From: Han-Wen Nienhuys <hanwen@xxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx>
---
refs.c | 8 +++++---
refs/files-backend.c | 31 ++++++++++++++++++++-----------
refs/refs-internal.h | 6 ++++--
t/t3200-branch.sh | 1 +
4 files changed, 30 insertions(+), 16 deletions(-)
diff --git a/refs.c b/refs.c
index 4c782fa2978..b83fd8c36b3 100644
--- a/refs.c
+++ b/refs.c
@@ -1654,7 +1654,8 @@ 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;
@@ -1664,7 +1665,8 @@ 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);
@@ -1679,7 +1681,7 @@ 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,
diff --git a/refs/files-backend.c b/refs/files-backend.c
index f962495e456..41efe5352b5 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -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 @@ static int files_read_raw_ref(struct ref_store *ref_store, const char *refname,
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 @@ static int files_read_raw_ref(struct ref_store *ref_store, const char *refname,
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 @@ static int files_read_raw_ref(struct ref_store *ref_store, const char *refname,
*/
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 @@ static int files_read_raw_ref(struct ref_store *ref_store, const char *refname,
*/
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 @@ static int files_read_raw_ref(struct ref_store *ref_store, const char *refname,
}
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;
diff --git a/refs/refs-internal.h b/refs/refs-internal.h
index 7ade286260c..7a3a61ac22f 100644
--- a/refs/refs-internal.h
+++ b/refs/refs-internal.h
@@ -692,10 +692,12 @@ 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
diff --git a/t/t3200-branch.sh b/t/t3200-branch.sh
index 9fae13c2dea..63fbd71dc5c 100755
--- a/t/t3200-branch.sh
+++ b/t/t3200-branch.sh
@@ -745,6 +745,7 @@ test_expect_success SYMLINKS 'git branch -m with symlinked .git/refs' '
) &&
git --git-dir subdir/.git/ branch rename-src &&
git rev-parse rename-src >expect &&
+ # Tests a BUG() assertion in files_read_raw_ref()
git --git-dir subdir/.git/ branch -m rename-src rename-dest &&
git rev-parse rename-dest >actual &&
test_cmp expect actual &&
--
2.33.0.662.g438caf9576d
