Re: [PATCH 08/12] util/oslib-win32: Revert warning on WSAEventSelect() failure

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

On Tue, Sep 09, 2025 at 01:50:56PM +0200, Markus Armbruster wrote:
> Daniel P. Berrangé <berrange@redhat.com> writes:
> 
> > On Fri, Aug 08, 2025 at 10:08:19AM +0200, Markus Armbruster wrote:
> >> qemu_socket_select() and its wrapper qemu_socket_unselect() treat a
> >> NULL @errp as &error_warn.  This is wildly inappropriate.  A caller
> >> passing NULL specifies that errors are to be ignored.  If warnings are
> >> wanted, the caller must pass &error_warn.
> >> 
> >> I'm not familiar with the calling code, so I can't say whether it will
> >> work after WSAEventSelect() failure.  If it doesn't, then this should
> >> be an error.  If it does, then why bother the user with a warning that
> >> isn't actionable, and likely confusing?
> >> 
> >> The warning goes back to commit f5fd677ae7cf (win32/socket: introduce
> >> qemu_socket_select() helper).  Before that commit, the error was
> >> ignored, as indicated by passing a null @errp.  Revert to that
> >> behavior.
> >> 
> >> Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
> >> Signed-off-by: Markus Armbruster <armbru@redhat.com>
> >> ---
> >>  util/oslib-win32.c | 4 ----
> >>  1 file changed, 4 deletions(-)
> >> 
> >> diff --git a/util/oslib-win32.c b/util/oslib-win32.c
> >> index b7351634ec..136a8fe118 100644
> >> --- a/util/oslib-win32.c
> >> +++ b/util/oslib-win32.c
> >> @@ -296,10 +296,6 @@ bool qemu_socket_select(int sockfd, WSAEVENT hEventObject,
> >>  {
> >>      SOCKET s = _get_osfhandle(sockfd);
> >>  
> >> -    if (errp == NULL) {
> >> -        errp = &error_warn;
> >> -    }
> >
> > This makes sense, but I'd want the callers to be using warn_report
> > instead. Ideally some (but not all) of the callers would propagate
> > the error, but this isn't practical with the QIOChannel create
> > watch function usage. I'd want to keep Error *errp on this function
> > though, and have warn_report as a sign to our future selves that
> > this is still not ideal.
> 
> The direct callers are qio_channel_create_socket_watch(),
> aio_set_fd_handler().  Callers via qemu_socket_unselect() are
> qio_channel_socket_finalize(), qio_channel_socket_close(),
> qemu_socket_set_block().
> 
> All but qio_channel_socket_close() cannot fail.  Would you like me to
> make them pass &error_warn, because warning is less bad than silence
> there?
> 
> qio_channel_socket_close() can fail, but it ignores
> qemu_socket_unselect() failure.  What do you want me to do there?

I think the overriding important thing is that we /must/ try to
close(), and if close() succeeds claim the whole qio_channel_socket_close
was successful. So I guess I'd say that &error_warn should be passed
from all callers.

> 
> >> -
> >>      if (s == INVALID_SOCKET) {
> >>          error_setg(errp, "invalid socket fd=%d", sockfd);
> >>          return false;
> >> -- 
> >> 2.49.0
> >> 
> >> 
> >
> > With regards,
> > Daniel
> 

With regards,
Daniel
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