diff --git a/R-package/configure b/R-package/configure
index f9d27803b..2a4153f6f 100755
--- a/R-package/configure
+++ b/R-package/configure
@@ -1,9 +1,10 @@
 #! /bin/sh
 # Guess values for system-dependent variables and create Makefiles.
-# Generated by GNU Autoconf 2.69 for xgboost 1.7.3.
+# Generated by GNU Autoconf 2.71 for xgboost 1.7.3.
 #
 #
-# Copyright (C) 1992-1996, 1998-2012 Free Software Foundation, Inc.
+# Copyright (C) 1992-1996, 1998-2017, 2020-2021 Free Software Foundation,
+# Inc.
 #
 #
 # This configure script is free software; the Free Software Foundation
@@ -14,14 +15,16 @@
 
 # Be more Bourne compatible
 DUALCASE=1; export DUALCASE # for MKS sh
-if test -n "${ZSH_VERSION+set}" && (emulate sh) >/dev/null 2>&1; then :
+as_nop=:
+if test ${ZSH_VERSION+y} && (emulate sh) >/dev/null 2>&1
+then :
   emulate sh
   NULLCMD=:
   # Pre-4.2 versions of Zsh do word splitting on ${1+"$@"}, which
   # is contrary to our usage.  Disable this feature.
   alias -g '${1+"$@"}'='"$@"'
   setopt NO_GLOB_SUBST
-else
+else $as_nop
   case `(set -o) 2>/dev/null` in #(
   *posix*) :
     set -o posix ;; #(
@@ -31,46 +34,46 @@ esac
 fi
 
 
+
+# Reset variables that may have inherited troublesome values from
+# the environment.
+
+# IFS needs to be set, to space, tab, and newline, in precisely that order.
+# (If _AS_PATH_WALK were called with IFS unset, it would have the
+# side effect of setting IFS to empty, thus disabling word splitting.)
+# Quoting is to prevent editors from complaining about space-tab.
 as_nl='
 '
 export as_nl
-# Printing a long string crashes Solaris 7 /usr/bin/printf.
-as_echo='\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\'
-as_echo=$as_echo$as_echo$as_echo$as_echo$as_echo
-as_echo=$as_echo$as_echo$as_echo$as_echo$as_echo$as_echo
-# Prefer a ksh shell builtin over an external printf program on Solaris,
-# but without wasting forks for bash or zsh.
-if test -z "$BASH_VERSION$ZSH_VERSION" \
-    && (test "X`print -r -- $as_echo`" = "X$as_echo") 2>/dev/null; then
-  as_echo='print -r --'
-  as_echo_n='print -rn --'
-elif (test "X`printf %s $as_echo`" = "X$as_echo") 2>/dev/null; then
-  as_echo='printf %s\n'
-  as_echo_n='printf %s'
-else
-  if test "X`(/usr/ucb/echo -n -n $as_echo) 2>/dev/null`" = "X-n $as_echo"; then
-    as_echo_body='eval /usr/ucb/echo -n "$1$as_nl"'
-    as_echo_n='/usr/ucb/echo -n'
-  else
-    as_echo_body='eval expr "X$1" : "X\\(.*\\)"'
-    as_echo_n_body='eval
-      arg=$1;
-      case $arg in #(
-      *"$as_nl"*)
-	expr "X$arg" : "X\\(.*\\)$as_nl";
-	arg=`expr "X$arg" : ".*$as_nl\\(.*\\)"`;;
-      esac;
-      expr "X$arg" : "X\\(.*\\)" | tr -d "$as_nl"
-    '
-    export as_echo_n_body
-    as_echo_n='sh -c $as_echo_n_body as_echo'
-  fi
-  export as_echo_body
-  as_echo='sh -c $as_echo_body as_echo'
-fi
+IFS=" ""	$as_nl"
+
+PS1='$ '
+PS2='> '
+PS4='+ '
+
+# Ensure predictable behavior from utilities with locale-dependent output.
+LC_ALL=C
+export LC_ALL
+LANGUAGE=C
+export LANGUAGE
+
+# We cannot yet rely on "unset" to work, but we need these variables
+# to be unset--not just set to an empty or harmless value--now, to
+# avoid bugs in old shells (e.g. pre-3.0 UWIN ksh).  This construct
+# also avoids known problems related to "unset" and subshell syntax
+# in other old shells (e.g. bash 2.01 and pdksh 5.2.14).
+for as_var in BASH_ENV ENV MAIL MAILPATH CDPATH
+do eval test \${$as_var+y} \
+  && ( (unset $as_var) || exit 1) >/dev/null 2>&1 && unset $as_var || :
+done
+
+# Ensure that fds 0, 1, and 2 are open.
+if (exec 3>&0) 2>/dev/null; then :; else exec 0</dev/null; fi
+if (exec 3>&1) 2>/dev/null; then :; else exec 1>/dev/null; fi
+if (exec 3>&2)            ; then :; else exec 2>/dev/null; fi
 
 # The user is always right.
-if test "${PATH_SEPARATOR+set}" != set; then
+if ${PATH_SEPARATOR+false} :; then
   PATH_SEPARATOR=:
   (PATH='/bin;/bin'; FPATH=$PATH; sh -c :) >/dev/null 2>&1 && {
     (PATH='/bin:/bin'; FPATH=$PATH; sh -c :) >/dev/null 2>&1 ||
@@ -79,13 +82,6 @@ if test "${PATH_SEPARATOR+set}" != set; then
 fi
 
 
-# IFS
-# We need space, tab and new line, in precisely that order.  Quoting is
-# there to prevent editors from complaining about space-tab.
-# (If _AS_PATH_WALK were called with IFS unset, it would disable word
-# splitting by setting IFS to empty value.)
-IFS=" ""	$as_nl"
-
 # Find who we are.  Look in the path if we contain no directory separator.
 as_myself=
 case $0 in #((
@@ -94,8 +90,12 @@ case $0 in #((
 for as_dir in $PATH
 do
   IFS=$as_save_IFS
-  test -z "$as_dir" && as_dir=.
-    test -r "$as_dir/$0" && as_myself=$as_dir/$0 && break
+  case $as_dir in #(((
+    '') as_dir=./ ;;
+    */) ;;
+    *) as_dir=$as_dir/ ;;
+  esac
+    test -r "$as_dir$0" && as_myself=$as_dir$0 && break
   done
 IFS=$as_save_IFS
 
@@ -107,30 +107,10 @@ if test "x$as_myself" = x; then
   as_myself=$0
 fi
 if test ! -f "$as_myself"; then
-  $as_echo "$as_myself: error: cannot find myself; rerun with an absolute file name" >&2
+  printf "%s\n" "$as_myself: error: cannot find myself; rerun with an absolute file name" >&2
   exit 1
 fi
 
-# Unset variables that we do not need and which cause bugs (e.g. in
-# pre-3.0 UWIN ksh).  But do not cause bugs in bash 2.01; the "|| exit 1"
-# suppresses any "Segmentation fault" message there.  '((' could
-# trigger a bug in pdksh 5.2.14.
-for as_var in BASH_ENV ENV MAIL MAILPATH
-do eval test x\${$as_var+set} = xset \
-  && ( (unset $as_var) || exit 1) >/dev/null 2>&1 && unset $as_var || :
-done
-PS1='$ '
-PS2='> '
-PS4='+ '
-
-# NLS nuisances.
-LC_ALL=C
-export LC_ALL
-LANGUAGE=C
-export LANGUAGE
-
-# CDPATH.
-(unset CDPATH) >/dev/null 2>&1 && unset CDPATH
 
 # Use a proper internal environment variable to ensure we don't fall
   # into an infinite loop, continuously re-executing ourselves.
@@ -152,20 +132,22 @@ esac
 exec $CONFIG_SHELL $as_opts "$as_myself" ${1+"$@"}
 # Admittedly, this is quite paranoid, since all the known shells bail
 # out after a failed `exec'.
-$as_echo "$0: could not re-execute with $CONFIG_SHELL" >&2
-as_fn_exit 255
+printf "%s\n" "$0: could not re-execute with $CONFIG_SHELL" >&2
+exit 255
   fi
   # We don't want this to propagate to other subprocesses.
           { _as_can_reexec=; unset _as_can_reexec;}
 if test "x$CONFIG_SHELL" = x; then
-  as_bourne_compatible="if test -n \"\${ZSH_VERSION+set}\" && (emulate sh) >/dev/null 2>&1; then :
+  as_bourne_compatible="as_nop=:
+if test \${ZSH_VERSION+y} && (emulate sh) >/dev/null 2>&1
+then :
   emulate sh
   NULLCMD=:
   # Pre-4.2 versions of Zsh do word splitting on \${1+\"\$@\"}, which
   # is contrary to our usage.  Disable this feature.
   alias -g '\${1+\"\$@\"}'='\"\$@\"'
   setopt NO_GLOB_SUBST
-else
+else \$as_nop
   case \`(set -o) 2>/dev/null\` in #(
   *posix*) :
     set -o posix ;; #(
@@ -185,41 +167,52 @@ as_fn_success || { exitcode=1; echo as_fn_success failed.; }
 as_fn_failure && { exitcode=1; echo as_fn_failure succeeded.; }
 as_fn_ret_success || { exitcode=1; echo as_fn_ret_success failed.; }
 as_fn_ret_failure && { exitcode=1; echo as_fn_ret_failure succeeded.; }
-if ( set x; as_fn_ret_success y && test x = \"\$1\" ); then :
+if ( set x; as_fn_ret_success y && test x = \"\$1\" )
+then :
 
-else
+else \$as_nop
   exitcode=1; echo positional parameters were not saved.
 fi
 test x\$exitcode = x0 || exit 1
+blah=\$(echo \$(echo blah))
+test x\"\$blah\" = xblah || exit 1
 test -x / || exit 1"
   as_suggested="  as_lineno_1=";as_suggested=$as_suggested$LINENO;as_suggested=$as_suggested" as_lineno_1a=\$LINENO
   as_lineno_2=";as_suggested=$as_suggested$LINENO;as_suggested=$as_suggested" as_lineno_2a=\$LINENO
   eval 'test \"x\$as_lineno_1'\$as_run'\" != \"x\$as_lineno_2'\$as_run'\" &&
   test \"x\`expr \$as_lineno_1'\$as_run' + 1\`\" = \"x\$as_lineno_2'\$as_run'\"' || exit 1"
-  if (eval "$as_required") 2>/dev/null; then :
+  if (eval "$as_required") 2>/dev/null
+then :
   as_have_required=yes
-else
+else $as_nop
   as_have_required=no
 fi
-  if test x$as_have_required = xyes && (eval "$as_suggested") 2>/dev/null; then :
+  if test x$as_have_required = xyes && (eval "$as_suggested") 2>/dev/null
+then :
 
-else
+else $as_nop
   as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
 as_found=false
 for as_dir in /bin$PATH_SEPARATOR/usr/bin$PATH_SEPARATOR$PATH
 do
   IFS=$as_save_IFS
-  test -z "$as_dir" && as_dir=.
+  case $as_dir in #(((
+    '') as_dir=./ ;;
+    */) ;;
+    *) as_dir=$as_dir/ ;;
+  esac
   as_found=:
   case $as_dir in #(
 	 /*)
 	   for as_base in sh bash ksh sh5; do
 	     # Try only shells that exist, to save several forks.
-	     as_shell=$as_dir/$as_base
+	     as_shell=$as_dir$as_base
 	     if { test -f "$as_shell" || test -f "$as_shell.exe"; } &&
-		    { $as_echo "$as_bourne_compatible""$as_required" | as_run=a "$as_shell"; } 2>/dev/null; then :
+		    as_run=a "$as_shell" -c "$as_bourne_compatible""$as_required" 2>/dev/null
+then :
   CONFIG_SHELL=$as_shell as_have_required=yes
-		   if { $as_echo "$as_bourne_compatible""$as_suggested" | as_run=a "$as_shell"; } 2>/dev/null; then :
+		   if as_run=a "$as_shell" -c "$as_bourne_compatible""$as_suggested" 2>/dev/null
+then :
   break 2
 fi
 fi
@@ -227,14 +220,21 @@ fi
        esac
   as_found=false
 done
-$as_found || { if { test -f "$SHELL" || test -f "$SHELL.exe"; } &&
-	      { $as_echo "$as_bourne_compatible""$as_required" | as_run=a "$SHELL"; } 2>/dev/null; then :
-  CONFIG_SHELL=$SHELL as_have_required=yes
-fi; }
 IFS=$as_save_IFS
+if $as_found
+then :
+
+else $as_nop
+  if { test -f "$SHELL" || test -f "$SHELL.exe"; } &&
+	      as_run=a "$SHELL" -c "$as_bourne_compatible""$as_required" 2>/dev/null
+then :
+  CONFIG_SHELL=$SHELL as_have_required=yes
+fi
+fi
 
 
-      if test "x$CONFIG_SHELL" != x; then :
+      if test "x$CONFIG_SHELL" != x
+then :
   export CONFIG_SHELL
              # We cannot yet assume a decent shell, so we have to provide a
 # neutralization value for shells without unset; and this also
@@ -252,18 +252,19 @@ esac
 exec $CONFIG_SHELL $as_opts "$as_myself" ${1+"$@"}
 # Admittedly, this is quite paranoid, since all the known shells bail
 # out after a failed `exec'.
-$as_echo "$0: could not re-execute with $CONFIG_SHELL" >&2
+printf "%s\n" "$0: could not re-execute with $CONFIG_SHELL" >&2
 exit 255
 fi
 
-    if test x$as_have_required = xno; then :
-  $as_echo "$0: This script requires a shell more modern than all"
-  $as_echo "$0: the shells that I found on your system."
-  if test x${ZSH_VERSION+set} = xset ; then
-    $as_echo "$0: In particular, zsh $ZSH_VERSION has bugs and should"
-    $as_echo "$0: be upgraded to zsh 4.3.4 or later."
+    if test x$as_have_required = xno
+then :
+  printf "%s\n" "$0: This script requires a shell more modern than all"
+  printf "%s\n" "$0: the shells that I found on your system."
+  if test ${ZSH_VERSION+y} ; then
+    printf "%s\n" "$0: In particular, zsh $ZSH_VERSION has bugs and should"
+    printf "%s\n" "$0: be upgraded to zsh 4.3.4 or later."
   else
-    $as_echo "$0: Please tell bug-autoconf@gnu.org about your system,
+    printf "%s\n" "$0: Please tell bug-autoconf@gnu.org about your system,
 $0: including any error possibly output before this
 $0: message. Then install a modern shell, or manually run
 $0: the script under such a shell if you do have one."
@@ -290,6 +291,7 @@ as_fn_unset ()
 }
 as_unset=as_fn_unset
 
+
 # as_fn_set_status STATUS
 # -----------------------
 # Set $? to STATUS, without forking.
@@ -307,6 +309,14 @@ as_fn_exit ()
   as_fn_set_status $1
   exit $1
 } # as_fn_exit
+# as_fn_nop
+# ---------
+# Do nothing but, unlike ":", preserve the value of $?.
+as_fn_nop ()
+{
+  return $?
+}
+as_nop=as_fn_nop
 
 # as_fn_mkdir_p
 # -------------
@@ -321,7 +331,7 @@ as_fn_mkdir_p ()
     as_dirs=
     while :; do
       case $as_dir in #(
-      *\'*) as_qdir=`$as_echo "$as_dir" | sed "s/'/'\\\\\\\\''/g"`;; #'(
+      *\'*) as_qdir=`printf "%s\n" "$as_dir" | sed "s/'/'\\\\\\\\''/g"`;; #'(
       *) as_qdir=$as_dir;;
       esac
       as_dirs="'$as_qdir' $as_dirs"
@@ -330,7 +340,7 @@ $as_expr X"$as_dir" : 'X\(.*[^/]\)//*[^/][^/]*/*$' \| \
 	 X"$as_dir" : 'X\(//\)[^/]' \| \
 	 X"$as_dir" : 'X\(//\)$' \| \
 	 X"$as_dir" : 'X\(/\)' \| . 2>/dev/null ||
-$as_echo X"$as_dir" |
+printf "%s\n" X"$as_dir" |
     sed '/^X\(.*[^/]\)\/\/*[^/][^/]*\/*$/{
 	    s//\1/
 	    q
@@ -369,12 +379,13 @@ as_fn_executable_p ()
 # advantage of any shell optimizations that allow amortized linear growth over
 # repeated appends, instead of the typical quadratic growth present in naive
 # implementations.
-if (eval "as_var=1; as_var+=2; test x\$as_var = x12") 2>/dev/null; then :
+if (eval "as_var=1; as_var+=2; test x\$as_var = x12") 2>/dev/null
+then :
   eval 'as_fn_append ()
   {
     eval $1+=\$2
   }'
-else
+else $as_nop
   as_fn_append ()
   {
     eval $1=\$$1\$2
@@ -386,18 +397,27 @@ fi # as_fn_append
 # Perform arithmetic evaluation on the ARGs, and store the result in the
 # global $as_val. Take advantage of shells that can avoid forks. The arguments
 # must be portable across $(()) and expr.
-if (eval "test \$(( 1 + 1 )) = 2") 2>/dev/null; then :
+if (eval "test \$(( 1 + 1 )) = 2") 2>/dev/null
+then :
   eval 'as_fn_arith ()
   {
     as_val=$(( $* ))
   }'
-else
+else $as_nop
   as_fn_arith ()
   {
     as_val=`expr "$@" || test $? -eq 1`
   }
 fi # as_fn_arith
 
+# as_fn_nop
+# ---------
+# Do nothing but, unlike ":", preserve the value of $?.
+as_fn_nop ()
+{
+  return $?
+}
+as_nop=as_fn_nop
 
 # as_fn_error STATUS ERROR [LINENO LOG_FD]
 # ----------------------------------------
@@ -409,9 +429,9 @@ as_fn_error ()
   as_status=$1; test $as_status -eq 0 && as_status=1
   if test "$4"; then
     as_lineno=${as_lineno-"$3"} as_lineno_stack=as_lineno_stack=$as_lineno_stack
-    $as_echo "$as_me:${as_lineno-$LINENO}: error: $2" >&$4
+    printf "%s\n" "$as_me:${as_lineno-$LINENO}: error: $2" >&$4
   fi
-  $as_echo "$as_me: error: $2" >&2
+  printf "%s\n" "$as_me: error: $2" >&2
   as_fn_exit $as_status
 } # as_fn_error
 
@@ -438,7 +458,7 @@ as_me=`$as_basename -- "$0" ||
 $as_expr X/"$0" : '.*/\([^/][^/]*\)/*$' \| \
 	 X"$0" : 'X\(//\)$' \| \
 	 X"$0" : 'X\(/\)' \| . 2>/dev/null ||
-$as_echo X/"$0" |
+printf "%s\n" X/"$0" |
     sed '/^.*\/\([^/][^/]*\)\/*$/{
 	    s//\1/
 	    q
@@ -482,7 +502,7 @@ as_cr_alnum=$as_cr_Letters$as_cr_digits
       s/-\n.*//
     ' >$as_me.lineno &&
   chmod +x "$as_me.lineno" ||
-    { $as_echo "$as_me: error: cannot create $as_me.lineno; rerun with a POSIX shell" >&2; as_fn_exit 1; }
+    { printf "%s\n" "$as_me: error: cannot create $as_me.lineno; rerun with a POSIX shell" >&2; as_fn_exit 1; }
 
   # If we had to re-execute with $CONFIG_SHELL, we're ensured to have
   # already done that, so ensure we don't try to do so again and fall
@@ -496,6 +516,10 @@ as_cr_alnum=$as_cr_Letters$as_cr_digits
   exit
 }
 
+
+# Determine whether it's possible to make 'echo' print without a newline.
+# These variables are no longer used directly by Autoconf, but are AC_SUBSTed
+# for compatibility with existing Makefiles.
 ECHO_C= ECHO_N= ECHO_T=
 case `echo -n x` in #(((((
 -n*)
@@ -509,6 +533,13 @@ case `echo -n x` in #(((((
   ECHO_N='-n';;
 esac
 
+# For backward compatibility with old third-party macros, we provide
+# the shell variables $as_echo and $as_echo_n.  New code should use
+# AS_ECHO(["message"]) and AS_ECHO_N(["message"]), respectively.
+as_echo='printf %s\n'
+as_echo_n='printf %s'
+
+
 rm -f conf$$ conf$$.exe conf$$.file
 if test -d conf$$.dir; then
   rm -f conf$$.dir/conf$$.file
@@ -589,11 +620,11 @@ OPENMP_LIB
 OPENMP_CXXFLAGS
 OBJEXT
 EXEEXT
-ac_ct_CC
+ac_ct_CXX
 CPPFLAGS
 LDFLAGS
-CFLAGS
-CC
+CXXFLAGS
+CXX
 target_alias
 host_alias
 build_alias
@@ -640,11 +671,12 @@ enable_option_checking
       ac_precious_vars='build_alias
 host_alias
 target_alias
-CC
-CFLAGS
+CXX
+CXXFLAGS
 LDFLAGS
 LIBS
-CPPFLAGS'
+CPPFLAGS
+CCC'
 
 
 # Initialize some variables set by options.
@@ -713,8 +745,6 @@ do
   *)    ac_optarg=yes ;;
   esac
 
-  # Accept the important Cygnus configure options, so we can diagnose typos.
-
   case $ac_dashdash$ac_option in
   --)
     ac_dashdash=yes ;;
@@ -755,9 +785,9 @@ do
     ac_useropt=`expr "x$ac_option" : 'x-*disable-\(.*\)'`
     # Reject names that are not valid shell variable names.
     expr "x$ac_useropt" : ".*[^-+._$as_cr_alnum]" >/dev/null &&
-      as_fn_error $? "invalid feature name: $ac_useropt"
+      as_fn_error $? "invalid feature name: \`$ac_useropt'"
     ac_useropt_orig=$ac_useropt
-    ac_useropt=`$as_echo "$ac_useropt" | sed 's/[-+.]/_/g'`
+    ac_useropt=`printf "%s\n" "$ac_useropt" | sed 's/[-+.]/_/g'`
     case $ac_user_opts in
       *"
 "enable_$ac_useropt"
@@ -781,9 +811,9 @@ do
     ac_useropt=`expr "x$ac_option" : 'x-*enable-\([^=]*\)'`
     # Reject names that are not valid shell variable names.
     expr "x$ac_useropt" : ".*[^-+._$as_cr_alnum]" >/dev/null &&
-      as_fn_error $? "invalid feature name: $ac_useropt"
+      as_fn_error $? "invalid feature name: \`$ac_useropt'"
     ac_useropt_orig=$ac_useropt
-    ac_useropt=`$as_echo "$ac_useropt" | sed 's/[-+.]/_/g'`
+    ac_useropt=`printf "%s\n" "$ac_useropt" | sed 's/[-+.]/_/g'`
     case $ac_user_opts in
       *"
 "enable_$ac_useropt"
@@ -994,9 +1024,9 @@ do
     ac_useropt=`expr "x$ac_option" : 'x-*with-\([^=]*\)'`
     # Reject names that are not valid shell variable names.
     expr "x$ac_useropt" : ".*[^-+._$as_cr_alnum]" >/dev/null &&
-      as_fn_error $? "invalid package name: $ac_useropt"
+      as_fn_error $? "invalid package name: \`$ac_useropt'"
     ac_useropt_orig=$ac_useropt
-    ac_useropt=`$as_echo "$ac_useropt" | sed 's/[-+.]/_/g'`
+    ac_useropt=`printf "%s\n" "$ac_useropt" | sed 's/[-+.]/_/g'`
     case $ac_user_opts in
       *"
 "with_$ac_useropt"
@@ -1010,9 +1040,9 @@ do
     ac_useropt=`expr "x$ac_option" : 'x-*without-\(.*\)'`
     # Reject names that are not valid shell variable names.
     expr "x$ac_useropt" : ".*[^-+._$as_cr_alnum]" >/dev/null &&
-      as_fn_error $? "invalid package name: $ac_useropt"
+      as_fn_error $? "invalid package name: \`$ac_useropt'"
     ac_useropt_orig=$ac_useropt
-    ac_useropt=`$as_echo "$ac_useropt" | sed 's/[-+.]/_/g'`
+    ac_useropt=`printf "%s\n" "$ac_useropt" | sed 's/[-+.]/_/g'`
     case $ac_user_opts in
       *"
 "with_$ac_useropt"
@@ -1056,9 +1086,9 @@ Try \`$0 --help' for more information"
 
   *)
     # FIXME: should be removed in autoconf 3.0.
-    $as_echo "$as_me: WARNING: you should use --build, --host, --target" >&2
+    printf "%s\n" "$as_me: WARNING: you should use --build, --host, --target" >&2
     expr "x$ac_option" : ".*[^-._$as_cr_alnum]" >/dev/null &&
-      $as_echo "$as_me: WARNING: invalid host type: $ac_option" >&2
+      printf "%s\n" "$as_me: WARNING: invalid host type: $ac_option" >&2
     : "${build_alias=$ac_option} ${host_alias=$ac_option} ${target_alias=$ac_option}"
     ;;
 
@@ -1074,7 +1104,7 @@ if test -n "$ac_unrecognized_opts"; then
   case $enable_option_checking in
     no) ;;
     fatal) as_fn_error $? "unrecognized options: $ac_unrecognized_opts" ;;
-    *)     $as_echo "$as_me: WARNING: unrecognized options: $ac_unrecognized_opts" >&2 ;;
+    *)     printf "%s\n" "$as_me: WARNING: unrecognized options: $ac_unrecognized_opts" >&2 ;;
   esac
 fi
 
@@ -1138,7 +1168,7 @@ $as_expr X"$as_myself" : 'X\(.*[^/]\)//*[^/][^/]*/*$' \| \
 	 X"$as_myself" : 'X\(//\)[^/]' \| \
 	 X"$as_myself" : 'X\(//\)$' \| \
 	 X"$as_myself" : 'X\(/\)' \| . 2>/dev/null ||
-$as_echo X"$as_myself" |
+printf "%s\n" X"$as_myself" |
     sed '/^X\(.*[^/]\)\/\/*[^/][^/]*\/*$/{
 	    s//\1/
 	    q
@@ -1262,8 +1292,8 @@ if test -n "$ac_init_help"; then
   cat <<\_ACEOF
 
 Some influential environment variables:
-  CC          C compiler command
-  CFLAGS      C compiler flags
+  CXX         C++ compiler command
+  CXXFLAGS    C++ compiler flags
   LDFLAGS     linker flags, e.g. -L<lib dir> if you have libraries in a
               nonstandard directory <lib dir>
   LIBS        libraries to pass to the linker, e.g. -l<library>
@@ -1289,9 +1319,9 @@ if test "$ac_init_help" = "recursive"; then
 case "$ac_dir" in
 .) ac_dir_suffix= ac_top_builddir_sub=. ac_top_build_prefix= ;;
 *)
-  ac_dir_suffix=/`$as_echo "$ac_dir" | sed 's|^\.[\\/]||'`
+  ac_dir_suffix=/`printf "%s\n" "$ac_dir" | sed 's|^\.[\\/]||'`
   # A ".." for each directory in $ac_dir_suffix.
-  ac_top_builddir_sub=`$as_echo "$ac_dir_suffix" | sed 's|/[^\\/]*|/..|g;s|/||'`
+  ac_top_builddir_sub=`printf "%s\n" "$ac_dir_suffix" | sed 's|/[^\\/]*|/..|g;s|/||'`
   case $ac_top_builddir_sub in
   "") ac_top_builddir_sub=. ac_top_build_prefix= ;;
   *)  ac_top_build_prefix=$ac_top_builddir_sub/ ;;
@@ -1319,7 +1349,8 @@ esac
 ac_abs_srcdir=$ac_abs_top_srcdir$ac_dir_suffix
 
     cd "$ac_dir" || { ac_status=$?; continue; }
-    # Check for guested configure.
+    # Check for configure.gnu first; this name is used for a wrapper for
+    # Metaconfig's "Configure" on case-insensitive file systems.
     if test -f "$ac_srcdir/configure.gnu"; then
       echo &&
       $SHELL "$ac_srcdir/configure.gnu" --help=recursive
@@ -1327,7 +1358,7 @@ ac_abs_srcdir=$ac_abs_top_srcdir$ac_dir_suffix
       echo &&
       $SHELL "$ac_srcdir/configure" --help=recursive
     else
-      $as_echo "$as_me: WARNING: no configuration information is in $ac_dir" >&2
+      printf "%s\n" "$as_me: WARNING: no configuration information is in $ac_dir" >&2
     fi || ac_status=$?
     cd "$ac_pwd" || { ac_status=$?; break; }
   done
@@ -1337,9 +1368,9 @@ test -n "$ac_init_help" && exit $ac_status
 if $ac_init_version; then
   cat <<\_ACEOF
 xgboost configure 1.7.3
-generated by GNU Autoconf 2.69
+generated by GNU Autoconf 2.71
 
-Copyright (C) 2012 Free Software Foundation, Inc.
+Copyright (C) 2021 Free Software Foundation, Inc.
 This configure script is free software; the Free Software Foundation
 gives unlimited permission to copy, distribute and modify it.
 _ACEOF
@@ -1350,20 +1381,20 @@ fi
 ## Autoconf initialization. ##
 ## ------------------------ ##
 
-# ac_fn_c_try_compile LINENO
-# --------------------------
+# ac_fn_cxx_try_compile LINENO
+# ----------------------------
 # Try to compile conftest.$ac_ext, and return whether this succeeded.
-ac_fn_c_try_compile ()
+ac_fn_cxx_try_compile ()
 {
   as_lineno=${as_lineno-"$1"} as_lineno_stack=as_lineno_stack=$as_lineno_stack
-  rm -f conftest.$ac_objext
+  rm -f conftest.$ac_objext conftest.beam
   if { { ac_try="$ac_compile"
 case "(($ac_try" in
   *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
   *) ac_try_echo=$ac_try;;
 esac
 eval ac_try_echo="\"\$as_me:${as_lineno-$LINENO}: $ac_try_echo\""
-$as_echo "$ac_try_echo"; } >&5
+printf "%s\n" "$ac_try_echo"; } >&5
   (eval "$ac_compile") 2>conftest.err
   ac_status=$?
   if test -s conftest.err; then
@@ -1371,14 +1402,15 @@ $as_echo "$ac_try_echo"; } >&5
     cat conftest.er1 >&5
     mv -f conftest.er1 conftest.err
   fi
-  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
   test $ac_status = 0; } && {
-	 test -z "$ac_c_werror_flag" ||
+	 test -z "$ac_cxx_werror_flag" ||
 	 test ! -s conftest.err
-       } && test -s conftest.$ac_objext; then :
+       } && test -s conftest.$ac_objext
+then :
   ac_retval=0
-else
-  $as_echo "$as_me: failed program was:" >&5
+else $as_nop
+  printf "%s\n" "$as_me: failed program was:" >&5
 sed 's/^/| /' conftest.$ac_ext >&5
 
 	ac_retval=1
@@ -1386,22 +1418,22 @@ fi
   eval $as_lineno_stack; ${as_lineno_stack:+:} unset as_lineno
   as_fn_set_status $ac_retval
 
-} # ac_fn_c_try_compile
+} # ac_fn_cxx_try_compile
 
-# ac_fn_c_try_link LINENO
-# -----------------------
+# ac_fn_cxx_try_link LINENO
+# -------------------------
 # Try to link conftest.$ac_ext, and return whether this succeeded.
-ac_fn_c_try_link ()
+ac_fn_cxx_try_link ()
 {
   as_lineno=${as_lineno-"$1"} as_lineno_stack=as_lineno_stack=$as_lineno_stack
-  rm -f conftest.$ac_objext conftest$ac_exeext
+  rm -f conftest.$ac_objext conftest.beam conftest$ac_exeext
   if { { ac_try="$ac_link"
 case "(($ac_try" in
   *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
   *) ac_try_echo=$ac_try;;
 esac
 eval ac_try_echo="\"\$as_me:${as_lineno-$LINENO}: $ac_try_echo\""
-$as_echo "$ac_try_echo"; } >&5
+printf "%s\n" "$ac_try_echo"; } >&5
   (eval "$ac_link") 2>conftest.err
   ac_status=$?
   if test -s conftest.err; then
@@ -1409,17 +1441,18 @@ $as_echo "$ac_try_echo"; } >&5
     cat conftest.er1 >&5
     mv -f conftest.er1 conftest.err
   fi
-  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
   test $ac_status = 0; } && {
-	 test -z "$ac_c_werror_flag" ||
+	 test -z "$ac_cxx_werror_flag" ||
 	 test ! -s conftest.err
        } && test -s conftest$ac_exeext && {
 	 test "$cross_compiling" = yes ||
 	 test -x conftest$ac_exeext
-       }; then :
+       }
+then :
   ac_retval=0
-else
-  $as_echo "$as_me: failed program was:" >&5
+else $as_nop
+  printf "%s\n" "$as_me: failed program was:" >&5
 sed 's/^/| /' conftest.$ac_ext >&5
 
 	ac_retval=1
@@ -1432,13 +1465,13 @@ fi
   eval $as_lineno_stack; ${as_lineno_stack:+:} unset as_lineno
   as_fn_set_status $ac_retval
 
-} # ac_fn_c_try_link
+} # ac_fn_cxx_try_link
 
-# ac_fn_c_try_run LINENO
-# ----------------------
-# Try to link conftest.$ac_ext, and return whether this succeeded. Assumes
-# that executables *can* be run.
-ac_fn_c_try_run ()
+# ac_fn_cxx_try_run LINENO
+# ------------------------
+# Try to run conftest.$ac_ext, and return whether this succeeded. Assumes that
+# executables *can* be run.
+ac_fn_cxx_try_run ()
 {
   as_lineno=${as_lineno-"$1"} as_lineno_stack=as_lineno_stack=$as_lineno_stack
   if { { ac_try="$ac_link"
@@ -1447,25 +1480,26 @@ case "(($ac_try" in
   *) ac_try_echo=$ac_try;;
 esac
 eval ac_try_echo="\"\$as_me:${as_lineno-$LINENO}: $ac_try_echo\""
-$as_echo "$ac_try_echo"; } >&5
+printf "%s\n" "$ac_try_echo"; } >&5
   (eval "$ac_link") 2>&5
   ac_status=$?
-  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
   test $ac_status = 0; } && { ac_try='./conftest$ac_exeext'
   { { case "(($ac_try" in
   *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
   *) ac_try_echo=$ac_try;;
 esac
 eval ac_try_echo="\"\$as_me:${as_lineno-$LINENO}: $ac_try_echo\""
-$as_echo "$ac_try_echo"; } >&5
+printf "%s\n" "$ac_try_echo"; } >&5
   (eval "$ac_try") 2>&5
   ac_status=$?
-  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
-  test $ac_status = 0; }; }; then :
+  printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; }
+then :
   ac_retval=0
-else
-  $as_echo "$as_me: program exited with status $ac_status" >&5
-       $as_echo "$as_me: failed program was:" >&5
+else $as_nop
+  printf "%s\n" "$as_me: program exited with status $ac_status" >&5
+       printf "%s\n" "$as_me: failed program was:" >&5
 sed 's/^/| /' conftest.$ac_ext >&5
 
        ac_retval=$ac_status
@@ -1474,15 +1508,35 @@ fi
   eval $as_lineno_stack; ${as_lineno_stack:+:} unset as_lineno
   as_fn_set_status $ac_retval
 
-} # ac_fn_c_try_run
+} # ac_fn_cxx_try_run
+ac_configure_args_raw=
+for ac_arg
+do
+  case $ac_arg in
+  *\'*)
+    ac_arg=`printf "%s\n" "$ac_arg" | sed "s/'/'\\\\\\\\''/g"` ;;
+  esac
+  as_fn_append ac_configure_args_raw " '$ac_arg'"
+done
+
+case $ac_configure_args_raw in
+  *$as_nl*)
+    ac_safe_unquote= ;;
+  *)
+    ac_unsafe_z='|&;<>()$`\\"*?[ ''	' # This string ends in space, tab.
+    ac_unsafe_a="$ac_unsafe_z#~"
+    ac_safe_unquote="s/ '\\([^$ac_unsafe_a][^$ac_unsafe_z]*\\)'/ \\1/g"
+    ac_configure_args_raw=`      printf "%s\n" "$ac_configure_args_raw" | sed "$ac_safe_unquote"`;;
+esac
+
 cat >config.log <<_ACEOF
 This file contains any messages produced by compilers while
 running configure, to aid debugging if configure makes a mistake.
 
 It was created by xgboost $as_me 1.7.3, which was
-generated by GNU Autoconf 2.69.  Invocation command line was
+generated by GNU Autoconf 2.71.  Invocation command line was
 
-  $ $0 $@
+  $ $0$ac_configure_args_raw
 
 _ACEOF
 exec 5>>config.log
@@ -1515,8 +1569,12 @@ as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
 for as_dir in $PATH
 do
   IFS=$as_save_IFS
-  test -z "$as_dir" && as_dir=.
-    $as_echo "PATH: $as_dir"
+  case $as_dir in #(((
+    '') as_dir=./ ;;
+    */) ;;
+    *) as_dir=$as_dir/ ;;
+  esac
+    printf "%s\n" "PATH: $as_dir"
   done
 IFS=$as_save_IFS
 
@@ -1551,7 +1609,7 @@ do
     | -silent | --silent | --silen | --sile | --sil)
       continue ;;
     *\'*)
-      ac_arg=`$as_echo "$ac_arg" | sed "s/'/'\\\\\\\\''/g"` ;;
+      ac_arg=`printf "%s\n" "$ac_arg" | sed "s/'/'\\\\\\\\''/g"` ;;
     esac
     case $ac_pass in
     1) as_fn_append ac_configure_args0 " '$ac_arg'" ;;
@@ -1586,11 +1644,13 @@ done
 # WARNING: Use '\'' to represent an apostrophe within the trap.
 # WARNING: Do not start the trap code with a newline, due to a FreeBSD 4.0 bug.
 trap 'exit_status=$?
+  # Sanitize IFS.
+  IFS=" ""	$as_nl"
   # Save into config.log some information that might help in debugging.
   {
     echo
 
-    $as_echo "## ---------------- ##
+    printf "%s\n" "## ---------------- ##
 ## Cache variables. ##
 ## ---------------- ##"
     echo
@@ -1601,8 +1661,8 @@ trap 'exit_status=$?
     case $ac_val in #(
     *${as_nl}*)
       case $ac_var in #(
-      *_cv_*) { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: cache variable $ac_var contains a newline" >&5
-$as_echo "$as_me: WARNING: cache variable $ac_var contains a newline" >&2;} ;;
+      *_cv_*) { printf "%s\n" "$as_me:${as_lineno-$LINENO}: WARNING: cache variable $ac_var contains a newline" >&5
+printf "%s\n" "$as_me: WARNING: cache variable $ac_var contains a newline" >&2;} ;;
       esac
       case $ac_var in #(
       _ | IFS | as_nl) ;; #(
@@ -1626,7 +1686,7 @@ $as_echo "$as_me: WARNING: cache variable $ac_var contains a newline" >&2;} ;;
 )
     echo
 
-    $as_echo "## ----------------- ##
+    printf "%s\n" "## ----------------- ##
 ## Output variables. ##
 ## ----------------- ##"
     echo
@@ -1634,14 +1694,14 @@ $as_echo "$as_me: WARNING: cache variable $ac_var contains a newline" >&2;} ;;
     do
       eval ac_val=\$$ac_var
       case $ac_val in
-      *\'\''*) ac_val=`$as_echo "$ac_val" | sed "s/'\''/'\''\\\\\\\\'\'''\''/g"`;;
+      *\'\''*) ac_val=`printf "%s\n" "$ac_val" | sed "s/'\''/'\''\\\\\\\\'\'''\''/g"`;;
       esac
-      $as_echo "$ac_var='\''$ac_val'\''"
+      printf "%s\n" "$ac_var='\''$ac_val'\''"
     done | sort
     echo
 
     if test -n "$ac_subst_files"; then
-      $as_echo "## ------------------- ##
+      printf "%s\n" "## ------------------- ##
 ## File substitutions. ##
 ## ------------------- ##"
       echo
@@ -1649,15 +1709,15 @@ $as_echo "$as_me: WARNING: cache variable $ac_var contains a newline" >&2;} ;;
       do
 	eval ac_val=\$$ac_var
 	case $ac_val in
-	*\'\''*) ac_val=`$as_echo "$ac_val" | sed "s/'\''/'\''\\\\\\\\'\'''\''/g"`;;
+	*\'\''*) ac_val=`printf "%s\n" "$ac_val" | sed "s/'\''/'\''\\\\\\\\'\'''\''/g"`;;
 	esac
-	$as_echo "$ac_var='\''$ac_val'\''"
+	printf "%s\n" "$ac_var='\''$ac_val'\''"
       done | sort
       echo
     fi
 
     if test -s confdefs.h; then
-      $as_echo "## ----------- ##
+      printf "%s\n" "## ----------- ##
 ## confdefs.h. ##
 ## ----------- ##"
       echo
@@ -1665,8 +1725,8 @@ $as_echo "$as_me: WARNING: cache variable $ac_var contains a newline" >&2;} ;;
       echo
     fi
     test "$ac_signal" != 0 &&
-      $as_echo "$as_me: caught signal $ac_signal"
-    $as_echo "$as_me: exit $exit_status"
+      printf "%s\n" "$as_me: caught signal $ac_signal"
+    printf "%s\n" "$as_me: exit $exit_status"
   } >&5
   rm -f core *.core core.conftest.* &&
     rm -f -r conftest* confdefs* conf$$* $ac_clean_files &&
@@ -1680,63 +1740,48 @@ ac_signal=0
 # confdefs.h avoids OS command line length limits that DEFS can exceed.
 rm -f -r conftest* confdefs.h
 
-$as_echo "/* confdefs.h */" > confdefs.h
+printf "%s\n" "/* confdefs.h */" > confdefs.h
 
 # Predefined preprocessor variables.
 
-cat >>confdefs.h <<_ACEOF
-#define PACKAGE_NAME "$PACKAGE_NAME"
-_ACEOF
+printf "%s\n" "#define PACKAGE_NAME \"$PACKAGE_NAME\"" >>confdefs.h
 
-cat >>confdefs.h <<_ACEOF
-#define PACKAGE_TARNAME "$PACKAGE_TARNAME"
-_ACEOF
+printf "%s\n" "#define PACKAGE_TARNAME \"$PACKAGE_TARNAME\"" >>confdefs.h
 
-cat >>confdefs.h <<_ACEOF
-#define PACKAGE_VERSION "$PACKAGE_VERSION"
-_ACEOF
+printf "%s\n" "#define PACKAGE_VERSION \"$PACKAGE_VERSION\"" >>confdefs.h
 
-cat >>confdefs.h <<_ACEOF
-#define PACKAGE_STRING "$PACKAGE_STRING"
-_ACEOF
+printf "%s\n" "#define PACKAGE_STRING \"$PACKAGE_STRING\"" >>confdefs.h
 
-cat >>confdefs.h <<_ACEOF
-#define PACKAGE_BUGREPORT "$PACKAGE_BUGREPORT"
-_ACEOF
+printf "%s\n" "#define PACKAGE_BUGREPORT \"$PACKAGE_BUGREPORT\"" >>confdefs.h
 
-cat >>confdefs.h <<_ACEOF
-#define PACKAGE_URL "$PACKAGE_URL"
-_ACEOF
+printf "%s\n" "#define PACKAGE_URL \"$PACKAGE_URL\"" >>confdefs.h
 
 
 # Let the site file select an alternate cache file if it wants to.
 # Prefer an explicitly selected file to automatically selected ones.
-ac_site_file1=NONE
-ac_site_file2=NONE
 if test -n "$CONFIG_SITE"; then
-  # We do not want a PATH search for config.site.
-  case $CONFIG_SITE in #((
-    -*)  ac_site_file1=./$CONFIG_SITE;;
-    */*) ac_site_file1=$CONFIG_SITE;;
-    *)   ac_site_file1=./$CONFIG_SITE;;
-  esac
+  ac_site_files="$CONFIG_SITE"
 elif test "x$prefix" != xNONE; then
-  ac_site_file1=$prefix/share/config.site
-  ac_site_file2=$prefix/etc/config.site
+  ac_site_files="$prefix/share/config.site $prefix/etc/config.site"
 else
-  ac_site_file1=$ac_default_prefix/share/config.site
-  ac_site_file2=$ac_default_prefix/etc/config.site
+  ac_site_files="$ac_default_prefix/share/config.site $ac_default_prefix/etc/config.site"
 fi
-for ac_site_file in "$ac_site_file1" "$ac_site_file2"
+
+for ac_site_file in $ac_site_files
 do
-  test "x$ac_site_file" = xNONE && continue
-  if test /dev/null != "$ac_site_file" && test -r "$ac_site_file"; then
-    { $as_echo "$as_me:${as_lineno-$LINENO}: loading site script $ac_site_file" >&5
-$as_echo "$as_me: loading site script $ac_site_file" >&6;}
+  case $ac_site_file in #(
+  */*) :
+     ;; #(
+  *) :
+    ac_site_file=./$ac_site_file ;;
+esac
+  if test -f "$ac_site_file" && test -r "$ac_site_file"; then
+    { printf "%s\n" "$as_me:${as_lineno-$LINENO}: loading site script $ac_site_file" >&5
+printf "%s\n" "$as_me: loading site script $ac_site_file" >&6;}
     sed 's/^/| /' "$ac_site_file" >&5
     . "$ac_site_file" \
-      || { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
-$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+      || { { printf "%s\n" "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+printf "%s\n" "$as_me: error: in \`$ac_pwd':" >&2;}
 as_fn_error $? "failed to load site script $ac_site_file
 See \`config.log' for more details" "$LINENO" 5; }
   fi
@@ -1746,19 +1791,235 @@ if test -r "$cache_file"; then
   # Some versions of bash will fail to source /dev/null (special files
   # actually), so we avoid doing that.  DJGPP emulates it as a regular file.
   if test /dev/null != "$cache_file" && test -f "$cache_file"; then
-    { $as_echo "$as_me:${as_lineno-$LINENO}: loading cache $cache_file" >&5
-$as_echo "$as_me: loading cache $cache_file" >&6;}
+    { printf "%s\n" "$as_me:${as_lineno-$LINENO}: loading cache $cache_file" >&5
+printf "%s\n" "$as_me: loading cache $cache_file" >&6;}
     case $cache_file in
       [\\/]* | ?:[\\/]* ) . "$cache_file";;
       *)                      . "./$cache_file";;
     esac
   fi
 else
-  { $as_echo "$as_me:${as_lineno-$LINENO}: creating cache $cache_file" >&5
-$as_echo "$as_me: creating cache $cache_file" >&6;}
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: creating cache $cache_file" >&5
+printf "%s\n" "$as_me: creating cache $cache_file" >&6;}
   >$cache_file
 fi
 
+# Test code for whether the C++ compiler supports C++98 (global declarations)
+ac_cxx_conftest_cxx98_globals='
+// Does the compiler advertise C++98 conformance?
+#if !defined __cplusplus || __cplusplus < 199711L
+# error "Compiler does not advertise C++98 conformance"
+#endif
+
+// These inclusions are to reject old compilers that
+// lack the unsuffixed header files.
+#include <cstdlib>
+#include <exception>
+
+// <cassert> and <cstring> are *not* freestanding headers in C++98.
+extern void assert (int);
+namespace std {
+  extern int strcmp (const char *, const char *);
+}
+
+// Namespaces, exceptions, and templates were all added after "C++ 2.0".
+using std::exception;
+using std::strcmp;
+
+namespace {
+
+void test_exception_syntax()
+{
+  try {
+    throw "test";
+  } catch (const char *s) {
+    // Extra parentheses suppress a warning when building autoconf itself,
+    // due to lint rules shared with more typical C programs.
+    assert (!(strcmp) (s, "test"));
+  }
+}
+
+template <typename T> struct test_template
+{
+  T const val;
+  explicit test_template(T t) : val(t) {}
+  template <typename U> T add(U u) { return static_cast<T>(u) + val; }
+};
+
+} // anonymous namespace
+'
+
+# Test code for whether the C++ compiler supports C++98 (body of main)
+ac_cxx_conftest_cxx98_main='
+  assert (argc);
+  assert (! argv[0]);
+{
+  test_exception_syntax ();
+  test_template<double> tt (2.0);
+  assert (tt.add (4) == 6.0);
+  assert (true && !false);
+}
+'
+
+# Test code for whether the C++ compiler supports C++11 (global declarations)
+ac_cxx_conftest_cxx11_globals='
+// Does the compiler advertise C++ 2011 conformance?
+#if !defined __cplusplus || __cplusplus < 201103L
+# error "Compiler does not advertise C++11 conformance"
+#endif
+
+namespace cxx11test
+{
+  constexpr int get_val() { return 20; }
+
+  struct testinit
+  {
+    int i;
+    double d;
+  };
+
+  class delegate
+  {
+  public:
+    delegate(int n) : n(n) {}
+    delegate(): delegate(2354) {}
+
+    virtual int getval() { return this->n; };
+  protected:
+    int n;
+  };
+
+  class overridden : public delegate
+  {
+  public:
+    overridden(int n): delegate(n) {}
+    virtual int getval() override final { return this->n * 2; }
+  };
+
+  class nocopy
+  {
+  public:
+    nocopy(int i): i(i) {}
+    nocopy() = default;
+    nocopy(const nocopy&) = delete;
+    nocopy & operator=(const nocopy&) = delete;
+  private:
+    int i;
+  };
+
+  // for testing lambda expressions
+  template <typename Ret, typename Fn> Ret eval(Fn f, Ret v)
+  {
+    return f(v);
+  }
+
+  // for testing variadic templates and trailing return types
+  template <typename V> auto sum(V first) -> V
+  {
+    return first;
+  }
+  template <typename V, typename... Args> auto sum(V first, Args... rest) -> V
+  {
+    return first + sum(rest...);
+  }
+}
+'
+
+# Test code for whether the C++ compiler supports C++11 (body of main)
+ac_cxx_conftest_cxx11_main='
+{
+  // Test auto and decltype
+  auto a1 = 6538;
+  auto a2 = 48573953.4;
+  auto a3 = "String literal";
+
+  int total = 0;
+  for (auto i = a3; *i; ++i) { total += *i; }
+
+  decltype(a2) a4 = 34895.034;
+}
+{
+  // Test constexpr
+  short sa[cxx11test::get_val()] = { 0 };
+}
+{
+  // Test initializer lists
+  cxx11test::testinit il = { 4323, 435234.23544 };
+}
+{
+  // Test range-based for
+  int array[] = {9, 7, 13, 15, 4, 18, 12, 10, 5, 3,
+                 14, 19, 17, 8, 6, 20, 16, 2, 11, 1};
+  for (auto &x : array) { x += 23; }
+}
+{
+  // Test lambda expressions
+  using cxx11test::eval;
+  assert (eval ([](int x) { return x*2; }, 21) == 42);
+  double d = 2.0;
+  assert (eval ([&](double x) { return d += x; }, 3.0) == 5.0);
+  assert (d == 5.0);
+  assert (eval ([=](double x) mutable { return d += x; }, 4.0) == 9.0);
+  assert (d == 5.0);
+}
+{
+  // Test use of variadic templates
+  using cxx11test::sum;
+  auto a = sum(1);
+  auto b = sum(1, 2);
+  auto c = sum(1.0, 2.0, 3.0);
+}
+{
+  // Test constructor delegation
+  cxx11test::delegate d1;
+  cxx11test::delegate d2();
+  cxx11test::delegate d3(45);
+}
+{
+  // Test override and final
+  cxx11test::overridden o1(55464);
+}
+{
+  // Test nullptr
+  char *c = nullptr;
+}
+{
+  // Test template brackets
+  test_template<::test_template<int>> v(test_template<int>(12));
+}
+{
+  // Unicode literals
+  char const *utf8 = u8"UTF-8 string \u2500";
+  char16_t const *utf16 = u"UTF-8 string \u2500";
+  char32_t const *utf32 = U"UTF-32 string \u2500";
+}
+'
+
+# Test code for whether the C compiler supports C++11 (complete).
+ac_cxx_conftest_cxx11_program="${ac_cxx_conftest_cxx98_globals}
+${ac_cxx_conftest_cxx11_globals}
+
+int
+main (int argc, char **argv)
+{
+  int ok = 0;
+  ${ac_cxx_conftest_cxx98_main}
+  ${ac_cxx_conftest_cxx11_main}
+  return ok;
+}
+"
+
+# Test code for whether the C compiler supports C++98 (complete).
+ac_cxx_conftest_cxx98_program="${ac_cxx_conftest_cxx98_globals}
+int
+main (int argc, char **argv)
+{
+  int ok = 0;
+  ${ac_cxx_conftest_cxx98_main}
+  return ok;
+}
+"
+
 # Check that the precious variables saved in the cache have kept the same
 # value.
 ac_cache_corrupted=false
@@ -1769,12 +2030,12 @@ for ac_var in $ac_precious_vars; do
   eval ac_new_val=\$ac_env_${ac_var}_value
   case $ac_old_set,$ac_new_set in
     set,)
-      { $as_echo "$as_me:${as_lineno-$LINENO}: error: \`$ac_var' was set to \`$ac_old_val' in the previous run" >&5
-$as_echo "$as_me: error: \`$ac_var' was set to \`$ac_old_val' in the previous run" >&2;}
+      { printf "%s\n" "$as_me:${as_lineno-$LINENO}: error: \`$ac_var' was set to \`$ac_old_val' in the previous run" >&5
+printf "%s\n" "$as_me: error: \`$ac_var' was set to \`$ac_old_val' in the previous run" >&2;}
       ac_cache_corrupted=: ;;
     ,set)
-      { $as_echo "$as_me:${as_lineno-$LINENO}: error: \`$ac_var' was not set in the previous run" >&5
-$as_echo "$as_me: error: \`$ac_var' was not set in the previous run" >&2;}
+      { printf "%s\n" "$as_me:${as_lineno-$LINENO}: error: \`$ac_var' was not set in the previous run" >&5
+printf "%s\n" "$as_me: error: \`$ac_var' was not set in the previous run" >&2;}
       ac_cache_corrupted=: ;;
     ,);;
     *)
@@ -1783,24 +2044,24 @@ $as_echo "$as_me: error: \`$ac_var' was not set in the previous run" >&2;}
 	ac_old_val_w=`echo x $ac_old_val`
 	ac_new_val_w=`echo x $ac_new_val`
 	if test "$ac_old_val_w" != "$ac_new_val_w"; then
-	  { $as_echo "$as_me:${as_lineno-$LINENO}: error: \`$ac_var' has changed since the previous run:" >&5
-$as_echo "$as_me: error: \`$ac_var' has changed since the previous run:" >&2;}
+	  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: error: \`$ac_var' has changed since the previous run:" >&5
+printf "%s\n" "$as_me: error: \`$ac_var' has changed since the previous run:" >&2;}
 	  ac_cache_corrupted=:
 	else
-	  { $as_echo "$as_me:${as_lineno-$LINENO}: warning: ignoring whitespace changes in \`$ac_var' since the previous run:" >&5
-$as_echo "$as_me: warning: ignoring whitespace changes in \`$ac_var' since the previous run:" >&2;}
+	  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: warning: ignoring whitespace changes in \`$ac_var' since the previous run:" >&5
+printf "%s\n" "$as_me: warning: ignoring whitespace changes in \`$ac_var' since the previous run:" >&2;}
 	  eval $ac_var=\$ac_old_val
 	fi
-	{ $as_echo "$as_me:${as_lineno-$LINENO}:   former value:  \`$ac_old_val'" >&5
-$as_echo "$as_me:   former value:  \`$ac_old_val'" >&2;}
-	{ $as_echo "$as_me:${as_lineno-$LINENO}:   current value: \`$ac_new_val'" >&5
-$as_echo "$as_me:   current value: \`$ac_new_val'" >&2;}
+	{ printf "%s\n" "$as_me:${as_lineno-$LINENO}:   former value:  \`$ac_old_val'" >&5
+printf "%s\n" "$as_me:   former value:  \`$ac_old_val'" >&2;}
+	{ printf "%s\n" "$as_me:${as_lineno-$LINENO}:   current value: \`$ac_new_val'" >&5
+printf "%s\n" "$as_me:   current value: \`$ac_new_val'" >&2;}
       fi;;
   esac
   # Pass precious variables to config.status.
   if test "$ac_new_set" = set; then
     case $ac_new_val in
-    *\'*) ac_arg=$ac_var=`$as_echo "$ac_new_val" | sed "s/'/'\\\\\\\\''/g"` ;;
+    *\'*) ac_arg=$ac_var=`printf "%s\n" "$ac_new_val" | sed "s/'/'\\\\\\\\''/g"` ;;
     *) ac_arg=$ac_var=$ac_new_val ;;
     esac
     case " $ac_configure_args " in
@@ -1810,11 +2071,12 @@ $as_echo "$as_me:   current value: \`$ac_new_val'" >&2;}
   fi
 done
 if $ac_cache_corrupted; then
-  { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
-$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
-  { $as_echo "$as_me:${as_lineno-$LINENO}: error: changes in the environment can compromise the build" >&5
-$as_echo "$as_me: error: changes in the environment can compromise the build" >&2;}
-  as_fn_error $? "run \`make distclean' and/or \`rm $cache_file' and start over" "$LINENO" 5
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+printf "%s\n" "$as_me: error: in \`$ac_pwd':" >&2;}
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: error: changes in the environment can compromise the build" >&5
+printf "%s\n" "$as_me: error: changes in the environment can compromise the build" >&2;}
+  as_fn_error $? "run \`${MAKE-make} distclean' and/or \`rm $cache_file'
+	    and start over" "$LINENO" 5
 fi
 ## -------------------- ##
 ## Main body of script. ##
@@ -1828,224 +2090,76 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
 
 
 
-# Use this line to set CC variable to a C compiler
-ac_ext=c
-ac_cpp='$CPP $CPPFLAGS'
-ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
-ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
-ac_compiler_gnu=$ac_cv_c_compiler_gnu
-if test -n "$ac_tool_prefix"; then
-  # Extract the first word of "${ac_tool_prefix}gcc", so it can be a program name with args.
-set dummy ${ac_tool_prefix}gcc; ac_word=$2
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
-$as_echo_n "checking for $ac_word... " >&6; }
-if ${ac_cv_prog_CC+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  if test -n "$CC"; then
-  ac_cv_prog_CC="$CC" # Let the user override the test.
-else
-as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
-for as_dir in $PATH
-do
-  IFS=$as_save_IFS
-  test -z "$as_dir" && as_dir=.
-    for ac_exec_ext in '' $ac_executable_extensions; do
-  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
-    ac_cv_prog_CC="${ac_tool_prefix}gcc"
-    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
-    break 2
-  fi
-done
-  done
-IFS=$as_save_IFS
-
-fi
-fi
-CC=$ac_cv_prog_CC
-if test -n "$CC"; then
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $CC" >&5
-$as_echo "$CC" >&6; }
-else
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
-$as_echo "no" >&6; }
+: ${R_HOME=`R RHOME`}
+if test -z "${R_HOME}"; then
+  echo "could not determine R_HOME"
+  exit 1
 fi
 
+CXX14=`"${R_HOME}/bin/R" CMD config CXX14`
+CXX14STD=`"${R_HOME}/bin/R" CMD config CXX14STD`
+CXX="${CXX14} ${CXX14STD}"
+CXXFLAGS=`"${R_HOME}/bin/R" CMD config CXXFLAGS`
 
-fi
-if test -z "$ac_cv_prog_CC"; then
-  ac_ct_CC=$CC
-  # Extract the first word of "gcc", so it can be a program name with args.
-set dummy gcc; ac_word=$2
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
-$as_echo_n "checking for $ac_word... " >&6; }
-if ${ac_cv_prog_ac_ct_CC+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  if test -n "$ac_ct_CC"; then
-  ac_cv_prog_ac_ct_CC="$ac_ct_CC" # Let the user override the test.
-else
-as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
-for as_dir in $PATH
-do
-  IFS=$as_save_IFS
-  test -z "$as_dir" && as_dir=.
-    for ac_exec_ext in '' $ac_executable_extensions; do
-  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
-    ac_cv_prog_ac_ct_CC="gcc"
-    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
-    break 2
-  fi
-done
-  done
-IFS=$as_save_IFS
+CC=`"${R_HOME}/bin/R" CMD config CC`
+CFLAGS=`"${R_HOME}/bin/R" CMD config CFLAGS`
+CPPFLAGS=`"${R_HOME}/bin/R" CMD config CPPFLAGS`
 
-fi
-fi
-ac_ct_CC=$ac_cv_prog_ac_ct_CC
-if test -n "$ac_ct_CC"; then
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_ct_CC" >&5
-$as_echo "$ac_ct_CC" >&6; }
-else
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
-$as_echo "no" >&6; }
-fi
+LDFLAGS=`"${R_HOME}/bin/R" CMD config LDFLAGS`
+ac_ext=cpp
+ac_cpp='$CXXCPP $CPPFLAGS'
+ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
 
-  if test "x$ac_ct_CC" = x; then
-    CC=""
+
+### Check whether backtrace() is part of libc or the external lib libexecinfo
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking Backtrace lib" >&5
+printf %s "checking Backtrace lib... " >&6; }
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: " >&5
+printf "%s\n" "" >&6; }
+
+
+
+
+
+
+ac_ext=cpp
+ac_cpp='$CXXCPP $CPPFLAGS'
+ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
+if test -z "$CXX"; then
+  if test -n "$CCC"; then
+    CXX=$CCC
   else
-    case $cross_compiling:$ac_tool_warned in
-yes:)
-{ $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: using cross tools not prefixed with host triplet" >&5
-$as_echo "$as_me: WARNING: using cross tools not prefixed with host triplet" >&2;}
-ac_tool_warned=yes ;;
-esac
-    CC=$ac_ct_CC
-  fi
-else
-  CC="$ac_cv_prog_CC"
-fi
-
-if test -z "$CC"; then
-          if test -n "$ac_tool_prefix"; then
-    # Extract the first word of "${ac_tool_prefix}cc", so it can be a program name with args.
-set dummy ${ac_tool_prefix}cc; ac_word=$2
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
-$as_echo_n "checking for $ac_word... " >&6; }
-if ${ac_cv_prog_CC+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  if test -n "$CC"; then
-  ac_cv_prog_CC="$CC" # Let the user override the test.
-else
-as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
-for as_dir in $PATH
-do
-  IFS=$as_save_IFS
-  test -z "$as_dir" && as_dir=.
-    for ac_exec_ext in '' $ac_executable_extensions; do
-  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
-    ac_cv_prog_CC="${ac_tool_prefix}cc"
-    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
-    break 2
-  fi
-done
-  done
-IFS=$as_save_IFS
-
-fi
-fi
-CC=$ac_cv_prog_CC
-if test -n "$CC"; then
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $CC" >&5
-$as_echo "$CC" >&6; }
-else
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
-$as_echo "no" >&6; }
-fi
-
-
-  fi
-fi
-if test -z "$CC"; then
-  # Extract the first word of "cc", so it can be a program name with args.
-set dummy cc; ac_word=$2
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
-$as_echo_n "checking for $ac_word... " >&6; }
-if ${ac_cv_prog_CC+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  if test -n "$CC"; then
-  ac_cv_prog_CC="$CC" # Let the user override the test.
-else
-  ac_prog_rejected=no
-as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
-for as_dir in $PATH
-do
-  IFS=$as_save_IFS
-  test -z "$as_dir" && as_dir=.
-    for ac_exec_ext in '' $ac_executable_extensions; do
-  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
-    if test "$as_dir/$ac_word$ac_exec_ext" = "/usr/ucb/cc"; then
-       ac_prog_rejected=yes
-       continue
-     fi
-    ac_cv_prog_CC="cc"
-    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
-    break 2
-  fi
-done
-  done
-IFS=$as_save_IFS
-
-if test $ac_prog_rejected = yes; then
-  # We found a bogon in the path, so make sure we never use it.
-  set dummy $ac_cv_prog_CC
-  shift
-  if test $# != 0; then
-    # We chose a different compiler from the bogus one.
-    # However, it has the same basename, so the bogon will be chosen
-    # first if we set CC to just the basename; use the full file name.
-    shift
-    ac_cv_prog_CC="$as_dir/$ac_word${1+' '}$@"
-  fi
-fi
-fi
-fi
-CC=$ac_cv_prog_CC
-if test -n "$CC"; then
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $CC" >&5
-$as_echo "$CC" >&6; }
-else
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
-$as_echo "no" >&6; }
-fi
-
-
-fi
-if test -z "$CC"; then
-  if test -n "$ac_tool_prefix"; then
-  for ac_prog in cl.exe
+    if test -n "$ac_tool_prefix"; then
+  for ac_prog in g++ c++ gpp aCC CC cxx cc++ cl.exe FCC KCC RCC xlC_r xlC clang++
   do
     # Extract the first word of "$ac_tool_prefix$ac_prog", so it can be a program name with args.
 set dummy $ac_tool_prefix$ac_prog; ac_word=$2
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
-$as_echo_n "checking for $ac_word... " >&6; }
-if ${ac_cv_prog_CC+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  if test -n "$CC"; then
-  ac_cv_prog_CC="$CC" # Let the user override the test.
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
+printf %s "checking for $ac_word... " >&6; }
+if test ${ac_cv_prog_CXX+y}
+then :
+  printf %s "(cached) " >&6
+else $as_nop
+  if test -n "$CXX"; then
+  ac_cv_prog_CXX="$CXX" # Let the user override the test.
 else
 as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
 for as_dir in $PATH
 do
   IFS=$as_save_IFS
-  test -z "$as_dir" && as_dir=.
+  case $as_dir in #(((
+    '') as_dir=./ ;;
+    */) ;;
+    *) as_dir=$as_dir/ ;;
+  esac
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
-    ac_cv_prog_CC="$ac_tool_prefix$ac_prog"
-    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
+  if as_fn_executable_p "$as_dir$ac_word$ac_exec_ext"; then
+    ac_cv_prog_CXX="$ac_tool_prefix$ac_prog"
+    printf "%s\n" "$as_me:${as_lineno-$LINENO}: found $as_dir$ac_word$ac_exec_ext" >&5
     break 2
   fi
 done
@@ -2054,42 +2168,47 @@ IFS=$as_save_IFS
 
 fi
 fi
-CC=$ac_cv_prog_CC
-if test -n "$CC"; then
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $CC" >&5
-$as_echo "$CC" >&6; }
+CXX=$ac_cv_prog_CXX
+if test -n "$CXX"; then
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $CXX" >&5
+printf "%s\n" "$CXX" >&6; }
 else
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
-$as_echo "no" >&6; }
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: no" >&5
+printf "%s\n" "no" >&6; }
 fi
 
 
-    test -n "$CC" && break
+    test -n "$CXX" && break
   done
 fi
-if test -z "$CC"; then
-  ac_ct_CC=$CC
-  for ac_prog in cl.exe
+if test -z "$CXX"; then
+  ac_ct_CXX=$CXX
+  for ac_prog in g++ c++ gpp aCC CC cxx cc++ cl.exe FCC KCC RCC xlC_r xlC clang++
 do
   # Extract the first word of "$ac_prog", so it can be a program name with args.
 set dummy $ac_prog; ac_word=$2
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
-$as_echo_n "checking for $ac_word... " >&6; }
-if ${ac_cv_prog_ac_ct_CC+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  if test -n "$ac_ct_CC"; then
-  ac_cv_prog_ac_ct_CC="$ac_ct_CC" # Let the user override the test.
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
+printf %s "checking for $ac_word... " >&6; }
+if test ${ac_cv_prog_ac_ct_CXX+y}
+then :
+  printf %s "(cached) " >&6
+else $as_nop
+  if test -n "$ac_ct_CXX"; then
+  ac_cv_prog_ac_ct_CXX="$ac_ct_CXX" # Let the user override the test.
 else
 as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
 for as_dir in $PATH
 do
   IFS=$as_save_IFS
-  test -z "$as_dir" && as_dir=.
+  case $as_dir in #(((
+    '') as_dir=./ ;;
+    */) ;;
+    *) as_dir=$as_dir/ ;;
+  esac
     for ac_exec_ext in '' $ac_executable_extensions; do
-  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
-    ac_cv_prog_ac_ct_CC="$ac_prog"
-    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
+  if as_fn_executable_p "$as_dir$ac_word$ac_exec_ext"; then
+    ac_cv_prog_ac_ct_CXX="$ac_prog"
+    printf "%s\n" "$as_me:${as_lineno-$LINENO}: found $as_dir$ac_word$ac_exec_ext" >&5
     break 2
   fi
 done
@@ -2098,42 +2217,36 @@ IFS=$as_save_IFS
 
 fi
 fi
-ac_ct_CC=$ac_cv_prog_ac_ct_CC
-if test -n "$ac_ct_CC"; then
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_ct_CC" >&5
-$as_echo "$ac_ct_CC" >&6; }
+ac_ct_CXX=$ac_cv_prog_ac_ct_CXX
+if test -n "$ac_ct_CXX"; then
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $ac_ct_CXX" >&5
+printf "%s\n" "$ac_ct_CXX" >&6; }
 else
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
-$as_echo "no" >&6; }
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: no" >&5
+printf "%s\n" "no" >&6; }
 fi
 
 
-  test -n "$ac_ct_CC" && break
+  test -n "$ac_ct_CXX" && break
 done
 
-  if test "x$ac_ct_CC" = x; then
-    CC=""
+  if test "x$ac_ct_CXX" = x; then
+    CXX="g++"
   else
     case $cross_compiling:$ac_tool_warned in
 yes:)
-{ $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: using cross tools not prefixed with host triplet" >&5
-$as_echo "$as_me: WARNING: using cross tools not prefixed with host triplet" >&2;}
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: WARNING: using cross tools not prefixed with host triplet" >&5
+printf "%s\n" "$as_me: WARNING: using cross tools not prefixed with host triplet" >&2;}
 ac_tool_warned=yes ;;
 esac
-    CC=$ac_ct_CC
+    CXX=$ac_ct_CXX
   fi
 fi
 
+  fi
 fi
-
-
-test -z "$CC" && { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
-$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
-as_fn_error $? "no acceptable C compiler found in \$PATH
-See \`config.log' for more details" "$LINENO" 5; }
-
 # Provide some information about the compiler.
-$as_echo "$as_me:${as_lineno-$LINENO}: checking for C compiler version" >&5
+printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for C++ compiler version" >&5
 set X $ac_compile
 ac_compiler=$2
 for ac_option in --version -v -V -qversion; do
@@ -2143,7 +2256,7 @@ case "(($ac_try" in
   *) ac_try_echo=$ac_try;;
 esac
 eval ac_try_echo="\"\$as_me:${as_lineno-$LINENO}: $ac_try_echo\""
-$as_echo "$ac_try_echo"; } >&5
+printf "%s\n" "$ac_try_echo"; } >&5
   (eval "$ac_compiler $ac_option >&5") 2>conftest.err
   ac_status=$?
   if test -s conftest.err; then
@@ -2153,7 +2266,7 @@ $as_echo "$ac_try_echo"; } >&5
     cat conftest.er1 >&5
   fi
   rm -f conftest.er1 conftest.err
-  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
   test $ac_status = 0; }
 done
 
@@ -2161,7 +2274,7 @@ cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
 int
-main ()
+main (void)
 {
 
   ;
@@ -2173,9 +2286,9 @@ ac_clean_files="$ac_clean_files a.out a.out.dSYM a.exe b.out"
 # Try to create an executable without -o first, disregard a.out.
 # It will help us diagnose broken compilers, and finding out an intuition
 # of exeext.
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether the C compiler works" >&5
-$as_echo_n "checking whether the C compiler works... " >&6; }
-ac_link_default=`$as_echo "$ac_link" | sed 's/ -o *conftest[^ ]*//'`
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking whether the C++ compiler works" >&5
+printf %s "checking whether the C++ compiler works... " >&6; }
+ac_link_default=`printf "%s\n" "$ac_link" | sed 's/ -o *conftest[^ ]*//'`
 
 # The possible output files:
 ac_files="a.out conftest.exe conftest a.exe a_out.exe b.out conftest.*"
@@ -2196,11 +2309,12 @@ case "(($ac_try" in
   *) ac_try_echo=$ac_try;;
 esac
 eval ac_try_echo="\"\$as_me:${as_lineno-$LINENO}: $ac_try_echo\""
-$as_echo "$ac_try_echo"; } >&5
+printf "%s\n" "$ac_try_echo"; } >&5
   (eval "$ac_link_default") 2>&5
   ac_status=$?
-  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
-  test $ac_status = 0; }; then :
+  printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }
+then :
   # Autoconf-2.13 could set the ac_cv_exeext variable to `no'.
 # So ignore a value of `no', otherwise this would lead to `EXEEXT = no'
 # in a Makefile.  We should not override ac_cv_exeext if it was cached,
@@ -2217,7 +2331,7 @@ do
 	# certainly right.
 	break;;
     *.* )
-	if test "${ac_cv_exeext+set}" = set && test "$ac_cv_exeext" != no;
+	if test ${ac_cv_exeext+y} && test "$ac_cv_exeext" != no;
 	then :; else
 	   ac_cv_exeext=`expr "$ac_file" : '[^.]*\(\..*\)'`
 	fi
@@ -2233,44 +2347,46 @@ do
 done
 test "$ac_cv_exeext" = no && ac_cv_exeext=
 
-else
+else $as_nop
   ac_file=''
 fi
-if test -z "$ac_file"; then :
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
-$as_echo "no" >&6; }
-$as_echo "$as_me: failed program was:" >&5
+if test -z "$ac_file"
+then :
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: no" >&5
+printf "%s\n" "no" >&6; }
+printf "%s\n" "$as_me: failed program was:" >&5
 sed 's/^/| /' conftest.$ac_ext >&5
 
-{ { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
-$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
-as_fn_error 77 "C compiler cannot create executables
+{ { printf "%s\n" "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+printf "%s\n" "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error 77 "C++ compiler cannot create executables
 See \`config.log' for more details" "$LINENO" 5; }
-else
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
-$as_echo "yes" >&6; }
+else $as_nop
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+printf "%s\n" "yes" >&6; }
 fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for C compiler default output file name" >&5
-$as_echo_n "checking for C compiler default output file name... " >&6; }
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_file" >&5
-$as_echo "$ac_file" >&6; }
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for C++ compiler default output file name" >&5
+printf %s "checking for C++ compiler default output file name... " >&6; }
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $ac_file" >&5
+printf "%s\n" "$ac_file" >&6; }
 ac_exeext=$ac_cv_exeext
 
 rm -f -r a.out a.out.dSYM a.exe conftest$ac_cv_exeext b.out
 ac_clean_files=$ac_clean_files_save
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for suffix of executables" >&5
-$as_echo_n "checking for suffix of executables... " >&6; }
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for suffix of executables" >&5
+printf %s "checking for suffix of executables... " >&6; }
 if { { ac_try="$ac_link"
 case "(($ac_try" in
   *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
   *) ac_try_echo=$ac_try;;
 esac
 eval ac_try_echo="\"\$as_me:${as_lineno-$LINENO}: $ac_try_echo\""
-$as_echo "$ac_try_echo"; } >&5
+printf "%s\n" "$ac_try_echo"; } >&5
   (eval "$ac_link") 2>&5
   ac_status=$?
-  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
-  test $ac_status = 0; }; then :
+  printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }
+then :
   # If both `conftest.exe' and `conftest' are `present' (well, observable)
 # catch `conftest.exe'.  For instance with Cygwin, `ls conftest' will
 # work properly (i.e., refer to `conftest.exe'), while it won't with
@@ -2284,15 +2400,15 @@ for ac_file in conftest.exe conftest conftest.*; do
     * ) break;;
   esac
 done
-else
-  { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
-$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+else $as_nop
+  { { printf "%s\n" "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+printf "%s\n" "$as_me: error: in \`$ac_pwd':" >&2;}
 as_fn_error $? "cannot compute suffix of executables: cannot compile and link
 See \`config.log' for more details" "$LINENO" 5; }
 fi
 rm -f conftest conftest$ac_cv_exeext
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_exeext" >&5
-$as_echo "$ac_cv_exeext" >&6; }
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $ac_cv_exeext" >&5
+printf "%s\n" "$ac_cv_exeext" >&6; }
 
 rm -f conftest.$ac_ext
 EXEEXT=$ac_cv_exeext
@@ -2301,7 +2417,7 @@ cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 #include <stdio.h>
 int
-main ()
+main (void)
 {
 FILE *f = fopen ("conftest.out", "w");
  return ferror (f) || fclose (f) != 0;
@@ -2313,8 +2429,8 @@ _ACEOF
 ac_clean_files="$ac_clean_files conftest.out"
 # Check that the compiler produces executables we can run.  If not, either
 # the compiler is broken, or we cross compile.
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether we are cross compiling" >&5
-$as_echo_n "checking whether we are cross compiling... " >&6; }
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking whether we are cross compiling" >&5
+printf %s "checking whether we are cross compiling... " >&6; }
 if test "$cross_compiling" != yes; then
   { { ac_try="$ac_link"
 case "(($ac_try" in
@@ -2322,10 +2438,10 @@ case "(($ac_try" in
   *) ac_try_echo=$ac_try;;
 esac
 eval ac_try_echo="\"\$as_me:${as_lineno-$LINENO}: $ac_try_echo\""
-$as_echo "$ac_try_echo"; } >&5
+printf "%s\n" "$ac_try_echo"; } >&5
   (eval "$ac_link") 2>&5
   ac_status=$?
-  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
   test $ac_status = 0; }
   if { ac_try='./conftest$ac_cv_exeext'
   { { case "(($ac_try" in
@@ -2333,39 +2449,40 @@ $as_echo "$ac_try_echo"; } >&5
   *) ac_try_echo=$ac_try;;
 esac
 eval ac_try_echo="\"\$as_me:${as_lineno-$LINENO}: $ac_try_echo\""
-$as_echo "$ac_try_echo"; } >&5
+printf "%s\n" "$ac_try_echo"; } >&5
   (eval "$ac_try") 2>&5
   ac_status=$?
-  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
   test $ac_status = 0; }; }; then
     cross_compiling=no
   else
     if test "$cross_compiling" = maybe; then
 	cross_compiling=yes
     else
-	{ { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
-$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
-as_fn_error $? "cannot run C compiled programs.
+	{ { printf "%s\n" "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+printf "%s\n" "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error 77 "cannot run C++ compiled programs.
 If you meant to cross compile, use \`--host'.
 See \`config.log' for more details" "$LINENO" 5; }
     fi
   fi
 fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $cross_compiling" >&5
-$as_echo "$cross_compiling" >&6; }
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $cross_compiling" >&5
+printf "%s\n" "$cross_compiling" >&6; }
 
 rm -f conftest.$ac_ext conftest$ac_cv_exeext conftest.out
 ac_clean_files=$ac_clean_files_save
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for suffix of object files" >&5
-$as_echo_n "checking for suffix of object files... " >&6; }
-if ${ac_cv_objext+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for suffix of object files" >&5
+printf %s "checking for suffix of object files... " >&6; }
+if test ${ac_cv_objext+y}
+then :
+  printf %s "(cached) " >&6
+else $as_nop
   cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
 int
-main ()
+main (void)
 {
 
   ;
@@ -2379,11 +2496,12 @@ case "(($ac_try" in
   *) ac_try_echo=$ac_try;;
 esac
 eval ac_try_echo="\"\$as_me:${as_lineno-$LINENO}: $ac_try_echo\""
-$as_echo "$ac_try_echo"; } >&5
+printf "%s\n" "$ac_try_echo"; } >&5
   (eval "$ac_compile") 2>&5
   ac_status=$?
-  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
-  test $ac_status = 0; }; then :
+  printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }
+then :
   for ac_file in conftest.o conftest.obj conftest.*; do
   test -f "$ac_file" || continue;
   case $ac_file in
@@ -2392,31 +2510,32 @@ $as_echo "$ac_try_echo"; } >&5
        break;;
   esac
 done
-else
-  $as_echo "$as_me: failed program was:" >&5
+else $as_nop
+  printf "%s\n" "$as_me: failed program was:" >&5
 sed 's/^/| /' conftest.$ac_ext >&5
 
-{ { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
-$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+{ { printf "%s\n" "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+printf "%s\n" "$as_me: error: in \`$ac_pwd':" >&2;}
 as_fn_error $? "cannot compute suffix of object files: cannot compile
 See \`config.log' for more details" "$LINENO" 5; }
 fi
 rm -f conftest.$ac_cv_objext conftest.$ac_ext
 fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_objext" >&5
-$as_echo "$ac_cv_objext" >&6; }
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $ac_cv_objext" >&5
+printf "%s\n" "$ac_cv_objext" >&6; }
 OBJEXT=$ac_cv_objext
 ac_objext=$OBJEXT
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether we are using the GNU C compiler" >&5
-$as_echo_n "checking whether we are using the GNU C compiler... " >&6; }
-if ${ac_cv_c_compiler_gnu+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking whether the compiler supports GNU C++" >&5
+printf %s "checking whether the compiler supports GNU C++... " >&6; }
+if test ${ac_cv_cxx_compiler_gnu+y}
+then :
+  printf %s "(cached) " >&6
+else $as_nop
   cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
 int
-main ()
+main (void)
 {
 #ifndef __GNUC__
        choke me
@@ -2426,273 +2545,279 @@ main ()
   return 0;
 }
 _ACEOF
-if ac_fn_c_try_compile "$LINENO"; then :
+if ac_fn_cxx_try_compile "$LINENO"
+then :
   ac_compiler_gnu=yes
-else
+else $as_nop
   ac_compiler_gnu=no
 fi
-rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
-ac_cv_c_compiler_gnu=$ac_compiler_gnu
+rm -f core conftest.err conftest.$ac_objext conftest.beam conftest.$ac_ext
+ac_cv_cxx_compiler_gnu=$ac_compiler_gnu
 
 fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_c_compiler_gnu" >&5
-$as_echo "$ac_cv_c_compiler_gnu" >&6; }
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $ac_cv_cxx_compiler_gnu" >&5
+printf "%s\n" "$ac_cv_cxx_compiler_gnu" >&6; }
+ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
+
 if test $ac_compiler_gnu = yes; then
-  GCC=yes
+  GXX=yes
 else
-  GCC=
+  GXX=
 fi
-ac_test_CFLAGS=${CFLAGS+set}
-ac_save_CFLAGS=$CFLAGS
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether $CC accepts -g" >&5
-$as_echo_n "checking whether $CC accepts -g... " >&6; }
-if ${ac_cv_prog_cc_g+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  ac_save_c_werror_flag=$ac_c_werror_flag
-   ac_c_werror_flag=yes
-   ac_cv_prog_cc_g=no
-   CFLAGS="-g"
+ac_test_CXXFLAGS=${CXXFLAGS+y}
+ac_save_CXXFLAGS=$CXXFLAGS
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking whether $CXX accepts -g" >&5
+printf %s "checking whether $CXX accepts -g... " >&6; }
+if test ${ac_cv_prog_cxx_g+y}
+then :
+  printf %s "(cached) " >&6
+else $as_nop
+  ac_save_cxx_werror_flag=$ac_cxx_werror_flag
+   ac_cxx_werror_flag=yes
+   ac_cv_prog_cxx_g=no
+   CXXFLAGS="-g"
    cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
 int
-main ()
+main (void)
 {
 
   ;
   return 0;
 }
 _ACEOF
-if ac_fn_c_try_compile "$LINENO"; then :
-  ac_cv_prog_cc_g=yes
-else
-  CFLAGS=""
+if ac_fn_cxx_try_compile "$LINENO"
+then :
+  ac_cv_prog_cxx_g=yes
+else $as_nop
+  CXXFLAGS=""
       cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
 int
-main ()
+main (void)
 {
 
   ;
   return 0;
 }
 _ACEOF
-if ac_fn_c_try_compile "$LINENO"; then :
+if ac_fn_cxx_try_compile "$LINENO"
+then :
 
-else
-  ac_c_werror_flag=$ac_save_c_werror_flag
-	 CFLAGS="-g"
+else $as_nop
+  ac_cxx_werror_flag=$ac_save_cxx_werror_flag
+	 CXXFLAGS="-g"
 	 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
 int
-main ()
+main (void)
 {
 
   ;
   return 0;
 }
 _ACEOF
-if ac_fn_c_try_compile "$LINENO"; then :
-  ac_cv_prog_cc_g=yes
+if ac_fn_cxx_try_compile "$LINENO"
+then :
+  ac_cv_prog_cxx_g=yes
 fi
-rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+rm -f core conftest.err conftest.$ac_objext conftest.beam conftest.$ac_ext
 fi
-rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+rm -f core conftest.err conftest.$ac_objext conftest.beam conftest.$ac_ext
 fi
-rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
-   ac_c_werror_flag=$ac_save_c_werror_flag
+rm -f core conftest.err conftest.$ac_objext conftest.beam conftest.$ac_ext
+   ac_cxx_werror_flag=$ac_save_cxx_werror_flag
 fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_prog_cc_g" >&5
-$as_echo "$ac_cv_prog_cc_g" >&6; }
-if test "$ac_test_CFLAGS" = set; then
-  CFLAGS=$ac_save_CFLAGS
-elif test $ac_cv_prog_cc_g = yes; then
-  if test "$GCC" = yes; then
-    CFLAGS="-g -O2"
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $ac_cv_prog_cxx_g" >&5
+printf "%s\n" "$ac_cv_prog_cxx_g" >&6; }
+if test $ac_test_CXXFLAGS; then
+  CXXFLAGS=$ac_save_CXXFLAGS
+elif test $ac_cv_prog_cxx_g = yes; then
+  if test "$GXX" = yes; then
+    CXXFLAGS="-g -O2"
   else
-    CFLAGS="-g"
+    CXXFLAGS="-g"
   fi
 else
-  if test "$GCC" = yes; then
-    CFLAGS="-O2"
+  if test "$GXX" = yes; then
+    CXXFLAGS="-O2"
   else
-    CFLAGS=
+    CXXFLAGS=
   fi
 fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $CC option to accept ISO C89" >&5
-$as_echo_n "checking for $CC option to accept ISO C89... " >&6; }
-if ${ac_cv_prog_cc_c89+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  ac_cv_prog_cc_c89=no
-ac_save_CC=$CC
+ac_prog_cxx_stdcxx=no
+if test x$ac_prog_cxx_stdcxx = xno
+then :
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for $CXX option to enable C++11 features" >&5
+printf %s "checking for $CXX option to enable C++11 features... " >&6; }
+if test ${ac_cv_prog_cxx_11+y}
+then :
+  printf %s "(cached) " >&6
+else $as_nop
+  ac_cv_prog_cxx_11=no
+ac_save_CXX=$CXX
 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
-#include <stdarg.h>
-#include <stdio.h>
-struct stat;
-/* Most of the following tests are stolen from RCS 5.7's src/conf.sh.  */
-struct buf { int x; };
-FILE * (*rcsopen) (struct buf *, struct stat *, int);
-static char *e (p, i)
-     char **p;
-     int i;
-{
-  return p[i];
-}
-static char *f (char * (*g) (char **, int), char **p, ...)
-{
-  char *s;
-  va_list v;
-  va_start (v,p);
-  s = g (p, va_arg (v,int));
-  va_end (v);
-  return s;
-}
-
-/* OSF 4.0 Compaq cc is some sort of almost-ANSI by default.  It has
-   function prototypes and stuff, but not '\xHH' hex character constants.
-   These don't provoke an error unfortunately, instead are silently treated
-   as 'x'.  The following induces an error, until -std is added to get
-   proper ANSI mode.  Curiously '\x00'!='x' always comes out true, for an
-   array size at least.  It's necessary to write '\x00'==0 to get something
-   that's true only with -std.  */
-int osf4_cc_array ['\x00' == 0 ? 1 : -1];
-
-/* IBM C 6 for AIX is almost-ANSI by default, but it replaces macro parameters
-   inside strings and character constants.  */
-#define FOO(x) 'x'
-int xlc6_cc_array[FOO(a) == 'x' ? 1 : -1];
-
-int test (int i, double x);
-struct s1 {int (*f) (int a);};
-struct s2 {int (*f) (double a);};
-int pairnames (int, char **, FILE *(*)(struct buf *, struct stat *, int), int, int);
-int argc;
-char **argv;
-int
-main ()
-{
-return f (e, argv, 0) != argv[0]  ||  f (e, argv, 1) != argv[1];
-  ;
-  return 0;
-}
+$ac_cxx_conftest_cxx11_program
 _ACEOF
-for ac_arg in '' -qlanglvl=extc89 -qlanglvl=ansi -std \
-	-Ae "-Aa -D_HPUX_SOURCE" "-Xc -D__EXTENSIONS__"
+for ac_arg in '' -std=gnu++11 -std=gnu++0x -std=c++11 -std=c++0x -qlanglvl=extended0x -AA
 do
-  CC="$ac_save_CC $ac_arg"
-  if ac_fn_c_try_compile "$LINENO"; then :
-  ac_cv_prog_cc_c89=$ac_arg
+  CXX="$ac_save_CXX $ac_arg"
+  if ac_fn_cxx_try_compile "$LINENO"
+then :
+  ac_cv_prog_cxx_cxx11=$ac_arg
 fi
-rm -f core conftest.err conftest.$ac_objext
-  test "x$ac_cv_prog_cc_c89" != "xno" && break
+rm -f core conftest.err conftest.$ac_objext conftest.beam
+  test "x$ac_cv_prog_cxx_cxx11" != "xno" && break
 done
 rm -f conftest.$ac_ext
-CC=$ac_save_CC
-
-fi
-# AC_CACHE_VAL
-case "x$ac_cv_prog_cc_c89" in
-  x)
-    { $as_echo "$as_me:${as_lineno-$LINENO}: result: none needed" >&5
-$as_echo "none needed" >&6; } ;;
-  xno)
-    { $as_echo "$as_me:${as_lineno-$LINENO}: result: unsupported" >&5
-$as_echo "unsupported" >&6; } ;;
-  *)
-    CC="$CC $ac_cv_prog_cc_c89"
-    { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_prog_cc_c89" >&5
-$as_echo "$ac_cv_prog_cc_c89" >&6; } ;;
-esac
-if test "x$ac_cv_prog_cc_c89" != xno; then :
-
+CXX=$ac_save_CXX
 fi
 
-ac_ext=c
-ac_cpp='$CPP $CPPFLAGS'
-ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
-ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
-ac_compiler_gnu=$ac_cv_c_compiler_gnu
+if test "x$ac_cv_prog_cxx_cxx11" = xno
+then :
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: unsupported" >&5
+printf "%s\n" "unsupported" >&6; }
+else $as_nop
+  if test "x$ac_cv_prog_cxx_cxx11" = x
+then :
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: none needed" >&5
+printf "%s\n" "none needed" >&6; }
+else $as_nop
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $ac_cv_prog_cxx_cxx11" >&5
+printf "%s\n" "$ac_cv_prog_cxx_cxx11" >&6; }
+     CXX="$CXX $ac_cv_prog_cxx_cxx11"
+fi
+  ac_cv_prog_cxx_stdcxx=$ac_cv_prog_cxx_cxx11
+  ac_prog_cxx_stdcxx=cxx11
+fi
+fi
+if test x$ac_prog_cxx_stdcxx = xno
+then :
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for $CXX option to enable C++98 features" >&5
+printf %s "checking for $CXX option to enable C++98 features... " >&6; }
+if test ${ac_cv_prog_cxx_98+y}
+then :
+  printf %s "(cached) " >&6
+else $as_nop
+  ac_cv_prog_cxx_98=no
+ac_save_CXX=$CXX
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+$ac_cxx_conftest_cxx98_program
+_ACEOF
+for ac_arg in '' -std=gnu++98 -std=c++98 -qlanglvl=extended -AA
+do
+  CXX="$ac_save_CXX $ac_arg"
+  if ac_fn_cxx_try_compile "$LINENO"
+then :
+  ac_cv_prog_cxx_cxx98=$ac_arg
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.beam
+  test "x$ac_cv_prog_cxx_cxx98" != "xno" && break
+done
+rm -f conftest.$ac_ext
+CXX=$ac_save_CXX
+fi
+
+if test "x$ac_cv_prog_cxx_cxx98" = xno
+then :
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: unsupported" >&5
+printf "%s\n" "unsupported" >&6; }
+else $as_nop
+  if test "x$ac_cv_prog_cxx_cxx98" = x
+then :
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: none needed" >&5
+printf "%s\n" "none needed" >&6; }
+else $as_nop
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $ac_cv_prog_cxx_cxx98" >&5
+printf "%s\n" "$ac_cv_prog_cxx_cxx98" >&6; }
+     CXX="$CXX $ac_cv_prog_cxx_cxx98"
+fi
+  ac_cv_prog_cxx_stdcxx=$ac_cv_prog_cxx_cxx98
+  ac_prog_cxx_stdcxx=cxx98
+fi
+fi
+
+ac_ext=cpp
+ac_cpp='$CXXCPP $CPPFLAGS'
+ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
 
 
-### Check whether backtrace() is part of libc or the external lib libexecinfo
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking Backtrace lib" >&5
-$as_echo_n "checking Backtrace lib... " >&6; }
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: " >&5
-$as_echo "" >&6; }
-
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for backtrace in -lexecinfo" >&5
-$as_echo_n "checking for backtrace in -lexecinfo... " >&6; }
-if ${ac_cv_lib_execinfo_backtrace+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for backtrace in -lexecinfo" >&5
+printf %s "checking for backtrace in -lexecinfo... " >&6; }
+if test ${ac_cv_lib_execinfo_backtrace+y}
+then :
+  printf %s "(cached) " >&6
+else $as_nop
   ac_check_lib_save_LIBS=$LIBS
 LIBS="-lexecinfo  $LIBS"
 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
-/* Override any GCC internal prototype to avoid an error.
-   Use char because int might match the return type of a GCC
-   builtin and then its argument prototype would still apply.  */
-#ifdef __cplusplus
-extern "C"
-#endif
-char backtrace ();
+namespace conftest {
+  extern "C" int backtrace ();
+}
 int
-main ()
+main (void)
 {
-return backtrace ();
+return conftest::backtrace ();
   ;
   return 0;
 }
 _ACEOF
-if ac_fn_c_try_link "$LINENO"; then :
+if ac_fn_cxx_try_link "$LINENO"
+then :
   ac_cv_lib_execinfo_backtrace=yes
-else
+else $as_nop
   ac_cv_lib_execinfo_backtrace=no
 fi
-rm -f core conftest.err conftest.$ac_objext \
+rm -f core conftest.err conftest.$ac_objext conftest.beam \
     conftest$ac_exeext conftest.$ac_ext
 LIBS=$ac_check_lib_save_LIBS
 fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_lib_execinfo_backtrace" >&5
-$as_echo "$ac_cv_lib_execinfo_backtrace" >&6; }
-if test "x$ac_cv_lib_execinfo_backtrace" = xyes; then :
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $ac_cv_lib_execinfo_backtrace" >&5
+printf "%s\n" "$ac_cv_lib_execinfo_backtrace" >&6; }
+if test "x$ac_cv_lib_execinfo_backtrace" = xyes
+then :
   BACKTRACE_LIB=-lexecinfo
-else
+else $as_nop
   BACKTRACE_LIB=''
 fi
 
 
 ### Endian detection
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking endian" >&5
-$as_echo_n "checking endian... " >&6; }
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: " >&5
-$as_echo "" >&6; }
-if test "$cross_compiling" = yes; then :
-  { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
-$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking endian" >&5
+printf %s "checking endian... " >&6; }
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: " >&5
+printf "%s\n" "" >&6; }
+if test "$cross_compiling" = yes
+then :
+  { { printf "%s\n" "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+printf "%s\n" "$as_me: error: in \`$ac_pwd':" >&2;}
 as_fn_error $? "cannot run test program while cross compiling
 See \`config.log' for more details" "$LINENO" 5; }
-else
+else $as_nop
   cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 #include <stdint.h>
 int
-main ()
+main (void)
 {
 const uint16_t endianness = 256; return !!(*(const uint8_t *)&endianness);
   ;
   return 0;
 }
 _ACEOF
-if ac_fn_c_try_run "$LINENO"; then :
+if ac_fn_cxx_try_run "$LINENO"
+then :
   ENDIAN_FLAG="-DDMLC_CMAKE_LITTLE_ENDIAN=1"
-else
+else $as_nop
   ENDIAN_FLAG="-DDMLC_CMAKE_LITTLE_ENDIAN=0"
 fi
 rm -f core *.core core.conftest.* gmon.out bb.out conftest$ac_exeext \
@@ -2719,13 +2844,13 @@ then
   OPENMP_CXXFLAGS="-Xpreprocessor -fopenmp -I${HOMEBREW_LIBOMP_PREFIX}/include"
   OPENMP_LIB="-lomp -L${HOMEBREW_LIBOMP_PREFIX}/lib"
   ac_pkg_openmp=no
-  { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether OpenMP will work in a package" >&5
-$as_echo_n "checking whether OpenMP will work in a package... " >&6; }
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking whether OpenMP will work in a package" >&5
+printf %s "checking whether OpenMP will work in a package... " >&6; }
   cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 #include <omp.h>
 int
-main ()
+main (void)
 {
  return (omp_get_max_threads() <= 1);
   ;
@@ -2733,8 +2858,8 @@ main ()
 }
 _ACEOF
   ${CC} -o conftest conftest.c ${CPPFLAGS} ${LDFLAGS} ${OPENMP_LIB} ${OPENMP_CXXFLAGS} 2>/dev/null && ./conftest && ac_pkg_openmp=yes
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: ${ac_pkg_openmp}" >&5
-$as_echo "${ac_pkg_openmp}" >&6; }
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: ${ac_pkg_openmp}" >&5
+printf "%s\n" "${ac_pkg_openmp}" >&6; }
   if test "${ac_pkg_openmp}" = no; then
     OPENMP_CXXFLAGS=''
     OPENMP_LIB=''
@@ -2779,8 +2904,8 @@ _ACEOF
     case $ac_val in #(
     *${as_nl}*)
       case $ac_var in #(
-      *_cv_*) { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: cache variable $ac_var contains a newline" >&5
-$as_echo "$as_me: WARNING: cache variable $ac_var contains a newline" >&2;} ;;
+      *_cv_*) { printf "%s\n" "$as_me:${as_lineno-$LINENO}: WARNING: cache variable $ac_var contains a newline" >&5
+printf "%s\n" "$as_me: WARNING: cache variable $ac_var contains a newline" >&2;} ;;
       esac
       case $ac_var in #(
       _ | IFS | as_nl) ;; #(
@@ -2810,15 +2935,15 @@ $as_echo "$as_me: WARNING: cache variable $ac_var contains a newline" >&2;} ;;
      /^ac_cv_env_/b end
      t clear
      :clear
-     s/^\([^=]*\)=\(.*[{}].*\)$/test "${\1+set}" = set || &/
+     s/^\([^=]*\)=\(.*[{}].*\)$/test ${\1+y} || &/
      t end
      s/^\([^=]*\)=\(.*\)$/\1=${\1=\2}/
      :end' >>confcache
 if diff "$cache_file" confcache >/dev/null 2>&1; then :; else
   if test -w "$cache_file"; then
     if test "x$cache_file" != "x/dev/null"; then
-      { $as_echo "$as_me:${as_lineno-$LINENO}: updating cache $cache_file" >&5
-$as_echo "$as_me: updating cache $cache_file" >&6;}
+      { printf "%s\n" "$as_me:${as_lineno-$LINENO}: updating cache $cache_file" >&5
+printf "%s\n" "$as_me: updating cache $cache_file" >&6;}
       if test ! -f "$cache_file" || test -h "$cache_file"; then
 	cat confcache >"$cache_file"
       else
@@ -2832,8 +2957,8 @@ $as_echo "$as_me: updating cache $cache_file" >&6;}
       fi
     fi
   else
-    { $as_echo "$as_me:${as_lineno-$LINENO}: not updating unwritable cache $cache_file" >&5
-$as_echo "$as_me: not updating unwritable cache $cache_file" >&6;}
+    { printf "%s\n" "$as_me:${as_lineno-$LINENO}: not updating unwritable cache $cache_file" >&5
+printf "%s\n" "$as_me: not updating unwritable cache $cache_file" >&6;}
   fi
 fi
 rm -f confcache
@@ -2886,7 +3011,7 @@ U=
 for ac_i in : $LIBOBJS; do test "x$ac_i" = x: && continue
   # 1. Remove the extension, and $U if already installed.
   ac_script='s/\$U\././;s/\.o$//;s/\.obj$//'
-  ac_i=`$as_echo "$ac_i" | sed "$ac_script"`
+  ac_i=`printf "%s\n" "$ac_i" | sed "$ac_script"`
   # 2. Prepend LIBOBJDIR.  When used with automake>=1.10 LIBOBJDIR
   #    will be set to the directory where LIBOBJS objects are built.
   as_fn_append ac_libobjs " \${LIBOBJDIR}$ac_i\$U.$ac_objext"
@@ -2902,8 +3027,8 @@ LTLIBOBJS=$ac_ltlibobjs
 ac_write_fail=0
 ac_clean_files_save=$ac_clean_files
 ac_clean_files="$ac_clean_files $CONFIG_STATUS"
-{ $as_echo "$as_me:${as_lineno-$LINENO}: creating $CONFIG_STATUS" >&5
-$as_echo "$as_me: creating $CONFIG_STATUS" >&6;}
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: creating $CONFIG_STATUS" >&5
+printf "%s\n" "$as_me: creating $CONFIG_STATUS" >&6;}
 as_write_fail=0
 cat >$CONFIG_STATUS <<_ASEOF || as_write_fail=1
 #! $SHELL
@@ -2926,14 +3051,16 @@ cat >>$CONFIG_STATUS <<\_ASEOF || as_write_fail=1
 
 # Be more Bourne compatible
 DUALCASE=1; export DUALCASE # for MKS sh
-if test -n "${ZSH_VERSION+set}" && (emulate sh) >/dev/null 2>&1; then :
+as_nop=:
+if test ${ZSH_VERSION+y} && (emulate sh) >/dev/null 2>&1
+then :
   emulate sh
   NULLCMD=:
   # Pre-4.2 versions of Zsh do word splitting on ${1+"$@"}, which
   # is contrary to our usage.  Disable this feature.
   alias -g '${1+"$@"}'='"$@"'
   setopt NO_GLOB_SUBST
-else
+else $as_nop
   case `(set -o) 2>/dev/null` in #(
   *posix*) :
     set -o posix ;; #(
@@ -2943,46 +3070,46 @@ esac
 fi
 
 
+
+# Reset variables that may have inherited troublesome values from
+# the environment.
+
+# IFS needs to be set, to space, tab, and newline, in precisely that order.
+# (If _AS_PATH_WALK were called with IFS unset, it would have the
+# side effect of setting IFS to empty, thus disabling word splitting.)
+# Quoting is to prevent editors from complaining about space-tab.
 as_nl='
 '
 export as_nl
-# Printing a long string crashes Solaris 7 /usr/bin/printf.
-as_echo='\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\'
-as_echo=$as_echo$as_echo$as_echo$as_echo$as_echo
-as_echo=$as_echo$as_echo$as_echo$as_echo$as_echo$as_echo
-# Prefer a ksh shell builtin over an external printf program on Solaris,
-# but without wasting forks for bash or zsh.
-if test -z "$BASH_VERSION$ZSH_VERSION" \
-    && (test "X`print -r -- $as_echo`" = "X$as_echo") 2>/dev/null; then
-  as_echo='print -r --'
-  as_echo_n='print -rn --'
-elif (test "X`printf %s $as_echo`" = "X$as_echo") 2>/dev/null; then
-  as_echo='printf %s\n'
-  as_echo_n='printf %s'
-else
-  if test "X`(/usr/ucb/echo -n -n $as_echo) 2>/dev/null`" = "X-n $as_echo"; then
-    as_echo_body='eval /usr/ucb/echo -n "$1$as_nl"'
-    as_echo_n='/usr/ucb/echo -n'
-  else
-    as_echo_body='eval expr "X$1" : "X\\(.*\\)"'
-    as_echo_n_body='eval
-      arg=$1;
-      case $arg in #(
-      *"$as_nl"*)
-	expr "X$arg" : "X\\(.*\\)$as_nl";
-	arg=`expr "X$arg" : ".*$as_nl\\(.*\\)"`;;
-      esac;
-      expr "X$arg" : "X\\(.*\\)" | tr -d "$as_nl"
-    '
-    export as_echo_n_body
-    as_echo_n='sh -c $as_echo_n_body as_echo'
-  fi
-  export as_echo_body
-  as_echo='sh -c $as_echo_body as_echo'
-fi
+IFS=" ""	$as_nl"
+
+PS1='$ '
+PS2='> '
+PS4='+ '
+
+# Ensure predictable behavior from utilities with locale-dependent output.
+LC_ALL=C
+export LC_ALL
+LANGUAGE=C
+export LANGUAGE
+
+# We cannot yet rely on "unset" to work, but we need these variables
+# to be unset--not just set to an empty or harmless value--now, to
+# avoid bugs in old shells (e.g. pre-3.0 UWIN ksh).  This construct
+# also avoids known problems related to "unset" and subshell syntax
+# in other old shells (e.g. bash 2.01 and pdksh 5.2.14).
+for as_var in BASH_ENV ENV MAIL MAILPATH CDPATH
+do eval test \${$as_var+y} \
+  && ( (unset $as_var) || exit 1) >/dev/null 2>&1 && unset $as_var || :
+done
+
+# Ensure that fds 0, 1, and 2 are open.
+if (exec 3>&0) 2>/dev/null; then :; else exec 0</dev/null; fi
+if (exec 3>&1) 2>/dev/null; then :; else exec 1>/dev/null; fi
+if (exec 3>&2)            ; then :; else exec 2>/dev/null; fi
 
 # The user is always right.
-if test "${PATH_SEPARATOR+set}" != set; then
+if ${PATH_SEPARATOR+false} :; then
   PATH_SEPARATOR=:
   (PATH='/bin;/bin'; FPATH=$PATH; sh -c :) >/dev/null 2>&1 && {
     (PATH='/bin:/bin'; FPATH=$PATH; sh -c :) >/dev/null 2>&1 ||
@@ -2991,13 +3118,6 @@ if test "${PATH_SEPARATOR+set}" != set; then
 fi
 
 
-# IFS
-# We need space, tab and new line, in precisely that order.  Quoting is
-# there to prevent editors from complaining about space-tab.
-# (If _AS_PATH_WALK were called with IFS unset, it would disable word
-# splitting by setting IFS to empty value.)
-IFS=" ""	$as_nl"
-
 # Find who we are.  Look in the path if we contain no directory separator.
 as_myself=
 case $0 in #((
@@ -3006,8 +3126,12 @@ case $0 in #((
 for as_dir in $PATH
 do
   IFS=$as_save_IFS
-  test -z "$as_dir" && as_dir=.
-    test -r "$as_dir/$0" && as_myself=$as_dir/$0 && break
+  case $as_dir in #(((
+    '') as_dir=./ ;;
+    */) ;;
+    *) as_dir=$as_dir/ ;;
+  esac
+    test -r "$as_dir$0" && as_myself=$as_dir$0 && break
   done
 IFS=$as_save_IFS
 
@@ -3019,30 +3143,10 @@ if test "x$as_myself" = x; then
   as_myself=$0
 fi
 if test ! -f "$as_myself"; then
-  $as_echo "$as_myself: error: cannot find myself; rerun with an absolute file name" >&2
+  printf "%s\n" "$as_myself: error: cannot find myself; rerun with an absolute file name" >&2
   exit 1
 fi
 
-# Unset variables that we do not need and which cause bugs (e.g. in
-# pre-3.0 UWIN ksh).  But do not cause bugs in bash 2.01; the "|| exit 1"
-# suppresses any "Segmentation fault" message there.  '((' could
-# trigger a bug in pdksh 5.2.14.
-for as_var in BASH_ENV ENV MAIL MAILPATH
-do eval test x\${$as_var+set} = xset \
-  && ( (unset $as_var) || exit 1) >/dev/null 2>&1 && unset $as_var || :
-done
-PS1='$ '
-PS2='> '
-PS4='+ '
-
-# NLS nuisances.
-LC_ALL=C
-export LC_ALL
-LANGUAGE=C
-export LANGUAGE
-
-# CDPATH.
-(unset CDPATH) >/dev/null 2>&1 && unset CDPATH
 
 
 # as_fn_error STATUS ERROR [LINENO LOG_FD]
@@ -3055,13 +3159,14 @@ as_fn_error ()
   as_status=$1; test $as_status -eq 0 && as_status=1
   if test "$4"; then
     as_lineno=${as_lineno-"$3"} as_lineno_stack=as_lineno_stack=$as_lineno_stack
-    $as_echo "$as_me:${as_lineno-$LINENO}: error: $2" >&$4
+    printf "%s\n" "$as_me:${as_lineno-$LINENO}: error: $2" >&$4
   fi
-  $as_echo "$as_me: error: $2" >&2
+  printf "%s\n" "$as_me: error: $2" >&2
   as_fn_exit $as_status
 } # as_fn_error
 
 
+
 # as_fn_set_status STATUS
 # -----------------------
 # Set $? to STATUS, without forking.
@@ -3088,18 +3193,20 @@ as_fn_unset ()
   { eval $1=; unset $1;}
 }
 as_unset=as_fn_unset
+
 # as_fn_append VAR VALUE
 # ----------------------
 # Append the text in VALUE to the end of the definition contained in VAR. Take
 # advantage of any shell optimizations that allow amortized linear growth over
 # repeated appends, instead of the typical quadratic growth present in naive
 # implementations.
-if (eval "as_var=1; as_var+=2; test x\$as_var = x12") 2>/dev/null; then :
+if (eval "as_var=1; as_var+=2; test x\$as_var = x12") 2>/dev/null
+then :
   eval 'as_fn_append ()
   {
     eval $1+=\$2
   }'
-else
+else $as_nop
   as_fn_append ()
   {
     eval $1=\$$1\$2
@@ -3111,12 +3218,13 @@ fi # as_fn_append
 # Perform arithmetic evaluation on the ARGs, and store the result in the
 # global $as_val. Take advantage of shells that can avoid forks. The arguments
 # must be portable across $(()) and expr.
-if (eval "test \$(( 1 + 1 )) = 2") 2>/dev/null; then :
+if (eval "test \$(( 1 + 1 )) = 2") 2>/dev/null
+then :
   eval 'as_fn_arith ()
   {
     as_val=$(( $* ))
   }'
-else
+else $as_nop
   as_fn_arith ()
   {
     as_val=`expr "$@" || test $? -eq 1`
@@ -3147,7 +3255,7 @@ as_me=`$as_basename -- "$0" ||
 $as_expr X/"$0" : '.*/\([^/][^/]*\)/*$' \| \
 	 X"$0" : 'X\(//\)$' \| \
 	 X"$0" : 'X\(/\)' \| . 2>/dev/null ||
-$as_echo X/"$0" |
+printf "%s\n" X/"$0" |
     sed '/^.*\/\([^/][^/]*\)\/*$/{
 	    s//\1/
 	    q
@@ -3169,6 +3277,10 @@ as_cr_Letters=$as_cr_letters$as_cr_LETTERS
 as_cr_digits='0123456789'
 as_cr_alnum=$as_cr_Letters$as_cr_digits
 
+
+# Determine whether it's possible to make 'echo' print without a newline.
+# These variables are no longer used directly by Autoconf, but are AC_SUBSTed
+# for compatibility with existing Makefiles.
 ECHO_C= ECHO_N= ECHO_T=
 case `echo -n x` in #(((((
 -n*)
@@ -3182,6 +3294,12 @@ case `echo -n x` in #(((((
   ECHO_N='-n';;
 esac
 
+# For backward compatibility with old third-party macros, we provide
+# the shell variables $as_echo and $as_echo_n.  New code should use
+# AS_ECHO(["message"]) and AS_ECHO_N(["message"]), respectively.
+as_echo='printf %s\n'
+as_echo_n='printf %s'
+
 rm -f conf$$ conf$$.exe conf$$.file
 if test -d conf$$.dir; then
   rm -f conf$$.dir/conf$$.file
@@ -3223,7 +3341,7 @@ as_fn_mkdir_p ()
     as_dirs=
     while :; do
       case $as_dir in #(
-      *\'*) as_qdir=`$as_echo "$as_dir" | sed "s/'/'\\\\\\\\''/g"`;; #'(
+      *\'*) as_qdir=`printf "%s\n" "$as_dir" | sed "s/'/'\\\\\\\\''/g"`;; #'(
       *) as_qdir=$as_dir;;
       esac
       as_dirs="'$as_qdir' $as_dirs"
@@ -3232,7 +3350,7 @@ $as_expr X"$as_dir" : 'X\(.*[^/]\)//*[^/][^/]*/*$' \| \
 	 X"$as_dir" : 'X\(//\)[^/]' \| \
 	 X"$as_dir" : 'X\(//\)$' \| \
 	 X"$as_dir" : 'X\(/\)' \| . 2>/dev/null ||
-$as_echo X"$as_dir" |
+printf "%s\n" X"$as_dir" |
     sed '/^X\(.*[^/]\)\/\/*[^/][^/]*\/*$/{
 	    s//\1/
 	    q
@@ -3295,7 +3413,7 @@ cat >>$CONFIG_STATUS <<\_ACEOF || ac_write_fail=1
 # values after options handling.
 ac_log="
 This file was extended by xgboost $as_me 1.7.3, which was
-generated by GNU Autoconf 2.69.  Invocation command line was
+generated by GNU Autoconf 2.71.  Invocation command line was
 
   CONFIG_FILES    = $CONFIG_FILES
   CONFIG_HEADERS  = $CONFIG_HEADERS
@@ -3344,14 +3462,16 @@ $config_files
 Report bugs to the package provider."
 
 _ACEOF
+ac_cs_config=`printf "%s\n" "$ac_configure_args" | sed "$ac_safe_unquote"`
+ac_cs_config_escaped=`printf "%s\n" "$ac_cs_config" | sed "s/^ //; s/'/'\\\\\\\\''/g"`
 cat >>$CONFIG_STATUS <<_ACEOF || ac_write_fail=1
-ac_cs_config="`$as_echo "$ac_configure_args" | sed 's/^ //; s/[\\""\`\$]/\\\\&/g'`"
+ac_cs_config='$ac_cs_config_escaped'
 ac_cs_version="\\
 xgboost config.status 1.7.3
-configured by $0, generated by GNU Autoconf 2.69,
+configured by $0, generated by GNU Autoconf 2.71,
   with options \\"\$ac_cs_config\\"
 
-Copyright (C) 2012 Free Software Foundation, Inc.
+Copyright (C) 2021 Free Software Foundation, Inc.
 This config.status script is free software; the Free Software Foundation
 gives unlimited permission to copy, distribute and modify it."
 
@@ -3388,21 +3508,21 @@ do
   -recheck | --recheck | --rechec | --reche | --rech | --rec | --re | --r)
     ac_cs_recheck=: ;;
   --version | --versio | --versi | --vers | --ver | --ve | --v | -V )
-    $as_echo "$ac_cs_version"; exit ;;
+    printf "%s\n" "$ac_cs_version"; exit ;;
   --config | --confi | --conf | --con | --co | --c )
-    $as_echo "$ac_cs_config"; exit ;;
+    printf "%s\n" "$ac_cs_config"; exit ;;
   --debug | --debu | --deb | --de | --d | -d )
     debug=: ;;
   --file | --fil | --fi | --f )
     $ac_shift
     case $ac_optarg in
-    *\'*) ac_optarg=`$as_echo "$ac_optarg" | sed "s/'/'\\\\\\\\''/g"` ;;
+    *\'*) ac_optarg=`printf "%s\n" "$ac_optarg" | sed "s/'/'\\\\\\\\''/g"` ;;
     '') as_fn_error $? "missing file argument" ;;
     esac
     as_fn_append CONFIG_FILES " '$ac_optarg'"
     ac_need_defaults=false;;
   --he | --h |  --help | --hel | -h )
-    $as_echo "$ac_cs_usage"; exit ;;
+    printf "%s\n" "$ac_cs_usage"; exit ;;
   -q | -quiet | --quiet | --quie | --qui | --qu | --q \
   | -silent | --silent | --silen | --sile | --sil | --si | --s)
     ac_cs_silent=: ;;
@@ -3430,7 +3550,7 @@ cat >>$CONFIG_STATUS <<_ACEOF || ac_write_fail=1
 if \$ac_cs_recheck; then
   set X $SHELL '$0' $ac_configure_args \$ac_configure_extra_args --no-create --no-recursion
   shift
-  \$as_echo "running CONFIG_SHELL=$SHELL \$*" >&6
+  \printf "%s\n" "running CONFIG_SHELL=$SHELL \$*" >&6
   CONFIG_SHELL='$SHELL'
   export CONFIG_SHELL
   exec "\$@"
@@ -3444,7 +3564,7 @@ exec 5>>config.log
   sed 'h;s/./-/g;s/^.../## /;s/...$/ ##/;p;x;p;x' <<_ASBOX
 ## Running $as_me. ##
 _ASBOX
-  $as_echo "$ac_log"
+  printf "%s\n" "$ac_log"
 } >&5
 
 _ACEOF
@@ -3469,7 +3589,7 @@ done
 # We use the long form for the default assignment because of an extremely
 # bizarre bug on SunOS 4.1.3.
 if $ac_need_defaults; then
-  test "${CONFIG_FILES+set}" = set || CONFIG_FILES=$config_files
+  test ${CONFIG_FILES+y} || CONFIG_FILES=$config_files
 fi
 
 # Have a temporary directory for convenience.  Make it in the build tree
@@ -3697,7 +3817,7 @@ do
 	   esac ||
 	   as_fn_error 1 "cannot find input file: \`$ac_f'" "$LINENO" 5;;
       esac
-      case $ac_f in *\'*) ac_f=`$as_echo "$ac_f" | sed "s/'/'\\\\\\\\''/g"`;; esac
+      case $ac_f in *\'*) ac_f=`printf "%s\n" "$ac_f" | sed "s/'/'\\\\\\\\''/g"`;; esac
       as_fn_append ac_file_inputs " '$ac_f'"
     done
 
@@ -3705,17 +3825,17 @@ do
     # use $as_me), people would be surprised to read:
     #    /* config.h.  Generated by config.status.  */
     configure_input='Generated from '`
-	  $as_echo "$*" | sed 's|^[^:]*/||;s|:[^:]*/|, |g'
+	  printf "%s\n" "$*" | sed 's|^[^:]*/||;s|:[^:]*/|, |g'
 	`' by configure.'
     if test x"$ac_file" != x-; then
       configure_input="$ac_file.  $configure_input"
-      { $as_echo "$as_me:${as_lineno-$LINENO}: creating $ac_file" >&5
-$as_echo "$as_me: creating $ac_file" >&6;}
+      { printf "%s\n" "$as_me:${as_lineno-$LINENO}: creating $ac_file" >&5
+printf "%s\n" "$as_me: creating $ac_file" >&6;}
     fi
     # Neutralize special characters interpreted by sed in replacement strings.
     case $configure_input in #(
     *\&* | *\|* | *\\* )
-       ac_sed_conf_input=`$as_echo "$configure_input" |
+       ac_sed_conf_input=`printf "%s\n" "$configure_input" |
        sed 's/[\\\\&|]/\\\\&/g'`;; #(
     *) ac_sed_conf_input=$configure_input;;
     esac
@@ -3732,7 +3852,7 @@ $as_expr X"$ac_file" : 'X\(.*[^/]\)//*[^/][^/]*/*$' \| \
 	 X"$ac_file" : 'X\(//\)[^/]' \| \
 	 X"$ac_file" : 'X\(//\)$' \| \
 	 X"$ac_file" : 'X\(/\)' \| . 2>/dev/null ||
-$as_echo X"$ac_file" |
+printf "%s\n" X"$ac_file" |
     sed '/^X\(.*[^/]\)\/\/*[^/][^/]*\/*$/{
 	    s//\1/
 	    q
@@ -3756,9 +3876,9 @@ $as_echo X"$ac_file" |
 case "$ac_dir" in
 .) ac_dir_suffix= ac_top_builddir_sub=. ac_top_build_prefix= ;;
 *)
-  ac_dir_suffix=/`$as_echo "$ac_dir" | sed 's|^\.[\\/]||'`
+  ac_dir_suffix=/`printf "%s\n" "$ac_dir" | sed 's|^\.[\\/]||'`
   # A ".." for each directory in $ac_dir_suffix.
-  ac_top_builddir_sub=`$as_echo "$ac_dir_suffix" | sed 's|/[^\\/]*|/..|g;s|/||'`
+  ac_top_builddir_sub=`printf "%s\n" "$ac_dir_suffix" | sed 's|/[^\\/]*|/..|g;s|/||'`
   case $ac_top_builddir_sub in
   "") ac_top_builddir_sub=. ac_top_build_prefix= ;;
   *)  ac_top_build_prefix=$ac_top_builddir_sub/ ;;
@@ -3811,8 +3931,8 @@ ac_sed_dataroot='
 case `eval "sed -n \"\$ac_sed_dataroot\" $ac_file_inputs"` in
 *datarootdir*) ac_datarootdir_seen=yes;;
 *@datadir@*|*@docdir@*|*@infodir@*|*@localedir@*|*@mandir@*)
-  { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: $ac_file_inputs seems to ignore the --datarootdir setting" >&5
-$as_echo "$as_me: WARNING: $ac_file_inputs seems to ignore the --datarootdir setting" >&2;}
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: WARNING: $ac_file_inputs seems to ignore the --datarootdir setting" >&5
+printf "%s\n" "$as_me: WARNING: $ac_file_inputs seems to ignore the --datarootdir setting" >&2;}
 _ACEOF
 cat >>$CONFIG_STATUS <<_ACEOF || ac_write_fail=1
   ac_datarootdir_hack='
@@ -3854,9 +3974,9 @@ test -z "$ac_datarootdir_hack$ac_datarootdir_seen" &&
   { ac_out=`sed -n '/\${datarootdir}/p' "$ac_tmp/out"`; test -n "$ac_out"; } &&
   { ac_out=`sed -n '/^[	 ]*datarootdir[	 ]*:*=/p' \
       "$ac_tmp/out"`; test -z "$ac_out"; } &&
-  { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: $ac_file contains a reference to the variable \`datarootdir'
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: WARNING: $ac_file contains a reference to the variable \`datarootdir'
 which seems to be undefined.  Please make sure it is defined" >&5
-$as_echo "$as_me: WARNING: $ac_file contains a reference to the variable \`datarootdir'
+printf "%s\n" "$as_me: WARNING: $ac_file contains a reference to the variable \`datarootdir'
 which seems to be undefined.  Please make sure it is defined" >&2;}
 
   rm -f "$ac_tmp/stdin"
@@ -3903,7 +4023,8 @@ if test "$no_create" != yes; then
   $ac_cs_success || as_fn_exit 1
 fi
 if test -n "$ac_unrecognized_opts" && test "$enable_option_checking" != no; then
-  { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: unrecognized options: $ac_unrecognized_opts" >&5
-$as_echo "$as_me: WARNING: unrecognized options: $ac_unrecognized_opts" >&2;}
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: WARNING: unrecognized options: $ac_unrecognized_opts" >&5
+printf "%s\n" "$as_me: WARNING: unrecognized options: $ac_unrecognized_opts" >&2;}
 fi
 
+
diff --git a/R-package/configure.ac b/R-package/configure.ac
index e5d2396e2..05a4a28e2 100644
--- a/R-package/configure.ac
+++ b/R-package/configure.ac
@@ -4,8 +4,23 @@ AC_PREREQ(2.69)
 
 AC_INIT([xgboost],[1.7.3],[],[xgboost],[])
 
-# Use this line to set CC variable to a C compiler
-AC_PROG_CC
+: ${R_HOME=`R RHOME`}
+if test -z "${R_HOME}"; then
+  echo "could not determine R_HOME"
+  exit 1
+fi
+
+CXX14=`"${R_HOME}/bin/R" CMD config CXX14`
+CXX14STD=`"${R_HOME}/bin/R" CMD config CXX14STD`
+CXX="${CXX14} ${CXX14STD}"
+CXXFLAGS=`"${R_HOME}/bin/R" CMD config CXXFLAGS`
+
+CC=`"${R_HOME}/bin/R" CMD config CC`
+CFLAGS=`"${R_HOME}/bin/R" CMD config CFLAGS`
+CPPFLAGS=`"${R_HOME}/bin/R" CMD config CPPFLAGS`
+
+LDFLAGS=`"${R_HOME}/bin/R" CMD config LDFLAGS`
+AC_LANG(C++)
 
 ### Check whether backtrace() is part of libc or the external lib libexecinfo
 AC_MSG_CHECKING([Backtrace lib])