From: Brandon Casey <drafnel@gmail.com>
To: Junio C Hamano <gitster@pobox.com>
Cc: git <git@vger.kernel.org>, Kyle Evans <kevans@freebsd.org>,
Jeff King <peff@peff.net>
Subject: Re: fread reading directories
Date: Mon, 8 Jun 2020 12:08:21 -0700 [thread overview]
Message-ID: <CA+sFfMcQ+HQPk3SMsBhWjfLiVLzfhHSv9OpzPHAJt5b50TEPeQ@mail.gmail.com> (raw)
In-Reply-To: <xmqqlfkxlbn4.fsf@gitster.c.googlers.com>
On Mon, Jun 8, 2020 at 10:18 AM Junio C Hamano <gitster@pobox.com> wrote:
>
> It may make sense to do one of the two things:
>
> - The lighter weight one is to rename the macro to the reflect the
> trait we are trying to capture more faithfully: "fopen opens
> directories" and leave the code and performance characteristics
> as-is.
>
> - Heavier weight one is to audit callers of fopen() and only let
> those that know they do not have a directory directly call
> fopen(). The other callers would call our wrapper under a
> different name. This way, the former won't have to pay the
> overhead of checking for "you gave me a directory but I only take
> a file" error twice. This is what Brandon proposed in the
> thread.
>
> Doing neither would leave this seed of confusion for later readers,
> which is not ideal. I am tempted to say that we for now should do
> an even lighter variant of the former, which is to give a comment.
>
> Thoughts?
I'd suggest a medium weight approach which would be to introduce a new
function with an appropriate name (fopen_file_only()?) that behaves
the way we want it to, and replace every existing fopen() call with
this new function. We could introduce a new macro, which I think
would only be used on Windows, to say "fopen already fails to open
directories" (FOPEN_FAILS_ON_DIRECTORIES?) so that fopen_file_only
could be simplified to just a bare fopen there. That way it's clear to
the reader, at the callsite, that the call does not have the standard
behavior of fopen.
Then, FREAD_READS_DIRECTORIES could be removed from all but the 1 or 2
platforms that it was originally set for. I'd imagine that we'd
basically just promote the git_fopen() function from compat to become
the implementation of the first tier fopen_file_only() function. On
the FREAD_READS_DIRECTORIES platforms, a bare fopen would also become
fopen_file_only(). The call to fopen() within fopen_file_only() would
obviously need to take this into account to ensure that it calls the
real fopen().
I think this would put the pieces in place for someone to audit all of
the existing uses of fopen_file_only() and potentially replace them
with a straight fopen() if appropriate. And it would allow future code
to explicitly make the choice between fopen_file_only() or just
fopen().
None of this would produce any functional change on any of our
platforms, but I think it would make things more clear.
-Brandon
next prev parent reply other threads:[~2020-06-08 19:08 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-06 22:36 fread reading directories Kyle Evans
2020-06-07 17:05 ` Junio C Hamano
2020-06-07 17:16 ` Kyle Evans
2020-06-08 17:18 ` Junio C Hamano
2020-06-08 19:08 ` Brandon Casey [this message]
2020-06-08 19:41 ` Randall S. Becker
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