From: Junio C Hamano <gitster@pobox.com>
Date: Tue, 06 Dec 2022 23:39:35 GMT
Subject: Re: [PATCH] setup: avoid unconditional open with write flags
Message-ID: <xmqqr0xc85l4.fsf@gitster.g>
In-Reply-To: <f49b915e-46d1-7e53-ae4f-b01c2028b70d@web.de>

René Scharfe <l.s.r@web.de> writes:

> Can opening /dev/null (or NUL on Windows) multiple times instead of dup'ing
> cause issues?  Can we e.g. lock ourselves out?

258e93a1 (daemon: if one of the standard fds is missing open it to
/dev/null, 2006-07-13) unfortunately does not explain why it was
done this way.

Given that "command </dev/null >/dev/null 2>/dev/null" should work fine,
I suspect that the "once we open a throw-away descriptor, instead of
opening the same file again, dup the fd and reuse" was done not for
correctness but for performance, under the assumption that open() is
more expensive?