Fix for few similar bugs:

  #841622 Assertion `t->rp->type == Gcalc_function::shape_line' failed in Gcalc_operation_reducer::end_line in maria-5.3-gi
  #841625 Assertion `m_poly_borders->next' failed in Gcalc_operation_reducer::count_slice in maria-5.3-gis
  #841638 Assertion `!m_prev || m_prev->x != x || m_prev->y != y' failed in Gcalc_shape_transporter::int_add_point in maria-5.3-gis
  #841662 Third assertion `n > 0 && n < SINUSES_CALCULATED*2+1' in get_n_sincos
  #841745 Assertion `!sp0->is_bottom()' failed in Gcalc_scan_iterator::find_intersections in maria-5.3-gis

  They mostly was caused by inprecision of double arithmetic.
  Fixed by changes in how to handle multiple intersections to keep their order right.

  Also ST_DISTANCE(GEOM, EMPTY_GEOM) was defined as NULL.


per-file comments:
  mysql-test/r/gis-precise.result
   GIS bugfixes.
        test result updated.
  mysql-test/t/gis-precise.test
   GIS bugfixes.
        test cases added.
  sql/gcalc_slicescan.cc
   GIS bugfixes.
        If intersections are close, add order checks to cope with the
        double calcualtions imprecision.
  sql/gcalc_slicescan.h
   GIS bugfixes.
        n_row parameter added to intersection to check their order.
  sql/item_geofunc.cc
   GIS bugfixes.
        ST_DISTANCE(GEOM, EMPTY_GEOM) returns NULL.

1 files changed, 2 insertions, 1 deletions

diff --git a/sql/gcalc_slicescan.h b/sql/gcalc_slicescan.h
index 9ffe39dd370..ebe2bcffe5c 100644
--- a/sql/gcalc_slicescan.h
+++ b/sql/gcalc_slicescan.h
@@ -303,6 +303,7 @@ public:
   class intersection : public Gcalc_dyn_list::Item
   {
   public:
+    int n_row;
     sc_thread_id thread_a;
     sc_thread_id thread_b;
     double x;
@@ -371,7 +372,7 @@ private:
   void sort_intersections();
   int handle_intersections();
   int insert_top_point();
-  int add_intersection(const point *a, const point *b,
+  int add_intersection(int n_row, const point *a, const point *b,
 		       Gcalc_dyn_list::Item ***p_hook);
   int find_intersections();