Re: [PATCH 1/2] sequencer: stop exporting GIT_REFLOG_ACTION

[Phillip Wood <phillip.wood123@xxxxxxxxx>]

Hi Ævar

On 07/11/2022 16:12, Ævar Arnfjörð Bjarmason wrote:
> On Fri, Nov 04 2022, Phillip Wood via GitGitGadget wrote:
>
> > From: Phillip Wood <phillip.wood@xxxxxxxxxxxxx>
>
> > +static const char *sequencer_reflog_action(struct replay_opts *opts)
> > +{
> > +	if (!opts->reflog_action) {
> > +		opts->reflog_action = getenv(GIT_REFLOG_ACTION);
> > +		opts->reflog_action =
> > +			xstrdup(opts->reflog_action ? opts->reflog_action
> > +						    : action_name(opts));
> > +	}
> > +
> > +	return opts->reflog_action;
> > +}
>
> We always return an xstrdup'd here, so this should be a "char *" return
> value, not a "const char *"., but

We always return the same string, it is only allocated on the first 
call. opt->reflog_action is freed at the end of the rebase in 
sequencer_remove_state().

> >   __attribute__((format (printf, 3, 4)))
> >   static const char *reflog_message(struct replay_opts *opts,
> >   	const char *sub_action, const char *fmt, ...)
> >   {
> >   	va_list ap;
> >   	static struct strbuf buf = STRBUF_INIT;
> > -	char *reflog_action = getenv(GIT_REFLOG_ACTION);
> >   
> >   	va_start(ap, fmt);
> >   	strbuf_reset(&buf);
>
> Here we just reset the strbuf...
>
> > -	strbuf_addstr(&buf, reflog_action ? reflog_action : action_name(opts));
> > +	strbuf_addstr(&buf, sequencer_reflog_action(opts));
>
> Here we leak the freshly xstrdup'd value, mostly untested, but shouldn't
> this instead be:
> 	
> 	diff --git a/sequencer.c b/sequencer.c
> 	index e23f6f0b718..58a97e04c67 100644
> 	--- a/sequencer.c
> 	+++ b/sequencer.c
> 	@@ -3695,10 +3695,11 @@ static const char *reflog_message(struct replay_opts *opts,
> 	 {
> 	 	va_list ap;
> 	 	static struct strbuf buf = STRBUF_INIT;
> 	+	char *msg = sequencer_reflog_action(opts);
> 	
> 	 	va_start(ap, fmt);
> 	 	strbuf_reset(&buf);
> 	-	strbuf_addstr(&buf, sequencer_reflog_action(opts));
> 	+	strbuf_attach(&buf, msg, strlen(msg), strlen(msg) + 1);
> 	 	if (sub_action)
> 	 		strbuf_addf(&buf, " (%s)", sub_action);
> 	 	if (fmt) {
>
> Of course that requires dropping the "const", per the above...
>
>
> >   	if (sub_action)
> >   		strbuf_addf(&buf, " (%s)", sub_action);
> >   	if (fmt) {
> > @@ -4497,7 +4511,7 @@ static int checkout_onto(struct repository *r, struct replay_opts *opts,
> >   				RESET_HEAD_RUN_POST_CHECKOUT_HOOK,
> >   		.head_msg = reflog_message(opts, "start", "checkout %s",
> >   					   onto_name),
> > -		.default_reflog_action = "rebase"
> > +		.default_reflog_action = sequencer_reflog_action(opts)
>
> Here we'd before hand a fixed string to reset_head(), but now it's
> xstrdup()'d, but the corresponding free() on that side is missing.
>
> But aren't we always just returing "rebase" here still?

Yes but I think it makes sense to call squencer_reflog_action() in case 
this changes in the future. Note I don't think this is leaking anything.

> > [...]
> > @@ -5116,7 +5121,7 @@ static int single_pick(struct repository *r,
> >   			TODO_PICK : TODO_REVERT;
> >   	item.commit = cmit;
> >   
> > -	setenv(GIT_REFLOG_ACTION, action_name(opts), 0);
> > +	opts->reflog_message = sequencer_reflog_action(opts);
> >   	return do_pick_commit(r, &item, opts, 0, &check_todo);
>
> Here you're adding a new memory leak, which you can see if you run
> e.g. the 1st test of ./t1013-read-tree-submodule.sh before & after this
> change.

I'm not sure how, opts->reflog_message will be a copy of 
opts->reflog_action which is freed at the end of the rebase. I'll have a 
proper look tomorrow to see if I'm missing something.

Best Wishes

Phillip