Subject: Re: [PATCH v2] trace2: refactor to avoid gcc warning under -O3

From: Junio C Hamano <[email-masked]>
Date: Thu, 20 May 2021 09:20:58 +0900

Jeff King <[email-masked]> 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;
>  	}
>  
> ...
>
> 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.
> :)

I think this alternative is more readable as well.

I'll mark the topic to be "Expecting a reroll" in the what's cooking
report.

Thanks.