diff -urNp old/include/net-snmp/library/large_fd_set.h new/include/net-snmp/library/large_fd_set.h
--- old/include/net-snmp/library/large_fd_set.h	2012-10-10 00:28:58.000000000 +0200
+++ new/include/net-snmp/library/large_fd_set.h	2017-04-04 14:36:27.307180033 +0200
@@ -55,8 +55,9 @@ extern "C" {
  * Number of bytes needed to store a number of file descriptors as a
  * struct fd_set.
  */
-#define NETSNMP_FD_SET_BYTES(setsize)                           \
-    (sizeof(fd_set) + ((setsize) - FD_SETSIZE) * sizeof(SOCKET))
+#define NETSNMP_FD_SET_BYTES(setsize)                                   \
+    (sizeof(fd_set) + ((setsize) > FD_SETSIZE ?                         \
+                       ((setsize) - FD_SETSIZE) * sizeof(SOCKET) : 0))
 
 /** Remove all sockets from the set *fdset. */
 #define NETSNMP_LARGE_FD_ZERO(fdset) \
@@ -91,9 +92,10 @@ int    netsnmp_large_fd_is_set(SOCKET fd
  * Number of bytes needed to store a number of file descriptors as a
  * struct fd_set.
  */
-#define NETSNMP_FD_SET_BYTES(setsize)                                   \
-    (sizeof(fd_set) + NETSNMP_FD_SET_ELEM_COUNT((setsize) - FD_SETSIZE) \
-     * NETSNMP_FD_MASK_SIZE)
+#define NETSNMP_FD_SET_BYTES(setsize)                                    \
+    (sizeof(fd_set) + ((setsize) > FD_SETSIZE ?                          \
+                       NETSNMP_FD_SET_ELEM_COUNT((setsize) - FD_SETSIZE) \
+                       * NETSNMP_FD_MASK_SIZE : 0))
 
 /** Remove all file descriptors from the set *fdset. */
 #define NETSNMP_LARGE_FD_ZERO(fdset)                            \
diff -urNp old/snmplib/large_fd_set.c new/snmplib/large_fd_set.c
--- old/snmplib/large_fd_set.c	2012-10-10 00:28:58.000000000 +0200
+++ new/snmplib/large_fd_set.c	2017-04-04 15:03:20.580810774 +0200
@@ -21,6 +21,10 @@
 
 #if !defined(cygwin) && defined(HAVE_WINSOCK_H)
 
+#define LFD_SET(n, p)    FD_SET(n, p)
+#define LFD_CLR(n, p)    FD_CLR(n, p)
+#define LFD_ISSET(n, p)  FD_ISSET(n, p)
+
 void
 netsnmp_large_fd_setfd(SOCKET fd, netsnmp_large_fd_set * fdset)
 {
@@ -28,18 +32,18 @@ netsnmp_large_fd_setfd(SOCKET fd, netsnm
 
     netsnmp_assert(fd != INVALID_SOCKET);
 
-    if (fdset->lfs_set.fd_count == fdset->lfs_setsize)
+    if (fdset->lfs_setptr->fd_count == fdset->lfs_setsize)
         netsnmp_large_fd_set_resize(fdset, 2 * (fdset->lfs_setsize + 1));
 
-    for (i = 0; i < fdset->lfs_set.fd_count; i++) {
-        if (fdset->lfs_set.fd_array[i] == (SOCKET) (fd))
+    for (i = 0; i < fdset->lfs_setptr->fd_count; i++) {
+        if (fdset->lfs_setptr->fd_array[i] == fd)
             break;
     }
 
-    if (i == fdset->lfs_set.fd_count
-        && fdset->lfs_set.fd_count < fdset->lfs_setsize) {
-        fdset->lfs_set.fd_count++;
-        fdset->lfs_set.fd_array[i] = fd;
+    if (i == fdset->lfs_setptr->fd_count &&
+        fdset->lfs_setptr->fd_count < fdset->lfs_setsize) {
+        fdset->lfs_setptr->fd_count++;
+        fdset->lfs_setptr->fd_array[i] = fd;
     }
 }
 
@@ -50,14 +54,14 @@ netsnmp_large_fd_clr(SOCKET fd, netsnmp_
 
     netsnmp_assert(fd != INVALID_SOCKET);
 
-    for (i = 0; i < fdset->lfs_set.fd_count; i++) {
-        if (fdset->lfs_set.fd_array[i] == fd) {
-            while (i < fdset->lfs_set.fd_count - 1) {
-                fdset->lfs_set.fd_array[i] =
-                    fdset->lfs_set.fd_array[i + 1];
+    for (i = 0; i < fdset->lfs_setptr->fd_count; i++) {
+        if (fdset->lfs_setptr->fd_array[i] == fd) {
+            while (i < fdset->lfs_setptr->fd_count - 1) {
+                fdset->lfs_setptr->fd_array[i] =
+                    fdset->lfs_setptr->fd_array[i + 1];
                 i++;
             }
-            fdset->lfs_set.fd_count--;
+            fdset->lfs_setptr->fd_count--;
             break;
         }
     }
@@ -70,8 +74,8 @@ netsnmp_large_fd_is_set(SOCKET fd, netsn
 
     netsnmp_assert(fd != INVALID_SOCKET);
 
-    for (i = 0; i < fdset->lfs_set.fd_count; i++) {
-        if (fdset->lfs_set.fd_array[i] == fd)
+    for (i = 0; i < fdset->lfs_setptr->fd_count; i++) {
+        if (fdset->lfs_setptr->fd_array[i] == fd)
             return 1;
     }
     return 0;
@@ -79,6 +83,43 @@ netsnmp_large_fd_is_set(SOCKET fd, netsn
 
 #else
 
+ /*
+ * Recent versions of glibc trigger abort() if FD_SET(), FD_CLR() or
+ * FD_ISSET() is invoked with n >= FD_SETSIZE. Hence these replacement
+ * functions. However, since NFDBITS != 8 * sizeof(fd_set.fds_bits[0]) for at
+ * least HP-UX on ia64 and since that combination uses big endian, use the
+ * macros from <sys/select.h> on such systems.
+ */
+NETSNMP_STATIC_INLINE void LFD_SET(unsigned n, fd_set *p)
+{
+    enum { nfdbits = 8 * sizeof(p->fds_bits[0]) };
+
+    if (nfdbits == NFDBITS)
+        p->fds_bits[n / nfdbits] |= (1ULL << (n % nfdbits));
+    else
+        FD_SET(n, p);
+}
+
+NETSNMP_STATIC_INLINE void LFD_CLR(unsigned n, fd_set *p)
+{
+    enum { nfdbits = 8 * sizeof(p->fds_bits[0]) };
+
+    if (nfdbits == NFDBITS)
+        p->fds_bits[n / nfdbits] &= ~(1ULL << (n % nfdbits));
+    else
+        FD_CLR(n, p);
+}
+
+NETSNMP_STATIC_INLINE unsigned LFD_ISSET(unsigned n, const fd_set *p)
+{
+    enum { nfdbits = 8 * sizeof(p->fds_bits[0]) };
+
+    if (nfdbits == NFDBITS)
+        return (p->fds_bits[n / nfdbits] & (1ULL << (n % nfdbits))) != 0;
+    else
+        return FD_ISSET(n, p) != 0;
+}
+
 void
 netsnmp_large_fd_setfd(int fd, netsnmp_large_fd_set * fdset)
 {
@@ -87,7 +128,7 @@ netsnmp_large_fd_setfd(int fd, netsnmp_l
     while (fd >= (int)fdset->lfs_setsize)
         netsnmp_large_fd_set_resize(fdset, 2 * (fdset->lfs_setsize + 1));
 
-    FD_SET(fd, fdset->lfs_setptr);
+    LFD_SET(fd, fdset->lfs_setptr);
 }
 
 void
@@ -96,7 +137,7 @@ netsnmp_large_fd_clr(int fd, netsnmp_lar
     netsnmp_assert(fd >= 0);
 
     if ((unsigned)fd < fdset->lfs_setsize)
-        FD_CLR(fd, fdset->lfs_setptr);
+        LFD_CLR(fd, fdset->lfs_setptr);
 }
 
 int
@@ -104,7 +145,7 @@ netsnmp_large_fd_is_set(int fd, netsnmp_
 {
     netsnmp_assert(fd >= 0);
 
-    return (unsigned)fd < fdset->lfs_setsize && FD_ISSET(fd, fdset->lfs_setptr);
+    return ((unsigned)fd < fdset->lfs_setsize && LFD_ISSET(fd, fdset->lfs_setptr));
 }
 
 #endif
@@ -174,22 +215,24 @@ netsnmp_large_fd_set_resize(netsnmp_larg
     }
 
 #if defined(cygwin) || !defined(HAVE_WINSOCK_H)
-    {
+    /*
+     * Unix: when enlarging, clear the file descriptors defined in the
+     * resized *fdset but that were not defined in the original *fdset.
+     */
+    if ( fdset->lfs_setsize == 0 && setsize == FD_SETSIZE ) {
+        /* In this case we can use the OS's FD_ZERO */
+        FD_ZERO(fdset->lfs_setptr);
+    } else {
         int             i;
-
-        /*
-         * Unix: when enlarging, clear the file descriptors defined in the
-         * resized *fdset but that were not defined in the original *fdset.
-         */
         for (i = fdset->lfs_setsize; i < setsize; i++)
-            FD_CLR(i, fdset->lfs_setptr);
+            LFD_CLR(i, fdset->lfs_setptr);
     }
 #endif
 
     fdset->lfs_setsize = setsize;
 #if !defined(cygwin) && defined(HAVE_WINSOCK_H)
-    if (setsize < fdset->lfs_set.fd_count)
-        fdset->lfs_set.fd_count = setsize;
+    if (setsize < fdset->lfs_setptr->fd_count)
+        fdset->lfs_setptr->fd_count = setsize;
 #endif
 success:
     return 1;
@@ -197,7 +240,7 @@ success:
 out_of_mem:
     fdset->lfs_setsize = 0;
 #if !defined(cygwin) && defined(HAVE_WINSOCK_H)
-    fdset->lfs_set.fd_count = 0;
+    fdset->lfs_setptr->fd_count = 0;
 #endif
     return 0;
 }