diff --git a/src/H5Dmpio.c b/src/H5Dmpio.c
index 80f878b9776..60d295250c8 100644
--- a/src/H5Dmpio.c
+++ b/src/H5Dmpio.c
@@ -3467,8 +3467,9 @@ H5D__mpio_redistribute_shared_chunks(H5D_filtered_collective_io_info_t *chunk_li
 static herr_t
 H5D__mpio_redistribute_shared_chunks_int(H5D_filtered_collective_io_info_t *chunk_list,
                                          size_t *num_chunks_assigned_map, hbool_t all_ranks_involved,
-                                         const H5D_io_info_t *io_info, const H5D_chunk_map_t *fm,
-                                         int mpi_rank, int mpi_size)
+                                         const H5D_io_info_t * io_info,
+                                         const H5D_chunk_map_t H5_ATTR_NDEBUG_UNUSED *fm, int mpi_rank,
+                                         int mpi_size)
 {
     MPI_Datatype struct_type;
     MPI_Datatype packed_type;
@@ -3797,7 +3798,8 @@ H5D__mpio_redistribute_shared_chunks_int(H5D_filtered_collective_io_info_t *chun
 static herr_t
 H5D__mpio_share_chunk_modification_data(H5D_filtered_collective_io_info_t *chunk_list,
                                         size_t *chunk_list_num_entries, H5D_io_info_t *io_info,
-                                        const H5D_type_info_t *type_info, int mpi_rank, int mpi_size,
+                                        const H5D_type_info_t *type_info, int mpi_rank,
+                                        int H5_ATTR_NDEBUG_UNUSED           mpi_size,
                                         H5D_filtered_collective_io_info_t **chunk_hash_table,
                                         unsigned char ***chunk_msg_bufs, int *chunk_msg_bufs_len)
 {
@@ -4547,7 +4549,7 @@ H5D__mpio_collective_filtered_chunk_update(H5D_filtered_collective_io_info_t *ch
                                            H5D_filtered_collective_io_info_t *chunk_hash_table,
                                            unsigned char **chunk_msg_bufs, int chunk_msg_bufs_len,
                                            const H5D_io_info_t *io_info, const H5D_type_info_t *type_info,
-                                           int mpi_rank, int mpi_size)
+                                           int H5_ATTR_NDEBUG_UNUSED mpi_rank, int mpi_size)
 {
     H5D_fill_buf_info_t fb_info;
     H5D_chunk_info_t *  chunk_info = NULL;
diff --git a/src/H5FD.c b/src/H5FD.c
index 11cbdc4868c..620e56ccceb 100644
--- a/src/H5FD.c
+++ b/src/H5FD.c
@@ -1746,8 +1746,10 @@ H5FDget_vfd_handle(H5FD_t *file, hid_t fapl_id, void **file_handle)
         HGOTO_ERROR(H5E_FILE, H5E_CANTGET, FAIL, "can't get file handle for file driver")
 
 done:
-    if (FAIL == ret_value)
-        *file_handle = NULL;
+    if (FAIL == ret_value) {
+        if (file_handle)
+            *file_handle = NULL;
+    }
 
     FUNC_LEAVE_API(ret_value)
 } /* end H5FDget_vfd_handle() */
diff --git a/test/dt_arith.c b/test/dt_arith.c
index d5653ad9cda..35a9d5d0352 100644
--- a/test/dt_arith.c
+++ b/test/dt_arith.c
@@ -2698,18 +2698,18 @@ my_isnan(dtype_t type, void *val)
     if (FLT_FLOAT == type) {
         float x = 0.0;
         HDmemcpy(&x, val, sizeof(float));
-        retval = (x != x);
+        retval = !H5_FLT_ABS_EQUAL(x, x);
     }
     else if (FLT_DOUBLE == type) {
         double x = 0.0;
         HDmemcpy(&x, val, sizeof(double));
-        retval = (x != x);
+        retval = !H5_DBL_ABS_EQUAL(x, x);
 #if H5_SIZEOF_LONG_DOUBLE != H5_SIZEOF_DOUBLE && H5_SIZEOF_LONG_DOUBLE != 0
     }
     else if (FLT_LDOUBLE == type) {
         long double x = 0.0;
         HDmemcpy(&x, val, sizeof(long double));
-        retval = (x != x);
+        retval = !H5_LDBL_ABS_EQUAL(x, x);
 #endif
     }
     else {
diff --git a/testpar/t_filters_parallel.c b/testpar/t_filters_parallel.c
index bfb5897d937..409c4ede0ae 100644
--- a/testpar/t_filters_parallel.c
+++ b/testpar/t_filters_parallel.c
@@ -7857,8 +7857,10 @@ test_edge_chunks_overlap(const char *parent_group, H5Z_filter_t filter_id, hid_t
  * edge chunk and writes to just a portion of the edge chunk.
  */
 static void
-test_edge_chunks_partial_write(const char *parent_group, H5Z_filter_t filter_id, hid_t fapl_id, hid_t dcpl_id,
-                               hid_t dxpl_id)
+test_edge_chunks_partial_write(const char H5_ATTR_PARALLEL_UNUSED * parent_group,
+                               H5Z_filter_t H5_ATTR_PARALLEL_UNUSED filter_id,
+                               hid_t H5_ATTR_PARALLEL_UNUSED fapl_id, hid_t H5_ATTR_PARALLEL_UNUSED dcpl_id,
+                               hid_t H5_ATTR_PARALLEL_UNUSED dxpl_id)
 {
     /* TODO */
 }
diff --git a/tools/src/h5diff/ph5diff_main.c b/tools/src/h5diff/ph5diff_main.c
index 8e5c3e84265..75fb9a457bb 100644
--- a/tools/src/h5diff/ph5diff_main.c
+++ b/tools/src/h5diff/ph5diff_main.c
@@ -312,5 +312,5 @@ h5diff_exit(int status)
     /* Always exit(0), since MPI implementations do weird stuff when they
      *  receive a non-zero exit value. - QAK
      */
-    HDexit(0);
+    HDexit(status);
 }