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[2a01:4f8:120:2468::2]) by smtp.gmail.com with ESMTPSA id l2sm12350713wmi.1.2021.08.23.04.52.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 23 Aug 2021 04:52:57 -0700 (PDT) From: =?UTF-8?q?=C3=86var=20Arnfj=C3=B6r=C3=B0=20Bjarmason?= To: git@vger.kernel.org Cc: Junio C Hamano , Jeff King , Han-Wen Nienhuys , Michael Haggerty , Jonathan Tan , =?UTF-8?q?=C3=86var=20Arnfj=C3=B6r=C3=B0=20Bjarmason?= Subject: [PATCH v10 7/8] refs: explicitly return failure_errno from parse_loose_ref_contents Date: Mon, 23 Aug 2021 13:52:43 +0200 Message-Id: X-Mailer: git-send-email 2.33.0.662.g438caf9576d In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org From: Han-Wen Nienhuys 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 Signed-off-by: Ævar Arnfjörð Bjarmason --- 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