Re: [PATCH 01/46] error: Improve examples in error.h's big comment

[Markus Armbruster]

Greg Kurz <groug@kaod.org> writes:

> On Wed, 24 Jun 2020 18:42:59 +0200
> Markus Armbruster <armbru@redhat.com> wrote:
>
>> Show errp instead of &err where &err is actually unusual.  Add a
>> missing declaration.  Add a second error pileup example.
>> 
>> Signed-off-by: Markus Armbruster <armbru@redhat.com>
>> ---
>>  include/qapi/error.h | 19 +++++++++++++++----
>>  1 file changed, 15 insertions(+), 4 deletions(-)
>> 
>> diff --git a/include/qapi/error.h b/include/qapi/error.h
>> index ad5b6e896d..1a5ea25e12 100644
>> --- a/include/qapi/error.h
>> +++ b/include/qapi/error.h
>> @@ -16,15 +16,15 @@
>>   * Error reporting system loosely patterned after Glib's GError.
>>   *
>>   * Create an error:
>> - *     error_setg(&err, "situation normal, all fouled up");
>> + *     error_setg(errp, "situation normal, all fouled up");
>>   *
>>   * Create an error and add additional explanation:
>> - *     error_setg(&err, "invalid quark");
>> - *     error_append_hint(&err, "Valid quarks are up, down, strange, "
>> + *     error_setg(errp, "invalid quark");
>> + *     error_append_hint(errp, "Valid quarks are up, down, strange, "
>>   *                       "charm, top, bottom.\n");
>>   *
>>   * Do *not* contract this to
>> - *     error_setg(&err, "invalid quark\n"
>> + *     error_setg(errp, "invalid quark\n" // WRONG!
>>   *                "Valid quarks are up, down, strange, charm, top, 
>> bottom.");
>>   *
>>   * Report an error to the current monitor if we have one, else stderr:
>> @@ -108,12 +108,23 @@
>>   *     }
>>   *
>>   * Do *not* "optimize" this to
>> + *     Error *err = NULL;
>>   *     foo(arg, &err);
>>   *     bar(arg, &err); // WRONG!
>>   *     if (err) {
>>   *         handle the error...
>>   *     }
>>   * because this may pass a non-null err to bar().
>> + *
>> + * Likewise, do *not*
>> + *     Error *err = NULL;
>> + *     if (cond1) {
>> + *         error_setg(err, ...);
>
> s/err/&err
>
>> + *     }
>> + *     if (cond2) {
>> + *         error_setg(err, ...); // WRONG!
>
> ditto

Good catch!

> With that fixed:
>
> Reviewed-by: Greg Kurz <groug@kaod.org>

Thanks!

>
>> + *     }
>> + * because this may pass a non-null err to error_setg().
>>   */
>>  
>>  #ifndef ERROR_H