Re: [PATCH v3 2/2] xgethostname: handle long hostnames

> Hi,
>
> David Turner wrote:
>
>> If the full hostname doesn't fit in the buffer supplied to
>> gethostname, POSIX does not specify whether the buffer will be
>> null-terminated, so to be safe, we should do it ourselves.  Introduce
>> new function, xgethostname, which ensures that there is always a \0
>> at the end of the buffer.
>
> I think we should detect the error instead of truncating the hostname.
> That (on top of your patch) would look like the following.
>
> Thoughts?
> Jonathan
>
> diff --git i/wrapper.c w/wrapper.c
> index d837417709..e218bd3bef 100644
> --- i/wrapper.c
> +++ w/wrapper.c
> @@ -660,11 +660,13 @@ int xgethostname(char *buf, size_t len)
>  {
>  	/*
>  	 * If the full hostname doesn't fit in buf, POSIX does not
> -	 * specify whether the buffer will be null-terminated, so to
> -	 * be safe, do it ourselves.
> +	 * guarantee that an error will be returned. Check for ourselves
> +	 * to be safe.
>  	 */
>  	int ret = gethostname(buf, len);
> -	if (!ret)
> -		buf[len - 1] = 0;
> +	if (!ret && !memchr(buf, 0, len)) {
> +		errno = ENAMETOOLONG;
> +		return -1;
> +	}