From: "René Scharfe" <l.s.r@web.de>
To: Junio C Hamano <gitster@pobox.com>, Jeff King <peff@peff.net>
Cc: Git List <git@vger.kernel.org>,
Chandra Pratap <chandrapratap3519@gmail.com>
Subject: Re: [RFC][PATCH] t-prio-queue: simplify using compound literals
Date: Sat, 6 Apr 2024 09:06:00 +0200 [thread overview]
Message-ID: <88f2063e-bddb-4479-a0c1-5bad582b9fe9@web.de> (raw)
In-Reply-To: <xmqqedbjtqnr.fsf@gitster.g>
Am 06.04.24 um 00:01 schrieb Junio C Hamano:
> Jeff King <peff@peff.net> writes:
>
>> Yeah, this seems pretty reasonable. I think we've traditionally been
>> hesitant to pass or return structs by value, but that's mostly
>> superstition.
>
> We should still be hesitant against the practice to the same degree
> that we are hesitant against struct assignment, especially when the
> struct is of nontrivial size, or the struct has a pointer member
> whose memory ownership semantics goes against shallow copying of the
> struct.
>
> In this particular case, I do not know offhand if .strftime_fmt is
> safe to be shallowly copied, but I trust you two know and/or have
> already looked at the implications.
date_mode_from_type() sets .strftime_fmt to NULL in the struct date_mode
it creates and returns. Giving a reference to it to date_mode_release()
is a safe NOOP.
show_date() passes .strftime_fmt to strbuf_addftime() and does not
retain a copy or change it.
show_ident_date() only passes its struct date_mode parameter to
show_date().
format_person_part() only passes its struct date_mode parameter to
show_ident_date().
format_reflog_person() only passes its struct date_mode parameter to
format_person_part().
get_reflog_selector() only passes its struct date_mode parameter to
show_date().
show_reflog_message() only passes its struct date_mode parameter to
get_reflog_selector().
The patch doesn't change any other function signatures.
strbuf_addftime() scans the format string and passes it to
strbuf_expand_step(), skip_prefix() and strftime(3). None of them
change it or retain a copy of the pointer.
In other words: This patch mostly affects the read-only side of struct
date_mode handling, and the date_mode_from_type() part is benign as
well.
René
next prev parent reply other threads:[~2024-04-06 7:06 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-02 18:30 [RFC][PATCH] t-prio-queue: simplify using compound literals René Scharfe
2024-04-02 20:31 ` Junio C Hamano
2024-04-02 20:41 ` Jeff King
2024-04-05 17:44 ` René Scharfe
2024-04-05 19:17 ` Jeff King
2024-04-05 22:01 ` Junio C Hamano
2024-04-06 7:06 ` René Scharfe [this message]
2024-04-07 1:28 ` Jeff King
2024-04-08 16:57 ` Junio C Hamano
2024-04-08 17:09 ` Jeff King
2024-04-11 21:23 ` Josh Steadmon
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