diff --git a/ChangeLog b/ChangeLog
index 94000ad7be..ff4b532bfa 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,14 @@
 2014-12-29  Siddhesh Poyarekar  <siddhesh@redhat.com>
 
+	* posix/posix-conf-vars.list (SPEC:XBS5): Add sysconf prefix.
+	* posix/confstr.c: Define NEED_SPEC_ARRAY to 0.
+	* posix/posix-envs.def: Likewise.
+	* sysdeps/posix/sysconf.c: Likewise.
+	* posix/getconf.c: Define NEED_SPEC_ARRAY to 1.
+	(specs): Remove array.
+	* scripts/gen-posix-conf-vars.awk: Support generation of specs
+	array.
+
 	* posix/posix-conf-vars.list: Add _POSIX sysconf namespace.
 	* sysdeps/posix/sysconf.c: Include posix-conf-vars.h.
 	(__sysconf): Use CONF_IS_* macros.
diff --git a/posix/confstr.c b/posix/confstr.c
index e4e0f4bdec..244a25c93f 100644
--- a/posix/confstr.c
+++ b/posix/confstr.c
@@ -21,6 +21,8 @@
 #include <string.h>
 #include <confstr.h>
 #include "../version.h"
+
+#define NEED_SPEC_ARRAY 0
 #include <posix-conf-vars.h>
 
 /* If BUF is not NULL and LEN > 0, fill in at most LEN - 1 bytes
diff --git a/posix/getconf.c b/posix/getconf.c
index 14d51d87ac..bcde4c58a1 100644
--- a/posix/getconf.c
+++ b/posix/getconf.c
@@ -26,6 +26,9 @@
 #include "../version.h"
 #define PACKAGE _libc_intl_domainname
 
+#define NEED_SPEC_ARRAY 1
+#include <posix-conf-vars.h>
+
 struct conf
   {
     const char *name;
@@ -387,23 +390,6 @@ static const struct conf vars[] =
   };
 
 
-static const struct { const char *name; int num; } specs[] =
-  {
-    { "XBS5_ILP32_OFF32", _SC_XBS5_ILP32_OFF32 },
-    { "XBS5_ILP32_OFFBIG", _SC_XBS5_ILP32_OFFBIG },
-    { "XBS5_LP64_OFF64", _SC_XBS5_LP64_OFF64 },
-    { "XBS5_LPBIG_OFFBIG", _SC_XBS5_LPBIG_OFFBIG },
-    { "POSIX_V6_ILP32_OFF32", _SC_V6_ILP32_OFF32 },
-    { "POSIX_V6_ILP32_OFFBIG", _SC_V6_ILP32_OFFBIG },
-    { "POSIX_V6_LP64_OFF64", _SC_V6_LP64_OFF64 },
-    { "POSIX_V6_LPBIG_OFFBIG", _SC_V6_LPBIG_OFFBIG },
-    { "POSIX_V7_ILP32_OFF32", _SC_V7_ILP32_OFF32 },
-    { "POSIX_V7_ILP32_OFFBIG", _SC_V7_ILP32_OFFBIG },
-    { "POSIX_V7_LP64_OFF64", _SC_V7_LP64_OFF64 },
-    { "POSIX_V7_LPBIG_OFFBIG", _SC_V7_LPBIG_OFFBIG },
-  };
-static const int nspecs = sizeof (specs) / sizeof (specs[0]);
-
 extern const char *__progname;
 
 
diff --git a/posix/posix-conf-vars.list b/posix/posix-conf-vars.list
index 3e7e7cdaa9..601bc2fd33 100644
--- a/posix/posix-conf-vars.list
+++ b/posix/posix-conf-vars.list
@@ -1,7 +1,8 @@
 # Configuration variables identified by getconf.  The heading of each section
-# is of the format TYPE PREFIX with the opening curly brace on the same line.
-# TYPE can either be SYSCONF, PATHCONF, CONFSTR or SPEC.  Variable names are
-# put one on each line with a curly brace on its own line ending the section.
+# is of the format TYPE PREFIX SC_PREFIX with the opening curly brace on the
+# same line.  TYPE can either be SYSCONF, PATHCONF, CONFSTR or SPEC.  In the
+# absence of SC_PREFIX, _SC is used as the SC_PREFIX.  Variable names are put
+# one on each line with a curly brace on its own line ending the section.
 
 SPEC POSIX {
   V6_ILP32_OFF32
@@ -104,7 +105,7 @@ SYSCONF POSIX {
   RAW_SOCKETS
 }
 
-SPEC XBS5 {
+SPEC XBS5 _SC_XBS5 {
   ILP32_OFF32
   ILP32_OFFBIG
   LP64_OFF64
diff --git a/posix/posix-envs.def b/posix/posix-envs.def
index 870d85a7db..fa271bbfc4 100644
--- a/posix/posix-envs.def
+++ b/posix/posix-envs.def
@@ -42,6 +42,7 @@
    defined.  These are called with arguments V5, V6, V7 before and
    after the relevant groups of environments.  */
 
+#define NEED_SPEC_ARRAY 0
 #include <posix-conf-vars.h>
 
 START_ENV_GROUP (V7)
diff --git a/scripts/gen-posix-conf-vars.awk b/scripts/gen-posix-conf-vars.awk
index 16e20fc100..0eca55d536 100644
--- a/scripts/gen-posix-conf-vars.awk
+++ b/scripts/gen-posix-conf-vars.awk
@@ -15,12 +15,19 @@ $1 ~ /^#/ || $0 ~ /^\s*$/ {
 $NF == "{" {
   type = $1
   prefix = $2
+
+  if (NF == 4)
+    sc_prefix = $3
+  else
+    sc_prefix = "_SC"
+
   next
 }
 
 $1 == "}" {
   prefix = ""
   type = ""
+  sc_prefix = ""
   next
 }
 
@@ -35,6 +42,7 @@ $1 == "}" {
   # CONFSTR: A configuration string
   # SYSCONF: A numeric value
   # SPEC: A specification
+  sc_prefixes[prefix][$1] = sc_prefix
   conf[prefix][$1] = type
 }
 
@@ -56,6 +64,26 @@ END {
 	printf "# endif\n"
       }
       printf "#endif\n\n"
+
+      # Build a name -> sysconf number associative array to print a C array at
+      # the end.
+      if (conf[p][c] == "SPEC") {
+	name = sprintf ("%s_%s", p, c)
+	num = sprintf ("%s_%s", sc_prefixes[p][c], c)
+	spec[name] = num
+      }
     }
   }
+
+  # Print the specification array.  Define the macro NEED_SPEC_ARRAY before
+  # including posix-conf-vars.h to make it available in the compilation unit.
+  print "#if NEED_SPEC_ARRAY"
+  print "static const struct { const char *name; int num; } specs[] ="
+  print "  {"
+  for (s in spec) {
+    printf "    { \"%s\", %s },\n", s, spec[s]
+  }
+  print "  };"
+  print "static const int nspecs = sizeof (specs) / sizeof (specs[0]);"
+  print "#endif"
 }
diff --git a/sysdeps/posix/sysconf.c b/sysdeps/posix/sysconf.c
index 968c5cb367..0ea5382ba0 100644
--- a/sysdeps/posix/sysconf.c
+++ b/sysdeps/posix/sysconf.c
@@ -31,9 +31,9 @@
 #include <sys/types.h>
 #include <regex.h>
 
+#define NEED_SPEC_ARRAY 0
 #include <posix-conf-vars.h>
 
-
 #define NEED_CHECK_SPEC \
   (!defined _XBS5_ILP32_OFF32 || !defined _XBS5_ILP32_OFFBIG \
    || !defined _XBS5_LP64_OFF64 || !defined _XBS5_LPBIG_OFFBIG \