[PATCH v2 0/6] add missing __attribute__((format))

Adds missing add missing __attribute__((format)) in various places, which improves compile-time checking.

v2: Let's drop the whole bending over backwards to do mostly/entirely useless strftime() checking. That's gone, I added a patch at the end with a comment for strbuf_addftime() to say why it's not there, and also split up the advise_if_enabled() change into its own commit.

I also removed the other cases of adding attribute checking to compat/*. I can't easily test those, and I don't know if there's potential bad interactions with git-compat-util.h.

Ævar Arnfjörð Bjarmason (6):
  *.c static functions: don't forward-declare __attribute__
  sequencer.c: move static function to avoid forward decl
  *.c static functions: add missing __attribute__((format))
  *.h: add a few missing  __attribute__((format))
  advice.h: add missing __attribute__((format)) & fix usage
  strbuf.h: add a comment about "missing" strftime() checking

 add-patch.c                                   |  1 +
 advice.h                                      |  1 +
 builtin/am.c                                  |  1 +
 builtin/bisect--helper.c                      |  2 +
 builtin/index-pack.c                          |  4 +-
 builtin/receive-pack.c                        |  5 +--
 cache.h                                       |  1 +
 commit-graph.c                                |  1 +
 .../osxkeychain/git-credential-osxkeychain.c  |  1 +
 .../wincred/git-credential-wincred.c          |  1 +
 gettext.c                                     |  1 +
 imap-send.c                                   |  3 ++
 mailmap.c                                     |  1 +
 merge-ort.c                                   |  1 +
 merge-recursive.c                             |  1 +
 midx.c                                        |  1 +
 quote.h                                       |  1 +
 ref-filter.c                                  |  1 +
 sequencer.c                                   | 43 +++++++++----------
 server-info.c                                 |  1 +
 strbuf.h                                      |  7 +++
 t/helper/test-advise.c                        |  2 +-
 worktree.c                                    |  1 +
 23 files changed, 53 insertions(+), 29 deletions(-)

Range-diff against v1:
1:  a855bfceb2 = 1:  a855bfceb2 *.c static functions: don't forward-declare __attribute__
2:  9c1492b006 = 2:  9c1492b006 sequencer.c: move static function to avoid forward decl
3:  bc3fee3b7a ! 3:  e2e039f481 *.c static functions: add missing __attribute__((format))
    @@ commit-graph.c: int write_commit_graph(struct object_directory *odb,
      {
      	va_list ap;
     
    - ## compat/mingw.c ##
    -@@ compat/mingw.c: static int read_yes_no_answer(void)
    - 	return -1;
    - }
    - 
    -+__attribute__((format (printf, 1, 2)))
    - static int ask_yes_no_if_possible(const char *format, ...)
    - {
    - 	char question[4096];
    -
    - ## compat/winansi.c ##
    -@@ compat/winansi.c: static void winansi_exit(void)
    - 	CloseHandle(hthread);
    - }
    - 
    -+__attribute__((format (printf, 1, 2)))
    - static void die_lasterr(const char *fmt, ...)
    - {
    - 	va_list params;
    -
      ## contrib/credential/osxkeychain/git-credential-osxkeychain.c ##
     @@ contrib/credential/osxkeychain/git-credential-osxkeychain.c: static char *username;
      static char *password;
4:  3bf8637c16 ! 4:  fd70d512b4 *.h: add a few missing  __attribute__((format))
    @@ Metadata
      ## Commit message ##
         *.h: add a few missing  __attribute__((format))
     
    -    Add missing format attributes to those function that were missing
    -    them.
    -
    -    In the case of advice_enabled() this revealed a trivial issue
    -    introduced in b3b18d16213 (advice: revamp advise API, 2020-03-02). We
    -    treated the argv[1] as a format string, but did not intend to do
    -    so. Let's use "%s" and pass argv[1] as an argument instead.
    -
    -    For strbuf_addftime() let's add a strftime() format checker. Our
    -    function understands the non-portable %z and %Z, see
    -    c3fbf81a853 (strbuf: let strbuf_addftime handle %z and %Z itself,
    -    2017-06-15).
    -
    -    That might be an issue in theory, but in practice we have existing
    -    codepath that supplies a fixed string to strbuf_addftime(). We're
    -    unlikely to run into the "%z" and "%Z" case at all, since it's used by
    -    date.c and passed via e.g. "git log --date=<format>".
    -
    -    In fact, we had no in-tree user of strbuf_addftime() with an inline
    -    fixed format string at all. A subsequent commit will tweak an existing
    -    one to use the format checking.
    +    Add missing format attributes to API functions that take printf
    +    arguments.
     
         Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
     
    - ## advice.h ##
    -@@ advice.h: int advice_enabled(enum advice_type type);
    - /**
    -  * Checks the visibility of the advice before printing.
    -  */
    -+__attribute__((format (printf, 2, 3)))
    - void advise_if_enabled(enum advice_type type, const char *advice, ...);
    - 
    - int error_resolve_conflict(const char *me);
    -
      ## cache.h ##
     @@ cache.h: enum get_oid_result {
      };
    @@ cache.h: enum get_oid_result {
      int repo_get_oid_commit(struct repository *r, const char *str, struct object_id *oid);
      int repo_get_oid_committish(struct repository *r, const char *str, struct object_id *oid);
     
    - ## compat/win32/syslog.h ##
    -@@
    - #define LOG_DAEMON  (3<<3)
    - 
    - void openlog(const char *ident, int logopt, int facility);
    -+__attribute__((format (printf, 2, 3)))
    - void syslog(int priority, const char *fmt, ...);
    - 
    - #endif /* SYSLOG_H */
    -
      ## quote.h ##
     @@ quote.h: struct strbuf;
      
    @@ strbuf.h: static inline void strbuf_insertstr(struct strbuf *sb, size_t pos,
      void strbuf_insertf(struct strbuf *sb, size_t pos, const char *fmt, ...);
      
      /**
    -@@ strbuf.h: void strbuf_vaddf(struct strbuf *sb, const char *fmt, va_list ap);
    -  * `suppress_tz_name`, when set, expands %Z internally to the empty
    -  * string rather than passing it to `strftime`.
    -  */
    -+__attribute__((format (strftime, 2, 0)))
    - void strbuf_addftime(struct strbuf *sb, const char *fmt,
    - 		    const struct tm *tm, int tz_offset,
    - 		    int suppress_tz_name);
    -
    - ## t/helper/test-advise.c ##
    -@@ t/helper/test-advise.c: int cmd__advise_if_enabled(int argc, const char **argv)
    - 	 * selected here and in t0018 where this command is being
    - 	 * executed.
    - 	 */
    --	advise_if_enabled(ADVICE_NESTED_TAG, argv[1]);
    -+	advise_if_enabled(ADVICE_NESTED_TAG, "%s", argv[1]);
    - 
    - 	return 0;
    - }
5:  daca344a16 < -:  ---------- bugreport.c: tweak cmd_bugreport() to use __attribute__((printf))
6:  365c5cf50b < -:  ---------- git-compat-util.h: add __attribute__((printf)) to git_*printf*
-:  ---------- > 5:  a001e851d2 advice.h: add missing __attribute__((format)) & fix usage
-:  ---------- > 6:  fe66e06754 strbuf.h: add a comment about "missing" strftime() checking