From: Junio C Hamano <gitster@pobox.com>
Date: Wed, 28 Apr 2021 04:20:51 GMT
Subject: Re: [PATCH v2 2/3] refs/files-backend: stop setting errno from lock_ref_oid_basic
Message-ID: <xmqqzgxjavks.fsf@gitster.g>
In-Reply-To: <db5da7d7fb5178c14c1f5733d35bb69813c9c644.1619191907.git.gitgitgadget@gmail.com>

"Han-Wen Nienhuys via GitGitGadget" <gitgitgadget@gmail.com> writes:

> From: Han-Wen Nienhuys <hanwen@google.com>
>
> Errno is a global variable written by almost all system calls, and therefore it
> is hard to reason about its state.
>
> This is a functional noop, because calls to lock_ref_oid_basic() in this file
> are followed by:
>
> * lock_ref_oid_basic (copy/rename rollback error path)
>
> * write_ref_to_lockfile (both in the rollback path and the success path of
>   copy/rename)
>
> * create_symref_locked (files_create_symref)
>
> * refs_reflog_exists (reflog expiry)
>
> These calls do I/O and therefore clobber errno. They are not inspecting the
> incoming errno.

Hmph, are you saying that these calls do I/O and always the I/O
would fail?  A system call that is successfull don't touch errno;
only the calls that resulted in failure do.