Re: [Qemu-devel] [PATCH] vl.c: move "if (fd < 0)" into "if (fd <= STDERR_FILENO)"

[Peter Maydell]

On 28 December 2013 08:52, Chen Gang <address@hidden> wrote:
> For valid 'fd' (in most cases), it is enough to only check whether it
> is larger than STDERR_FILENO, so recommend to move "if (fd < 0)" into
> failure processing block.

> @@ -1064,15 +1064,10 @@ static int parse_add_fd(QemuOpts *opts, void *opaque)
>      fdset_id = qemu_opt_get_number(opts, "set", -1);
>      fd_opaque = qemu_opt_get(opts, "opaque");
>
> -    if (fd < 0) {
> -        qerror_report(ERROR_CLASS_GENERIC_ERROR,
> -                      "fd option is required and must be non-negative");
> -        return -1;
> -    }
> -
>      if (fd <= STDERR_FILENO) {
>          qerror_report(ERROR_CLASS_GENERIC_ERROR,
> -                      "fd cannot be a standard I/O stream");
> +                      fd < 0 ? "fd option is required and must be 
> non-negative"
> +                             : "fd cannot be a standard I/O stream");
>          return -1;
>      }

This patch doesn't change the behaviour, but I think it
makes the code less clear to read (because we've
folded two different error cases into one and then split
them out again with a ternary operator on the string).
This isn't performance critical code (it's run only a few
times and only at startup), so I think we should favour
clarity and ease-of-reading, and I think the existing code
is better here.

thanks
-- PMM