More warning eliminations.

configure.ac

@@ -466,7 +466,7 @@ if test "$enable_warn" != "no"; then
     # We will do this by hand instead and only default to the macro for unknown compilers
     case "$ax_cv_c_compiler_vendor" in
           gnu | clang)
-             CFLAGS="$CFLAGS -Wall"
+             CFLAGS="$CFLAGS -Wall -Wextra -Wno-unused-parameter"
           ;;
 	  intel)
              CFLAGS="$CFLAGS -w2 -Wunused-variable"

src/runner_doiact.h

@@ -2862,7 +2862,7 @@ void DOSUB_SUBSET(struct runner *r, struct cell *ci, struct part *parts,
       }
 
       /* Get the sorting index. */
-      int sid = 0;
+      int new_sid = 0;
       for (int k = 0; k < 3; k++)
         new_sid = 3 * new_sid +
                   ((cj->loc[k] - ci->loc[k] + shift[k] < 0)

src/serial_io.c

@@ -179,7 +179,7 @@ void readArray(hid_t grp, const struct io_props props, size_t N,
 
 void prepareArray(struct engine* e, hid_t grp, char* fileName, FILE* xmfFile,
                   char* partTypeGroupName, const struct io_props props,
-                  long long N_total, const struct UnitSystem* internal_units,
+                  unsigned long long N_total, const struct UnitSystem* internal_units,
                   const struct UnitSystem* snapshot_units) {
 
   /* Create data space */

src/space.c

@@ -707,7 +707,7 @@ void space_parts_sort(struct space *s, int *ind, size_t N, int min, int max,
   if ((sort_struct.stack =
            malloc(sizeof(struct qstack) * sort_struct.stack_size)) == NULL)
     error("Failed to allocate sorting stack.");
-  for (int i = 0; i < sort_struct.stack_size; i++)
+  for (unsigned int i = 0; i < sort_struct.stack_size; i++)
     sort_struct.stack[i].ready = 0;
 
   /* Add the first interval. */
@@ -892,7 +892,7 @@ void space_gparts_sort(struct space *s, int *ind, size_t N, int min, int max,
   if ((sort_struct.stack =
            malloc(sizeof(struct qstack) * sort_struct.stack_size)) == NULL)
     error("Failed to allocate sorting stack.");
-  for (int i = 0; i < sort_struct.stack_size; i++)
+  for (unsigned int i = 0; i < sort_struct.stack_size; i++)
     sort_struct.stack[i].ready = 0;
 
   /* Add the first interval. */