Subject: Re: [PATCH v3 04/11] reftable/stack: verify that `reftable_stack_add()` uses auto-compaction

From: Patrick Steinhardt <[email-masked]>
Date: Tue, 12 Dec 2023 04:44:37 +0100

On Mon, Dec 11, 2023 at 03:15:19PM -0500, Taylor Blau wrote:
> On Mon, Dec 11, 2023 at 10:07:42AM +0100, Patrick Steinhardt wrote:
> > While we have several tests that check whether we correctly perform
> > auto-compaction when manually calling `reftable_stack_auto_compact()`,
> > we don't have any tests that verify whether `reftable_stack_add()` does
> > call it automatically. Add one.
> >
> > Signed-off-by: Patrick Steinhardt <[email-masked]>
> > ---
> >  reftable/stack_test.c | 49 +++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 49 insertions(+)
> >
> > diff --git a/reftable/stack_test.c b/reftable/stack_test.c
> > index 0644c8ad2e..52b4dc3b14 100644
> > --- a/reftable/stack_test.c
> > +++ b/reftable/stack_test.c
> > @@ -850,6 +850,54 @@ static void test_reftable_stack_auto_compaction(void)
> >  	clear_dir(dir);
> >  }
> >
> > +static void test_reftable_stack_add_performs_auto_compaction(void)
> > +{
> > +	struct reftable_write_options cfg = { 0 };
> > +	struct reftable_stack *st = NULL;
> > +	struct strbuf refname = STRBUF_INIT;
> > +	char *dir = get_tmp_dir(__LINE__);
> > +	int err, i, n = 20;
> > +
> > +	err = reftable_new_stack(&st, dir, cfg);
> > +	EXPECT_ERR(err);
> > +
> > +	for (i = 0; i <= n; i++) {
> > +		struct reftable_ref_record ref = {
> > +			.update_index = reftable_stack_next_update_index(st),
> > +			.value_type = REFTABLE_REF_SYMREF,
> > +			.value.symref = "master",
> > +		};
> > +
> > +		/*
> > +		 * Disable auto-compaction for all but the last runs. Like this
> > +		 * we can ensure that we indeed honor this setting and have
> > +		 * better control over when exactly auto compaction runs.
> > +		 */
> > +		st->disable_auto_compact = i != n;
> > +
> > +		strbuf_reset(&refname);
> > +		strbuf_addf(&refname, "branch-%04d", i);
> > +		ref.refname = refname.buf;
> 
> Does the reftable backend take ownership of the "refname" field? If so,
> then I think we'd want to use strbuf_detach() here to avoid a
> double-free() when you call strbuf_release() below.

No it doesn't. `reftable_stack_add()` will lock the stack and commit the
new table immediately, so there's no need to transfer ownership of
memory here.

Patrick