From: Junio C Hamano <gitster@pobox.com>
To: Jeff King <peff@peff.net>
Cc: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
git@vger.kernel.org, "Denton Liu" <liu.denton@gmail.com>,
"Jeff Hostetler" <jeffhost@microsoft.com>,
"Johannes Schindelin" <Johannes.Schindelin@gmx.de>
Subject: Re: [PATCH v2] trace2: refactor to avoid gcc warning under -O3
Date: Wed, 12 May 2021 06:09:29 +0900 [thread overview]
Message-ID: <xmqqcztxkmeu.fsf@gitster.g> (raw)
In-Reply-To: <YJrIMbr6VkYGQMfs@coredump.intra.peff.net> (Jeff King's message of "Tue, 11 May 2021 14:08:49 -0400")
Jeff King <peff@peff.net> writes:
> I also wondered briefly why we needed the out-parameter at all, and not
> just letting the caller look at errno. The answer is that we need to
> preserve it across the close() call. The more usual thing in our code
> base _would_ be to use saved_errno, but not have it as an out-parameter.
>
> I.e.:
>
> diff --git a/trace2/tr2_dst.c b/trace2/tr2_dst.c
> index ae052a07fe..bda283e7f4 100644
> --- a/trace2/tr2_dst.c
> +++ b/trace2/tr2_dst.c
> @@ -204,15 +204,16 @@ static int tr2_dst_try_uds_connect(const char *path, int sock_type, int *out_fd)
>
> fd = socket(AF_UNIX, sock_type, 0);
> if (fd == -1)
> - return errno;
> + return -1;
>
> sa.sun_family = AF_UNIX;
> strlcpy(sa.sun_path, path, sizeof(sa.sun_path));
>
> if (connect(fd, (struct sockaddr *)&sa, sizeof(sa)) == -1) {
> - int e = errno;
> + int saved_errno = errno;
> close(fd);
> - return e;
> + errno = saved_errno;
> + return -1;
> }
>
> *out_fd = fd;
> @@ -227,7 +228,6 @@ static int tr2_dst_try_unix_domain_socket(struct tr2_dst *dst,
> {
> unsigned int uds_try = 0;
> int fd;
> - int e;
> const char *path = NULL;
>
> /*
> @@ -271,23 +271,21 @@ static int tr2_dst_try_unix_domain_socket(struct tr2_dst *dst,
> }
>
> if (uds_try & TR2_DST_UDS_TRY_STREAM) {
> - e = tr2_dst_try_uds_connect(path, SOCK_STREAM, &fd);
> - if (!e)
> + if (!tr2_dst_try_uds_connect(path, SOCK_STREAM, &fd))
> goto connected;
> - if (e != EPROTOTYPE)
> + if (errno != EPROTOTYPE)
> goto error;
> }
> if (uds_try & TR2_DST_UDS_TRY_DGRAM) {
> - e = tr2_dst_try_uds_connect(path, SOCK_DGRAM, &fd);
> - if (!e)
> + if (!tr2_dst_try_uds_connect(path, SOCK_DGRAM, &fd))
> goto connected;
> }
>
> error:
> if (tr2_dst_want_warning())
> warning("trace2: could not connect to socket '%s' for '%s' tracing: %s",
> path, tr2_sysenv_display_name(dst->sysenv_var),
> - strerror(e));
> + strerror(errno));
>
> tr2_dst_trace_disable(dst);
> return 0;
>
>
> I do prefer that approach, since I think it's more idiomatic for our
> code base, but for the sake of wrapping up this simple fix which has
> been discussed much more than I think it deserves, I am OK with either.
> :)
Yeah, the above looks nicer to me too.
>
> (I also found it interesting that the "error" goto in the caller only
> has one source. I think the code would be easier to reason about if it
> were inlined, but I'm happy to stop here for now).
>
> -Peff
next prev parent reply other threads:[~2021-05-11 21:09 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-01 7:30 [PATCH] Fix -Wmaybe-uninitialized warnings under -O0 Denton Liu
[not found] ` <CAPUEspgBkmxszgBee8C9hZnEwqztf-XKEj7LB_jWVFJaJCge0w@mail.gmail.com>
2020-04-01 9:05 ` Denton Liu
2020-04-01 9:52 ` Jeff King
2020-04-01 14:06 ` Denton Liu
2020-04-03 14:04 ` Jeff King
2020-04-03 14:38 ` Jeff King
2020-04-04 12:07 ` Denton Liu
2020-04-04 14:21 ` Jeff King
2021-05-05 8:40 ` [PATCH] trace2: refactor to avoid gcc warning under -O3 Ævar Arnfjörð Bjarmason
2021-05-05 9:47 ` Junio C Hamano
2021-05-05 13:34 ` Jeff King
2021-05-05 14:38 ` Johannes Schindelin
2021-05-06 1:26 ` Junio C Hamano
2021-05-06 20:29 ` Johannes Schindelin
2021-05-06 21:10 ` Junio C Hamano
2021-05-11 14:34 ` Johannes Schindelin
2021-05-11 18:00 ` Jeff King
2021-05-11 20:58 ` Junio C Hamano
2021-05-11 21:07 ` Jeff King
2021-05-11 21:33 ` Junio C Hamano
2021-05-11 7:03 ` Junio C Hamano
2021-05-11 13:04 ` [PATCH v2] " Ævar Arnfjörð Bjarmason
2021-05-11 16:40 ` Jeff Hostetler
2021-05-11 17:54 ` Jeff King
2021-05-11 18:08 ` Jeff King
2021-05-11 21:09 ` Junio C Hamano [this message]
2021-05-20 0:20 ` Junio C Hamano
2021-05-20 11:05 ` [PATCH v3] " Ævar Arnfjörð Bjarmason
2021-05-20 13:13 ` Jeff King
2021-05-20 22:08 ` Junio C Hamano
2021-05-21 9:34 ` Jeff King
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