The GLib g_size_checked_mul() function is not quite the
same signature, and gives compiler warnings due to not
correctly casting from gsize to guint64/32. Implementing
a replacement for INT_MULTIPLY_OVERFLOW is easy enough
to do ourselves.
Reviewed-by: NPavel Hrdina <phrdina@redhat.com>
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>