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From: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
To: Jeff King <peff@peff.net>
Cc: Junio C Hamano <gitster@pobox.com>,
	git@vger.kernel.org, Emily Shaffer <emilyshaffer@google.com>,
	Derrick Stolee <stolee@gmail.com>
Subject: Re: [PATCH v3 2/5] strvec: add a strvec_pushvec()
Date: Fri, 03 Sep 2021 01:19:33 +0200	[thread overview]
Message-ID: <87v93i8svd.fsf@evledraar.gmail.com> (raw)
In-Reply-To: <YSm3ofxlRB1ViBf5@coredump.intra.peff.net>


On Sat, Aug 28 2021, Jeff King wrote:

> On Fri, Aug 27, 2021 at 06:29:30PM -0700, Junio C Hamano wrote:
>
>> Junio C Hamano <gitster@pobox.com> writes:
>> 
>> >> +void strvec_pushvec(struct strvec *array, const struct strvec *items)
>> >> +{
>> >> +	int i;
>> >> +
>> >> +	for (i = 0; i < items->nr; i++)
>> >> +		strvec_push(array, items->v[i]);
>> >> +}
>> >
>> > This implementation is not wrong per-se, but is somewhat
>> > disappointing.  When items->nr is large, especially relative to the
>> > original array->alloc, it would incur unnecessary reallocations that
>> > we can easily avoid by pre-sizing the array before pushing the
>> > elements of items from it.
>> >
>> > In the original code that became the first user of this helper, it
>> > may not have made much difference, but now it is becoming a more
>> > generally reusable API function, we should care.
>> 
>> And if we do not care, you can rewrite the code that became the
>> first user of this helper to instead call strvec_pushv() on the
>> items->v array that is guaranteed to be NULL terminated, without
>> inventing this new helper.
>
> I came here to say that. ;)
>
> I do not mind using pushv() directly, or a pushvec() that is a
> convenience wrapper for pushv(). Even better if that wrapper is smart
> enough to pre-allocate based on items->nr, as you mentioned, but that
> can also come later.
>
> One thing that did surprise me: the use of "int" here for iterating,
> rather than size_t. But it seems that strvec is already storing ints,
> which is an accident!

Is it really? If you temporarily try to say convert that to "size_t *nr"
to have the compiler catch all the cases where we use "nr", and then
s/size_t/int/g those all, you'll find that e.g. setup_revisions() and
the like expect to take either "int argc" or the strvec equivalent.

We can sensibly convert some of those to size_t, but not all, and the
int v.s. size_t inconsistency as a result feels weird.

Since the main point of this API is to be a wrapper for what a C main()
would take, shouldn't its prototype mirror its prototype? I.e. we should
stick to "int" here?

> I think we'd want the patch below. It can be applied independently
> (though if we do take the index-iterating version of Ævar's patch, I
> think it should switch to size_t).
>
> -- >8 --
> Subject: [PATCH] strvec: use size_t to store nr and alloc
>
> We converted argv_array (which later became strvec) to use size_t in
> 819f0e76b1 (argv-array: use size_t for count and alloc, 2020-07-28) in
> order to avoid the possibility of integer overflow. But later, commit
> d70a9eb611 (strvec: rename struct fields, 2020-07-28) accidentally
> converted these back to ints!
>
> Those two commits were part of the same patch series. I'm pretty sure
> what happened is that they were originally written in the opposite order
> and then cleaned up and re-ordered during an interactive rebase. And
> when resolving the inevitable conflict, I mistakenly took the "rename"
> patch completely, accidentally dropping the type change.
>
> We can correct it now; better late than never.
>
> Signed-off-by: Jeff King <peff@peff.net>
> ---
>  strvec.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/strvec.h b/strvec.h
> index fdcad75b45..6b3cbd6758 100644
> --- a/strvec.h
> +++ b/strvec.h
> @@ -29,8 +29,8 @@ extern const char *empty_strvec[];
>   */
>  struct strvec {
>  	const char **v;
> -	int nr;
> -	int alloc;
> +	size_t nr;
> +	size_t alloc;
>  };
>  
>  #define STRVEC_INIT { empty_strvec, 0, 0 }


  parent reply	other threads:[~2021-09-02 23:23 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-27  0:41 [PATCH 0/4] bundle: show progress on "unbundle" Ævar Arnfjörð Bjarmason
2021-07-27  0:41 ` [PATCH 1/4] bundle API: start writing API documentation Ævar Arnfjörð Bjarmason
2021-07-27  0:41 ` [PATCH 2/4] bundle API: change "flags" to be "extra_index_pack_args" Ævar Arnfjörð Bjarmason
2021-07-27  0:41 ` [PATCH 3/4] index-pack: add --progress-title option Ævar Arnfjörð Bjarmason
2021-07-27  0:41 ` [PATCH 4/4] bundle: show progress on "unbundle" Ævar Arnfjörð Bjarmason
2021-08-23 11:02 ` [PATCH v2 0/4] " Ævar Arnfjörð Bjarmason
2021-08-23 11:02   ` [PATCH v2 1/4] bundle API: start writing API documentation Ævar Arnfjörð Bjarmason
2021-08-24 17:01     ` Derrick Stolee
2021-08-24 21:48       ` Ævar Arnfjörð Bjarmason
2021-08-23 11:02   ` [PATCH v2 2/4] bundle API: change "flags" to be "extra_index_pack_args" Ævar Arnfjörð Bjarmason
2021-08-24 17:09     ` Derrick Stolee
2021-08-24 21:41       ` Ævar Arnfjörð Bjarmason
2021-08-24 21:48         ` Derrick Stolee
2021-08-23 11:02   ` [PATCH v2 3/4] index-pack: add --progress-title option Ævar Arnfjörð Bjarmason
2021-08-24 17:18     ` Derrick Stolee
2021-08-24 21:40       ` Ævar Arnfjörð Bjarmason
2021-08-23 11:02   ` [PATCH v2 4/4] bundle: show progress on "unbundle" Ævar Arnfjörð Bjarmason
2021-08-24 17:23     ` Derrick Stolee
2021-08-24 21:39       ` Ævar Arnfjörð Bjarmason
2021-08-26 14:05 ` [PATCH v3 0/5] " Ævar Arnfjörð Bjarmason
2021-08-26 14:05   ` [PATCH v3 1/5] bundle API: start writing API documentation Ævar Arnfjörð Bjarmason
2021-08-26 14:05   ` [PATCH v3 2/5] strvec: add a strvec_pushvec() Ævar Arnfjörð Bjarmason
2021-08-28  1:23     ` Junio C Hamano
2021-08-28  1:29       ` Junio C Hamano
2021-08-28  4:12         ` Jeff King
2021-08-29 23:54           ` Junio C Hamano
2021-08-30 17:30             ` Derrick Stolee
2021-09-02 23:19           ` Ævar Arnfjörð Bjarmason [this message]
2021-09-03  5:05             ` Junio C Hamano
2021-09-03 11:06             ` Jeff King
2021-08-26 14:05   ` [PATCH v3 3/5] bundle API: change "flags" to be "extra_index_pack_args" Ævar Arnfjörð Bjarmason
2021-08-28  1:44     ` Junio C Hamano
2021-08-26 14:05   ` [PATCH v3 4/5] index-pack: add --progress-title option Ævar Arnfjörð Bjarmason
2021-08-28  1:50     ` Junio C Hamano
2021-08-26 14:05   ` [PATCH v3 5/5] bundle: show progress on "unbundle" Ævar Arnfjörð Bjarmason
2021-08-28  1:54     ` Junio C Hamano
2021-09-02 22:47       ` Ævar Arnfjörð Bjarmason
2021-09-05  7:34   ` [PATCH v4 0/4] " Ævar Arnfjörð Bjarmason
2021-09-05  7:34     ` [PATCH v4 1/4] bundle API: start writing API documentation Ævar Arnfjörð Bjarmason
2021-09-05  7:34     ` [PATCH v4 2/4] bundle API: change "flags" to be "extra_index_pack_args" Ævar Arnfjörð Bjarmason
2021-09-05  7:34     ` [PATCH v4 3/4] index-pack: add --progress-title option Ævar Arnfjörð Bjarmason
2021-09-05  7:34     ` [PATCH v4 4/4] bundle: show progress on "unbundle" Ævar Arnfjörð Bjarmason

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