git.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Johannes Schindelin <Johannes.Schindelin@gmx.de>
To: Junio C Hamano <gitster@pobox.com>
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 22:39:20 +0200 (CEST)	[thread overview]
Message-ID: <nycvar.QRO.7.76.6.2010122236130.50@tvgsbejvaqbjf.bet> (raw)
In-Reply-To: <xmqqo8l7nrjc.fsf@gitster.c.googlers.com>

[-- Attachment #1: Type: text/plain, Size: 2158 bytes --]

Hi Junio,

On Mon, 12 Oct 2020, Junio C Hamano wrote:

> 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.

True, such an implementation detail is totally conceivable.

Thanks for the sanity check.

Having said that, my suggestion to use `ALLOC_GROW_BY()` was triggered by
the use of `xcalloc()`, and now that I think further about it, an
`xmalloc()` should be plenty enough: `regcomp()` does not need that struct
to be initialized to all zero.

Ciao,
Dscho

  reply	other threads:[~2020-10-12 20:39 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
2020-10-12 20:39         ` Johannes Schindelin [this message]
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=nycvar.QRO.7.76.6.2010122236130.50@tvgsbejvaqbjf.bet \
    --to=johannes.schindelin@gmx.de \
    --cc=git@vger.kernel.org \
    --cc=gitster@pobox.com \
    --cc=michal@isc.org \
    --subject='Re: [PATCH v2 2/3] diff: add -I<regex> that ignores matching changes' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).