Re: [Qemu-devel] [RFC v2 2/3] qemu-error: Implement a more generic error reporting

[Markus Armbruster]

"Daniel P. Berrange" <address@hidden> writes:

> On Mon, Jul 03, 2017 at 04:07:21PM +0200, Markus Armbruster wrote:
>> "Daniel P. Berrange" <address@hidden> writes:
>> 
>> > On Thu, Jun 29, 2017 at 12:42:38PM -0700, Alistair Francis wrote:
>> >> This patch removes the exisinting error_vreport() function and replaces it
>> >> with a more generic vreport() function that takes an enum describing the
>> >> information to be reported.
>> 
>> Why remove error_vreport()?
>> 
>> >> As part of this change a report() function is added as well with the
>> >> same capability.
>> >> 
>> >> To maintain full compatibility the original error_report() function is
>> >> maintained and no changes to the way errors are printed have been made.
>> >> 
>> >> Signed-off-by: Alistair Francis <address@hidden>
>> >> ---
>> >> 
>> >>  hw/virtio/virtio.c          |  2 +-
>> >>  include/qemu/error-report.h | 10 +++++++++-
>> >>  scripts/checkpatch.pl       |  3 ++-
>> >>  util/qemu-error.c           | 33 ++++++++++++++++++++++++++++++---
>> >>  4 files changed, 42 insertions(+), 6 deletions(-)
>> >> 
>> >> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
>> >> index 464947f76d..bd3d26abb7 100644
>> >> --- a/hw/virtio/virtio.c
>> >> +++ b/hw/virtio/virtio.c
>> >> @@ -2448,7 +2448,7 @@ void GCC_FMT_ATTR(2, 3) virtio_error(VirtIODevice 
>> >> *vdev, const char *fmt, ...)
>> >>      va_list ap;
>> >>  
>> >>      va_start(ap, fmt);
>> >> -    error_vreport(fmt, ap);
>> >> +    vreport(ERROR, fmt, ap);
>> >>      va_end(ap);
>> >>  
>> >>      if (virtio_vdev_has_feature(vdev, VIRTIO_F_VERSION_1)) {
>> >> diff --git a/include/qemu/error-report.h b/include/qemu/error-report.h
>> >> index 3001865896..39b554c3b9 100644
>> >> --- a/include/qemu/error-report.h
>> >> +++ b/include/qemu/error-report.h
>> >> @@ -21,6 +21,12 @@ typedef struct Location {
>> >>      struct Location *prev;
>> >>  } Location;
>> >>  
>> >> +typedef enum {
>> >> +    ERROR,
>> >> +    WARN,
>> >> +    INFO,
>> >> +} report_types;
>> >
>> > Woah, those are faaar to generic names to be used. There is way too much
>> > chance of those clashing with definitions from headers we pull in - 
>> > particularly
>> > windows which pollutes its system headers with loads of generic names.
>> >
>> > I'd suggest  QMSG_ERROR, QMSG_WARN, QMSG_INFO
>> >
>> >> +
>> >>  Location *loc_push_restore(Location *loc);
>> >>  Location *loc_push_none(Location *loc);
>> >>  Location *loc_pop(Location *loc);
>> >> @@ -30,12 +36,14 @@ void loc_set_none(void);
>> >>  void loc_set_cmdline(char **argv, int idx, int cnt);
>> >>  void loc_set_file(const char *fname, int lno);
>> >>  
>> >> +void vreport(report_types type, const char *fmt, va_list ap) 
>> >> GCC_FMT_ATTR(2, 0);
>> >> +void report(report_types type, const char *fmt, ...)  GCC_FMT_ATTR(2, 3);
>> >
>> > Those names are too generic too IMHO.  I'd suggest  qmsg_report, 
>> > qmsg_vreport
>> >
>> > As mentioned in the previous review, there should be wrappers which
>> > call these with suitable enum to make usage less verbose. eg
>> >
>> >   qmsg_info(fmt, ....)  should call qmsg_report(QMSG_INFO, fmt, ...)
>> >   qmsg_vinfo(fmt, ....)  should call qmsg_vreport(QMSG_INFO, fmt, ...)
>> >
>> > likewise, for other message levels
>> 
>> We then have qmsg_warning() for warnings, and error_report() for errors.
>> Ugh!
>> 
>> If I had known back then what I know now, I wouldn't have used the
>> error_ prefix.
>> 
>> Naming things is hard.
>> 
>> Ideas anyone?
>
> I guess implicit in my suggestion would be to switch to qmsg_error()
> over some (long) period of time, but that would be a massive amount
> of churn that would harm backporting.
>
> So perhaps, just have error_report warning_report, info_report, and
> accept that the naming convention is slightly reversed from "normality"

That's not half bad.

The matching enum would be

    typedef enum {
        REPORT_TYPE_ERROR,
        REPORT_TYPE_WARNING,
        REPORT_TYPE_INFO,
    } report_type;

Note the typedef name is *singular*.  Compare

    report_type rtype;

to

    report_types rtype;

@rtype is *one* report type, not multiple.

Let's stick report_type, report() and vreport() into qemu-error.c
(static linkage) until we have a genuine need for them elsewhere.