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refs API: make parse_loose_ref_contents() not set errno

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Change the parse_loose_ref_contents() function to stop setting "errno"
and failure, and to instead pass up a "failure_errno" via a
parameter. This requires changing its callers to do the same.

The EINVAL error from parse_loose_ref_contents is used in files-backend
to create a custom error message.

In untangling this we discovered a tricky edge case. The
refs_read_special_head() function was relying on
parse_loose_ref_contents() setting EINVAL.

By converting it to use "saved_errno" we can migrate away from "errno"
in this part of the code entirely, and do away with an existing
"save_errno" pattern, its only purpose was to not clobber the "errno"
we previously needed at the end of files_read_raw_ref().

Let's assert that we can do that by not having files_read_raw_ref()
itself operate on *failure_errno in addition to passing it on. Instead
we'll assert that if we return non-zero we actually do set errno, thus
assuring ourselves and callers that they can trust the resulting
"failure_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 2021-10-16 11:39:10 +02:00 committed by Junio C Hamano
parent 8b72fea7e9
commit df3458e957
3 changed files with 29 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
refs.c
View File

@ -1648,7 +1648,8 @@ int for_each_fullref_in_prefixes(const char *namespace,
static int refs_read_special_head(struct ref_store *ref_store,
const char *refname, struct object_id *oid,
struct strbuf *referent, unsigned int *type)
struct strbuf *referent, unsigned int *type,
int *failure_errno)
{
struct strbuf full_path = STRBUF_INIT;
struct strbuf content = STRBUF_INIT;
@ -1658,7 +1659,8 @@ static int refs_read_special_head(struct ref_store *ref_store,
if (strbuf_read_file(&content, full_path.buf, 0) < 0)
goto done;
result = parse_loose_ref_contents(content.buf, oid, referent, type);
result = parse_loose_ref_contents(content.buf, oid, referent, type,
failure_errno);
done:
strbuf_release(&full_path);
@ -1673,7 +1675,7 @@ int refs_read_raw_ref(struct ref_store *ref_store, const char *refname,
assert(failure_errno);
if (!strcmp(refname, "FETCH_HEAD") || !strcmp(refname, "MERGE_HEAD")) {
return refs_read_special_head(ref_store, refname, oid, referent,
type);
type, failure_errno);
}
return ref_store->be->read_raw_ref(ref_store, refname, oid, referent,

31
refs/files-backend.c
View File

@ -355,6 +355,7 @@ static int files_read_raw_ref(struct ref_store *ref_store, const char *refname,
int fd;
int ret = -1;
int remaining_retries = 3;
int myerr = 0;
*type = 0;
strbuf_reset(&sb_path);
@ -382,11 +383,13 @@ stat_ref:
if (lstat(path, &st) < 0) {
int ignore_errno;
if (errno != ENOENT)
myerr = errno;
errno = 0;
if (myerr != ENOENT)
goto out;
if (refs_read_raw_ref(refs->packed_ref_store, refname, oid,
referent, type, &ignore_errno)) {
errno = ENOENT;
myerr = ENOENT;
goto out;
}
ret = 0;
@ -397,7 +400,9 @@ stat_ref:
if (S_ISLNK(st.st_mode)) {
strbuf_reset(&sb_contents);
if (strbuf_readlink(&sb_contents, path, st.st_size) < 0) {
if (errno == ENOENT || errno == EINVAL)
myerr = errno;
errno = 0;
if (myerr == ENOENT || myerr == EINVAL)
/* inconsistent with lstat; retry */
goto stat_ref;
else
@ -427,7 +432,7 @@ stat_ref:
*/
if (refs_read_raw_ref(refs->packed_ref_store, refname, oid,
referent, type, &ignore_errno)) {
errno = EISDIR;
myerr = EISDIR;
goto out;
}
ret = 0;
@ -440,7 +445,8 @@ stat_ref:
*/
fd = open(path, O_RDONLY);
if (fd < 0) {
if (errno == ENOENT && !S_ISLNK(st.st_mode))
myerr = errno;
if (myerr == ENOENT && !S_ISLNK(st.st_mode))
/* inconsistent with lstat; retry */
goto stat_ref;
else
@ -448,26 +454,29 @@ stat_ref:
}
strbuf_reset(&sb_contents);
if (strbuf_read(&sb_contents, fd, 256) < 0) {
int save_errno = errno;
myerr = errno;
close(fd);
errno = save_errno;
goto out;
}
close(fd);
strbuf_rtrim(&sb_contents);
buf = sb_contents.buf;
ret = parse_loose_ref_contents(buf, oid, referent, type);
ret = parse_loose_ref_contents(buf, oid, referent, type, &myerr);
out:
*failure_errno = errno;
if (ret && !myerr)
BUG("returning non-zero %d, should have set myerr!", ret);
*failure_errno = myerr;
strbuf_release(&sb_path);
strbuf_release(&sb_contents);
return ret;
}
int parse_loose_ref_contents(const char *buf, struct object_id *oid,
struct strbuf *referent, unsigned int *type)
struct strbuf *referent, unsigned int *type,
int *failure_errno)
{
const char *p;
if (skip_prefix(buf, "ref:", &buf)) {
@ -486,7 +495,7 @@ int parse_loose_ref_contents(const char *buf, struct object_id *oid,
if (parse_oid_hex(buf, oid, &p) ||
(*p != '\0' && !isspace(*p))) {
*type |= REF_ISBROKEN;
errno = EINVAL;
*failure_errno = EINVAL;
return -1;
}
return 0;

6
refs/refs-internal.h
View File

@ -706,10 +706,12 @@ struct ref_store {
};
/*
* Parse contents of a loose ref file.
* Parse contents of a loose ref file. *failure_errno maybe be set to EINVAL for
* invalid contents.
*/
int parse_loose_ref_contents(const char *buf, struct object_id *oid,
struct strbuf *referent, unsigned int *type);
struct strbuf *referent, unsigned int *type,
int *failure_errno);
/*
* Fill in the generic part of refs and add it to our collection of