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From: Junio C Hamano <gitster@pobox.com>
To: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Cc: "Michał Kępień" <michal@isc.org>, git@vger.kernel.org
Subject: Re: [PATCH v2 2/3] diff: add -I<regex> that ignores matching changes
Date: Mon, 12 Oct 2020 13:00:23 -0700	[thread overview]
Message-ID: <xmqqo8l7nrjc.fsf@gitster.c.googlers.com> (raw)
In-Reply-To: <nycvar.QRO.7.76.6.2010121315170.50@tvgsbejvaqbjf.bet> (Johannes Schindelin's message of "Mon, 12 Oct 2020 13:20:13 +0200 (CEST)")

Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:

> Hi Michał,
>
> On Mon, 12 Oct 2020, Michał Kępień wrote:
>
>> @@ -5203,6 +5207,22 @@ static int diff_opt_patience(const struct option *opt,
>>  	return 0;
>>  }
>>
>> +static int diff_opt_ignore_regex(const struct option *opt,
>> +				 const char *arg, int unset)
>> +{
>> +	struct diff_options *options = opt->value;
>> +	regex_t *regex;
>> +
>> +	BUG_ON_OPT_NEG(unset);
>> +	regex = xcalloc(1, sizeof(*regex));
>> +	if (regcomp(regex, arg, REG_EXTENDED | REG_NEWLINE))
>> +		die("invalid regex: %s", arg);
>> +	ALLOC_GROW(options->ignore_regex, options->ignore_regex_nr + 1,
>> +		   options->ignore_regex_alloc);
>> +	options->ignore_regex[options->ignore_regex_nr++] = regex;
>
> A slightly more elegant way would be to have `ignore_regex` have the type
> `regex_t *` and use `ALLOC_GROW_BY()` (which zeroes the newly-added
> elements automagically).

It may be "elegant", but we we know if it is "correct" on
everybody's implementation of regex_t?

A struct like

	struct foo {
		char *str;
		char in_place_buffer[10];
	};

where str points at in_place_buffer[] only when it needs to point at
a very short string, and points at an allocated memory on heap, can
not be safely copied and used, and an array of such a struct breaks
when ALLOC_GROW_BY() needs to call realloc().  Keeping an array of
pointers to regex_t and growing it would not break even for such a
structure type.

Since we cannot rely on the implementation detail of regex_t on a
single platform, I'd rather not to see anybody suggest such an
"elegant" approach.

Thanks.

  reply	other threads:[~2020-10-12 20:01 UTC|newest]

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-01 12:06 [PATCH 0/2] " Michał Kępień
2020-10-01 12:06 ` [PATCH 1/2] " Michał Kępień
2020-10-01 18:21   ` Junio C Hamano
2020-10-07 19:48     ` Michał Kępień
2020-10-07 20:08       ` Junio C Hamano
2020-10-01 12:06 ` [PATCH 2/2] t: add -I<regex> tests Michał Kępień
2020-10-01 17:02 ` [PATCH 0/2] diff: add -I<regex> that ignores matching changes Junio C Hamano
2020-10-12  9:17 ` [PATCH v2 0/3] " Michał Kępień
2020-10-12  9:17   ` [PATCH v2 1/3] merge-base, xdiff: zero out xpparam_t structures Michał Kępień
2020-10-12 11:14     ` Johannes Schindelin
2020-10-12 17:09       ` Junio C Hamano
2020-10-12 19:52     ` Junio C Hamano
2020-10-13  6:35       ` Michał Kępień
2020-10-12  9:17   ` [PATCH v2 2/3] diff: add -I<regex> that ignores matching changes Michał Kępień
2020-10-12 11:20     ` Johannes Schindelin
2020-10-12 20:00       ` Junio C Hamano [this message]
2020-10-12 20:39         ` Johannes Schindelin
2020-10-12 21:43           ` Junio C Hamano
2020-10-13  6:37             ` Michał Kępień
2020-10-13 15:49               ` Junio C Hamano
2020-10-13  6:36       ` Michał Kępień
2020-10-13 12:02         ` Johannes Schindelin
2020-10-13 15:53           ` Junio C Hamano
2020-10-13 18:45           ` Michał Kępień
2020-10-12 18:01     ` Junio C Hamano
2020-10-13  6:38       ` Michał Kępień
2020-10-12 20:04     ` Junio C Hamano
2020-10-13  6:38       ` Michał Kępień
2020-10-12  9:17   ` [PATCH v2 3/3] t: add -I<regex> tests Michał Kępień
2020-10-12 11:49     ` Johannes Schindelin
2020-10-13  6:38       ` Michał Kępień
2020-10-13 12:00         ` Johannes Schindelin
2020-10-13 16:00           ` Junio C Hamano
2020-10-13 19:01           ` Michał Kępień
2020-10-15 11:45             ` Johannes Schindelin
2020-10-15  7:24   ` [PATCH v3 0/2] diff: add -I<regex> that ignores matching changes Michał Kępień
2020-10-15  7:24     ` [PATCH v3 1/2] merge-base, xdiff: zero out xpparam_t structures Michał Kępień
2020-10-15  7:24     ` [PATCH v3 2/2] diff: add -I<regex> that ignores matching changes Michał Kępień
2020-10-16 15:32       ` Phillip Wood
2020-10-16 18:04         ` Junio C Hamano
2020-10-19  9:48           ` Michał Kępień
2020-10-16 18:16       ` Junio C Hamano
2020-10-19  9:55         ` Michał Kępień
2020-10-19 17:29           ` Junio C Hamano
2020-10-16 10:00     ` [PATCH v3 0/2] " Johannes Schindelin
2020-10-20  6:48     ` [PATCH v4 " Michał Kępień
2020-10-20  6:48       ` [PATCH v4 1/2] merge-base, xdiff: zero out xpparam_t structures Michał Kępień
2020-10-20  6:48       ` [PATCH v4 2/2] diff: add -I<regex> that ignores matching changes Michał Kępień
2021-02-05 14:13       ` [PATCH 1/2] diff: add an API for deferred freeing Ævar Arnfjörð Bjarmason
2021-02-10 16:00         ` Johannes Schindelin
2021-02-11  3:00           ` Ævar Arnfjörð Bjarmason
2021-02-11  9:40             ` Johannes Schindelin
2021-02-11 10:21               ` Jeff King
2021-02-11 10:45                 ` [PATCH v2 0/2] " Ævar Arnfjörð Bjarmason
2021-02-11 10:45                 ` [PATCH v2 1/2] " Ævar Arnfjörð Bjarmason
2021-02-11 10:45                 ` [PATCH v2 2/2] diff: plug memory leak from regcomp() on {log,diff} -I Ævar Arnfjörð Bjarmason
2021-02-05 14:13       ` [PATCH " Ævar Arnfjörð Bjarmason

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