From: Phillip Wood <phillip.wood123@gmail.com>
To: Taylor Blau <me@ttaylorr.com>, phillip.wood@dunelm.org.uk
Cc: "Git Mailing List" <git@vger.kernel.org>,
"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Subject: Re: Bug in unused.cocci?
Date: Fri, 12 May 2023 16:07:08 +0100 [thread overview]
Message-ID: <20d1d7a2-049e-cb53-e276-101995b7c9bb@gmail.com> (raw)
In-Reply-To: <ZF0B2Prhc7jsqa3p@nand.local>
Hi Taylor
On 11/05/2023 15:55, Taylor Blau wrote:
> On Thu, May 11, 2023 at 10:16:21AM +0100, Phillip Wood wrote:
>> I think this is due to a bug in unused.cocci. I'm not sure what is going
>> wrong and admittedly we're unlikely to see code where an strbuf is
>> initialized and then used it without calling any of the strbuf_* functions
>> within our main codebase but it would be nice if the rule could handle this.
>
> I don't think that this is a bug in unused.cocci, but rather a bug in
> spatch not being able to read t/unit-tests/test-lib.h.
>
> $ spatch --verbose-parsing --debug --all-includes \
> --sp-file contrib/coccinelle/unused.old.cocci \
> t/unit-tests/t-strbuf.c | grep '^bad'
> init_defs_builtins: /usr/lib/coccinelle/standard.h
> -----------------------------------------------------------------------
> processing semantic patch file: contrib/coccinelle/unused.old.cocci
> with isos from: /usr/lib/coccinelle/standard.iso
> -----------------------------------------------------------------------
>
> HANDLING: t/unit-tests/t-strbuf.c
> parse error
> = error in t/unit-tests/test-lib.h; set verbose_parsing for more info
> badcount: 3
> bad: int test_done(void);
> bad:
> bad: /* Skip the current test. */
> BAD:!!!!! __attribute__((format (printf, 1, 2)))
>
> From my understanding, spatch happily ignores macros that it doesn't
> understand (like check_uint() and check_char()), so to it this code
> looks like:
>
> struct strbuf buf;
>
> strbuf_init(&buf, 1024);
> strbuf_release(&buf);
>
> which it marks as unused and applies the patch. Strangely, if you force
> it to pre-process with the appropriate macro file by passing it
> explicitly, it works as expected:
>
> $ spatch --macro-file t/unit-tests/test-lib.h \
> --sp-file contrib/coccinelle/unused.old.cocci \
> t/unit-tests/t-strbuf.c
> init_defs_builtins: /usr/lib/coccinelle/standard.h
> init_defs: t/unit-tests/test-lib.h
> HANDLING: t/unit-tests/t-strbuf.c
>
> I am puzzled by spatch's behavior here.
Thanks for looking at this. It's good that unused.cocci is not buggy but
I agree spatch's behavior is confusing. There is a similar test for
STRBUF_INIT which looks like
static void t_static_init(void)
{
struct strbuf buf = STRBUF_INIT;
check_uint(buf.len, ==, 0);
check_uint(buf.alloc, ==, 0);
if (check(buf.buf == strbuf_slopbuf))
return; /* avoid de-referencing buf.buf */
check_char(buf.buf[0], ==, '\0');
}
Which does not trigger this issue. Presumably the "if" statement is
stopping it from ignoring the check() macro even though it does not
understand it. If I change t_dynamic_init() to do
if (!check(buf.buf != NULL))
check_char(buf.buf[0], ==, '\0');
Then the static analysis job passes but I don't think that is really
fixing the problem.
Thanks
Phillip
prev parent reply other threads:[~2023-05-12 15:07 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-11 9:16 Bug in unused.cocci? Phillip Wood
2023-05-11 14:55 ` Taylor Blau
2023-05-12 15:07 ` Phillip Wood [this message]
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