From: Jeff King <peff@peff.net>
To: Junio C Hamano <gitster@pobox.com>
Cc: git@vger.kernel.org
Subject: Re: [PATCH] builtin/mv.c: use correct type to compute size of an array element
Date: Thu, 7 Jul 2022 14:42:21 -0400 [thread overview]
Message-ID: <YscpDTgwxUko/aZM@coredump.intra.peff.net> (raw)
In-Reply-To: <xmqq8rp54r4l.fsf@gitster.g>
On Wed, Jul 06, 2022 at 07:02:18PM -0700, Junio C Hamano wrote:
> * Should we in general use sizeof(TYPE) in these cases, instead
> of the size of the zeroth element, e.g.
>
> memmove(source + i, source + i + 1,
> n * sizeof(source[i]));
>
> It would have been caught by the above Coccinelle rule (we are
> taking the size of *dst).
I'm not sure I understand this. As you noted in a later email, using
sizeof(TYPE) is less maintainable if the type of "source" changes. But
later you mention using "*source" instead of "source[i]". I don't think
there is a particular reason to prefer one over the other from the
compiler perspective. I find "*source" more idiomatic (but better still
of course is MOVE_ARRAY, which removes the choice entirely).
> * Shouldn't we have an array of struct with four members, instead
> of four parallel arrays, e.g.
>
> struct {
> const char *source;
> const char *destination;
> enum update_mode mode;
> const char *submodule_gitfile;
> } *mv_file;
>
> The latter question is important to answer before we accept
> Coccinelle-suggested rewrite to use four MOVE_ARRAY() on these
> four parallel arrays on top of this fix.
I think that would make the code a lot cleaner. But it looks like
"source" and "destination" come from separate calls to
internal_prefix_pathspec(). So you'd have to reconcile that. And
there's some extra trickiness that sometimes "destination" comes from
"dest_path", which _isn't_ always the same size as "source".
So I suspect the code which uses these arrays would be cleaner with a
struct, but the setup may get worse. :)
-Peff
next prev parent reply other threads:[~2022-07-07 18:42 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-07 2:02 [PATCH] builtin/mv.c: use correct type to compute size of an array element Junio C Hamano
2022-07-07 5:52 ` [PATCH v2] builtin/mv.c: use the MOVE_ARRAY() macro instead of memmove() Junio C Hamano
2022-07-10 1:33 ` [PATCH v3] " Junio C Hamano
2022-07-18 20:30 ` Derrick Stolee
2022-07-07 12:11 ` [PATCH] builtin/mv.c: use correct type to compute size of an array element Ævar Arnfjörð Bjarmason
2022-07-07 18:10 ` Junio C Hamano
2022-07-07 19:11 ` René Scharfe
2022-07-09 8:16 ` René Scharfe
2022-07-10 5:38 ` Junio C Hamano
2022-07-10 10:05 ` [PATCH] cocci: avoid normalization rules for memcpy René Scharfe
2022-07-10 14:45 ` Ævar Arnfjörð Bjarmason
2022-07-10 16:32 ` Ævar Arnfjörð Bjarmason
2022-07-10 19:30 ` Junio C Hamano
2022-07-11 17:11 ` René Scharfe
2022-07-11 20:05 ` Ævar Arnfjörð Bjarmason
2022-07-07 18:27 ` [PATCH] builtin/mv.c: use correct type to compute size of an array element René Scharfe
2022-07-07 18:42 ` Jeff King [this message]
2022-07-07 20:25 ` Junio C Hamano
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