Build with C11 if available

* admin/merge-gnulib (GNULIB_MODULES): Add std-gnu11.
* m4/std-gnu11.m4: New file, from gnulib.
* lib/gnulib.mk, m4/gnulib-comp.m4: Regenerate.

4 files changed, 822 insertions, 2 deletions

diff --git a/admin/merge-gnulib b/admin/merge-gnulib
index 40b5b78ee8..5463d1b667 100755
--- a/admin/merge-gnulib
+++ b/admin/merge-gnulib
@@ -35,7 +35,7 @@ GNULIB_MODULES='
   ignore-value intprops largefile lstat
   manywarnings memrchr mkostemp mktime
   pipe2 pselect pthread_sigmask putenv qcopy-acl readlink readlinkat
-  sig2str socklen stat-time stdalign stddef stdio
+  sig2str socklen stat-time std-gnu11 stdalign stddef stdio
   stpcpy strftime strtoimax strtoumax symlink sys_stat
   sys_time time time_r time_rz timegm timer-time timespec-add timespec-sub
   unsetenv update-copyright utimens
diff --git a/lib/gnulib.mk b/lib/gnulib.mk
index b920cbbc9b..b1edd86f92 100644
--- a/lib/gnulib.mk
+++ b/lib/gnulib.mk
@@ -21,7 +21,7 @@
 # the same distribution terms as the rest of that program.
 #
 # Generated by gnulib-tool.
-# Reproduce by: gnulib-tool --import --lib=libgnu --source-base=lib --m4-base=m4 --doc-base=doc --tests-base=tests --aux-dir=build-aux --avoid=close --avoid=dup --avoid=fchdir --avoid=flexmember --avoid=fstat --avoid=malloc-posix --avoid=msvc-inval --avoid=msvc-nothrow --avoid=open --avoid=openat-die --avoid=opendir --avoid=raise --avoid=save-cwd --avoid=select --avoid=setenv --avoid=sigprocmask --avoid=stdarg --avoid=stdbool --avoid=threadlib --avoid=unsetenv --makefile-name=gnulib.mk --conditional-dependencies --no-libtool --macro-prefix=gl --no-vc-files alloca-opt binary-io byteswap c-ctype c-strcase careadlinkat close-stream count-one-bits count-trailing-zeros crypto/md5 crypto/sha1 crypto/sha256 crypto/sha512 dtoastr dtotimespec dup2 environ execinfo faccessat fcntl fcntl-h fdatasync fdopendir filemode fstatat fsync getloadavg getopt-gnu gettime gettimeofday gitlog-to-changelog ignore-value intprops largefile lstat manywarnings memrchr mkostemp mktime pipe2 pselect pthread_sigmask putenv qcopy-acl readlink readlinkat sig2str socklen stat-time stdalign stddef stdio stpcpy strftime strtoimax strtoumax symlink sys_stat sys_time time time_r time_rz timegm timer-time timespec-add timespec-sub unsetenv update-copyright utimens vla warnings
+# Reproduce by: gnulib-tool --import --lib=libgnu --source-base=lib --m4-base=m4 --doc-base=doc --tests-base=tests --aux-dir=build-aux --avoid=close --avoid=dup --avoid=fchdir --avoid=flexmember --avoid=fstat --avoid=malloc-posix --avoid=msvc-inval --avoid=msvc-nothrow --avoid=open --avoid=openat-die --avoid=opendir --avoid=raise --avoid=save-cwd --avoid=select --avoid=setenv --avoid=sigprocmask --avoid=stdarg --avoid=stdbool --avoid=threadlib --avoid=unsetenv --makefile-name=gnulib.mk --conditional-dependencies --no-libtool --macro-prefix=gl --no-vc-files alloca-opt binary-io byteswap c-ctype c-strcase careadlinkat close-stream count-one-bits count-trailing-zeros crypto/md5 crypto/sha1 crypto/sha256 crypto/sha512 dtoastr dtotimespec dup2 environ execinfo faccessat fcntl fcntl-h fdatasync fdopendir filemode fstatat fsync getloadavg getopt-gnu gettime gettimeofday gitlog-to-changelog ignore-value intprops largefile lstat manywarnings memrchr mkostemp mktime pipe2 pselect pthread_sigmask putenv qcopy-acl readlink readlinkat sig2str socklen stat-time std-gnu11 stdalign stddef stdio stpcpy strftime strtoimax strtoumax symlink sys_stat sys_time time time_r time_rz timegm timer-time timespec-add timespec-sub unsetenv update-copyright utimens vla warnings
 
 
 MOSTLYCLEANFILES += core *.stackdump
diff --git a/m4/gnulib-comp.m4 b/m4/gnulib-comp.m4
index 547af6641a..831bb4c4f4 100644
--- a/m4/gnulib-comp.m4
+++ b/m4/gnulib-comp.m4
@@ -126,6 +126,7 @@ AC_DEFUN([gl_EARLY],
   # Code from module ssize_t:
   # Code from module stat:
   # Code from module stat-time:
+  # Code from module std-gnu11:
   # Code from module stdalign:
   # Code from module stddef:
   # Code from module stdint:
@@ -1052,6 +1053,7 @@ AC_DEFUN([gl_FILE_LIST], [
   m4/st_dm_mode.m4
   m4/stat-time.m4
   m4/stat.m4
+  m4/std-gnu11.m4
   m4/stdalign.m4
   m4/stddef_h.m4
   m4/stdint.m4
diff --git a/m4/std-gnu11.m4 b/m4/std-gnu11.m4
new file mode 100644
index 0000000000..a687cdbba1
--- /dev/null
+++ b/m4/std-gnu11.m4
@@ -0,0 +1,818 @@
+# Prefer GNU C11 and C++11 to earlier versions.  -*- coding: utf-8 -*-
+
+# This implementation is taken from GNU Autoconf lib/autoconf/c.m4
+# commit 5ad3567c3cbd90b4faa6539c35bc4a8c6500f535
+# dated 2015-10-08 10:12:41 2015 +0200.
+# This implementation will be obsolete once we can assume Autoconf 2.70
+# or later is installed everywhere a Gnulib program might be developed.
+
+
+# Copyright (C) 2001-2016 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Written by David MacKenzie, with help from
+# Akim Demaille, Paul Eggert,
+# François Pinard, Karl Berry, Richard Pixley, Ian Lance Taylor,
+# Roland McGrath, Noah Friedman, david d zuhn, and many others.
+
+
+# AC_PROG_CC([COMPILER ...])
+# --------------------------
+# COMPILER ... is a space separated list of C compilers to search for.
+# This just gives the user an opportunity to specify an alternative
+# search list for the C compiler.
+AC_DEFUN_ONCE([AC_PROG_CC],
+[AC_LANG_PUSH(C)dnl
+AC_ARG_VAR([CC],     [C compiler command])dnl
+AC_ARG_VAR([CFLAGS], [C compiler flags])dnl
+_AC_ARG_VAR_LDFLAGS()dnl
+_AC_ARG_VAR_LIBS()dnl
+_AC_ARG_VAR_CPPFLAGS()dnl
+m4_ifval([$1],
+      [AC_CHECK_TOOLS(CC, [$1])],
+[AC_CHECK_TOOL(CC, gcc)
+if test -z "$CC"; then
+  dnl Here we want:
+  dnl	AC_CHECK_TOOL(CC, cc)
+  dnl but without the check for a tool without the prefix.
+  dnl Until the check is removed from there, copy the code:
+  if test -n "$ac_tool_prefix"; then
+    AC_CHECK_PROG(CC, [${ac_tool_prefix}cc], [${ac_tool_prefix}cc])
+  fi
+fi
+if test -z "$CC"; then
+  AC_CHECK_PROG(CC, cc, cc, , , /usr/ucb/cc)
+fi
+if test -z "$CC"; then
+  AC_CHECK_TOOLS(CC, cl.exe)
+fi
+])
+
+test -z "$CC" && AC_MSG_FAILURE([no acceptable C compiler found in \$PATH])
+
+# Provide some information about the compiler.
+_AS_ECHO_LOG([checking for _AC_LANG compiler version])
+set X $ac_compile
+ac_compiler=$[2]
+for ac_option in --version -v -V -qversion -version; do
+  _AC_DO_LIMIT([$ac_compiler $ac_option >&AS_MESSAGE_LOG_FD])
+done
+
+m4_expand_once([_AC_COMPILER_EXEEXT])[]dnl
+m4_expand_once([_AC_COMPILER_OBJEXT])[]dnl
+_AC_LANG_COMPILER_GNU
+if test $ac_compiler_gnu = yes; then
+  GCC=yes
+else
+  GCC=
+fi
+_AC_PROG_CC_G
+dnl
+dnl Set ac_prog_cc_stdc to the supported C version.
+dnl Also set the documented variable ac_cv_prog_cc_stdc;
+dnl its name was chosen when it was cached, but it is no longer cached.
+_AC_PROG_CC_C11([ac_prog_cc_stdc=c11
+		 ac_cv_prog_cc_stdc=$ac_cv_prog_cc_c11],
+  [_AC_PROG_CC_C99([ac_prog_cc_stdc=c99
+		    ac_cv_prog_cc_stdc=$ac_cv_prog_cc_c99],
+     [_AC_PROG_CC_C89([ac_prog_cc_stdc=c89
+		       ac_cv_prog_cc_stdc=$ac_cv_prog_cc_c89],
+		      [ac_prog_cc_stdc=no
+		       ac_cv_prog_cc_stdc=no])])])
+dnl
+AC_LANG_POP(C)dnl
+])# AC_PROG_CC
+
+
+
+# AC_PROG_CXX([LIST-OF-COMPILERS])
+# --------------------------------
+# LIST-OF-COMPILERS is a space separated list of C++ compilers to search
+# for (if not specified, a default list is used).  This just gives the
+# user an opportunity to specify an alternative search list for the C++
+# compiler.
+# aCC	HP-UX C++ compiler much better than `CC', so test before.
+# FCC   Fujitsu C++ compiler
+# KCC	KAI C++ compiler
+# RCC	Rational C++
+# xlC_r	AIX C Set++ (with support for reentrant code)
+# xlC	AIX C Set++
+AC_DEFUN([AC_PROG_CXX],
+[AC_LANG_PUSH(C++)dnl
+AC_ARG_VAR([CXX],      [C++ compiler command])dnl
+AC_ARG_VAR([CXXFLAGS], [C++ compiler flags])dnl
+_AC_ARG_VAR_LDFLAGS()dnl
+_AC_ARG_VAR_LIBS()dnl
+_AC_ARG_VAR_CPPFLAGS()dnl
+_AC_ARG_VAR_PRECIOUS([CCC])dnl
+if test -z "$CXX"; then
+  if test -n "$CCC"; then
+    CXX=$CCC
+  else
+    AC_CHECK_TOOLS(CXX,
+		   [m4_default([$1],
+			       [g++ c++ gpp aCC CC cxx cc++ cl.exe FCC KCC RCC xlC_r xlC])],
+		   g++)
+  fi
+fi
+# Provide some information about the compiler.
+_AS_ECHO_LOG([checking for _AC_LANG compiler version])
+set X $ac_compile
+ac_compiler=$[2]
+for ac_option in --version -v -V -qversion; do
+  _AC_DO_LIMIT([$ac_compiler $ac_option >&AS_MESSAGE_LOG_FD])
+done
+
+m4_expand_once([_AC_COMPILER_EXEEXT])[]dnl
+m4_expand_once([_AC_COMPILER_OBJEXT])[]dnl
+_AC_LANG_COMPILER_GNU
+if test $ac_compiler_gnu = yes; then
+  GXX=yes
+else
+  GXX=
+fi
+_AC_PROG_CXX_G
+_AC_PROG_CXX_CXX11([ac_prog_cxx_stdcxx=cxx11
+		    ac_cv_prog_cxx_stdcxx=$ac_cv_prog_cxx_cxx11
+		    ac_cv_prog_cxx_cxx98=$ac_cv_prog_cxx_cxx11],
+   [_AC_PROG_CXX_CXX98([ac_prog_cxx_stdcxx=cxx98
+		        ac_cv_prog_cxx_stdcxx=$ac_cv_prog_cxx_cxx98],
+		       [ac_prog_cxx_stdcxx=no
+		        ac_cv_prog_cxx_stdcxx=no])])
+AC_LANG_POP(C++)dnl
+])# AC_PROG_CXX
+
+
+# _AC_C_STD_TRY(STANDARD, TEST-PROLOGUE, TEST-BODY, OPTION-LIST,
+#		ACTION-IF-AVAILABLE, ACTION-IF-UNAVAILABLE)
+# --------------------------------------------------------------
+# Check whether the C compiler accepts features of STANDARD (e.g `c89', `c99')
+# by trying to compile a program of TEST-PROLOGUE and TEST-BODY.  If this fails,
+# try again with each compiler option in the space-separated OPTION-LIST; if one
+# helps, append it to CC.  If eventually successful, run ACTION-IF-AVAILABLE,
+# else ACTION-IF-UNAVAILABLE.
+AC_DEFUN([_AC_C_STD_TRY],
+[AC_MSG_CHECKING([for $CC option to enable ]m4_translit($1, [c], [C])[ features])
+AC_CACHE_VAL(ac_cv_prog_cc_$1,
+[ac_cv_prog_cc_$1=no
+ac_save_CC=$CC
+AC_LANG_CONFTEST([AC_LANG_PROGRAM([$2], [$3])])
+for ac_arg in '' $4
+do
+  CC="$ac_save_CC $ac_arg"
+  _AC_COMPILE_IFELSE([], [ac_cv_prog_cc_$1=$ac_arg])
+  test "x$ac_cv_prog_cc_$1" != "xno" && break
+done
+rm -f conftest.$ac_ext
+CC=$ac_save_CC
+])# AC_CACHE_VAL
+ac_prog_cc_stdc_options=
+case "x$ac_cv_prog_cc_$1" in
+  x)
+    AC_MSG_RESULT([none needed]) ;;
+  xno)
+    AC_MSG_RESULT([unsupported]) ;;
+  *)
+    ac_prog_cc_stdc_options=" $ac_cv_prog_cc_$1"
+    CC=$CC$ac_prog_cc_stdc_options
+    AC_MSG_RESULT([$ac_cv_prog_cc_$1]) ;;
+esac
+AS_IF([test "x$ac_cv_prog_cc_$1" != xno], [$5], [$6])
+])# _AC_C_STD_TRY
+
+# _AC_C_C99_TEST_HEADER
+# ---------------------
+# A C header suitable for testing for C99.
+AC_DEFUN([_AC_C_C99_TEST_HEADER],
+[[#include <stdarg.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <wchar.h>
+#include <stdio.h>
+
+// Check varargs macros.  These examples are taken from C99 6.10.3.5.
+#define debug(...) fprintf (stderr, __VA_ARGS__)
+#define showlist(...) puts (#__VA_ARGS__)
+#define report(test,...) ((test) ? puts (#test) : printf (__VA_ARGS__))
+static void
+test_varargs_macros (void)
+{
+  int x = 1234;
+  int y = 5678;
+  debug ("Flag");
+  debug ("X = %d\n", x);
+  showlist (The first, second, and third items.);
+  report (x>y, "x is %d but y is %d", x, y);
+}
+
+// Check long long types.
+#define BIG64 18446744073709551615ull
+#define BIG32 4294967295ul
+#define BIG_OK (BIG64 / BIG32 == 4294967297ull && BIG64 % BIG32 == 0)
+#if !BIG_OK
+  your preprocessor is broken;
+#endif
+#if BIG_OK
+#else
+  your preprocessor is broken;
+#endif
+static long long int bignum = -9223372036854775807LL;
+static unsigned long long int ubignum = BIG64;
+
+struct incomplete_array
+{
+  int datasize;
+  double data[];
+};
+
+struct named_init {
+  int number;
+  const wchar_t *name;
+  double average;
+};
+
+typedef const char *ccp;
+
+static inline int
+test_restrict (ccp restrict text)
+{
+  // See if C++-style comments work.
+  // Iterate through items via the restricted pointer.
+  // Also check for declarations in for loops.
+  for (unsigned int i = 0; *(text+i) != '\0'; ++i)
+    continue;
+  return 0;
+}
+
+// Check varargs and va_copy.
+static bool
+test_varargs (const char *format, ...)
+{
+  va_list args;
+  va_start (args, format);
+  va_list args_copy;
+  va_copy (args_copy, args);
+
+  const char *str = "";
+  int number = 0;
+  float fnumber = 0;
+
+  while (*format)
+    {
+      switch (*format++)
+	{
+	case 's': // string
+	  str = va_arg (args_copy, const char *);
+	  break;
+	case 'd': // int
+	  number = va_arg (args_copy, int);
+	  break;
+	case 'f': // float
+	  fnumber = va_arg (args_copy, double);
+	  break;
+	default:
+	  break;
+	}
+    }
+  va_end (args_copy);
+  va_end (args);
+
+  return *str && number && fnumber;
+}]])# _AC_C_C99_TEST_HEADER
+
+# _AC_C_C99_TEST_BODY
+# -------------------
+# A C body suitable for testing for C99, assuming the corresponding header.
+AC_DEFUN([_AC_C_C99_TEST_BODY],
+[[
+  // Check bool.
+  _Bool success = false;
+
+  // Check restrict.
+  if (test_restrict ("String literal") == 0)
+    success = true;
+  char *restrict newvar = "Another string";
+
+  // Check varargs.
+  success &= test_varargs ("s, d' f .", "string", 65, 34.234);
+  test_varargs_macros ();
+
+  // Check flexible array members.
+  struct incomplete_array *ia =
+    malloc (sizeof (struct incomplete_array) + (sizeof (double) * 10));
+  ia->datasize = 10;
+  for (int i = 0; i < ia->datasize; ++i)
+    ia->data[i] = i * 1.234;
+
+  // Check named initializers.
+  struct named_init ni = {
+    .number = 34,
+    .name = L"Test wide string",
+    .average = 543.34343,
+  };
+
+  ni.number = 58;
+
+  int dynamic_array[ni.number];
+  dynamic_array[ni.number - 1] = 543;
+
+  // work around unused variable warnings
+  return (!success || bignum == 0LL || ubignum == 0uLL || newvar[0] == 'x'
+	  || dynamic_array[ni.number - 1] != 543);
+]])
+
+# _AC_PROG_CC_C99 ([ACTION-IF-AVAILABLE], [ACTION-IF-UNAVAILABLE])
+# ----------------------------------------------------------------
+# If the C compiler is not in ISO C99 mode by default, try to add an
+# option to output variable CC to make it so.  This macro tries
+# various options that select ISO C99 on some system or another.  It
+# considers the compiler to be in ISO C99 mode if it handles _Bool,
+# // comments, flexible array members, inline, long long int, mixed
+# code and declarations, named initialization of structs, restrict,
+# va_copy, varargs macros, variable declarations in for loops and
+# variable length arrays.
+AC_DEFUN([_AC_PROG_CC_C99],
+[_AC_C_STD_TRY([c99],
+[_AC_C_C99_TEST_HEADER],
+[_AC_C_C99_TEST_BODY],
+dnl Try
+dnl GCC		-std=gnu99 (unused restrictive modes: -std=c99 -std=iso9899:1999)
+dnl IBM XL C	-qlanglvl=extc1x (V12.1; does not pass C11 test)
+dnl IBM XL C	-qlanglvl=extc99
+dnl		(pre-V12.1; unused restrictive mode: -qlanglvl=stdc99)
+dnl HP cc	-AC99
+dnl Intel ICC	-std=c99, -c99 (deprecated)
+dnl IRIX	-c99
+dnl Solaris	-D_STDC_C99=
+dnl		cc's -xc99 option uses linker magic to define the external
+dnl		symbol __xpg4 as if by "int __xpg4 = 1;", which enables C99
+dnl		behavior for C library functions.  This is not wanted here,
+dnl		because it means that a single module compiled with -xc99
+dnl		alters C runtime behavior for the entire program, not for
+dnl		just the module.  Instead, define the (private) symbol
+dnl		_STDC_C99, which suppresses a bogus failure in <stdbool.h>.
+dnl		The resulting compiler passes the test case here, and that's
+dnl		good enough.  For more, please see the thread starting at:
+dnl            http://lists.gnu.org/archive/html/autoconf/2010-12/msg00059.html
+dnl Tru64	-c99
+dnl with extended modes being tried first.
+[[-std=gnu99 -std=c99 -c99 -AC99 -D_STDC_C99= -qlanglvl=extc1x -qlanglvl=extc99]], [$1], [$2])[]dnl
+])# _AC_PROG_CC_C99
+
+
+# _AC_PROG_CC_C11 ([ACTION-IF-AVAILABLE], [ACTION-IF-UNAVAILABLE])
+# ----------------------------------------------------------------
+# If the C compiler is not in ISO C11 mode by default, try to add an
+# option to output variable CC to make it so.  This macro tries
+# various options that select ISO C11 on some system or another.  It
+# considers the compiler to be in ISO C11 mode if it handles _Alignas,
+# _Alignof, _Noreturn, _Static_assert, UTF-8 string literals,
+# duplicate typedefs, and anonymous structures and unions.
+AC_DEFUN([_AC_PROG_CC_C11],
+[_AC_C_STD_TRY([c11],
+[_AC_C_C99_TEST_HEADER[
+// Check _Alignas.
+char _Alignas (double) aligned_as_double;
+char _Alignas (0) no_special_alignment;
+extern char aligned_as_int;
+char _Alignas (0) _Alignas (int) aligned_as_int;
+
+// Check _Alignof.
+enum
+{
+  int_alignment = _Alignof (int),
+  int_array_alignment = _Alignof (int[100]),
+  char_alignment = _Alignof (char)
+};
+_Static_assert (0 < -_Alignof (int), "_Alignof is signed");
+
+// Check _Noreturn.
+int _Noreturn does_not_return (void) { for (;;) continue; }
+
+// Check _Static_assert.
+struct test_static_assert
+{
+  int x;
+  _Static_assert (sizeof (int) <= sizeof (long int),
+                  "_Static_assert does not work in struct");
+  long int y;
+};
+
+// Check UTF-8 literals.
+#define u8 syntax error!
+char const utf8_literal[] = u8"happens to be ASCII" "another string";
+
+// Check duplicate typedefs.
+typedef long *long_ptr;
+typedef long int *long_ptr;
+typedef long_ptr long_ptr;
+
+// Anonymous structures and unions -- taken from C11 6.7.2.1 Example 1.
+struct anonymous
+{
+  union {
+    struct { int i; int j; };
+    struct { int k; long int l; } w;
+  };
+  int m;
+} v1;
+]],
+[_AC_C_C99_TEST_BODY[
+  v1.i = 2;
+  v1.w.k = 5;
+  _Static_assert (&v1.i == &v1.w.k, "Anonymous union alignment botch");
+]],
+dnl Try
+dnl GCC		-std=gnu11 (unused restrictive mode: -std=c11)
+dnl with extended modes being tried first.
+dnl
+dnl Do not try -qlanglvl=extc1x, because IBM XL C V12.1 (the latest version as
+dnl of September 2012) does not pass the C11 test.  For now, try extc1x when
+dnl compiling the C99 test instead, since it enables _Static_assert and
+dnl _Noreturn, which is a win.  If -qlanglvl=extc11 or -qlanglvl=extc1x passes
+dnl the C11 test in some future version of IBM XL C, we'll add it here,
+dnl preferably extc11.
+[[-std=gnu11]], [$1], [$2])[]dnl
+])# _AC_PROG_CC_C11
+
+
+# AC_PROG_CC_C89
+# --------------
+# Do not use AU_ALIAS here and in AC_PROG_CC_C99 and AC_PROG_CC_STDC,
+# as that'd be incompatible with how Automake redefines AC_PROG_CC.  See
+# <http://lists.gnu.org/archive/html/autoconf/2012-10/msg00048.html>.
+AU_DEFUN([AC_PROG_CC_C89],
+  [AC_REQUIRE([AC_PROG_CC])],
+  [$0 is obsolete; use AC_PROG_CC]
+)
+
+# AC_PROG_CC_C99
+# --------------
+AU_DEFUN([AC_PROG_CC_C99],
+  [AC_REQUIRE([AC_PROG_CC])],
+  [$0 is obsolete; use AC_PROG_CC]
+)
+
+# AC_PROG_CC_STDC
+# ---------------
+AU_DEFUN([AC_PROG_CC_STDC],
+  [AC_REQUIRE([AC_PROG_CC])],
+  [$0 is obsolete; use AC_PROG_CC]
+)
+
+
+# AC_C_PROTOTYPES
+# ---------------
+# Check if the C compiler supports prototypes, included if it needs
+# options.
+AC_DEFUN([AC_C_PROTOTYPES],
+[AC_REQUIRE([AC_PROG_CC])dnl
+if test "$ac_prog_cc_stdc" != no; then
+  AC_DEFINE(PROTOTYPES, 1,
+	    [Define to 1 if the C compiler supports function prototypes.])
+  AC_DEFINE(__PROTOTYPES, 1,
+	    [Define like PROTOTYPES; this can be used by system headers.])
+fi
+])# AC_C_PROTOTYPES
+
+
+# _AC_CXX_STD_TRY(STANDARD, TEST-PROLOGUE, TEST-BODY, OPTION-LIST,
+#		  ACTION-IF-AVAILABLE, ACTION-IF-UNAVAILABLE)
+# ----------------------------------------------------------------
+# Check whether the C++ compiler accepts features of STANDARD (e.g
+# `cxx98', `cxx11') by trying to compile a program of TEST-PROLOGUE
+# and TEST-BODY.  If this fails, try again with each compiler option
+# in the space-separated OPTION-LIST; if one helps, append it to CXX.
+# If eventually successful, run ACTION-IF-AVAILABLE, else
+# ACTION-IF-UNAVAILABLE.
+AC_DEFUN([_AC_CXX_STD_TRY],
+[AC_MSG_CHECKING([for $CXX option to enable ]m4_translit(m4_translit($1, [x], [+]), [a-z], [A-Z])[ features])
+AC_LANG_PUSH(C++)dnl
+AC_CACHE_VAL(ac_cv_prog_cxx_$1,
+[ac_cv_prog_cxx_$1=no
+ac_save_CXX=$CXX
+AC_LANG_CONFTEST([AC_LANG_PROGRAM([$2], [$3])])
+for ac_arg in '' $4
+do
+  CXX="$ac_save_CXX $ac_arg"
+  _AC_COMPILE_IFELSE([], [ac_cv_prog_cxx_$1=$ac_arg])
+  test "x$ac_cv_prog_cxx_$1" != "xno" && break
+done
+rm -f conftest.$ac_ext
+CXX=$ac_save_CXX
+])# AC_CACHE_VAL
+ac_prog_cxx_stdcxx_options=
+case "x$ac_cv_prog_cxx_$1" in
+  x)
+    AC_MSG_RESULT([none needed]) ;;
+  xno)
+    AC_MSG_RESULT([unsupported]) ;;
+  *)
+    ac_prog_cxx_stdcxx_options=" $ac_cv_prog_cxx_$1"
+    CXX=$CXX$ac_prog_cxx_stdcxx_options
+    AC_MSG_RESULT([$ac_cv_prog_cxx_$1]) ;;
+esac
+AC_LANG_POP(C++)dnl
+AS_IF([test "x$ac_cv_prog_cxx_$1" != xno], [$5], [$6])
+])# _AC_CXX_STD_TRY
+
+# _AC_CXX_CXX98_TEST_HEADER
+# -------------------------
+# A C++ header suitable for testing for CXX98.
+AC_DEFUN([_AC_CXX_CXX98_TEST_HEADER],
+[[
+#include <algorithm>
+#include <cstdlib>
+#include <fstream>
+#include <iomanip>
+#include <iostream>
+#include <list>
+#include <map>
+#include <set>
+#include <sstream>
+#include <stdexcept>
+#include <string>
+#include <utility>
+#include <vector>
+
+namespace test {
+  typedef std::vector<std::string> string_vec;
+  typedef std::pair<int,bool> map_value;
+  typedef std::map<std::string,map_value> map_type;
+  typedef std::set<int> set_type;
+
+  template<typename T>
+  class printer {
+  public:
+    printer(std::ostringstream& os): os(os) {}
+    void operator() (T elem) { os << elem << std::endl; }
+  private:
+    std::ostringstream& os;
+  };
+}
+]])# _AC_CXX_CXX98_TEST_HEADER
+
+# _AC_CXX_CXX98_TEST_BODY
+# -----------------------
+# A C++ body suitable for testing for CXX98, assuming the corresponding header.
+AC_DEFUN([_AC_CXX_CXX98_TEST_BODY],
+[[
+
+try {
+  // Basic string.
+  std::string teststr("ASCII text");
+  teststr += " string";
+
+  // Simple vector.
+  test::string_vec testvec;
+  testvec.push_back(teststr);
+  testvec.push_back("foo");
+  testvec.push_back("bar");
+  if (testvec.size() != 3) {
+    throw std::runtime_error("vector size is not 1");
+  }
+
+  // Dump vector into stringstream and obtain string.
+  std::ostringstream os;
+  for (test::string_vec::const_iterator i = testvec.begin();
+       i != testvec.end(); ++i) {
+    if (i + 1 != testvec.end()) {
+      os << teststr << '\n';
+    }
+  }
+  // Check algorithms work.
+  std::for_each(testvec.begin(), testvec.end(), test::printer<std::string>(os));
+  std::string os_out = os.str();
+
+  // Test pair and map.
+  test::map_type testmap;
+  testmap.insert(std::make_pair(std::string("key"),
+                                std::make_pair(53,false)));
+
+  // Test set.
+  int values[] = {9, 7, 13, 15, 4, 18, 12, 10, 5, 3, 14, 19, 17, 8, 6, 20, 16, 2, 11, 1};
+  test::set_type testset(values, values + sizeof(values)/sizeof(values[0]));
+  std::list<int> testlist(testset.begin(), testset.end());
+  std::copy(testset.begin(), testset.end(), std::back_inserter(testlist));
+} catch (const std::exception& e) {
+  std::cerr << "Caught exception: " << e.what() << std::endl;
+
+  // Test fstream
+  std::ofstream of("test.txt");
+  of << "Test ASCII text\n" << std::flush;
+  of << "N= " << std::hex << std::setw(8) << std::left << 534 << std::endl;
+  of.close();
+}
+std::exit(0);
+]])
+
+# _AC_CXX_CXX11_TEST_HEADER
+# -------------------------
+# A C++ header suitable for testing for CXX11.
+AC_DEFUN([_AC_CXX_CXX11_TEST_HEADER],
+[[
+#include <deque>
+#include <functional>
+#include <memory>
+#include <tuple>
+#include <array>
+#include <regex>
+#include <iostream>
+
+namespace cxx11test
+{
+  typedef std::shared_ptr<std::string> sptr;
+  typedef std::weak_ptr<std::string> wptr;
+
+  typedef std::tuple<std::string,int,double> tp;
+  typedef std::array<int, 20> int_array;
+
+  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;
+  };
+}
+]])# _AC_CXX_CXX11_TEST_HEADER
+
+# _AC_CXX_CXX11_TEST_BODY
+# -----------------------
+# A C++ body suitable for testing for CXX11, assuming the corresponding header.
+AC_DEFUN([_AC_CXX_CXX11_TEST_BODY],
+[[
+{
+  // Test auto and decltype
+  std::deque<int> d;
+  d.push_front(43);
+  d.push_front(484);
+  d.push_front(3);
+  d.push_front(844);
+  int total = 0;
+  for (auto i = d.begin(); i != d.end(); ++i) { total += *i; }
+
+  auto a1 = 6538;
+  auto a2 = 48573953.4;
+  auto a3 = "String literal";
+
+  decltype(a2) a4 = 34895.034;
+}
+{
+  // Test constexpr
+  short sa[cxx11test::get_val()] = { 0 };
+}
+{
+  // Test initialiser lists
+  cxx11test::testinit il = { 4323, 435234.23544 };
+}
+{
+  // Test range-based for and lambda
+  cxx11test::int_array array = {9, 7, 13, 15, 4, 18, 12, 10, 5, 3, 14, 19, 17, 8, 6, 20, 16, 2, 11, 1};
+  for (int &x : array) { x += 23; }
+  std::for_each(array.begin(), array.end(), [](int v1){ std::cout << v1; });
+}
+{
+  using cxx11test::sptr;
+  using cxx11test::wptr;
+
+  sptr sp(new std::string("ASCII string"));
+  wptr wp(sp);
+  sptr sp2(wp);
+}
+{
+  cxx11test::tp tuple("test", 54, 45.53434);
+  double d = std::get<2>(tuple);
+  std::string s;
+  int i;
+  std::tie(s,i,d) = tuple;
+}
+{
+  static std::regex filename_regex("^_?([a-z0-9_.]+-)+[a-z0-9]+$");
+  std::string testmatch("Test if this string matches");
+  bool match = std::regex_search(testmatch, filename_regex);
+}
+{
+  cxx11test::int_array array = {9, 7, 13, 15, 4, 18, 12, 10, 5, 3, 14, 19, 17, 8, 6, 20, 16, 2, 11, 1};
+  cxx11test::int_array::size_type size = array.size();
+}
+{
+  // 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
+  std::vector<std::pair<int,char*>> v1;
+}
+{
+  // Unicode literals
+  char *utf8 = u8"UTF-8 string \u2500";
+  char16_t *utf16 = u"UTF-8 string \u2500";
+  char32_t *utf32 = U"UTF-32 string \u2500";
+}
+]])
+
+# _AC_PROG_CXX_CXX98 ([ACTION-IF-AVAILABLE], [ACTION-IF-UNAVAILABLE])
+# -------------------------------------------------------------------
+
+# If the C++ compiler is not in ISO C++98 mode by default, try to add
+# an option to output variable CXX to make it so.  This macro tries
+# various options that select ISO C++98 on some system or another.  It
+# considers the compiler to be in ISO C++98 mode if it handles basic
+# features of the std namespace including: string, containers (list,
+# map, set, vector), streams (fstreams, iostreams, stringstreams,
+# iomanip), pair, exceptions and algorithms.
+
+
+AC_DEFUN([_AC_PROG_CXX_CXX98],
+[_AC_CXX_STD_TRY([cxx98],
+[_AC_CXX_CXX98_TEST_HEADER],
+[_AC_CXX_CXX98_TEST_BODY],
+dnl Try
+dnl GCC		-std=gnu++98 (unused restrictive mode: -std=c++98)
+dnl IBM XL C	-qlanglvl=extended
+dnl HP aC++	-AA
+dnl Intel ICC	-std=gnu++98
+dnl Solaris	N/A (default)
+dnl Tru64	N/A (default, but -std gnu could be used)
+dnl with extended modes being tried first.
+[[-std=gnu++98 -std=c++98 -qlanglvl=extended -AA]], [$1], [$2])[]dnl
+])# _AC_PROG_CXX_CXX98
+
+# _AC_PROG_CXX_CXX11 ([ACTION-IF-AVAILABLE], [ACTION-IF-UNAVAILABLE])
+# -------------------------------------------------------------------
+# If the C++ compiler is not in ISO CXX11 mode by default, try to add
+# an option to output variable CXX to make it so.  This macro tries
+# various options that select ISO C++11 on some system or another.  It
+# considers the compiler to be in ISO C++11 mode if it handles all the
+# tests from the C++98 checks, plus the following: Language features
+# (auto, constexpr, decltype, default/deleted constructors, delegate
+# constructors, final, initialiser lists, lambda functions, nullptr,
+# override, range-based for loops, template brackets without spaces,
+# unicode literals) and library features (array, memory (shared_ptr,
+# weak_ptr), regex and tuple types).
+AC_DEFUN([_AC_PROG_CXX_CXX11],
+[_AC_CXX_STD_TRY([cxx11],
+[_AC_CXX_CXX11_TEST_HEADER
+_AC_CXX_CXX98_TEST_HEADER],
+[_AC_CXX_CXX11_TEST_BODY
+_AC_CXX_CXX98_TEST_BODY],
+dnl Try
+dnl GCC		-std=gnu++11 (unused restrictive mode: -std=c++11) [and 0x variants]
+dnl IBM XL C	-qlanglvl=extended0x
+dnl		(pre-V12.1; unused restrictive mode: -qlanglvl=stdcxx11)
+dnl HP aC++	-AA
+dnl Intel ICC	-std=c++11 -std=c++0x
+dnl Solaris	N/A (no support)
+dnl Tru64	N/A (no support)
+dnl with extended modes being tried first.
+[[-std=gnu++11 -std=c++11 -std=gnu++0x -std=c++0x -qlanglvl=extended0x -AA]], [$1], [$2])[]dnl
+])# _AC_PROG_CXX_CXX11