diff --git a/opal/include/opal_config_bottom.h b/opal/include/opal_config_bottom.h
index f906278b83..2fed0820ea 100644
--- a/opal/include/opal_config_bottom.h
+++ b/opal/include/opal_config_bottom.h
@@ -285,6 +285,14 @@ typedef OPAL_PTRDIFF_TYPE ptrdiff_t;
 #define OPAL_PATH_SEP "/"
 #define OPAL_ENV_SEP  ':'
 
+#if defined(MAXHOSTNAMELEN)
+#define OPAL_MAXHOSTNAMELEN (MAXHOSTNAMELEN + 1)
+#elif defined(HOST_NAME_MAX)
+#define OPAL_MAXHOSTNAMELEN (HOST_NAME_MAX + 1)
+#else
+/* SUSv2 guarantees that "Host names are limited to 255 bytes". */
+#define OPAL_MAXHOSTNAMELEN (255 + 1)
+#endif
 
 /*
  * Do we want memory debugging?
@@ -489,14 +497,9 @@ static inline uint16_t ntohs(uint16_t netvar) { return netvar; }
 #ifdef HAVE_HOSTLIB_H
 /* gethostname() */
 #include <hostLib.h>
-
-#ifndef MAXHOSTNAMELEN
-#define MAXHOSTNAMELEN 64
 #endif
 #endif
 
-#endif
-
 /* If we're in C++, then just undefine restrict and then define it to
    nothing.  "restrict" is not part of the C++ language, and we don't
    have a corresponding AC_CXX_RESTRICT to figure out what the C++
diff --git a/opal/mca/base/mca_base_component_find.c b/opal/mca/base/mca_base_component_find.c
index 7739399c5b..899673dfaf 100644
--- a/opal/mca/base/mca_base_component_find.c
+++ b/opal/mca/base/mca_base_component_find.c
@@ -330,7 +330,7 @@ static int component_find_check (mca_base_framework_t *framework, char **request
         }
 
         if (!found) {
-            char h[MAXHOSTNAMELEN];
+            char h[OPAL_MAXHOSTNAMELEN];
             gethostname(h, sizeof(h));
             opal_show_help("help-mca-base.txt",
                            "find-available:not-valid", true,
diff --git a/opal/mca/base/mca_base_open.c b/opal/mca/base/mca_base_open.c
index aeb01e4afe..7f14ffaf02 100644
--- a/opal/mca/base/mca_base_open.c
+++ b/opal/mca/base/mca_base_open.c
@@ -66,7 +66,7 @@ int mca_base_open(void)
 {
     char *value;
     opal_output_stream_t lds;
-    char hostname[64];
+    char hostname[OPAL_MAXHOSTNAMELEN];
     int var_id;
 
     if (mca_base_opened++) {
@@ -137,7 +137,7 @@ int mca_base_open(void)
     } else {
         set_defaults(&lds);
     }
-    gethostname(hostname, 64);
+    gethostname(hostname, sizeof(hostname));
     asprintf(&lds.lds_prefix, "[%s:%05d] ", hostname, getpid());
     opal_output_reopen(0, &lds);
     opal_output_verbose (MCA_BASE_VERBOSE_COMPONENT, 0, "mca: base: opening components");
diff --git a/opal/mca/event/libevent2022/libevent/evdns.c b/opal/mca/event/libevent2022/libevent/evdns.c
index 60b1048511..f55a50a0bc 100644
--- a/opal/mca/event/libevent2022/libevent/evdns.c
+++ b/opal/mca/event/libevent2022/libevent/evdns.c
@@ -48,6 +48,8 @@
  * Version: 0.1b
  */
 
+#include "opal_config.h"
+
 #include <sys/types.h>
 #include "event2/event-config.h"
 
@@ -121,10 +123,6 @@
 #define EVDNS_LOG_WARN 1
 #define EVDNS_LOG_MSG 2
 
-#ifndef HOST_NAME_MAX
-#define HOST_NAME_MAX 255
-#endif
-
 #include <stdio.h>
 
 #undef MIN
@@ -3108,7 +3106,7 @@ evdns_search_ndots_set(const int ndots) {
 
 static void
 search_set_from_hostname(struct evdns_base *base) {
-	char hostname[HOST_NAME_MAX + 1], *domainname;
+	char hostname[OPAL_MAXHOSTNAMELEN], *domainname;
 
 	ASSERT_LOCKED(base);
 	search_postfix_clear(base);
diff --git a/opal/mca/hwloc/base/hwloc_base_util.c b/opal/mca/hwloc/base/hwloc_base_util.c
index 50e389025f..a9c487c514 100644
--- a/opal/mca/hwloc/base/hwloc_base_util.c
+++ b/opal/mca/hwloc/base/hwloc_base_util.c
@@ -399,7 +399,7 @@ int opal_hwloc_base_report_bind_failure(const char *file,
 
     if (!already_reported &&
         OPAL_HWLOC_BASE_MBFA_SILENT != opal_hwloc_base_mbfa) {
-        char hostname[64];
+        char hostname[OPAL_MAXHOSTNAMELEN];
         gethostname(hostname, sizeof(hostname));
 
         opal_show_help("help-opal-hwloc-base.txt", "mbind failure", true,
diff --git a/opal/mca/pmix/pmix114/pmix/examples/dynamic.c b/opal/mca/pmix/pmix114/pmix/examples/dynamic.c
index 11f3712146..7e9fbd352e 100644
--- a/opal/mca/pmix/pmix114/pmix/examples/dynamic.c
+++ b/opal/mca/pmix/pmix114/pmix/examples/dynamic.c
@@ -45,12 +45,12 @@ int main(int argc, char **argv)
     uint32_t nprocs;
     char nsp2[PMIX_MAX_NSLEN+1];
     pmix_app_t *app;
-    char hostname[1024], dir[1024];
+    char hostname[PMIX_MAXHOSTNAMELEN], dir[1024];
     pmix_proc_t *peers;
     size_t npeers, ntmp=0;
     char *nodelist;
 
-    gethostname(hostname, 1024);
+    gethostname(hostname, sizeof(hostname));
     getcwd(dir, 1024);
 
     /* init us */
diff --git a/opal/mca/pmix/pmix114/pmix/include/pmix/autogen/pmix_config_bottom.h b/opal/mca/pmix/pmix114/pmix/include/pmix/autogen/pmix_config_bottom.h
index fc7b6a25d5..82d62f76d6 100644
--- a/opal/mca/pmix/pmix114/pmix/include/pmix/autogen/pmix_config_bottom.h
+++ b/opal/mca/pmix/pmix114/pmix/include/pmix/autogen/pmix_config_bottom.h
@@ -258,6 +258,15 @@ typedef PMIX_PTRDIFF_TYPE ptrdiff_t;
 #define PMIX_PATH_MAX	256
 #endif
 
+#if defined(MAXHOSTNAMELEN)
+#define PMIX_MAXHOSTNAMELEN (MAXHOSTNAMELEN + 1)
+#elif defined(HOST_NAME_MAX)
+#define PMIX_MAXHOSTNAMELEN (HOST_NAME_MAX + 1)
+#else
+/* SUSv2 guarantees that "Host names are limited to 255 bytes". */
+#define PMIX_MAXHOSTNAMELEN (255 + 1)
+#endif
+
 /*
  * Set the compile-time path-separator on this system and variable separator
  */
@@ -387,14 +396,9 @@ typedef PMIX_PTRDIFF_TYPE ptrdiff_t;
 #ifdef HAVE_HOSTLIB_H
 /* gethostname() */
 #include <hostLib.h>
-
-#ifndef MAXHOSTNAMELEN
-#define MAXHOSTNAMELEN 64
 #endif
 #endif
 
-#endif
-
 /* If we're in C++, then just undefine restrict and then define it to
    nothing.  "restrict" is not part of the C++ language, and we don't
    have a corresponding AC_CXX_RESTRICT to figure out what the C++
diff --git a/opal/mca/pmix/pmix114/pmix/src/util/output.c b/opal/mca/pmix/pmix114/pmix/src/util/output.c
index 5d406e0aad..424b6814f2 100644
--- a/opal/mca/pmix/pmix114/pmix/src/util/output.c
+++ b/opal/mca/pmix/pmix114/pmix/src/util/output.c
@@ -125,7 +125,7 @@ PMIX_CLASS_INSTANCE(pmix_output_stream_t, pmix_object_t, construct, NULL);
 bool pmix_output_init(void)
 {
     int i;
-    char hostname[32];
+    char hostname[PMIX_MAXHOSTNAMELEN];
     char *str;
 
     if (initialized) {
@@ -250,7 +250,7 @@ bool pmix_output_switch(int output_id, bool enable)
 void pmix_output_reopen_all(void)
 {
     char *str;
-    char hostname[32];
+    char hostname[PMIX_MAXHOSTNAMELEN];
 
     str = getenv("PMIX_OUTPUT_STDERR_FD");
     if (NULL != str) {
diff --git a/opal/mca/pmix/pmix114/pmix/test/simple/simpdyn.c b/opal/mca/pmix/pmix114/pmix/test/simple/simpdyn.c
index f5c0b94a51..06c955486f 100644
--- a/opal/mca/pmix/pmix114/pmix/test/simple/simpdyn.c
+++ b/opal/mca/pmix/pmix114/pmix/test/simple/simpdyn.c
@@ -49,12 +49,12 @@ int main(int argc, char **argv)
     uint32_t nprocs;
     char nsp2[PMIX_MAX_NSLEN+1];
     pmix_app_t *app;
-    char hostname[1024];
+    char hostname[PMIX_MAXHOSTNAMELEN];
     pmix_proc_t *peers;
     size_t npeers, ntmp=0;
     char *nodelist;
     
-    gethostname(hostname, 1024);
+    gethostname(hostname, sizeof(hostname));
     
     /* init us */
     if (PMIX_SUCCESS != (rc = PMIx_Init(&myproc))) {
diff --git a/opal/mca/pmix/pmix114/pmix/test/simple/simptest.c b/opal/mca/pmix/pmix114/pmix/test/simple/simptest.c
index c0bf43fcc8..87f23d6d58 100644
--- a/opal/mca/pmix/pmix114/pmix/test/simple/simptest.c
+++ b/opal/mca/pmix/pmix114/pmix/test/simple/simptest.c
@@ -316,9 +316,9 @@ static void set_namespace(int nprocs, char *ranks, char *nspace,
                           pmix_op_cbfunc_t cbfunc, myxfer_t *x)
 {
     char *regex, *ppn;
-    char hostname[1024];
+    char hostname[PMIX_MAXHOSTNAMELEN];
 
-    gethostname(hostname, 1024);
+    gethostname(hostname, sizeof(hostname));
     x->ninfo = 6;
 
     PMIX_INFO_CREATE(x->info, x->ninfo);
diff --git a/opal/mca/pstat/test/pstat_test.c b/opal/mca/pstat/test/pstat_test.c
index 22da5f058c..6d616afe2a 100644
--- a/opal/mca/pstat/test/pstat_test.c
+++ b/opal/mca/pstat/test/pstat_test.c
@@ -65,7 +65,7 @@ static int query(pid_t pid,
                  opal_node_stats_t *nstats)
 {
     double dtime;
-    char hostname[128];
+    char hostname[OPAL_MAXHOSTNAMELEN];
 
     if (NULL != stats) {
         /* record the time of this sample */
@@ -83,7 +83,7 @@ static int query(pid_t pid,
     }
 
     if (NULL != stats) {
-        gethostname(hostname, 128);
+        gethostname(hostname, sizeof(hostname));
         strncpy(stats->node, hostname, OPAL_PSTAT_MAX_STRING_LEN);
 
         stats->pid = pid;
diff --git a/opal/mca/shmem/mmap/shmem_mmap_module.c b/opal/mca/shmem/mmap/shmem_mmap_module.c
index 619a54adcc..d567c485b5 100644
--- a/opal/mca/shmem/mmap/shmem_mmap_module.c
+++ b/opal/mca/shmem/mmap/shmem_mmap_module.c
@@ -365,9 +365,8 @@ segment_create(opal_shmem_ds_t *ds_buf,
      * a network filesystem, the user may see a shared memory performance hit.
      */
     if (opal_shmem_mmap_nfs_warning && opal_path_nfs(real_file_name, NULL)) {
-        char hn[MAXHOSTNAMELEN];
-        gethostname(hn, MAXHOSTNAMELEN - 1);
-        hn[MAXHOSTNAMELEN - 1] = '\0';
+        char hn[OPAL_MAXHOSTNAMELEN];
+        gethostname(hn, sizeof(hn));
         opal_show_help("help-opal-shmem-mmap.txt", "mmap on nfs", 1, hn,
                        real_file_name);
     }
@@ -382,9 +381,8 @@ segment_create(opal_shmem_ds_t *ds_buf,
         goto out;
     }
     if (!space_available) {
-        char hn[MAXHOSTNAMELEN];
-        gethostname(hn, MAXHOSTNAMELEN - 1);
-        hn[MAXHOSTNAMELEN - 1] = '\0';
+        char hn[OPAL_MAXHOSTNAMELEN];
+        gethostname(hn, sizeof(hn));
         rc = OPAL_ERR_OUT_OF_RESOURCE;
         opal_show_help("help-opal-shmem-mmap.txt", "target full", 1,
                        real_file_name, hn, (unsigned long)real_size,
@@ -394,9 +392,8 @@ segment_create(opal_shmem_ds_t *ds_buf,
     /* enough space is available, so create the segment */
     if (-1 == (ds_buf->seg_id = open(real_file_name, O_CREAT | O_RDWR, 0600))) {
         int err = errno;
-        char hn[MAXHOSTNAMELEN];
-        gethostname(hn, MAXHOSTNAMELEN - 1);
-        hn[MAXHOSTNAMELEN - 1] = '\0';
+        char hn[OPAL_MAXHOSTNAMELEN];
+        gethostname(hn, sizeof(hn));
         opal_show_help("help-opal-shmem-mmap.txt", "sys call fail", 1, hn,
                        "open(2)", "", strerror(err), err);
         rc = OPAL_ERROR;
@@ -405,9 +402,8 @@ segment_create(opal_shmem_ds_t *ds_buf,
     /* size backing file - note the use of real_size here */
     if (0 != ftruncate(ds_buf->seg_id, real_size)) {
         int err = errno;
-        char hn[MAXHOSTNAMELEN];
-        gethostname(hn, MAXHOSTNAMELEN - 1);
-        hn[MAXHOSTNAMELEN - 1] = '\0';
+        char hn[OPAL_MAXHOSTNAMELEN];
+        gethostname(hn, sizeof(hn));
         opal_show_help("help-opal-shmem-mmap.txt", "sys call fail", 1, hn,
                        "ftruncate(2)", "", strerror(err), err);
         rc = OPAL_ERROR;
@@ -418,9 +414,8 @@ segment_create(opal_shmem_ds_t *ds_buf,
                                        PROT_READ | PROT_WRITE, MAP_SHARED,
                                        ds_buf->seg_id, 0))) {
         int err = errno;
-        char hn[MAXHOSTNAMELEN];
-        gethostname(hn, MAXHOSTNAMELEN - 1);
-        hn[MAXHOSTNAMELEN - 1] = '\0';
+        char hn[OPAL_MAXHOSTNAMELEN];
+        gethostname(hn, sizeof(hn));
         opal_show_help("help-opal-shmem-mmap.txt", "sys call fail", 1, hn,
                        "mmap(2)", "", strerror(err), err);
         rc = OPAL_ERROR;
@@ -466,9 +461,8 @@ out:
     if (-1 != ds_buf->seg_id) {
         if (0 != close(ds_buf->seg_id)) {
             int err = errno;
-            char hn[MAXHOSTNAMELEN];
-            gethostname(hn, MAXHOSTNAMELEN - 1);
-            hn[MAXHOSTNAMELEN - 1] = '\0';
+            char hn[OPAL_MAXHOSTNAMELEN];
+            gethostname(hn, sizeof(hn));
             opal_show_help("help-opal-shmem-mmap.txt", "sys call fail", 1, hn,
                            "close(2)", "", strerror(err), err);
             rc = OPAL_ERROR;
@@ -500,9 +494,8 @@ segment_attach(opal_shmem_ds_t *ds_buf)
     if (my_pid != ds_buf->seg_cpid) {
         if (-1 == (ds_buf->seg_id = open(ds_buf->seg_name, O_RDWR))) {
             int err = errno;
-            char hn[MAXHOSTNAMELEN];
-            gethostname(hn, MAXHOSTNAMELEN - 1);
-            hn[MAXHOSTNAMELEN - 1] = '\0';
+            char hn[OPAL_MAXHOSTNAMELEN];
+            gethostname(hn, sizeof(hn));
             opal_show_help("help-opal-shmem-mmap.txt", "sys call fail", 1, hn,
                            "open(2)", "", strerror(err), err);
             return NULL;
@@ -512,9 +505,8 @@ segment_attach(opal_shmem_ds_t *ds_buf)
                                    PROT_READ | PROT_WRITE, MAP_SHARED,
                                    ds_buf->seg_id, 0))) {
             int err = errno;
-            char hn[MAXHOSTNAMELEN];
-            gethostname(hn, MAXHOSTNAMELEN - 1);
-            hn[MAXHOSTNAMELEN - 1] = '\0';
+            char hn[OPAL_MAXHOSTNAMELEN];
+            gethostname(hn, sizeof(hn));
             opal_show_help("help-opal-shmem-mmap.txt", "sys call fail", 1, hn,
                            "mmap(2)", "", strerror(err), err);
             /* mmap failed, so close the file and return NULL - no error check
@@ -529,9 +521,8 @@ segment_attach(opal_shmem_ds_t *ds_buf)
          */
         if (0 != close(ds_buf->seg_id)) {
             int err = errno;
-            char hn[MAXHOSTNAMELEN];
-            gethostname(hn, MAXHOSTNAMELEN - 1);
-            hn[MAXHOSTNAMELEN - 1] = '\0';
+            char hn[OPAL_MAXHOSTNAMELEN];
+            gethostname(hn, sizeof(hn));
             opal_show_help("help-opal-shmem-mmap.txt", "sys call fail", 1,
                            hn, "close(2)", "", strerror(err), err);
         }
@@ -570,9 +561,8 @@ segment_detach(opal_shmem_ds_t *ds_buf)
 
     if (0 != munmap((void *)ds_buf->seg_base_addr, ds_buf->seg_size)) {
         int err = errno;
-        char hn[MAXHOSTNAMELEN];
-        gethostname(hn, MAXHOSTNAMELEN - 1);
-        hn[MAXHOSTNAMELEN - 1] = '\0';
+        char hn[OPAL_MAXHOSTNAMELEN];
+        gethostname(hn, sizeof(hn));
         opal_show_help("help-opal-shmem-mmap.txt", "sys call fail", 1, hn,
                        "munmap(2)", "", strerror(err), err);
         rc = OPAL_ERROR;
@@ -599,9 +589,8 @@ segment_unlink(opal_shmem_ds_t *ds_buf)
 
     if (-1 == unlink(ds_buf->seg_name)) {
         int err = errno;
-        char hn[MAXHOSTNAMELEN];
-        gethostname(hn, MAXHOSTNAMELEN - 1);
-        hn[MAXHOSTNAMELEN - 1] = '\0';
+        char hn[OPAL_MAXHOSTNAMELEN];
+        gethostname(hn, sizeof(hn));
         opal_show_help("help-opal-shmem-mmap.txt", "sys call fail", 1, hn,
                        "unlink(2)", ds_buf->seg_name, strerror(err), err);
         return OPAL_ERROR;
diff --git a/opal/mca/shmem/posix/shmem_posix_common_utils.c b/opal/mca/shmem/posix/shmem_posix_common_utils.c
index 58517aff49..82c5ae65ce 100644
--- a/opal/mca/shmem/posix/shmem_posix_common_utils.c
+++ b/opal/mca/shmem/posix/shmem_posix_common_utils.c
@@ -88,9 +88,8 @@ shmem_posix_shm_open(char *posix_file_name_buff, size_t size)
              * of here. we can't be selected :-(.
              */
             else {
-                char hn[MAXHOSTNAMELEN];
-                gethostname(hn, MAXHOSTNAMELEN - 1);
-                hn[MAXHOSTNAMELEN - 1] = '\0';
+                char hn[OPAL_MAXHOSTNAMELEN];
+                gethostname(hn, sizeof(hn));
                 opal_output_verbose(10, opal_shmem_base_framework.framework_output,
                      "shmem_posix_shm_open: disqualifying posix because "
                      "shm_open(2) failed with error: %s (errno %d)\n",
diff --git a/opal/mca/shmem/posix/shmem_posix_component.c b/opal/mca/shmem/posix/shmem_posix_component.c
index 9ac4549bf1..fa8ea7d71b 100644
--- a/opal/mca/shmem/posix/shmem_posix_component.c
+++ b/opal/mca/shmem/posix/shmem_posix_component.c
@@ -178,9 +178,8 @@ posix_runtime_query(mca_base_module_t **module,
         /* free up allocated resources before we return */
         if (0 != shm_unlink(tmp_buff)) {
             int err = errno;
-            char hn[MAXHOSTNAMELEN];
-            gethostname(hn, MAXHOSTNAMELEN - 1);
-            hn[MAXHOSTNAMELEN - 1] = '\0';
+            char hn[OPAL_MAXHOSTNAMELEN];
+            gethostname(hn, sizeof(hn));
             opal_show_help("help-opal-shmem-posix.txt", "sys call fail", 1,
                            hn, "shm_unlink(2)", "", strerror(err), err);
             /* something strange happened, so consider this a run-time test
diff --git a/opal/mca/shmem/posix/shmem_posix_module.c b/opal/mca/shmem/posix/shmem_posix_module.c
index d441b635b9..0c8781ec6c 100644
--- a/opal/mca/shmem/posix/shmem_posix_module.c
+++ b/opal/mca/shmem/posix/shmem_posix_module.c
@@ -203,9 +203,8 @@ segment_create(opal_shmem_ds_t *ds_buf,
     /* size backing file - note the use of real_size here */
     else if (0 != ftruncate(ds_buf->seg_id, real_size)) {
         int err = errno;
-        char hn[MAXHOSTNAMELEN];
-        gethostname(hn, MAXHOSTNAMELEN - 1);
-        hn[MAXHOSTNAMELEN - 1] = '\0';
+        char hn[OPAL_MAXHOSTNAMELEN];
+        gethostname(hn, sizeof(hn));
         opal_show_help("help-opal-shmem-posix.txt", "sys call fail", 1, hn,
                        "ftruncate(2)", "", strerror(err), err);
         rc = OPAL_ERROR;
@@ -215,9 +214,8 @@ segment_create(opal_shmem_ds_t *ds_buf,
                                                                    PROT_READ | PROT_WRITE, MAP_SHARED,
                                                                    ds_buf->seg_id, 0))) {
         int err = errno;
-        char hn[MAXHOSTNAMELEN];
-        gethostname(hn, MAXHOSTNAMELEN - 1);
-        hn[MAXHOSTNAMELEN - 1] = '\0';
+        char hn[OPAL_MAXHOSTNAMELEN];
+        gethostname(hn, sizeof(hn));
         opal_show_help("help-opal-shmem-posix.txt", "sys call fail", 1, hn,
                        "mmap(2)", "", strerror(err), err);
         rc = OPAL_ERROR;
@@ -267,9 +265,8 @@ out:
     if (-1 != ds_buf->seg_id) {
         if (0 != close(ds_buf->seg_id)) {
             int err = errno;
-            char hn[MAXHOSTNAMELEN];
-            gethostname(hn, MAXHOSTNAMELEN - 1);
-            hn[MAXHOSTNAMELEN - 1] = '\0';
+            char hn[OPAL_MAXHOSTNAMELEN];
+            gethostname(hn, sizeof(hn));
             opal_show_help("help-opal-shmem-mmap.txt", "sys call fail", 1, hn,
                            "close(2)", "", strerror(err), err);
             rc = OPAL_ERROR;
@@ -307,9 +304,8 @@ segment_attach(opal_shmem_ds_t *ds_buf)
     if (my_pid != ds_buf->seg_cpid) {
         if (-1 == (ds_buf->seg_id = shm_open(ds_buf->seg_name, O_RDWR, 0600))) {
             int err = errno;
-            char hn[MAXHOSTNAMELEN];
-            gethostname(hn, MAXHOSTNAMELEN - 1);
-            hn[MAXHOSTNAMELEN - 1] = '\0';
+            char hn[OPAL_MAXHOSTNAMELEN];
+            gethostname(hn, sizeof(hn));
             opal_show_help("help-opal-shmem-posix.txt", "sys call fail", 1, hn,
                            "open(2)", "", strerror(err), err);
             return NULL;
@@ -319,9 +315,8 @@ segment_attach(opal_shmem_ds_t *ds_buf)
                                                      PROT_READ | PROT_WRITE, MAP_SHARED,
                                                      ds_buf->seg_id, 0))) {
             int err = errno;
-            char hn[MAXHOSTNAMELEN];
-            gethostname(hn, MAXHOSTNAMELEN - 1);
-            hn[MAXHOSTNAMELEN - 1] = '\0';
+            char hn[OPAL_MAXHOSTNAMELEN];
+            gethostname(hn, sizeof(hn));
             opal_show_help("help-opal-shmem-posix.txt", "sys call fail", 1, hn,
                            "mmap(2)", "", strerror(err), err);
             /* mmap failed, so shm_unlink and return NULL - no error check here
@@ -337,9 +332,8 @@ segment_attach(opal_shmem_ds_t *ds_buf)
              */
             if (0 != close(ds_buf->seg_id)) {
                 int err = errno;
-                char hn[MAXHOSTNAMELEN];
-                gethostname(hn, MAXHOSTNAMELEN - 1);
-                hn[MAXHOSTNAMELEN - 1] = '\0';
+                char hn[OPAL_MAXHOSTNAMELEN];
+                gethostname(hn, sizeof(hn));
                 opal_show_help("help-opal-shmem-mmap.txt", "sys call fail", 1,
                                hn, "close(2)", "", strerror(err), err);
              }
@@ -379,9 +373,8 @@ segment_detach(opal_shmem_ds_t *ds_buf)
 
     if (0 != munmap((void*)ds_buf->seg_base_addr, ds_buf->seg_size)) {
         int err = errno;
-        char hn[MAXHOSTNAMELEN];
-        gethostname(hn, MAXHOSTNAMELEN - 1);
-        hn[MAXHOSTNAMELEN - 1] = '\0';
+        char hn[OPAL_MAXHOSTNAMELEN];
+        gethostname(hn, sizeof(hn));
         opal_show_help("help-opal-shmem-posix.txt", "sys call fail", 1, hn,
                        "munmap(2)", "", strerror(err), err);
         rc = OPAL_ERROR;
@@ -408,9 +401,8 @@ segment_unlink(opal_shmem_ds_t *ds_buf)
 
     if (-1 == shm_unlink(ds_buf->seg_name)) {
         int err = errno;
-        char hn[MAXHOSTNAMELEN];
-        gethostname(hn, MAXHOSTNAMELEN - 1);
-        hn[MAXHOSTNAMELEN - 1] = '\0';
+        char hn[OPAL_MAXHOSTNAMELEN];
+        gethostname(hn, sizeof(hn));
         opal_show_help("help-opal-shmem-posix.txt", "sys call fail", 1, hn,
                        "shm_unlink(2)", ds_buf->seg_name, strerror(err), err);
         return OPAL_ERROR;
diff --git a/opal/mca/shmem/sysv/shmem_sysv_module.c b/opal/mca/shmem/sysv/shmem_sysv_module.c
index 0ab88dc464..f6a3531aff 100644
--- a/opal/mca/shmem/sysv/shmem_sysv_module.c
+++ b/opal/mca/shmem/sysv/shmem_sysv_module.c
@@ -195,9 +195,8 @@ segment_create(opal_shmem_ds_t *ds_buf,
     if (-1 == (ds_buf->seg_id = shmget(IPC_PRIVATE, real_size,
                                        IPC_CREAT | IPC_EXCL | S_IRWXU))) {
         int err = errno;
-        char hn[MAXHOSTNAMELEN];
-        gethostname(hn, MAXHOSTNAMELEN - 1);
-        hn[MAXHOSTNAMELEN - 1] = '\0';
+        char hn[OPAL_MAXHOSTNAMELEN];
+        gethostname(hn, sizeof(hn));
         opal_show_help("help-opal-shmem-sysv.txt", "sys call fail", 1, hn,
                        "shmget(2)", "", strerror(err), err);
         rc = OPAL_ERROR;
@@ -206,9 +205,8 @@ segment_create(opal_shmem_ds_t *ds_buf,
     /* attach to the sement */
     else if ((void *)-1 == (seg_hdrp = shmat(ds_buf->seg_id, NULL, 0))) {
         int err = errno;
-        char hn[MAXHOSTNAMELEN];
-        gethostname(hn, MAXHOSTNAMELEN - 1);
-        hn[MAXHOSTNAMELEN - 1] = '\0';
+        char hn[OPAL_MAXHOSTNAMELEN];
+        gethostname(hn, sizeof(hn));
         opal_show_help("help-opal-shmem-sysv.txt", "sys call fail", 1, hn,
                        "shmat(2)", "", strerror(err), err);
         shmctl(ds_buf->seg_id, IPC_RMID, NULL);
@@ -221,9 +219,8 @@ segment_create(opal_shmem_ds_t *ds_buf,
      */
     else if (0 != shmctl(ds_buf->seg_id, IPC_RMID, NULL)) {
         int err = errno;
-        char hn[MAXHOSTNAMELEN];
-        gethostname(hn, MAXHOSTNAMELEN - 1);
-        hn[MAXHOSTNAMELEN - 1] = '\0';
+        char hn[OPAL_MAXHOSTNAMELEN];
+        gethostname(hn, sizeof(hn));
         opal_show_help("help-opal-shmem-sysv.txt", "sys call fail", 1, hn,
                        "shmctl(2)", "", strerror(err), err);
         rc = OPAL_ERROR;
@@ -294,9 +291,8 @@ segment_attach(opal_shmem_ds_t *ds_buf)
         if ((void *)-1 == (ds_buf->seg_base_addr = shmat(ds_buf->seg_id, NULL,
                                                          0))) {
             int err = errno;
-            char hn[MAXHOSTNAMELEN];
-            gethostname(hn, MAXHOSTNAMELEN - 1);
-            hn[MAXHOSTNAMELEN - 1] = '\0';
+            char hn[OPAL_MAXHOSTNAMELEN];
+            gethostname(hn, sizeof(hn));
             opal_show_help("help-opal-shmem-sysv.txt", "sys call fail", 1, hn,
                            "shmat(2)", "", strerror(err), err);
             shmctl(ds_buf->seg_id, IPC_RMID, NULL);
@@ -337,9 +333,8 @@ segment_detach(opal_shmem_ds_t *ds_buf)
 
     if (0 != shmdt((char*)ds_buf->seg_base_addr)) {
         int err = errno;
-        char hn[MAXHOSTNAMELEN];
-        gethostname(hn, MAXHOSTNAMELEN - 1);
-        hn[MAXHOSTNAMELEN - 1] = '\0';
+        char hn[OPAL_MAXHOSTNAMELEN];
+        gethostname(hn, sizeof(hn));
         opal_show_help("help-opal-shmem-sysv.txt", "sys call fail", 1, hn,
                        "shmdt(2)", "", strerror(err), err);
         rc = OPAL_ERROR;
diff --git a/opal/runtime/opal_init.c b/opal/runtime/opal_init.c
index 6140b77652..6cf2f1ba04 100644
--- a/opal/runtime/opal_init.c
+++ b/opal/runtime/opal_init.c
@@ -269,7 +269,7 @@ opal_init_util(int* pargc, char*** pargv)
 {
     int ret;
     char *error = NULL;
-    char hostname[512];
+    char hostname[OPAL_MAXHOSTNAMELEN];
 
     if( ++opal_util_initialized != 1 ) {
         if( opal_util_initialized < 1 ) {
@@ -294,7 +294,7 @@ opal_init_util(int* pargc, char*** pargv)
      * that we don't bother with fqdn and prefix issues here - we let
      * the RTE later replace this with a modified name if the user
      * requests it */
-    gethostname(hostname, 512);
+    gethostname(hostname, sizeof(hostname));
     opal_process_info.nodename = strdup(hostname);
 
     /* initialize the memory allocator */
diff --git a/opal/util/output.c b/opal/util/output.c
index dd950a8c84..b17ce05779 100644
--- a/opal/util/output.c
+++ b/opal/util/output.c
@@ -127,7 +127,7 @@ OBJ_CLASS_INSTANCE(opal_output_stream_t, opal_object_t, construct, NULL);
 bool opal_output_init(void)
 {
     int i;
-    char hostname[32];
+    char hostname[OPAL_MAXHOSTNAMELEN];
     char *str;
 
     if (initialized) {
@@ -177,7 +177,6 @@ bool opal_output_init(void)
         verbose.lds_want_stderr = true;
     }
     gethostname(hostname, sizeof(hostname));
-    hostname[sizeof(hostname)-1] = '\0';
     asprintf(&verbose.lds_prefix, "[%s:%05d] ", hostname, getpid());
 
     for (i = 0; i < OPAL_OUTPUT_MAX_STREAMS; ++i) {
@@ -254,7 +253,7 @@ bool opal_output_switch(int output_id, bool enable)
 void opal_output_reopen_all(void)
 {
     char *str;
-    char hostname[32];
+    char hostname[OPAL_MAXHOSTNAMELEN];
 
     str = getenv("OPAL_OUTPUT_STDERR_FD");
     if (NULL != str) {
diff --git a/opal/util/stacktrace.c b/opal/util/stacktrace.c
index 9c631ea275..d05275032b 100644
--- a/opal/util/stacktrace.c
+++ b/opal/util/stacktrace.c
@@ -42,7 +42,7 @@
 
 #define HOSTFORMAT "[%s:%05d] "
 
-static char stacktrace_hostname[64];
+static char stacktrace_hostname[OPAL_MAXHOSTNAMELEN];
 static char *unable_to_print_msg = "Unable to print stack trace!\n";
 
 /**
@@ -427,7 +427,6 @@ int opal_util_register_stackhandlers (void)
     bool complain, showed_help = false;
 
     gethostname(stacktrace_hostname, sizeof(stacktrace_hostname));
-    stacktrace_hostname[sizeof(stacktrace_hostname) - 1] = '\0';
     /* to keep these somewhat readable, only print the machine name */
     for (i = 0 ; i < (int)strlen(stacktrace_hostname) ; ++i) {
         if (stacktrace_hostname[i] == '.') {
diff --git a/opal/util/timings.c b/opal/util/timings.c
index 9459ab5205..e2e0e45bba 100644
--- a/opal/util/timings.c
+++ b/opal/util/timings.c
@@ -75,8 +75,8 @@ int opal_timing_clocksync_read(char *fname)
     bool found = false;
     char *ptr = NULL;
 
-    char hname[1024] = "NA";
-    if( gethostname(hname, 1024) ){
+    char hname[OPAL_MAXHOSTNAMELEN] = "NA";
+    if( gethostname(hname, sizeof(hname)) ){
         opal_output(0, "opal_timing_clocksync_read(%s): Cannot gethostname",
                     fname);
     }
diff --git a/opal/win32/win_compat.h b/opal/win32/win_compat.h
index dc7aeb45f6..c31d3bb74d 100644
--- a/opal/win32/win_compat.h
+++ b/opal/win32/win_compat.h
@@ -176,6 +176,7 @@ typedef unsigned int uint;
 
 #define MAXPATHLEN _MAX_PATH
 #define MAXHOSTNAMELEN _MAX_PATH
+#define OPAL_MAXHOSTNAMELEN (MAXHOSTNAMELEN + 1)
 #define PATH_MAX _MAX_PATH
 #define WTERMSIG(EXIT_CODE)    (1)
 #define WIFEXITED(EXIT_CODE)   (1)