When building gnome-calendar-3.21.91-1.fc26 on Fedora Rawhide on s390x arch I';m getting a warning that's threated as error dur compiler flags and build breaks.


from build.log at http://s390.koji.fedoraproject.org/koji/taskinfo?taskID=2333211
...
  CC       gcal-multi-choice.o
  CC       gcal-quick-add-popover.o
  CC       gcal-search-view.o
  CC       gcal-shell-search-provider.o
gcal-month-view.c: In function 'gcal_month_view_drag_drop':
gcal-month-view.c:908:32: error: 'timespan' may be used uninitialized in this function [-Werror=maybe-uninitialized]
           GDateTime *new_end = g_date_time_add (new_start, timespan);
                                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  CC       gcal-source-dialog.o
  CC       gcal-subscriber-view.o
  CC       gcal-time-selector.o
cc1: all warnings being treated as errors
Makefile:569: recipe for target 'gcal-month-view.o' failed
make[3]: *** [gcal-month-view.o] Error 1
...

But it looks to me rather as a compiler deficiency (gcc-6.1.1-6.fc26.s390x).