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refs/files-backend: stop setting errno from lock_ref_oid_basic

Browse source 
refs/files-backend.c::lock_ref_oid_basic() tries to signal how it failed
to its callers using errno.

It is safe to stop setting errno here, because the callers of this
file-scope static function are

* files_copy_or_rename_ref()
* files_create_symref()
* files_reflog_expire()

None of them looks at errno after seeing a negative return from
lock_ref_oid_basic() to make any decision, and no caller of these three
functions looks at errno after they signal a failure by returning a
negative value. In particular,

* files_copy_or_rename_ref() - here, calls are followed by error()
(which performs I/O) or write_ref_to_lockfile() (which calls
parse_object() which may perform I/O)

* files_create_symref() - here, calls are followed by error() or
create_symref_locked() (which performs I/O and does not inspect
errno)

* files_reflog_expire() - here, calls are followed by error() or
refs_reflog_exists() (which calls a function in a vtable that is not
documented to use and/or preserve errno)

Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Han-Wen Nienhuys 2021-08-23 13:52:39 +02:00 committed by Junio C Hamano
parent 20d422cfd7
commit 1ae6ed230a
1 changed files with 2 additions and 9 deletions
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11
refs/files-backend.c
View file

@ -982,7 +982,6 @@ static int create_reflock(const char *path, void *cb)
/*
* 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, int *type,
@ -990,7 +989,6 @@ 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;
files_assert_main_repository(refs, "lock_ref_oid_basic");
assert(err);
@ -1001,11 +999,10 @@ static struct ref_lock *lock_ref_oid_basic(struct files_ref_store *refs,
if (!refs_resolve_ref_unsafe(&refs->base, refname,
RESOLVE_REF_NO_RECURSE,
&lock->old_oid, type)) {
last_errno = errno;
if (!refs_verify_refname_available(&refs->base, refname,
NULL, NULL, err))
strbuf_addf(err, "unable to resolve reference '%s': %s",
refname, strerror(last_errno));
refname, strerror(errno));
goto error_return;
}
@ -1018,15 +1015,12 @@ static struct ref_lock *lock_ref_oid_basic(struct files_ref_store *refs,
*/
if (is_null_oid(&lock->old_oid) &&
refs_verify_refname_available(refs->packed_ref_store, refname,
NULL, NULL, err)) {
last_errno = ENOTDIR;
NULL, NULL, err))
goto error_return;
}
lock->ref_name = xstrdup(refname);
if (raceproof_create_file(ref_file.buf, create_reflock, &lock->lk)) {
last_errno = errno;
unable_to_lock_message(ref_file.buf, errno, err);
goto error_return;
}
@ -1043,7 +1037,6 @@ static struct ref_lock *lock_ref_oid_basic(struct files_ref_store *refs,
out:
strbuf_release(&ref_file);
errno = last_errno;
return lock;
}