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

["Daniel P. Berrange" <berrange@redhat.com>]

On Mon, Jul 03, 2017 at 04:07:21PM +0200, Markus Armbruster wrote:
> "Daniel P. Berrange" <berrange@redhat.com> 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 <alistair.francis@xilinx.com>
> >> ---
> >> 
> >>  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"


Regards,
Daniel
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