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

["Cédric Le Goater" <clg@redhat.com>]

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.

Thanks,

C.



> Alex
> 
>>   /*
>>    * Convenience function to error_report() and free @err.
>>    * The report includes hints added with error_append_hint().
>> diff --git a/util/error.c b/util/error.c
>> index e5e247209a9e0796074a9794f5598325f22f8d35..b8a211cccaa609a93091b86316144a0ad0a02662 100644
>> --- a/util/error.c
>> +++ b/util/error.c
>> @@ -247,6 +247,15 @@ void warn_report_err(Error *err)
>>       error_free(err);
>>   }
>>   
>> +void warn_report_once_err(Error *err)
>> +{
>> +        static bool print_once_;
>> +        if (!print_once_) {
>> +            warn_report_err(err);
>> +            print_once_ = true;
>> +        }
>> +}
>> +
>>   void error_reportf_err(Error *err, const char *fmt, ...)
>>   {
>>       va_list ap;
>