diff --git a/src/H5Dmpio.c b/src/H5Dmpio.c
index 0620459883..655d475cc5 100644
--- a/src/H5Dmpio.c
+++ b/src/H5Dmpio.c
@@ -4068,10 +4068,18 @@ H5D__mpio_share_chunk_modification_data(H5D_filtered_collective_io_info_t *chunk
         else {
             int all_sends_completed;
 
-            /* Determine if all send requests have completed */
+            /* Determine if all send requests have completed
+             *
+             * gcc 11 complains about passing MPI_STATUSES_IGNORE as an MPI_Status
+             * array. See the discussion here:
+             *
+             * https://github.com/pmodels/mpich/issues/5687
+             */
+            H5_GCC_DIAG_OFF("stringop-overflow")
             if (MPI_SUCCESS != (mpi_code = MPI_Testall((int)num_send_requests, send_requests,
                                                        &all_sends_completed, MPI_STATUSES_IGNORE)))
                 HMPI_GOTO_ERROR(FAIL, "MPI_Testall failed", mpi_code)
+            H5_GCC_DIAG_ON("stringop-overflow")
 
             if (all_sends_completed) {
                 /* Post non-blocking barrier */
@@ -4105,9 +4113,16 @@ H5D__mpio_share_chunk_modification_data(H5D_filtered_collective_io_info_t *chunk
      * in the order that chunks are processed. So, the safest way to
      * support both I/O modes is to simply make sure all messages
      * are available.
+     *
+     * gcc 11 complains about passing MPI_STATUSES_IGNORE as an MPI_Status
+     * array. See the discussion here:
+     *
+     * https://github.com/pmodels/mpich/issues/5687
      */
+    H5_GCC_DIAG_OFF("stringop-overflow")
     if (MPI_SUCCESS != (mpi_code = MPI_Waitall((int)num_recv_requests, recv_requests, MPI_STATUSES_IGNORE)))
         HMPI_GOTO_ERROR(FAIL, "MPI_Waitall failed", mpi_code)
+    H5_GCC_DIAG_ON("stringop-overflow")
 
     /* Set the new number of locally-selected chunks */
     *chunk_list_num_entries = last_assigned_idx;
diff --git a/testpar/t_prop.c b/testpar/t_prop.c
index 930b895243..c08a022ea5 100644
--- a/testpar/t_prop.c
+++ b/testpar/t_prop.c
@@ -69,14 +69,22 @@ test_encode_decode(hid_t orig_pl, int mpi_rank, int recv_proc)
             HDfree(rbuf);
     } /* end if */
 
-    if (0 == mpi_rank)
+    if (0 == mpi_rank) {
+        /* gcc 11 complains about passing MPI_STATUSES_IGNORE as an MPI_Status
+         * array. See the discussion here:
+         *
+         * https://github.com/pmodels/mpich/issues/5687
+         */
+        H5_GCC_DIAG_OFF("stringop-overflow")
         MPI_Waitall(2, req, MPI_STATUSES_IGNORE);
+        H5_GCC_DIAG_ON("stringop-overflow")
+    }
 
     if (NULL != sbuf)
         HDfree(sbuf);
 
     MPI_Barrier(MPI_COMM_WORLD);
-    return (0);
+    return 0;
 }
 
 void
diff --git a/tools/src/h5perf/perf.c b/tools/src/h5perf/perf.c
index 84be7e8e0f..270af57e89 100644
--- a/tools/src/h5perf/perf.c
+++ b/tools/src/h5perf/perf.c
@@ -457,7 +457,7 @@ parse_args(int argc, char **argv)
         }
     }
 
-    return (0);
+    return 0;
 }
 /*-------------------------------------------------------------------------
  * Function:  getenv_all
@@ -478,14 +478,9 @@ parse_args(int argc, char **argv)
  * Programmer:  Leon Arber
  *              4/4/05
  *
- * Modifications:
- *    Use original getenv if MPI is not initialized. This happens
- *    one uses the PHDF5 library to build a serial nature code.
- *    Albert 2006/04/07
- *
  *-------------------------------------------------------------------------
  */
-char *
+static char *
 getenv_all(MPI_Comm comm, int root, const char *name)
 {
     int          mpi_size, mpi_rank, mpi_initialized, mpi_finalized;
@@ -539,7 +534,9 @@ getenv_all(MPI_Comm comm, int root, const char *name)
 #endif
     }
     else {
-        /* use original getenv */
+        /* Use the original getenv if MPI is not initialized. This happens
+         * if you use the parallel HDF5 library to build a serial program.
+         */
         if (env)
             HDfree(env);
         env = HDgetenv(name);
diff --git a/tools/src/h5perf/pio_engine.c b/tools/src/h5perf/pio_engine.c
index 9d08938bc9..d50e783d79 100644
--- a/tools/src/h5perf/pio_engine.c
+++ b/tools/src/h5perf/pio_engine.c
@@ -146,7 +146,7 @@ do_pio(parameters param)
     file_descr fd;
     iotype     iot;
 
-    char  fname[FILENAME_MAX];
+    char *fname = NULL;
     long  nf;
     long  ndsets;
     off_t nbytes;         /*number of bytes per dataset  */
@@ -168,6 +168,9 @@ do_pio(parameters param)
     /* IO type */
     iot = param.io_type;
 
+    if (NULL == (fname = HDcalloc(FILENAME_MAX, sizeof(char))))
+        GOTOERROR(FAIL);
+
     switch (iot) {
         case MPIO:
             fd.mpifd   = MPI_FILE_NULL;
@@ -365,8 +368,8 @@ done:
     }
 
     /* release generic resources */
-    if (buffer)
-        HDfree(buffer);
+    HDfree(buffer);
+    HDfree(fname);
     res.ret_code = ret_code;
     return res;
 }