Ævar Arnfjörð Bjarmason
2021-07-16 14:22 ` [PATCH v8 3/7] refs/files-backend: stop setting errno from lock_ref_oid_basic Ævar Arnfjörð Bjarmason
2021-07-16 14:22 ` [PATCH v8 4/7] refs: make errno output explicit for read_raw_ref_fn Ævar Arnfjörð Bjarmason
2021-07-16 14:22 ` [PATCH v8 5/7] refs: add failure_errno to refs_read_raw_ref() signature Ævar Arnfjörð Bjarmason
2021-07-16 14:22 ` [PATCH v8 6/7] refs: explicitly return failure_errno from parse_loose_ref_contents Ævar Arnfjörð Bjarmason
2021-07-16 14:22 ` [PATCH v8 7/7] refs: make errno output explicit for refs_resolve_ref_unsafe Ævar Arnfjörð Bjarmason
2021-07-20 10:33 ` [PATCH v9 0/7] refs: cleanup errno sideband ref related functions Ævar Arnfjörð Bjarmason
2021-07-20 10:33 ` [PATCH v9 1/7] refs file backend: move raceproof_create_file() here Ævar Arnfjörð Bjarmason
2021-07-20 10:33 ` [PATCH v9 2/7] refs: remove EINVAL errno output from specification of read_raw_ref_fn Ævar Arnfjörð Bjarmason
2021-07-20 10:33 ` [PATCH v9 3/7] refs/files-backend: stop setting errno from lock_ref_oid_basic Ævar Arnfjörð Bjarmason
2021-07-20 10:33 ` [PATCH v9 4/7] refs: make errno output explicit for read_raw_ref_fn Ævar Arnfjörð Bjarmason
2021-08-16 13:00 ` Han-Wen Nienhuys
2021-07-20 10:33 ` [PATCH v9 5/7] refs: add failure_errno to refs_read_raw_ref() signature Ævar Arnfjörð Bjarmason
2021-07-20 10:33 ` [PATCH v9 6/7] refs: explicitly return failure_errno from parse_loose_ref_contents Ævar Arnfjörð Bjarmason
2021-08-13 20:54 ` Jonathan Tan
2021-07-20 10:33 ` [PATCH v9 7/7] refs: make errno output explicit for refs_resolve_ref_unsafe Ævar Arnfjörð Bjarmason
2021-07-26 23:49 ` [PATCH v9 0/7] refs: cleanup errno sideband ref related functions Ævar Arnfjörð Bjarmason
2021-07-27 0:18 ` Junio C Hamano
2021-08-23 11:52 ` [PATCH v10 0/8] " Ævar Arnfjörð Bjarmason
2021-08-23 11:52 ` [PATCH v10 1/8] refs file backend: move raceproof_create_file() here Ævar Arnfjörð Bjarmason
2021-08-23 11:52 ` [PATCH v10 2/8] refs: remove EINVAL errno output from specification of read_raw_ref_fn Ævar Arnfjörð Bjarmason
2021-08-23 11:52 ` [PATCH v10 3/8] refs/files-backend: stop setting errno from lock_ref_oid_basic Ævar Arnfjörð Bjarmason
2021-08-23 11:52 ` [PATCH v10 4/8] refs: make errno output explicit for read_raw_ref_fn Ævar Arnfjörð Bjarmason
2021-08-23 11:52 ` [PATCH v10 5/8] refs: add failure_errno to refs_read_raw_ref() signature Ævar Arnfjörð Bjarmason
2021-08-23 11:52 ` [PATCH v10 6/8] branch tests: test for errno propagating on failing read Ævar Arnfjörð Bjarmason
2021-08-23 11:52 ` [PATCH v10 7/8] refs: explicitly return failure_errno from parse_loose_ref_contents Ævar Arnfjörð Bjarmason
2021-08-23 11:52 ` [PATCH v10 8/8] refs: make errno output explicit for refs_resolve_ref_unsafe Ævar Arnfjörð Bjarmason
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