Re: [PATCH 06/15] copy.c: make copy_fd preserve meaningful errno

[Junio C Hamano <gitster@pobox.com>]

Ronnie Sahlberg <sahlberg@google.com> writes:

> commit 306805ccd147bfdf160b288a8d51fdf9b77ae0fa upstream.
>
> Update copy_fd to return a meaningful errno on failure.

These two are good changes, but makes me wonder if more places
benefit from having error_errno() that does the "save away errno,
use strerror(errno) to give an error message and restore errno"
for us.

Not meant as a suggestion for further changes in this series, but as
a future discussion item.

>
> Change-Id: I771f9703acc816902affcf35ff2a56d9426315ac
> Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
> Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
> ---
>  copy.c | 15 ++++++++++-----
>  1 file changed, 10 insertions(+), 5 deletions(-)
>
> diff --git a/copy.c b/copy.c
> index f2970ec..a8d366e 100644
> --- a/copy.c
> +++ b/copy.c
> @@ -8,12 +8,17 @@ int copy_fd(int ifd, int ofd)
>  		if (!len)
>  			break;
>  		if (len < 0) {
> -			return error("copy-fd: read returned %s",
> -				     strerror(errno));
> +			int save_errno = errno;
> +			error("copy-fd: read returned %s", strerror(errno));
> +			errno = save_errno;
> +			return -1;
> +		}
> +		if (write_in_full(ofd, buffer, len) < 0) {
> +			int save_errno = errno;
> +			error("copy-fd: write returned %s", strerror(errno));
> +			errno = save_errno;
> +			return -1;
>  		}
> -		if (write_in_full(ofd, buffer, len) < 0)
> -			return error("copy-fd: write returned %s",
> -				     strerror(errno));
>  	}
>  	return 0;
>  }