fix some things.

src/part.c

@@ -37,7 +37,7 @@
  */
 void part_relink_gparts(struct part *parts, size_t N, ptrdiff_t offset) {
   for (size_t k = 0; k < N; k++) {
-    parts[k]->gpart->id_or_neg_offset = -(k + offset);
+    parts[k].gpart->id_or_neg_offset = -(k + offset);
   }
 }
 

src/part.h

@@ -24,6 +24,7 @@
 
 /* Some standard headers. */
 #include <stdlib.h>
+#include <stddef.h>
 
 /* MPI headers. */
 #ifdef WITH_MPI
@@ -51,8 +52,8 @@
 
 #include "./gravity/Default/gravity_part.h"
 
-void part_relink_gparts(struct parts *parts, size_t N, ptrdiff_t offset);
-void part_relink_parts(struct gparts *parts, size_t N);
+void part_relink_gparts(struct part *parts, size_t N, ptrdiff_t offset);
+void part_relink_parts(struct gpart *gparts, size_t N, struct part *parts);
 #ifdef WITH_MPI
 void part_create_mpi_type(MPI_Datatype* part_type);
 void xpart_create_mpi_type(MPI_Datatype* xpart_type);