Only relink parts and gparts when we actually have parts and gparts

src/cell.c

@@ -580,7 +580,7 @@ void cell_split(struct cell *c, ptrdiff_t parts_offset) {
   }
 
   /* Re-link the gparts. */
-  part_relink_gparts(parts, count, parts_offset);
+  if (count > 0 && gcount > 0) part_relink_gparts(parts, count, parts_offset);
 
 #ifdef SWIFT_DEBUG_CHECKS
   /* Verify that _all_ the parts have been assigned to a cell. */
@@ -675,7 +675,8 @@ void cell_split(struct cell *c, ptrdiff_t parts_offset) {
   }
 
   /* Re-link the parts. */
-  part_relink_parts(gparts, gcount, parts - parts_offset);
+  if (count > 0 && gcount > 0)
+    part_relink_parts(gparts, gcount, parts - parts_offset);
 }
 
 /**

src/engine.c

@@ -2936,7 +2936,8 @@ void engine_split(struct engine *e, struct partition *initial_partition) {
   s->xparts = xparts_new;
 
   /* Re-link the gparts. */
-  part_relink_gparts(s->parts, s->nr_parts, 0);
+  if (s->nr_parts > 0 && s->nr_gparts > 0)
+    part_relink_gparts(s->parts, s->nr_parts, 0);
 
   /* Re-allocate the local gparts. */
   if (e->verbose)
@@ -2952,7 +2953,8 @@ void engine_split(struct engine *e, struct partition *initial_partition) {
   s->gparts = gparts_new;
 
   /* Re-link the parts. */
-  part_relink_parts(s->gparts, s->nr_gparts, s->parts);
+  if (s->nr_parts > 0 && s->nr_gparts > 0)
+    part_relink_parts(s->gparts, s->nr_gparts, s->parts);
 
 #ifdef SWIFT_DEBUG_CHECKS
 

src/space.c

@@ -565,7 +565,7 @@ void space_rebuild(struct space *s, double cell_max, int verbose) {
   space_parts_sort(s, ind, nr_parts, 0, s->nr_cells - 1, verbose);
 
   /* Re-link the gparts. */
-  part_relink_gparts(s->parts, nr_parts, 0);
+  if (nr_parts > 0 && nr_gparts > 0) part_relink_gparts(s->parts, nr_parts, 0);
 
 #ifdef SWIFT_DEBUG_CHECKS
   /* Verify space_sort_struct. */
@@ -613,7 +613,8 @@ void space_rebuild(struct space *s, double cell_max, int verbose) {
   space_gparts_sort(s, gind, nr_gparts, 0, s->nr_cells - 1, verbose);
 
   /* Re-link the parts. */
-  part_relink_parts(s->gparts, nr_gparts, s->parts);
+  if (nr_parts > 0 && nr_gparts > 0)
+    part_relink_parts(s->gparts, nr_gparts, s->parts);
 
   /* We no longer need the indices as of here. */
   free(gind);