git.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Johannes Schindelin <Johannes.Schindelin@gmx.de>
To: Jeff King <peff@peff.net>
Cc: "René Scharfe" <l.s.r@web.de>,
	"Git Mailing List" <git@vger.kernel.org>,
	"Junio C Hamano" <gitster@pobox.com>
Subject: sizeof(var) vs sizeof(type), was Re: [PATCH] git: use COPY_ARRAY and MOVE_ARRAY in handle_alias()
Date: Thu, 26 Sep 2019 15:22:45 +0200 (CEST)	[thread overview]
Message-ID: <nycvar.QRO.7.76.6.1909261521380.15067@tvgsbejvaqbjf.bet> (raw)
In-Reply-To: <20190923222659.GA22645@sigill.intra.peff.net>

[-- Attachment #1: Type: text/plain, Size: 1101 bytes --]

Hi Peff,

On Mon, 23 Sep 2019, Jeff King wrote:

> On Thu, Sep 19, 2019 at 10:48:30PM +0200, René Scharfe wrote:
>
> > Use the macro COPY_ARRAY to copy array elements and MOVE_ARRAY to do the
> > same for moving them backwards in an array with potential overlap.  The
> > result is shorter and safer, as it infers the element type automatically
> > and does a (very) basic type compatibility check for its first two
> > arguments.
> >
> > These cases were missed by Coccinelle and contrib/coccinelle/array.cocci
> > because the type of the elements is "const char *", not "char *", and
> > the rules in the semantic patch cautiously insist on the sizeof operator
> > being used on exactly the same type to avoid generating transformations
> > that introduce subtle bugs into tricky code.
>
> Another good reason to use "sizeof(var)" instead of sizeof(type)". :)

That is indeed a very good reason, in addition to getting the type right
automatically (by virtue of letting the compiler pick it).

Should we make this an explicit guideline in our documentation?

Ciao,
Dscho

  reply	other threads:[~2019-09-26 13:23 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-19 20:48 [PATCH] git: use COPY_ARRAY and MOVE_ARRAY in handle_alias() René Scharfe
2019-09-23 22:27 ` Jeff King
2019-09-26 13:22   ` Johannes Schindelin [this message]
2019-09-26 13:36     ` sizeof(var) vs sizeof(type), was " Derrick Stolee
2019-09-26 13:43       ` SZEDER Gábor
2019-09-26 15:24       ` Philip Oakley
2019-09-26 16:16         ` Derrick Stolee

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.7.76.6.1909261521380.15067@tvgsbejvaqbjf.bet \
    --to=johannes.schindelin@gmx.de \
    --cc=git@vger.kernel.org \
    --cc=gitster@pobox.com \
    --cc=l.s.r@web.de \
    --cc=peff@peff.net \
    /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
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
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).