Re: [PATCH v2 1/9] util/error: Introduce warn_report_once_err()

[Markus Armbruster]

Cédric Le Goater <clg@redhat.com> writes:

> On 1/30/25 18:55, Alex Williamson wrote:
>> On Thu, 30 Jan 2025 14:43:38 +0100
>> Cédric Le Goater <clg@redhat.com> wrote:
>> 
>>> Depending on the configuration, a passthrough device may produce
>>> recurring DMA mapping errors at runtime and produce a lot of
>>> output. It is useful to report only once.
>>>
>>> Cc: Markus Armbruster <armbru@redhat.com>
>>> Signed-off-by: Cédric Le Goater <clg@redhat.com>
>>> ---
>>>   include/qapi/error.h | 5 +++++
>>>   util/error.c         | 9 +++++++++
>>>   2 files changed, 14 insertions(+)
>>>
>>> diff --git a/include/qapi/error.h b/include/qapi/error.h
>>> index 
>>> 71f8fb2c50eee9a544992d0c05263c9793956fe1..b6ea274882b9788b64d4bb213c3458d7c674a881
>>>  100644
>>> --- a/include/qapi/error.h
>>> +++ b/include/qapi/error.h
>>> @@ -448,6 +448,11 @@ void error_free_or_abort(Error **errp);
>>>    */
>>>   void warn_report_err(Error *err);
>>>   +/*
>>> + * Convenience function to call warn_report_err() once.
>>> + */
>>> +void warn_report_once_err(Error *err);
>>> +
>> Turning it into a macro would do what you want:
>> #define warn_report_once_err(err) ({ \
>>      static bool print_once_;         \
>>      if (!print_once_) {              \
>>          warn_report_err(err);        \
>>          print_once_ = true;          \
>>      }                                \
>> })
>> So long as we only want once per call site and not once per object,
>> which would pull in something like warn_report_once_cond().  Thanks,
>
> yeah. I came up with this :
>
> /*
>  * TODO: move to util/
>  */
> static bool warn_report_once_err_cond(bool *printed, Error *err)
> {
>     if (*printed) {
>         error_free(err);
>         return false;
>     }
>     *printed = true;
>     warn_report_err(err);
>     return true;
> }
>
> #define warn_report_once_err(err)                           \
>     ({                                                      \
>         static bool print_once_;                            \
>         warn_report_once_err_cond(&print_once_, err);       \
>     })
>
>
> I don't know where to put it though. It sits in between qapi/error.h
> and qemu/error-report.h.

Stuff involving the Error type should not go into qemu/error-report.h.
Precedence: warn_report_err() & friends are in qapi/error.h even though
they're straightforward wrappers around warn_report() & friends for easy
use with Error.