Re: [PATCH v5 2/6] refs/files-backend: stop setting errno from lock_ref_oid_basic
From: Han-Wen Nienhuys <hidden>
Date: 2021-07-13 08:00:36
On Sun, Jul 11, 2021 at 1:48 PM Ævar Arnfjörð Bjarmason [off-list ref] wrote:
On Wed, Jul 07 2021, Han-Wen Nienhuys via GitGitGadget wrote:quoted
/* * Locks a ref returning the lock on success and NULL on failure. - * On failure errno is set to something meaningful. */ static struct ref_lock *lock_ref_oid_basic(struct files_ref_store *refs, const char *refname,@@ -922,7 +921,6 @@ static struct ref_lock *lock_ref_oid_basic(struct files_ref_store *refs, { struct strbuf ref_file = STRBUF_INIT; struct ref_lock *lock; - int last_errno = 0; int mustexist = (old_oid && !is_null_oid(old_oid)); int resolve_flags = RESOLVE_REF_NO_RECURSE; int resolved;@@ -949,7 +947,6 @@ static struct ref_lock *lock_ref_oid_basic(struct files_ref_store *refs, * to remain. */ if (remove_empty_directories(&ref_file)) { - last_errno = errno; if (!refs_verify_refname_available( &refs->base, refname, extras, skip, err))@@ -962,10 +959,13 @@ static struct ref_lock *lock_ref_oid_basic(struct files_ref_store *refs, &lock->old_oid, type); } if (!resolved) { - last_errno = errno; + int last_errno = errno; if (last_errno != ENOTDIR || - !refs_verify_refname_available(&refs->base, refname, - extras, skip, err)) + /* in case of D/F conflict, try to generate a better error + * message. If that fails, fall back to strerror(ENOTDIR). + */ + !refs_verify_refname_available(&refs->base, refname, extras, + skip, err)) strbuf_addf(err, "unable to resolve reference '%s': %s", refname, strerror(last_errno));I don't think it's some dealbreaker and we can move on, but just FWIW I think what I mentioned ending in your https://lore.kernel.org/git/CAFQ2z_NpyJQLuM70MhJ8K1h2v3QXFuAZRjN=SvSsjnukNRJ8pw@mail.gmail.com/ (local) is still outstanding. I.e. you added the comment, which is just says what the error emitting looks like, that's all well & good. But what I was pointing out that it didn't make sense to do any "last_errno" here at all anymore. You pointed to 5b2d8d6f218 (lock_ref_sha1_basic(): improve diagnostics for ref D/F conflicts, 2015-05-11), we started setting "last_errno" there, but that was *not* to avoid clobbering between the !resolved and the strbuf_add(strerror(last_errno)) here, but rather to carry the "last_errno" forward to the end of this lock_ref_oid_basic(), because other things (after this hunk) might reset/clear errno.
I disagree. In your suggested change
quoted hunk ↗ jump to hunk
+ if (!resolved && + (errno != ENOTDIR || + /* in case of D/F conflict, try to generate a better error + * message. If that fails, fall back to strerror(ENOTDIR). + */ + !refs_verify_refname_available(&refs->base, refname, extras, + skip, err))) { + strbuf_addf(err, "unable to resolve reference '%s': %s", + refname, strerror(errno)); goto error_return;
the refs_verify_refname_available() call happens only if errno==ENOTDIR. The call might clobber the ENOTDIR errno and then fail. Then we'd be printing the last errno that refs_verify_refname_available() saw, which may be different from ENOTDIR. Other than that, for clarity's sake, it's always better to avoid the use of global errno if we can. -- 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 Geschäftsführer: Paul Manicle, Halimah DeLaine Prado