Fam Zheng <f...@redhat.com> writes:
> On Tue, 11/17 17:05, Markus Armbruster wrote:
>> Suggested-by: Eric Blake <ebl...@redhat.com>
>> Signed-off-by: Markus Armbruster <arm...@redhat.com>
>> Reviewed-by: Eric Blake <ebl...@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?
The documentation above is about keeping the first and throwing away the
second, i.e. first one wins. I haven't seen in "last one wins" the
code, yet. How to do it is thus left as exercise to the reader.
You can only return one *error*. You can still combine multiple
*messages* into one error. There is no recommended way, at least not
yet.
You could use the hint mechanism to append additional messages:
foo(arg, &err);
bar(arg, &err2);
if (err2) {
error_append_hint(err, "additionally, %s", error_get_pretty(err2));
error_free(err2);
}
Just an example, the wording of the hint is probably not a good idea.
You may want to modify the first message, too. The obvious technique
for receiving, modifying and passing on an error:
frob(arg, &err)
error_setg(errp, "Could not frobnicate: %s",
error_get_pretty(local_err));
