Re: [Qemu-devel] [PATCH] error: Document how to accumulate multiple errors

[Fam Zheng <famz@redhat.com>]

On Tue, 11/17 17:05, Markus Armbruster wrote:
> Suggested-by: Eric Blake <eblake@redhat.com>
> Signed-off-by: Markus Armbruster <armbru@redhat.com>
> Reviewed-by: Eric Blake <eblake@redhat.com>
> ---
>  include/qapi/error.h | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/include/qapi/error.h b/include/qapi/error.h
> index 4d42cdc..b2362a5 100644
> --- a/include/qapi/error.h
> +++ b/include/qapi/error.h
> @@ -76,6 +76,23 @@
>   * But when all you do with the error is pass it on, please use
>   *     foo(arg, errp);
>   * for readability.
> + *
> + * Receive and accumulate multiple errors (first one wins):
> + *     Error *err = NULL, *local_err = NULL;
> + *     foo(arg, &err);
> + *     bar(arg, &local_err);
> + *     error_propagate(&err, local_err);
> + *     if (err) {
> + *         handle the error...
> + *     }
> + *
> + * Do *not* "optimize" this to
> + *     foo(arg, &err);
> + *     bar(arg, &err); // WRONG!
> + *     if (err) {
> + *         handle the error...
> + *     }
> + * because this may pass a non-null err to bar().
>   */
>  
>  #ifndef ERROR_H
> -- 
> 2.4.3
> 
> 

Curious if there is a recommended way to report both error messages to caller,
rather than overwriting the first with the second?

Fam