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[autoconf.git] / lib / autoconf / c.m4

# This file is part of Autoconf.                        -*- Autoconf -*-
# Programming languages support.
# Copyright (C) 2001-2017, 2020-2024 Free Software Foundation, Inc.

# This file is part of Autoconf.  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
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# (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.
#
# Under Section 7 of GPL version 3, you are granted additional
# permissions described in the Autoconf Configure Script Exception,
# version 3.0, as published by the Free Software Foundation.
#
# You should have received a copy of the GNU General Public License
# and a copy of the Autoconf Configure Script Exception along with
# this program; see the files COPYINGv3 and COPYING.EXCEPTION
# respectively.  If not, see <https://www.gnu.org/licenses/> and
# <https://git.savannah.gnu.org/gitweb/?p=autoconf.git;a=blob_plain;f=COPYING.EXCEPTION>.

# 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.


# Table of Contents:
#
# 1. Language selection
# 2. and routines to produce programs in a given language.
#      1a. C   2a. C
#      1b. C++
#      1c. Objective C
#      1d. Objective C++
#
# 3. Looking for a compiler
#    And possibly the associated preprocessor.
#      3a. C   3b. C++   3c. Objective C   3d. Objective C++
#
# 4. Compilers' characteristics.
#      4a. C



## ----------------------- ##
## 1a/2a. The C language.  ##
## ----------------------- ##


# ------------------------ #
# 1a. Language selection.  #
# ------------------------ #

# AC_LANG(C)
# ----------
# CFLAGS is not in ac_cpp because -g, -O, etc. are not valid cpp options.
AC_LANG_DEFINE([C], [c], [C], [CC], [],
[ac_ext=c
ac_cpp='$CPP $CPPFLAGS'
ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&AS_MESSAGE_LOG_FD'
ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&AS_MESSAGE_LOG_FD'
ac_compiler_gnu=$ac_cv_c_compiler_gnu
])


# AC_LANG_C
# ---------
AU_DEFUN([AC_LANG_C], [AC_LANG(C)])


# ------------------------ #
# 2a. Producing programs.  #
# ------------------------ #


# AC_LANG_CONFTEST(C)(BODY)
# -------------------------
# We can't use '#line $LINENO "configure"' here, since
# Sun c89 (Sun WorkShop 6 update 2 C 5.3 Patch 111679-08 2002/05/09)
# rejects $LINENO greater than 32767, and some configure scripts
# are longer than 32767 lines.
m4_define([AC_LANG_CONFTEST(C)],
[cat confdefs.h - <<_ACEOF >conftest.$ac_ext
/* end confdefs.h.  */
$1
_ACEOF])


# AC_LANG_PROGRAM(C)([PROLOGUE], [BODY])
# --------------------------------------
m4_define([AC_LANG_PROGRAM(C)],
[$1
m4_ifdef([_AC_LANG_PROGRAM_C_F77_HOOKS], [_AC_LANG_PROGRAM_C_F77_HOOKS])[]dnl
m4_ifdef([_AC_LANG_PROGRAM_C_FC_HOOKS], [_AC_LANG_PROGRAM_C_FC_HOOKS])[]dnl
int
main (void)
{
dnl Do *not* indent the following line: there may be CPP directives.
dnl Don't move the ';' right after for the same reason.
$2
  ;
  return 0;
}])


# _AC_LANG_IO_PROGRAM(C)
# ----------------------
# Produce source that performs I/O, necessary for proper
# cross-compiler detection.
m4_define([_AC_LANG_IO_PROGRAM(C)],
[AC_LANG_PROGRAM([@%:@include <stdio.h>],
[FILE *f = fopen ("conftest.out", "w");
 if (!f)
  return 1;
 return ferror (f) || fclose (f) != 0;
])])


# AC_LANG_CALL(C)(PROLOGUE, FUNCTION)
# -----------------------------------
# Avoid conflicting decl of main.
m4_define([AC_LANG_CALL(C)],
[AC_LANG_PROGRAM([$1
m4_if([$2], [main], ,
[/* 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.
   The 'extern "C"' is for builds by C++ compilers;
   although this is not generally supported in C code supporting it here
   has little cost and some practical benefit (sr 110532).  */
#ifdef __cplusplus
extern "C"
#endif
char $2 (void);])], [return $2 ();])])


# AC_LANG_FUNC_LINK_TRY(C)(FUNCTION)
# ----------------------------------
# Don't include <ctype.h> because on OSF/1 3.0 it includes
# <sys/types.h> which includes <sys/select.h> which contains a
# prototype for select.  Similarly for bzero.
#
# This test used to merely assign f=$1 in main(), but that was
# optimized away by HP unbundled cc A.05.36 for ia64 under +O3,
# presumably on the basis that there's no need to do that store if the
# program is about to exit.  Conversely, the AIX linker optimizes an
# unused external declaration that initializes f=$1.  So this test
# program has both an external initialization of f, and a use of f in
# main that affects the exit status.
#
m4_define([AC_LANG_FUNC_LINK_TRY(C)],
[AC_LANG_PROGRAM(
[/* Define $1 to an innocuous variant, in case <limits.h> declares $1.
   For example, HP-UX 11i <limits.h> declares gettimeofday.  */
#define $1 innocuous_$1

/* System header to define __stub macros and hopefully few prototypes,
   which can conflict with char $1 (void); below.  */

#include <limits.h>
#undef $1

/* 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 $1 (void);
/* The GNU C library defines this for functions which it implements
    to always fail with ENOSYS.  Some functions are actually named
    something starting with __ and the normal name is an alias.  */
#if defined __stub_$1 || defined __stub___$1
choke me
#endif
], [return $1 ();])])


# AC_LANG_BOOL_COMPILE_TRY(C)(PROLOGUE, EXPRESSION)
# -------------------------------------------------
# Return a program that is valid if EXPRESSION is nonzero.
# EXPRESSION must be an integer constant expression.
# Be sure to use this array to avoid 'unused' warnings, which are even
# errors with '-W error'.
m4_define([AC_LANG_BOOL_COMPILE_TRY(C)],
[AC_LANG_PROGRAM([$1], [static int test_array @<:@1 - 2 * !($2)@:>@;
test_array @<:@0@:>@ = 0;
return test_array @<:@0@:>@;
])])


# AC_LANG_INT_SAVE(C)(PROLOGUE, EXPRESSION)
# -----------------------------------------
# We need 'stdio.h' to open a 'FILE' and 'stdlib.h' for 'exit'.
# But we include them only after the EXPRESSION has been evaluated.
m4_define([AC_LANG_INT_SAVE(C)],
[AC_LANG_PROGRAM([$1
static long int longval (void) { return $2; }
static unsigned long int ulongval (void) { return $2; }
@%:@include <stdio.h>
@%:@include <stdlib.h>],
[
  FILE *f = fopen ("conftest.val", "w");
  if (! f)
    return 1;
  if (($2) < 0)
    {
      long int i = longval ();
      if (i != ($2))
        return 1;
      fprintf (f, "%ld", i);
    }
  else
    {
      unsigned long int i = ulongval ();
      if (i != ($2))
        return 1;
      fprintf (f, "%lu", i);
    }
  /* Do not output a trailing newline, as this causes \r\n confusion
     on some platforms.  */
  return ferror (f) || fclose (f) != 0;
])])



## ---------------------- ##
## 1b. The C++ language.  ##
## ---------------------- ##


# AC_LANG(C++)
# ------------
# CXXFLAGS is not in ac_cpp because -g, -O, etc. are not valid cpp options.
AC_LANG_DEFINE([C++], [cxx], [CXX], [CXX], [C],
[ac_ext=cpp
ac_cpp='$CXXCPP $CPPFLAGS'
ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&AS_MESSAGE_LOG_FD'
ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&AS_MESSAGE_LOG_FD'
ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
])


# AC_LANG_CALL(C++)(PROLOGUE, FUNCTION)
# -------------------------------------
m4_define([AC_LANG_CALL(C++)],
dnl We do not know the function signature of the real $2.
dnl Declare it in a namespace so the compiler doesn't recognize it
dnl (with, most likely, a clashing prototype); the 'extern "C"' hides
dnl the namespace from the linker.
dnl Use 'int' for the return type, because some C++ compilers consider
dnl 'namespace conftest { extern "C" void main (); }' to be an
dnl erroneous redeclaration of ::main, namespace notwithstanding.
dnl The logic they're applying could be extended in the future to
dnl other built-in extern "C" functions, but let's worry about that
dnl when it actually happens.
[AC_LANG_PROGRAM([[$1
namespace conftest {
  extern "C" int $2 ();
}]],
[[return conftest::$2 ();]])])


# AC_LANG_CPLUSPLUS
# -----------------
AU_DEFUN([AC_LANG_CPLUSPLUS], [AC_LANG(C++)])



## ------------------------------ ##
## 1c. The Objective C language.  ##
## ------------------------------ ##


# AC_LANG(Objective C)
# --------------------
AC_LANG_DEFINE([Objective C], [objc], [OBJC], [OBJC], [C],
[ac_ext=m
ac_cpp='$OBJCPP $CPPFLAGS'
ac_compile='$OBJC -c $OBJCFLAGS $CPPFLAGS conftest.$ac_ext >&AS_MESSAGE_LOG_FD'
ac_link='$OBJC -o conftest$ac_exeext $OBJCFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&AS_MESSAGE_LOG_FD'
ac_compiler_gnu=$ac_cv_objc_compiler_gnu
])


# AC_LANG_OBJC
# ------------
AU_DEFUN([AC_LANG_OBJC], [AC_LANG(Objective C)])



## -------------------------------- ##
## 1d. The Objective C++ language.  ##
## -------------------------------- ##


# AC_LANG(Objective C++)
# ----------------------
AC_LANG_DEFINE([Objective C++], [objcxx], [OBJCXX], [OBJCXX], [C++],
[ac_ext=mm
ac_cpp='$OBJCXXCPP $CPPFLAGS'
ac_compile='$OBJCXX -c $OBJCXXFLAGS $CPPFLAGS conftest.$ac_ext >&AS_MESSAGE_LOG_FD'
ac_link='$OBJCXX -o conftest$ac_exeext $OBJCXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&AS_MESSAGE_LOG_FD'
ac_compiler_gnu=$ac_cv_objcxx_compiler_gnu
])



## -------------------------------------------- ##
## 3. Looking for Compilers and Preprocessors.  ##
## -------------------------------------------- ##

# -------------------- #
# 3a. The C compiler.  #
# -------------------- #


# _AC_ARG_VAR_CPPFLAGS
# --------------------
# Document and register CPPFLAGS, which is used by
# AC_PROG_{CC, CPP, CXX, CXXCPP, OBJC, OBJCPP, OBJCXX, OBJCXXCPP}.
AC_DEFUN([_AC_ARG_VAR_CPPFLAGS],
[AC_ARG_VAR([CPPFLAGS],
            [(Objective) C/C++ preprocessor flags, e.g. -I<include dir>
             if you have headers in a nonstandard directory <include dir>])])


# _AC_ARG_VAR_LDFLAGS
# -------------------
# Document and register LDFLAGS, which is used by
# AC_PROG_{CC, CXX, F77, FC, OBJC, OBJCXX}.
AC_DEFUN([_AC_ARG_VAR_LDFLAGS],
[AC_ARG_VAR([LDFLAGS],
            [linker flags, e.g. -L<lib dir> if you have libraries in a
             nonstandard directory <lib dir>])])


# _AC_ARG_VAR_LIBS
# ----------------
# Document and register LIBS, which is used by
# AC_PROG_{CC, CXX, F77, FC, OBJC, OBJCXX}.
AC_DEFUN([_AC_ARG_VAR_LIBS],
[AC_ARG_VAR([LIBS],
            [libraries to pass to the linker, e.g. -l<library>])])


# AC_LANG_PREPROC(C)
# ------------------
# Find the C preprocessor.  Must be AC_DEFUN'd to be AC_REQUIRE'able.
AC_DEFUN([AC_LANG_PREPROC(C)],
[AC_REQUIRE([AC_PROG_CPP])])


# _AC_PROG_PREPROC_WORKS_IFELSE(IF-WORKS, IF-NOT)
# -----------------------------------------------
# Check if $ac_cpp is a working preprocessor that can flag absent
# includes either by the exit status or by warnings.
# This macro is for all languages, not only C.
AC_DEFUN([_AC_PROG_PREPROC_WORKS_IFELSE],
[ac_preproc_ok=false
for ac_[]_AC_LANG_ABBREV[]_preproc_warn_flag in '' yes
do
  # Use a header file that comes with gcc, so configuring glibc
  # with a fresh cross-compiler works.
  # On the NeXT, cc -E runs the code through the compiler's parser,
  # not just through cpp. "Syntax error" is here to catch this case.
  _AC_PREPROC_IFELSE([AC_LANG_SOURCE([[@%:@include <limits.h>
                     Syntax error]])],
                     [],
                     [# Broken: fails on valid input.
continue])

  # OK, works on sane cases.  Now check whether nonexistent headers
  # can be detected and how.
  _AC_PREPROC_IFELSE([AC_LANG_SOURCE([[@%:@include <ac_nonexistent.h>]])],
                     [# Broken: success on invalid input.
continue],
                     [# Passes both tests.
ac_preproc_ok=:
break])

done
# Because of 'break', _AC_PREPROC_IFELSE's cleaning code was skipped.
rm -f conftest.i conftest.err conftest.$ac_ext
AS_IF([$ac_preproc_ok], [$1], [$2])
])# _AC_PROG_PREPROC_WORKS_IFELSE


# AC_PROG_CPP
# -----------
# Find a working C preprocessor.
# We shouldn't have to require AC_PROG_CC, but this is due to the concurrency
# between the AC_LANG_COMPILER_REQUIRE family and that of AC_PROG_CC.
AN_MAKEVAR([CPP], [AC_PROG_CPP])
AN_PROGRAM([cpp], [AC_PROG_CPP])
AC_DEFUN([AC_PROG_CPP],
[AC_REQUIRE([AC_PROG_CC])dnl
AC_ARG_VAR([CPP],      [C preprocessor])dnl
_AC_ARG_VAR_CPPFLAGS()dnl
AC_LANG_PUSH(C)dnl
AC_MSG_CHECKING([how to run the C preprocessor])
# On Suns, sometimes $CPP names a directory.
if test -n "$CPP" && test -d "$CPP"; then
  CPP=
fi
if test -z "$CPP"; then
  AC_CACHE_VAL([ac_cv_prog_CPP],
  [dnl
    # Double quotes because $CC needs to be expanded
    for CPP in "$CC -E" "$CC -E -traditional-cpp" cpp /lib/cpp
    do
      _AC_PROG_PREPROC_WORKS_IFELSE([break])
    done
    ac_cv_prog_CPP=$CPP
  ])dnl
  CPP=$ac_cv_prog_CPP
else
  ac_cv_prog_CPP=$CPP
fi
AC_MSG_RESULT([$CPP])
_AC_PROG_PREPROC_WORKS_IFELSE([],
                [AC_MSG_FAILURE([C preprocessor "$CPP" fails sanity check])])
AC_SUBST(CPP)dnl
AC_LANG_POP(C)dnl
])# AC_PROG_CPP

# AC_PROG_CPP_WERROR
# ------------------
# Treat warnings from the preprocessor as errors.
AC_DEFUN([AC_PROG_CPP_WERROR],
[AC_REQUIRE([AC_PROG_CPP])dnl
ac_c_preproc_warn_flag=yes])# AC_PROG_CPP_WERROR

# AC_LANG_COMPILER(C)
# -------------------
# Find the C compiler.  Must be AC_DEFUN'd to be AC_REQUIRE'able.
AC_DEFUN([AC_LANG_COMPILER(C)],
[AC_REQUIRE([AC_PROG_CC])])


# ac_cv_prog_gcc
# --------------
# We used to name the cache variable this way.
AU_DEFUN([ac_cv_prog_gcc],
[ac_cv_c_compiler_gnu])


# 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.
AN_MAKEVAR([CC],  [AC_PROG_CC])
AN_PROGRAM([cc],  [AC_PROG_CC])
AN_PROGRAM([gcc], [AC_PROG_CC])
AC_DEFUN([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 "$CC"; then
  AC_CHECK_TOOLS(CC, cl.exe)
fi
if test -z "$CC"; then
  AC_CHECK_TOOL(CC, clang)
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
_AC_PROG_CC_STDC_EDITION
AC_LANG_POP(C)dnl
])# AC_PROG_CC


# _AC_PROG_CC_G
# -------------
# Check whether -g works, even if CFLAGS is set, in case the package
# plays around with CFLAGS (such as to build both debugging and normal
# versions of a library), tasteless as that idea is.
# Don't consider -g to work if it generates warnings when plain compiles don't.
m4_define([_AC_PROG_CC_G],
[ac_test_CFLAGS=${CFLAGS+y}
ac_save_CFLAGS=$CFLAGS
AC_CACHE_CHECK(whether $CC accepts -g, ac_cv_prog_cc_g,
  [ac_save_c_werror_flag=$ac_c_werror_flag
   ac_c_werror_flag=yes
   ac_cv_prog_cc_g=no
   CFLAGS="-g"
   _AC_COMPILE_IFELSE([AC_LANG_PROGRAM()],
     [ac_cv_prog_cc_g=yes],
     [CFLAGS=""
      _AC_COMPILE_IFELSE([AC_LANG_PROGRAM()],
        [],
        [ac_c_werror_flag=$ac_save_c_werror_flag
         CFLAGS="-g"
         _AC_COMPILE_IFELSE([AC_LANG_PROGRAM()],
           [ac_cv_prog_cc_g=yes])])])
   ac_c_werror_flag=$ac_save_c_werror_flag])
if test $ac_test_CFLAGS; then
  CFLAGS=$ac_save_CFLAGS
elif test $ac_cv_prog_cc_g = yes; then
  if test "$GCC" = yes; then
    CFLAGS="-g -O2"
  else
    CFLAGS="-g"
  fi
else
  if test "$GCC" = yes; then
    CFLAGS="-O2"
  else
    CFLAGS=
  fi
fi[]dnl
])# _AC_PROG_CC_G


# AC_PROG_CC_C_O
# --------------
AC_DEFUN([AC_PROG_CC_C_O],
[AC_REQUIRE([AC_PROG_CC])dnl
AC_LANG_PUSH([C])
if test "x$CC" != xcc; then
  AC_MSG_CHECKING([whether $CC and cc understand -c and -o together])
else
  AC_MSG_CHECKING([whether cc understands -c and -o together])
fi
set dummy $CC; ac_cc=`AS_ECHO(["$[2]"]) |
                      sed 's/[[^a-zA-Z0-9_]]/_/g;s/^[[0-9]]/_/'`
AC_CACHE_VAL(ac_cv_prog_cc_${ac_cc}_c_o,
[AC_LANG_CONFTEST([AC_LANG_PROGRAM([])])
# Make sure it works both with $CC and with simple cc.
# We do the test twice because some compilers refuse to overwrite an
# existing .o file with -o, though they will create one.
ac_try='$CC -c conftest.$ac_ext -o conftest2.$ac_objext >&AS_MESSAGE_LOG_FD'
rm -f conftest2.*
if _AC_DO_VAR(ac_try) &&
   test -f conftest2.$ac_objext && _AC_DO_VAR(ac_try);
then
  eval ac_cv_prog_cc_${ac_cc}_c_o=yes
  if test "x$CC" != xcc; then
    # Test first that cc exists at all.
    if _AC_DO_TOKENS(cc -c conftest.$ac_ext >&AS_MESSAGE_LOG_FD); then
      ac_try='cc -c conftest.$ac_ext -o conftest2.$ac_objext >&AS_MESSAGE_LOG_FD'
      rm -f conftest2.*
      if _AC_DO_VAR(ac_try) &&
         test -f conftest2.$ac_objext && _AC_DO_VAR(ac_try);
      then
        # cc works too.
        :
      else
        # cc exists but doesn't like -o.
        eval ac_cv_prog_cc_${ac_cc}_c_o=no
      fi
    fi
  fi
else
  eval ac_cv_prog_cc_${ac_cc}_c_o=no
fi
rm -rf core conftest*
])dnl
if eval test \$ac_cv_prog_cc_${ac_cc}_c_o = yes; then
  AC_MSG_RESULT([yes])
else
  AC_MSG_RESULT([no])
  AC_DEFINE(NO_MINUS_C_MINUS_O, 1,
           [Define to 1 if your C compiler doesn't accept -c and -o together.])
fi
AC_LANG_POP([C])
])# AC_PROG_CC_C_O



# ---------------------- #
# 3b. The C++ compiler.  #
# ---------------------- #


# AC_LANG_PREPROC(C++)
# --------------------
# Find the C++ preprocessor.  Must be AC_DEFUN'd to be AC_REQUIRE'able.
AC_DEFUN([AC_LANG_PREPROC(C++)],
[AC_REQUIRE([AC_PROG_CXXCPP])])


# AC_PROG_CXXCPP
# --------------
# Find a working C++ preprocessor.
# We shouldn't have to require AC_PROG_CC, but this is due to the concurrency
# between the AC_LANG_COMPILER_REQUIRE family and that of AC_PROG_CXX.
AC_DEFUN([AC_PROG_CXXCPP],
[AC_REQUIRE([AC_PROG_CXX])dnl
AC_ARG_VAR([CXXCPP],   [C++ preprocessor])dnl
_AC_ARG_VAR_CPPFLAGS()dnl
AC_LANG_PUSH(C++)dnl
AC_MSG_CHECKING([how to run the C++ preprocessor])
if test -z "$CXXCPP"; then
  AC_CACHE_VAL(ac_cv_prog_CXXCPP,
  [dnl
    # Double quotes because $CXX needs to be expanded
    for CXXCPP in "$CXX -E" cpp /lib/cpp
    do
      _AC_PROG_PREPROC_WORKS_IFELSE([break])
    done
    ac_cv_prog_CXXCPP=$CXXCPP
  ])dnl
  CXXCPP=$ac_cv_prog_CXXCPP
else
  ac_cv_prog_CXXCPP=$CXXCPP
fi
AC_MSG_RESULT([$CXXCPP])
_AC_PROG_PREPROC_WORKS_IFELSE([],
          [AC_MSG_FAILURE([C++ preprocessor "$CXXCPP" fails sanity check])])
AC_SUBST(CXXCPP)dnl
AC_LANG_POP(C++)dnl
])# AC_PROG_CXXCPP


# AC_LANG_COMPILER(C++)
# ---------------------
# Find the C++ compiler.  Must be AC_DEFUN'd to be AC_REQUIRE'able.
AC_DEFUN([AC_LANG_COMPILER(C++)],
[AC_REQUIRE([AC_PROG_CXX])])


# ac_cv_prog_gxx
# --------------
# We used to name the cache variable this way.
AU_DEFUN([ac_cv_prog_gxx],
[ac_cv_cxx_compiler_gnu])


# 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 IBM XL C++ for AIX (with support for reentrant code)
# xlC   IBM XL C++ for AIX
AN_MAKEVAR([CXX],  [AC_PROG_CXX])
AN_PROGRAM([CC],   [AC_PROG_CXX])
AN_PROGRAM([c++],  [AC_PROG_CXX])
AN_PROGRAM([g++],  [AC_PROG_CXX])
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 clang++])],
                   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_LANG_POP(C++)dnl
])# AC_PROG_CXX


# _AC_PROG_CXX_G
# --------------
# Check whether -g works, even if CXXFLAGS is set, in case the package
# plays around with CXXFLAGS (such as to build both debugging and
# normal versions of a library), tasteless as that idea is.
# Don't consider -g to work if it generates warnings when plain compiles don't.
m4_define([_AC_PROG_CXX_G],
[ac_test_CXXFLAGS=${CXXFLAGS+y}
ac_save_CXXFLAGS=$CXXFLAGS
AC_CACHE_CHECK(whether $CXX accepts -g, ac_cv_prog_cxx_g,
  [ac_save_cxx_werror_flag=$ac_cxx_werror_flag
   ac_cxx_werror_flag=yes
   ac_cv_prog_cxx_g=no
   CXXFLAGS="-g"
   _AC_COMPILE_IFELSE([AC_LANG_PROGRAM()],
     [ac_cv_prog_cxx_g=yes],
     [CXXFLAGS=""
      _AC_COMPILE_IFELSE([AC_LANG_PROGRAM()],
        [],
        [ac_cxx_werror_flag=$ac_save_cxx_werror_flag
         CXXFLAGS="-g"
         _AC_COMPILE_IFELSE([AC_LANG_PROGRAM()],
           [ac_cv_prog_cxx_g=yes])])])
   ac_cxx_werror_flag=$ac_save_cxx_werror_flag])
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
    CXXFLAGS="-g"
  fi
else
  if test "$GXX" = yes; then
    CXXFLAGS="-O2"
  else
    CXXFLAGS=
  fi
fi[]dnl
])# _AC_PROG_CXX_G


# AC_PROG_CXX_C_O
# ---------------
# Test if the C++ compiler accepts the options '-c' and '-o'
# simultaneously, and define 'CXX_NO_MINUS_C_MINUS_O' if it does not.
AC_DEFUN([AC_PROG_CXX_C_O],
[AC_REQUIRE([AC_PROG_CXX])dnl
AC_LANG_PUSH([C++])dnl
AC_CACHE_CHECK([whether $CXX understands -c and -o together],
               [ac_cv_prog_cxx_c_o],
[AC_LANG_CONFTEST([AC_LANG_PROGRAM([])])
# We test twice because some compilers refuse to overwrite an existing
# '.o' file with '-o', although they will create one.
ac_try='$CXX $CXXFLAGS -c conftest.$ac_ext -o conftest2.$ac_objext >&AS_MESSAGE_LOG_FD'
rm -f conftest2.*
if _AC_DO_VAR(ac_try) &&
     test -f conftest2.$ac_objext &&
     _AC_DO_VAR(ac_try); then
  ac_cv_prog_cxx_c_o=yes
else
  ac_cv_prog_cxx_c_o=no
fi
rm -rf conftest*])
if test $ac_cv_prog_cxx_c_o = no; then
  AC_DEFINE(CXX_NO_MINUS_C_MINUS_O, 1,
            [Define to 1 if your C++ compiler doesn't accept
             -c and -o together.])
fi
AC_LANG_POP([C++])dnl
])# AC_PROG_CXX_C_O



# ------------------------------ #
# 3c. The Objective C compiler.  #
# ------------------------------ #


# AC_LANG_PREPROC(Objective C)
# ----------------------------
# Find the Objective C preprocessor.  Must be AC_DEFUN'd to be AC_REQUIRE'able.
AC_DEFUN([AC_LANG_PREPROC(Objective C)],
[AC_REQUIRE([AC_PROG_OBJCPP])])


# AC_PROG_OBJCPP
# --------------
# Find a working Objective C preprocessor.
AC_DEFUN([AC_PROG_OBJCPP],
[AC_REQUIRE([AC_PROG_OBJC])dnl
AC_ARG_VAR([OBJCPP],   [Objective C preprocessor])dnl
_AC_ARG_VAR_CPPFLAGS()dnl
AC_LANG_PUSH(Objective C)dnl
AC_MSG_CHECKING([how to run the Objective C preprocessor])
if test -z "$OBJCPP"; then
  AC_CACHE_VAL(ac_cv_prog_OBJCPP,
  [dnl
    # Double quotes because $OBJC needs to be expanded
    for OBJCPP in "$OBJC -E" cpp /lib/cpp
    do
      _AC_PROG_PREPROC_WORKS_IFELSE([break])
    done
    ac_cv_prog_OBJCPP=$OBJCPP
  ])dnl
  OBJCPP=$ac_cv_prog_OBJCPP
else
  ac_cv_prog_OBJCPP=$OBJCPP
fi
AC_MSG_RESULT([$OBJCPP])
_AC_PROG_PREPROC_WORKS_IFELSE([],
          [AC_MSG_FAILURE([Objective C preprocessor "$OBJCPP" fails sanity check])])
AC_SUBST(OBJCPP)dnl
AC_LANG_POP(Objective C)dnl
])# AC_PROG_OBJCPP


# AC_LANG_COMPILER(Objective C)
# -----------------------------
# Find the Objective C compiler.  Must be AC_DEFUN'd to be AC_REQUIRE'able.
AC_DEFUN([AC_LANG_COMPILER(Objective C)],
[AC_REQUIRE([AC_PROG_OBJC])])



# AC_PROG_OBJC([LIST-OF-COMPILERS])
# ---------------------------------
# LIST-OF-COMPILERS is a space separated list of Objective 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
# Objective C compiler.
# gobjc  GNU Objective-C compiler packaged in EPEL (for systems where gcc
#        does not support Objective-C)
# gcc    GNU Objective-C compiler on most systems
# objcc  StepStone Objective-C compiler (also "standard" name for OBJC)
# objc   David Stes' POC.  If you installed this, you likely want it.
# cc     Native C compiler (for instance, Apple).
# CC     You never know.
AN_MAKEVAR([OBJC],  [AC_PROG_OBJC])
AN_PROGRAM([objcc],  [AC_PROG_OBJC])
AN_PROGRAM([objc],  [AC_PROG_OBJC])
AC_DEFUN([AC_PROG_OBJC],
[AC_LANG_PUSH(Objective C)dnl
AC_ARG_VAR([OBJC],      [Objective C compiler command])dnl
AC_ARG_VAR([OBJCFLAGS], [Objective C compiler flags])dnl
_AC_ARG_VAR_LDFLAGS()dnl
_AC_ARG_VAR_LIBS()dnl
_AC_ARG_VAR_CPPFLAGS()dnl
_AC_ARG_VAR_PRECIOUS([OBJC])dnl
AC_CHECK_TOOLS(OBJC,
               [m4_default([$1], [gobjc gcc objcc objc cc CC clang])],
               gcc)
# 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
  GOBJC=yes
else
  GOBJC=
fi
_AC_PROG_OBJC_G
AC_LANG_POP(Objective C)dnl
])# AC_PROG_OBJC


# _AC_PROG_OBJC_G
# ---------------
# Check whether -g works, even if OBJCFLAGS is set, in case the package
# plays around with OBJCFLAGS (such as to build both debugging and
# normal versions of a library), tasteless as that idea is.
# Don't consider -g to work if it generates warnings when plain compiles don't.
m4_define([_AC_PROG_OBJC_G],
[ac_test_OBJCFLAGS=${OBJCFLAGS+y}
ac_save_OBJCFLAGS=$OBJCFLAGS
AC_CACHE_CHECK(whether $OBJC accepts -g, ac_cv_prog_objc_g,
  [ac_save_objc_werror_flag=$ac_objc_werror_flag
   ac_objc_werror_flag=yes
   ac_cv_prog_objc_g=no
   OBJCFLAGS="-g"
   _AC_COMPILE_IFELSE([AC_LANG_PROGRAM()],
     [ac_cv_prog_objc_g=yes],
     [OBJCFLAGS=""
      _AC_COMPILE_IFELSE([AC_LANG_PROGRAM()],
        [],
        [ac_objc_werror_flag=$ac_save_objc_werror_flag
         OBJCFLAGS="-g"
         _AC_COMPILE_IFELSE([AC_LANG_PROGRAM()],
           [ac_cv_prog_objc_g=yes])])])
   ac_objc_werror_flag=$ac_save_objc_werror_flag])
if test $ac_test_OBJCFLAGS; then
  OBJCFLAGS=$ac_save_OBJCFLAGS
elif test $ac_cv_prog_objc_g = yes; then
  if test "$GOBJC" = yes; then
    OBJCFLAGS="-g -O2"
  else
    OBJCFLAGS="-g"
  fi
else
  if test "$GOBJC" = yes; then
    OBJCFLAGS="-O2"
  else
    OBJCFLAGS=
  fi
fi[]dnl
])# _AC_PROG_OBJC_G



# -------------------------------- #
# 3d. The Objective C++ compiler.  #
# -------------------------------- #


# AC_LANG_PREPROC(Objective C++)
# ------------------------------
# Find the Objective C++ preprocessor.  Must be AC_DEFUN'd to be AC_REQUIRE'able.
AC_DEFUN([AC_LANG_PREPROC(Objective C++)],
[AC_REQUIRE([AC_PROG_OBJCXXCPP])])


# AC_PROG_OBJCXXCPP
# -----------------
# Find a working Objective C++ preprocessor.
AC_DEFUN([AC_PROG_OBJCXXCPP],
[AC_REQUIRE([AC_PROG_OBJCXX])dnl
AC_ARG_VAR([OBJCXXCPP],   [Objective C++ preprocessor])dnl
_AC_ARG_VAR_CPPFLAGS()dnl
AC_LANG_PUSH(Objective C++)dnl
AC_MSG_CHECKING([how to run the Objective C++ preprocessor])
if test -z "$OBJCXXCPP"; then
  AC_CACHE_VAL(ac_cv_prog_OBJCXXCPP,
  [dnl
    # Double quotes because $OBJCXX needs to be expanded
    for OBJCXXCPP in "$OBJCXX -E" cpp /lib/cpp
    do
      _AC_PROG_PREPROC_WORKS_IFELSE([break])
    done
    ac_cv_prog_OBJCXXCPP=$OBJCXXCPP
  ])dnl
  OBJCXXCPP=$ac_cv_prog_OBJCXXCPP
else
  ac_cv_prog_OBJCXXCPP=$OBJCXXCPP
fi
AC_MSG_RESULT([$OBJCXXCPP])
_AC_PROG_PREPROC_WORKS_IFELSE([],
          [AC_MSG_FAILURE([Objective C++ preprocessor "$OBJCXXCPP" fails sanity check])])
AC_SUBST(OBJCXXCPP)dnl
AC_LANG_POP(Objective C++)dnl
])# AC_PROG_OBJCXXCPP


# AC_LANG_COMPILER(Objective C++)
# -------------------------------
# Find the Objective C++ compiler.  Must be AC_DEFUN'd to be AC_REQUIRE'able.
AC_DEFUN([AC_LANG_COMPILER(Objective C++)],
[AC_REQUIRE([AC_PROG_OBJCXX])])



# AC_PROG_OBJCXX([LIST-OF-COMPILERS])
# -----------------------------------
# LIST-OF-COMPILERS is a space separated list of Objective 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
# Objective C++ compiler.
# FIXME: this list is pure guesswork
# objc++ StepStone Objective-C++ compiler (also "standard" name for OBJCXX)
# objcxx David Stes' POC.  If you installed this, you likely want it.
# c++    Native C++ compiler (for instance, Apple).
# CXX    You never know.
AN_MAKEVAR([OBJCXX],  [AC_PROG_OBJCXX])
AN_PROGRAM([objcxx],  [AC_PROG_OBJCXX])
AC_DEFUN([AC_PROG_OBJCXX],
[AC_LANG_PUSH(Objective C++)dnl
AC_ARG_VAR([OBJCXX],      [Objective C++ compiler command])dnl
AC_ARG_VAR([OBJCXXFLAGS], [Objective C++ compiler flags])dnl
_AC_ARG_VAR_LDFLAGS()dnl
_AC_ARG_VAR_LIBS()dnl
_AC_ARG_VAR_CPPFLAGS()dnl
_AC_ARG_VAR_PRECIOUS([OBJCXX])dnl
AC_CHECK_TOOLS(OBJCXX,
               [m4_default([$1], [g++ objc++ objcxx c++ CXX])],
               g++)
# 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
  GOBJCXX=yes
else
  GOBJCXX=
fi
_AC_PROG_OBJCXX_G
AC_LANG_POP(Objective C++)dnl
])# AC_PROG_OBJCXX


# _AC_PROG_OBJCXX_G
# -----------------
# Check whether -g works, even if OBJCFLAGS is set, in case the package
# plays around with OBJCFLAGS (such as to build both debugging and
# normal versions of a library), tasteless as that idea is.
# Don't consider -g to work if it generates warnings when plain compiles don't.
m4_define([_AC_PROG_OBJCXX_G],
[ac_test_OBJCXXFLAGS=${OBJCXXFLAGS+y}
ac_save_OBJCXXFLAGS=$OBJCXXFLAGS
AC_CACHE_CHECK(whether $OBJCXX accepts -g, ac_cv_prog_objcxx_g,
  [ac_save_objcxx_werror_flag=$ac_objcxx_werror_flag
   ac_objcxx_werror_flag=yes
   ac_cv_prog_objcxx_g=no
   OBJCXXFLAGS="-g"
   _AC_COMPILE_IFELSE([AC_LANG_PROGRAM()],
     [ac_cv_prog_objcxx_g=yes],
     [OBJCXXFLAGS=""
      _AC_COMPILE_IFELSE([AC_LANG_PROGRAM()],
        [],
        [ac_objcxx_werror_flag=$ac_save_objcxx_werror_flag
         OBJCXXFLAGS="-g"
         _AC_COMPILE_IFELSE([AC_LANG_PROGRAM()],
           [ac_cv_prog_objcxx_g=yes])])])
   ac_objcxx_werror_flag=$ac_save_objcx_werror_flag])
if test $ac_test_OBJCXXFLAGS; then
  OBJCXXFLAGS=$ac_save_OBJCXXFLAGS
elif test $ac_cv_prog_objcxx_g = yes; then
  if test "$GOBJCXX" = yes; then
    OBJCXXFLAGS="-g -O2"
  else
    OBJCXXFLAGS="-g"
  fi
else
  if test "$GOBJCXX" = yes; then
    OBJCXXFLAGS="-O2"
  else
    OBJCXXFLAGS=
  fi
fi[]dnl
])# _AC_PROG_OBJCXX_G



## ------------------------------- ##
## 4. Compilers' characteristics.  ##
## ------------------------------- ##

# -------------------------------- #
# 4a. C compiler characteristics.  #
# -------------------------------- #

# Fragments of these programs are emitted as shell variables in the
# INIT_PREPARE diversion, because they can get long and we want only
# one copy of each fragment in the generated configure.  This also
# makes quoting control a bit easier.  Try to avoid using ', however,
# because putting single quotes into a single-quoted shell string is
# awkward (you must write '\'' for each ' you want in the program).
#
# Warning: to avoid incorrect answers due to unused-variable warnings
# and/or overly aggressive optimizers, each variable (global or not)
# in these programs should be used, and each function should be
# called.  Unlike how AC_LANG_PROGRAM(C) usually does it, we declare
# main with its usual two arguments, to give the test fragments some
# convenient non-compile-time-constant values to pass around.  In main,
# there is an int variable 'ok' which will eventually become the return
# value; use 'ok |= ...' to consume the results of operations.
#
# Warning: each test program may only use the headers required to
# exist in the relevant standard's *freestanding* environment, in case
# the C compiler targets such an environment.  (Therefore, almost no
# features of the C89/C99/C11/C23 standard *library* are probed.  Use
# AC_CHECK_HEADER, AC_CHECK_FUNC, etc. for that.)  However, these
# programs are only compiled and not linked, so it is ok to declare
# external functions and then call them without worrying about whether
# they actually exist.
#
# The C89 freestanding headers are:
#     <float.h> <limits.h> <stdarg.h> <stddef.h>
# C99 adds:
#     <iso646.h> <stdbool.h> <stdint.h>
# C11 adds:
#     <stdalign.h> <stdnoreturn.h>
# C23 adds:
#     <stdbit.h>

AC_DEFUN([_AC_C_C89_TEST_GLOBALS],
[m4_divert_text([INIT_PREPARE],
[[# Test code for whether the C compiler supports C89 (global declarations)
ac_c_conftest_c89_globals='
/* Do not test the value of __STDC__, because some compilers define it to 0
   or do not define it, while otherwise adequately conforming.  */

#include <stddef.h>
#include <stdarg.h>
struct stat;
/* Most of the following tests are stolen from RCS 5.7 src/conf.sh.  */
struct buf { int x; };
struct buf * (*rcsopen) (struct buf *, struct stat *, int);
static char *e (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;
}

/* C89 style stringification. */
#define noexpand_stringify(a) #a
const char *stringified = noexpand_stringify(arbitrary+token=sequence);

/* C89 style token pasting.  Exercises some of the corner cases that
   e.g. old MSVC gets wrong, but not very hard. */
#define noexpand_concat(a,b) a##b
#define expand_concat(a,b) noexpand_concat(a,b)
extern int vA;
extern int vbee;
#define aye A
#define bee B
int *pvA = &expand_concat(v,aye);
int *pvbee = &noexpand_concat(v,bee);

/* 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 do not provoke an error unfortunately, instead are silently treated
   as an "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 is necessary to write \x00 == 0 to get something
   that is 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 **, int *(*)(struct buf *, struct stat *, int),
               int, int);'
]])])

AC_DEFUN([_AC_C_C89_TEST_MAIN],
[m4_divert_text([INIT_PREPARE],
[[# Test code for whether the C compiler supports C89 (body of main).
ac_c_conftest_c89_main='
ok |= (argc == 0 || f (e, argv, 0) != argv[0] || f (e, argv, 1) != argv[1]);
'
]])])

AC_DEFUN([_AC_C_C99_TEST_GLOBALS],
[m4_divert_text([INIT_PREPARE],
[[# Test code for whether the C compiler supports C99 (global declarations)
ac_c_conftest_c99_globals='
/* Does the compiler advertise C99 conformance? */
#if !defined __STDC_VERSION__ || __STDC_VERSION__ < 199901L
# error "Compiler does not advertise C99 conformance"
#endif

// See if C++-style comments work.

#include <stdbool.h>
extern int puts (const char *);
extern int printf (const char *, ...);
extern int dprintf (int, const char *, ...);
extern void *malloc (size_t);
extern void free (void *);

// Check varargs macros.  These examples are taken from C99 6.10.3.5.
// dprintf is used instead of fprintf to avoid needing to declare
// FILE and stderr.
#define debug(...) dprintf (2, __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
  #error "your preprocessor is broken"
#endif
#if BIG_OK
#else
  #error "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)
{
  // 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_DEFUN([_AC_C_C99_TEST_MAIN],
[m4_divert_text([INIT_PREPARE],
[[# Test code for whether the C compiler supports C99 (body of main).
ac_c_conftest_c99_main='
  // Check bool.
  _Bool success = false;
  success |= (argc != 0);

  // 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;
  // Work around memory leak warnings.
  free (ia);

  // Check named initializers.
  struct named_init ni = {
    .number = 34,
    .name = L"Test wide string",
    .average = 543.34343,
  };

  ni.number = 58;

  // Do not test for VLAs, as some otherwise-conforming compilers lack them.
  // C code should instead use __STDC_NO_VLA__; see Autoconf manual.

  // work around unused variable warnings
  ok |= (!success || bignum == 0LL || ubignum == 0uLL || newvar[0] == '\''x'\''
         || ni.number != 58);
'
]])])

AC_DEFUN([_AC_C_C11_TEST_GLOBALS],
[m4_divert_text([INIT_PREPARE],
[[# Test code for whether the C compiler supports C11 (global declarations)
ac_c_conftest_c11_globals='
/* Does the compiler advertise C11 conformance? */
#if !defined __STDC_VERSION__ || __STDC_VERSION__ < 201112L
# error "Compiler does not advertise C11 conformance"
#endif

// 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_DEFUN([_AC_C_C11_TEST_MAIN],
[m4_divert_text([INIT_PREPARE],
[[# Test code for whether the C compiler supports C11 (body of main).
ac_c_conftest_c11_main='
  _Static_assert ((offsetof (struct anonymous, i)
                   == offsetof (struct anonymous, w.k)),
                  "Anonymous union alignment botch");
  v1.i = 2;
  v1.w.k = 5;
  ok |= v1.i != 5;
'
]])])

AC_DEFUN([_AC_C_C23_TEST_GLOBALS],
[m4_divert_text([INIT_PREPARE],
[[# Test code for whether the C compiler supports C23 (global declarations)
ac_c_conftest_c23_globals='
/* Does the compiler advertise conformance to C17 or earlier?
   Although GCC 14 does not do that, even with -std=gnu23,
   it is close enough, and defines __STDC_VERSION == 202000L.  */
#if !defined __STDC_VERSION__ || __STDC_VERSION__ <= 201710L
# error "Compiler advertises conformance to C17 or earlier"
#endif

// Check alignas.
char alignas (double) c23_aligned_as_double;
char alignas (0) c23_no_special_alignment;
extern char c23_aligned_as_int;
char alignas (0) alignas (int) c23_aligned_as_int;

// Check alignof.
enum
{
  c23_int_alignment = alignof (int),
  c23_int_array_alignment = alignof (int[100]),
  c23_char_alignment = alignof (char)
};
static_assert (0 < -alignof (int), "alignof is signed");

int function_with_unnamed_parameter (int) { return 0; }

void c23_noreturn ();

bool use_u8 = !u8"\xFF" == u8'\''x'\'';

bool check_that_bool_works = true | false | !nullptr;
#if !true
# error "true does not work in #if"
#endif
#if false
#elifdef __STDC_VERSION__
#else
# error "#elifdef does not work"
#endif

#ifndef __has_c_attribute
# error "__has_c_attribute not defined"
#endif

#ifndef __has_include
# error "__has_include not defined"
#endif

#define LPAREN() (
#define FORTY_TWO(x) 42
#define VA_OPT_TEST(r, x, ...) __VA_OPT__ (FORTY_TWO r x))
static_assert (VA_OPT_TEST (LPAREN (), 0, <:-) == 42);

static_assert (0b101010 == 42);
static_assert (0B101010 == 42);
static_assert (0xDEAD'\''BEEF == 3'\''735'\''928'\''559);
static_assert (0.500'\''000'\''000 == 0.5);

enum unsignedish : unsigned int { uione = 1 };
static_assert (0 < -uione);

#include <stddef.h>
constexpr nullptr_t null_pointer = nullptr;

#include <stdbit.h>
static_assert (__STDC_ENDIAN_LITTLE__ != __STDC_ENDIAN_BIG__);

static typeof (1 + 1L) two () { return 2; }
static long int three () { return 3; }
'
]])])

AC_DEFUN([_AC_C_C23_TEST_MAIN],
[m4_divert_text([INIT_PREPARE],
[[# Test code for whether the C compiler supports C23 (body of main).
ac_c_conftest_c23_main='
  {
    label_before_declaration:
      int arr[10] = {};
      if (arr[0])
        goto label_before_declaration;
      if (!arr[0])
        goto label_at_end_of_block;
    label_at_end_of_block:
  }
  ok |= two != three;
'
]])])

AC_DEFUN([_AC_C_C89_TEST_PROGRAM],
[AC_REQUIRE([_AC_C_C89_TEST_GLOBALS])dnl
AC_REQUIRE([_AC_C_C89_TEST_MAIN])dnl
m4_divert_text([INIT_PREPARE],
[[# Test code for whether the C compiler supports C89 (complete).
ac_c_conftest_c89_program="${ac_c_conftest_c89_globals}

int
main (int argc, char **argv)
{
  int ok = 0;
  ${ac_c_conftest_c89_main}
  return ok;
}
"
]])])

AC_DEFUN([_AC_C_C99_TEST_PROGRAM],
[AC_REQUIRE([_AC_C_C89_TEST_GLOBALS])dnl
AC_REQUIRE([_AC_C_C89_TEST_MAIN])dnl
AC_REQUIRE([_AC_C_C99_TEST_GLOBALS])dnl
AC_REQUIRE([_AC_C_C99_TEST_MAIN])dnl
m4_divert_text([INIT_PREPARE],
[[# Test code for whether the C compiler supports C99 (complete).
ac_c_conftest_c99_program="${ac_c_conftest_c89_globals}
${ac_c_conftest_c99_globals}

int
main (int argc, char **argv)
{
  int ok = 0;
  ${ac_c_conftest_c89_main}
  ${ac_c_conftest_c99_main}
  return ok;
}
"
]])])

AC_DEFUN([_AC_C_C11_TEST_PROGRAM],
[AC_REQUIRE([_AC_C_C89_TEST_GLOBALS])dnl
AC_REQUIRE([_AC_C_C89_TEST_MAIN])dnl
AC_REQUIRE([_AC_C_C99_TEST_GLOBALS])dnl
AC_REQUIRE([_AC_C_C99_TEST_MAIN])dnl
AC_REQUIRE([_AC_C_C11_TEST_GLOBALS])dnl
AC_REQUIRE([_AC_C_C11_TEST_MAIN])dnl
m4_divert_text([INIT_PREPARE],
[[# Test code for whether the C compiler supports C11 (complete).
ac_c_conftest_c11_program="${ac_c_conftest_c89_globals}
${ac_c_conftest_c99_globals}
${ac_c_conftest_c11_globals}

int
main (int argc, char **argv)
{
  int ok = 0;
  ${ac_c_conftest_c89_main}
  ${ac_c_conftest_c99_main}
  ${ac_c_conftest_c11_main}
  return ok;
}
"
]])])

AC_DEFUN([_AC_C_C23_TEST_PROGRAM],
[AC_REQUIRE([_AC_C_C23_TEST_GLOBALS])dnl
AC_REQUIRE([_AC_C_C23_TEST_MAIN])dnl
m4_divert_text([INIT_PREPARE],
[[# Test code for whether the C compiler supports C23 (complete).
ac_c_conftest_c23_program="${ac_c_conftest_c23_globals}

int
main (int, char **)
{
  int ok = 0;
  ${ac_c_conftest_c23_main}
  return ok;
}
"
]])])


# _AC_C_C89_OPTIONS
# -----------------
# Whitespace-separated list of options that might put the C compiler
# into a mode conforming to ISO C1990 with extensions.  Do not try
# "strictly conforming" modes (e.g. gcc's -std=c90); they break some
# systems' header files.  If more than one option is needed, put
# shell quotes around the group.
#
# AIX circa 2003         -qlanglvl=extc89
# old AIX                -qlanglvl=ansi
# Ultrix, OSF/1, Tru64   -std
# HP-UX 10.20 and later  -Ae
# HP-UX older versions   -Aa -D_HPUX_SOURCE
# SVR4                   -Xc -D__EXTENSIONS__
m4_define([_AC_C_C89_OPTIONS], [
    -qlanglvl=extc89
    -qlanglvl=ansi
    -std
    -Ae
    "-Aa -D_HPUX_SOURCE"
    "-Xc -D__EXTENSIONS__"
])


# _AC_C_C99_OPTIONS
# -----------------
# Whitespace-separated list of options that might put the C compiler
# into a mode conforming to ISO C1999 with extensions.  Do not try
# "strictly conforming" modes (e.g. gcc's -std=c99); they break some
# systems' header files.  If more than one option is needed, put
# shell quotes around the group.
#
# GCC, Clang    -std=gnu99
# Intel ICC     -std=c99, -c99 (deprecated)
#   Note: because -std=c99 puts GCC in strictly conforming mode,
#   this option must be tested *after* -std=gnu99.
# IRIX          -c99
# Tru64         -c99
# IBM XL C      -qlanglvl=extc1x (V12.1; does not pass C11 test)
# IBM XL C      -qlanglvl=extc99 (pre-V12.1)
# HP cc         -AC99
# Solaris       -D_STDC_C99=
#   Note: acc's -xc99 option uses linker magic to define the external
#   symbol __xpg4 as if by "int __xpg4 = 1;", which enables C99
#   behavior for C library functions.  This is not wanted here,
#   because it means that a single module compiled with -xc99 alters
#   C runtime behavior for the entire program, not for just the
#   module.  Instead, define the (private) symbol _STDC_C99, which
#   suppresses a bogus failure in <stdbool.h>.  The resulting compiler
#   passes the test case here, and that's good enough.
#   For more, please see the thread starting at:
#   https://lists.gnu.org/archive/html/autoconf/2010-12/msg00059.html
m4_define([_AC_C_C99_OPTIONS], [
    -std=gnu99
    -std=c99
    -c99
    -qlanglvl=extc1x
    -qlanglvl=extc99
    -AC99
    -D_STDC_C99=
])


# _AC_C_C11_OPTIONS
# -----------------
# Whitespace-separated list of options that might put the C compiler
# into a mode conforming to ISO C2011 with extensions.  Do not try
# "strictly conforming" modes (e.g. gcc's -std=c11); they break some
# systems' header files.  If more than one option is needed, put
# shell quotes around the group.
#
# GCC, Clang    -std=gnu11
# MSVC          -std:c11
#
# For IBM XL C for AIX V16.1 or later, '-std=gnu11' should work if
# the user configured with CC='xlclang'.  Otherwise, do not try
# -qlanglvl=extc1x as xlc with IBM XL C V16.1 (the latest version as
# of August 2020) does not pass the C11 test.  Instead, try extc1x when
# compiling the C99 test instead, since it enables _Static_assert and
# _Noreturn, which is a win.
m4_define([_AC_C_C11_OPTIONS], [
    -std=gnu11
    -std:c11
])

# _AC_C_C23_OPTIONS
# -----------------
# Whitespace-separated list of options that might put the C compiler
# into a mode conforming to ISO C 2023 with extensions.  Do not try
# "strictly conforming" modes (e.g. gcc's -std=c23); they break some
# systems' header files.  If more than one option is needed, put
# shell quotes around the group.
#
# GCC, Clang    -std=gnu23
m4_define([_AC_C_C23_OPTIONS], [
    -std=gnu23
])


# _AC_PROG_CC_STDC_EDITION_TRY(EDITION)
# -------------------------------------
# Subroutine of _AC_PROG_CC_STDC_EDITION.  Not to be called directly.
#
# Check whether the C compiler accepts features of EDITION of the
# C standard.  EDITION should be a two-digit year (e.g. 89, 99, 11, 23).
# (FIXME: Switch to four-digit years for futureproofing.)
# This is done by compiling the test program defined by
# _AC_C_C{EDITION}_TEST_PROGRAM, first with no additional
# command-line options, and then with each of the options
# in the space-separated list defined by _AC_C_C{EDITION}_OPTIONS.
#
# If we find a way to make the test program compile, set cache variable
# ac_cv_prog_cc_cEDITION to the options required (if any), and add those
# options to $CC.  Set shell variable ac_prog_cc_stdc to 'cEDITION',
# and set shell variable ac_cv_prog_cc_stdc to the options required.
# (Neither of these variables is AC_SUBSTed.  ac_cv_prog_cc_stdc used
# to be a cache variable and is preserved with this name for backward
# compatibility.)  Otherwise, ac_cv_prog_cc_cEDITION is set to 'no'
# and the other variables are not changed.
#
# If ac_prog_cc_stdc is already set to a value other than 'no',
# the shell code produced by this macro does nothing.  This is so
# _AC_PROG_CC_STDC_EDITION can use m4_map to iterate through
# all the editions.
AC_DEFUN([_AC_PROG_CC_STDC_EDITION_TRY],
[AC_LANG_ASSERT([C])]dnl
[AC_REQUIRE([_AC_C_C$1_TEST_PROGRAM])]dnl
[AS_IF([test x$ac_prog_cc_stdc = xno],
[AC_MSG_CHECKING([for $CC option to enable C$1 features])
AC_CACHE_VAL([ac_cv_prog_cc_c$1],
[ac_cv_prog_cc_c$1=no
ac_save_CC=$CC
AC_LANG_CONFTEST([AC_LANG_DEFINES_PROVIDED][$][ac_c_conftest_c$1_program])
for ac_arg in '' m4_normalize(m4_defn([_AC_C_C$1_OPTIONS]))
do
  CC="$ac_save_CC $ac_arg"
  _AC_COMPILE_IFELSE([], [ac_cv_prog_cc_c$1=$ac_arg])
  test "x$ac_cv_prog_cc_c$1" != "xno" && break
done
rm -f conftest.$ac_ext
CC=$ac_save_CC])
AS_IF([test "x$ac_cv_prog_cc_c$1" = xno],
  [AC_MSG_RESULT([unsupported])],
  [AS_IF([test "x$ac_cv_prog_cc_c$1" = x],
    [AC_MSG_RESULT([none needed])],
    [AC_MSG_RESULT([$ac_cv_prog_cc_c$1])
     CC="$CC $ac_cv_prog_cc_c$1"])
  ac_cv_prog_cc_stdc=$ac_cv_prog_cc_c$1
  ac_prog_cc_stdc=c$1])])
])


# _AC_PROG_CC_STDC_EDITION
# ------------------------
# Detect the most recent edition of the ISO C standard that is
# supported by the C compiler.  Add command-line options to $CC, if
# necessary, to enable support for this edition.  Set the shell
# variable ac_prog_cc_stdc to indicate the edition.
AC_DEFUN([_AC_PROG_CC_STDC_EDITION],
[ac_prog_cc_stdc=no
m4_map([_AC_PROG_CC_STDC_EDITION_TRY], [[23], [11], [99], [89]])])


# _AC_PROG_CC_C89(ACTION-IF-SUPPORTED, ACTION-IF-NOT-SUPPORTED)
# -------------------------------------------------------------
# Obsolete internal macro.  No longer used by Autoconf itself, but
# preserved for backward compatibility with pre-December 2020 versions
# of Gnulib's std-gnu11.m4, which replaced the entire definition of
# AC_PROG_CC *except* for this macro.  Can be removed once everyone is
# using Autoconf 2.70 and/or a current std-gnu11.m4.
AC_DEFUN([_AC_PROG_CC_C89],
[AC_REQUIRE([_AC_C_C89_TEST_GLOBALS])]dnl
[AC_REQUIRE([_AC_C_C89_TEST_MAIN])]dnl
[_AC_C_STD_TRY([c89],
  [$ac_c_conftest_c89_globals], [$ac_c_conftest_c89_main],
  m4_quote(m4_normalize(m4_defn([_AC_C_C89_OPTIONS]))),
  [$1],
  [$2])])



# 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
# <https://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_PROG_GCC_TRADITIONAL
# -----------------------
AU_DEFUN([AC_PROG_GCC_TRADITIONAL],
  [AC_REQUIRE([AC_PROG_CC])],
  [$0 is obsolete; use AC_PROG_CC]
)

# AC_C_BACKSLASH_A
# ----------------
AC_DEFUN([AC_C_BACKSLASH_A],
[
  AC_CACHE_CHECK([whether backslash-a works in strings], ac_cv_c_backslash_a,
   [AC_COMPILE_IFELSE([AC_LANG_PROGRAM([],
     [[
#if '\a' == 'a'
      syntax error;
#endif
      char buf['\a' == 'a' ? -1 : 1];
      buf[0] = '\a';
      return buf[0] != "\a"[0];
     ]])],
     [ac_cv_c_backslash_a=yes],
     [ac_cv_c_backslash_a=no])])
  if test $ac_cv_c_backslash_a = yes; then
    AC_DEFINE(HAVE_C_BACKSLASH_A, 1,
      [Define if backslash-a works in C strings.])
  fi
])


# AC_C_CROSS
# ----------
# Has been merged into AC_PROG_CC.
AU_DEFUN([AC_C_CROSS], [])


# AC_C_CHAR_UNSIGNED
# ------------------
AC_DEFUN([AC_C_CHAR_UNSIGNED],
[AH_VERBATIM([__CHAR_UNSIGNED__],
[/* Define to 1 if type 'char' is unsigned and your compiler does not
   predefine this macro.  */
#ifndef __CHAR_UNSIGNED__
# undef __CHAR_UNSIGNED__
#endif])dnl
AC_CACHE_CHECK(whether char is unsigned, ac_cv_c_char_unsigned,
[AC_COMPILE_IFELSE([AC_LANG_BOOL_COMPILE_TRY([AC_INCLUDES_DEFAULT([])],
                                             [((char) -1) < 0])],
                   ac_cv_c_char_unsigned=no, ac_cv_c_char_unsigned=yes)])
if test $ac_cv_c_char_unsigned = yes; then
  AC_DEFINE(__CHAR_UNSIGNED__)
fi
])# AC_C_CHAR_UNSIGNED


# AC_C_BIGENDIAN ([ACTION-IF-TRUE], [ACTION-IF-FALSE], [ACTION-IF-UNKNOWN],
#                 [ACTION-IF-UNIVERSAL])
# -------------------------------------------------------------------------
AC_DEFUN([AC_C_BIGENDIAN],
[AH_VERBATIM([WORDS_BIGENDIAN],
[/* Define WORDS_BIGENDIAN to 1 if your processor stores words with the most
   significant byte first (like Motorola and SPARC, unlike Intel). */
#if defined AC_APPLE_UNIVERSAL_BUILD
# if defined __BIG_ENDIAN__
#  define WORDS_BIGENDIAN 1
# endif
#else
# ifndef WORDS_BIGENDIAN
#  undef WORDS_BIGENDIAN
# endif
#endif])dnl
 AC_CACHE_CHECK([whether byte ordering is bigendian], [ac_cv_c_bigendian],
   [ac_cv_c_bigendian=unknown
    # See if we're dealing with a universal compiler.
    AC_COMPILE_IFELSE(
         [AC_LANG_SOURCE(
            [[#ifndef __APPLE_CC__
               not a universal capable compiler
             #endif
             typedef int dummy;
            ]])],
         [
        # Check for potential -arch flags.  It is not universal unless
        # there are at least two -arch flags with different values.
        ac_arch=
        ac_prev=
        for ac_word in $CC $CFLAGS $CPPFLAGS $LDFLAGS; do
         if test -n "$ac_prev"; then
           case $ac_word in
             i?86 | x86_64 | ppc | ppc64)
               if test -z "$ac_arch" || test "$ac_arch" = "$ac_word"; then
                 ac_arch=$ac_word
               else
                 ac_cv_c_bigendian=universal
                 break
               fi
               ;;
           esac
           ac_prev=
         elif test "x$ac_word" = "x-arch"; then
           ac_prev=arch
         fi
       done])
    if test $ac_cv_c_bigendian = unknown; then
      # See if sys/param.h defines the BYTE_ORDER macro.
      AC_COMPILE_IFELSE(
        [AC_LANG_PROGRAM(
           [[#include <sys/types.h>
             #include <sys/param.h>
           ]],
           [[#if ! (defined BYTE_ORDER && defined BIG_ENDIAN \\
                     && defined LITTLE_ENDIAN && BYTE_ORDER && BIG_ENDIAN \\
                     && LITTLE_ENDIAN)
              bogus endian macros
             #endif
           ]])],
        [# It does; now see whether it defined to BIG_ENDIAN or not.
         AC_COMPILE_IFELSE(
           [AC_LANG_PROGRAM(
              [[#include <sys/types.h>
                #include <sys/param.h>
              ]],
              [[#if BYTE_ORDER != BIG_ENDIAN
                 not big endian
                #endif
              ]])],
           [ac_cv_c_bigendian=yes],
           [ac_cv_c_bigendian=no])])
    fi
    if test $ac_cv_c_bigendian = unknown; then
      # See if <limits.h> defines _LITTLE_ENDIAN or _BIG_ENDIAN (e.g., Solaris).
      AC_COMPILE_IFELSE(
        [AC_LANG_PROGRAM(
           [[#include <limits.h>
           ]],
           [[#if ! (defined _LITTLE_ENDIAN || defined _BIG_ENDIAN)
              bogus endian macros
             #endif
           ]])],
        [# It does; now see whether it defined to _BIG_ENDIAN or not.
         AC_COMPILE_IFELSE(
           [AC_LANG_PROGRAM(
              [[#include <limits.h>
              ]],
              [[#ifndef _BIG_ENDIAN
                 not big endian
                #endif
              ]])],
           [ac_cv_c_bigendian=yes],
           [ac_cv_c_bigendian=no])])
    fi
    if test $ac_cv_c_bigendian = unknown; then
      # Compile a test program.
      AC_RUN_IFELSE(
        [AC_LANG_PROGRAM([AC_INCLUDES_DEFAULT],
           [[
             /* Are we little or big endian?  From Harbison&Steele.  */
             union
             {
               long int l;
               char c[sizeof (long int)];
             } u;
             u.l = 1;
             return u.c[sizeof (long int) - 1] == 1;
           ]])],
        [ac_cv_c_bigendian=no],
        [ac_cv_c_bigendian=yes],
        [# Try to guess by grepping values from an object file.
         AC_LINK_IFELSE(
           [AC_LANG_SOURCE(
              [[unsigned short int ascii_mm[] =
                  { 0x4249, 0x4765, 0x6E44, 0x6961, 0x6E53, 0x7953, 0 };
                unsigned short int ascii_ii[] =
                  { 0x694C, 0x5454, 0x656C, 0x6E45, 0x6944, 0x6E61, 0 };
                int use_ascii (int i) {
                  return ascii_mm[i] + ascii_ii[i];
                }
                unsigned short int ebcdic_ii[] =
                  { 0x89D3, 0xE3E3, 0x8593, 0x95C5, 0x89C4, 0x9581, 0 };
                unsigned short int ebcdic_mm[] =
                  { 0xC2C9, 0xC785, 0x95C4, 0x8981, 0x95E2, 0xA8E2, 0 };
                int use_ebcdic (int i) {
                  return ebcdic_mm[i] + ebcdic_ii[i];
                }
                int
                main (int argc, char **argv)
                {
                  /* Intimidate the compiler so that it does not
                     optimize the arrays away.  */
                  char *p = argv[0];
                  ascii_mm[1] = *p++; ebcdic_mm[1] = *p++;
                  ascii_ii[1] = *p++; ebcdic_ii[1] = *p++;
                  return use_ascii (argc) == use_ebcdic (*p);
                }]])],
           [if grep BIGenDianSyS conftest$ac_exeext >/dev/null; then
              ac_cv_c_bigendian=yes
            fi
            if grep LiTTleEnDian conftest$ac_exeext >/dev/null ; then
              if test "$ac_cv_c_bigendian" = unknown; then
                ac_cv_c_bigendian=no
              else
                # finding both strings is unlikely to happen, but who knows?
                ac_cv_c_bigendian=unknown
              fi
            fi])])
    fi])
 case $ac_cv_c_bigendian in #(
   yes)
     m4_default([$1],
       [AC_DEFINE([WORDS_BIGENDIAN], 1)]);; #(
   no)
     $2 ;; #(
   universal)
dnl Note that AC_APPLE_UNIVERSAL_BUILD sorts less than WORDS_BIGENDIAN;
dnl this is a necessity for proper config header operation.  Warn if
dnl the user did not specify a config header but is relying on the
dnl default behavior for universal builds.
     m4_default([$4],
       [AC_CONFIG_COMMANDS_PRE([m4_ifset([AH_HEADER], [],
         [m4_warn([obsolete],
           [AC_C_BIGENDIAN should be used with AC_CONFIG_HEADERS])])])dnl
        AC_DEFINE([AC_APPLE_UNIVERSAL_BUILD],1,
          [Define if building universal (internal helper macro)])])
     ;; #(
   *)
     m4_default([$3],
       [AC_MSG_ERROR([unknown endianness
 presetting ac_cv_c_bigendian=no (or yes) will help])]) ;;
 esac
])# AC_C_BIGENDIAN


# AC_C__GENERIC
# -------------
# Define HAVE_C__GENERIC if _Generic works, a la C11.
AN_IDENTIFIER([_Generic], [AC_C__GENERIC])
AC_DEFUN([AC_C__GENERIC],
[AC_CACHE_CHECK([for _Generic], ac_cv_c__Generic,
[AC_COMPILE_IFELSE(
   [AC_LANG_SOURCE(
      [[int
         main (int argc, char **argv)
         {
           int a = _Generic (argc, int: argc = 1);
           int *b = &_Generic (argc, default: argc);
           char ***c = _Generic (argv, int: argc, default: argv ? &argv : 0);
           _Generic (1 ? 0 : b, int: a, default: b) = &argc;
           _Generic (a = 1, default: a) = 3;
           return a + !b + !c;
         }
      ]])],
   [ac_cv_c__Generic=yes],
   [ac_cv_c__Generic=no])])
if test $ac_cv_c__Generic = yes; then
  AC_DEFINE([HAVE_C__GENERIC], 1,
            [Define to 1 if C11-style _Generic works.])
fi
])# AC_C__GENERIC

# AC_C_INLINE
# -----------
# Do nothing if the compiler accepts the inline keyword.
# Otherwise define inline to __inline__ or __inline if one of those work,
# otherwise define inline to be empty.
#
# HP C version B.11.11.04 doesn't allow a typedef as the return value for an
# inline function, only builtin types.
#
AN_IDENTIFIER([inline], [AC_C_INLINE])
AC_DEFUN([AC_C_INLINE],
[AC_CACHE_CHECK([for inline], ac_cv_c_inline,
[ac_cv_c_inline=no
for ac_kw in inline __inline__ __inline; do
  AC_COMPILE_IFELSE([AC_LANG_SOURCE(
[#ifndef __cplusplus
typedef int foo_t;
static $ac_kw foo_t static_foo (void) {return 0; }
$ac_kw foo_t foo (void) {return 0; }
#endif
])],
                    [ac_cv_c_inline=$ac_kw])
  test "$ac_cv_c_inline" != no && break
done
])
AH_VERBATIM([inline],
[/* Define to '__inline__' or '__inline' if that's what the C compiler
   calls it, or to nothing if 'inline' is not supported under any name.  */
#ifndef __cplusplus
#undef inline
#endif])
case $ac_cv_c_inline in
  inline | yes) ;;
  *)
    case $ac_cv_c_inline in
      no) ac_val=;;
      *) ac_val=$ac_cv_c_inline;;
    esac
    cat >>confdefs.h <<_ACEOF
#ifndef __cplusplus
#define inline $ac_val
#endif
_ACEOF
    ;;
esac
])# AC_C_INLINE


# AC_C_CONST
# ----------
AC_DEFUN([AC_C_CONST],
[AC_CACHE_CHECK([for an ANSI C-conforming const], ac_cv_c_const,
[AC_COMPILE_IFELSE([AC_LANG_PROGRAM([],
[[
#ifndef __cplusplus
  /* Ultrix mips cc rejects this sort of thing.  */
  typedef int charset[2];
  const charset cs = { 0, 0 };
  /* SunOS 4.1.1 cc rejects this.  */
  char const *const *pcpcc;
  char **ppc;
  /* NEC SVR4.0.2 mips cc rejects this.  */
  struct point {int x, y;};
  static struct point const zero = {0,0};
  /* IBM XL C 1.02.0.0 rejects this.
     It does not let you subtract one const X* pointer from another in
     an arm of an if-expression whose if-part is not a constant
     expression */
  const char *g = "string";
  pcpcc = &g + (g ? g-g : 0);
  /* HPUX 7.0 cc rejects these. */
  ++pcpcc;
  ppc = (char**) pcpcc;
  pcpcc = (char const *const *) ppc;
  { /* SCO 3.2v4 cc rejects this sort of thing.  */
    char tx;
    char *t = &tx;
    char const *s = 0 ? (char *) 0 : (char const *) 0;

    *t++ = 0;
    if (s) return 0;
  }
  { /* Someone thinks the Sun supposedly-ANSI compiler will reject this.  */
    int x[] = {25, 17};
    const int *foo = &x[0];
    ++foo;
  }
  { /* Sun SC1.0 ANSI compiler rejects this -- but not the above. */
    typedef const int *iptr;
    iptr p = 0;
    ++p;
  }
  { /* IBM XL C 1.02.0.0 rejects this sort of thing, saying
       "k.c", line 2.27: 1506-025 (S) Operand must be a modifiable lvalue. */
    struct s { int j; const int *ap[3]; } bx;
    struct s *b = &bx; b->j = 5;
  }
  { /* ULTRIX-32 V3.1 (Rev 9) vcc rejects this */
    const int foo = 10;
    if (!foo) return 0;
  }
  return !cs[0] && !zero.x;
#endif
]])],
                   [ac_cv_c_const=yes],
                   [ac_cv_c_const=no])])
if test $ac_cv_c_const = no; then
  AC_DEFINE(const,,
            [Define to empty if 'const' does not conform to ANSI C.])
fi
])# AC_C_CONST


# AC_C_RESTRICT
# -------------
# based on acx_restrict.m4, from the GNU Autoconf Macro Archive
#
# Determine whether the C/C++ compiler supports the "restrict" keyword
# introduced in ANSI C99, or an equivalent.  Define "restrict" to the alternate
# spelling, if any; these are more likely to work in both C and C++ compilers of
# the same family, and in the presence of varying compiler options.  If only
# plain "restrict" works, do nothing.  Here are some variants:
# - GCC supports both __restrict and __restrict__
# - older DEC Alpha C compilers support only __restrict
# - _Restrict is the only spelling accepted by Sun WorkShop 6 update 2 C
# Otherwise, define "restrict" to be empty.
AN_IDENTIFIER([restrict], [AC_C_RESTRICT])
AC_DEFUN([AC_C_RESTRICT],
[AC_CACHE_CHECK([for C/C++ restrict keyword], [ac_cv_c_restrict],
  [ac_cv_c_restrict=no
   # Put '__restrict__' first, to avoid problems with glibc and non-GCC; see:
   # https://lists.gnu.org/archive/html/bug-autoconf/2016-02/msg00006.html
   # Put 'restrict' last, because C++ lacks it.
   for ac_kw in __restrict__ __restrict _Restrict restrict; do
     AC_COMPILE_IFELSE(
      [AC_LANG_PROGRAM(
         [[typedef int *int_ptr;
           int foo (int_ptr $ac_kw ip) { return ip[0]; }
           int bar (int [$ac_kw]); /* Catch GCC bug 14050.  */
           int bar (int ip[$ac_kw]) { return ip[0]; }
         ]],
         [[int s[1];
           int *$ac_kw t = s;
           t[0] = 0;
           return foo (t) + bar (t);
         ]])],
      [ac_cv_c_restrict=$ac_kw])
     test "$ac_cv_c_restrict" != no && break
   done
  ])
 AH_VERBATIM([restrict],
[/* Define to the equivalent of the C99 'restrict' keyword, or to
   nothing if this is not supported.  Do not define if restrict is
   supported only directly.  */
#undef restrict
/* Work around a bug in older versions of Sun C++, which did not
   #define __restrict__ or support _Restrict or __restrict__
   even though the corresponding Sun C compiler ended up with
   "#define restrict _Restrict" or "#define restrict __restrict__"
   in the previous line.  This workaround can be removed once
   we assume Oracle Developer Studio 12.5 (2016) or later.  */
#if defined __SUNPRO_CC && !defined __RESTRICT && !defined __restrict__
# define _Restrict
# define __restrict__
#endif])
 case $ac_cv_c_restrict in
   restrict) ;;
   no) AC_DEFINE([restrict], []) ;;
   *)  AC_DEFINE_UNQUOTED([restrict], [$ac_cv_c_restrict]) ;;
 esac
])# AC_C_RESTRICT


# AC_C_VOLATILE
# -------------
# Note that, unlike const, #defining volatile to be the empty string can
# actually turn a correct program into an incorrect one, since removing
# uses of volatile actually grants the compiler permission to perform
# optimizations that could break the user's code.  So, do not #define
# volatile away unless it is really necessary to allow the user's code
# to compile cleanly.  Benign compiler failures should be tolerated.
AC_DEFUN([AC_C_VOLATILE],
[AC_CACHE_CHECK([for working volatile], ac_cv_c_volatile,
[AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [
volatile int x;
int * volatile y = (int *) 0;
return !x && !y;])],
                   [ac_cv_c_volatile=yes],
                   [ac_cv_c_volatile=no])])
if test $ac_cv_c_volatile = no; then
  AC_DEFINE(volatile,,
            [Define to empty if the keyword 'volatile' does not work.
             Warning: valid code using 'volatile' can become incorrect
             without.  Disable with care.])
fi
])# AC_C_VOLATILE


# AC_C_STRINGIZE
# --------------
# Checks if '#' can be used to glue strings together at the CPP level.
# Defines HAVE_STRINGIZE if positive.
# Obsolete - new code should assume C89 compliance.
AC_DEFUN([AC_C_STRINGIZE],
[AC_REQUIRE([AC_PROG_CC])
if test "$ac_prog_cc_stdc" != no; then
  AC_DEFINE(HAVE_STRINGIZE, 1,
            [Define to 1 if cpp supports the ANSI @%:@ stringizing operator.])
fi
])# AC_C_STRINGIZE


# AC_C_PROTOTYPES
# ---------------
# Check if the C compiler supports prototypes.
# Obsolete - new code should assume C89 compliance.
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_C_FLEXIBLE_ARRAY_MEMBER
# --------------------------
# Check whether the C compiler supports flexible array members.
AC_DEFUN([AC_C_FLEXIBLE_ARRAY_MEMBER],
[
  AC_CACHE_CHECK([for flexible array members],
    ac_cv_c_flexmember,
    [AC_COMPILE_IFELSE(
       [AC_LANG_PROGRAM(
          [[#include <stdlib.h>
            #include <stdio.h>
            #include <stddef.h>
            struct s { int n; double d[]; };]],
          [[int m = getchar ();
            struct s *p = (struct s *) malloc (offsetof (struct s, d)
                                               + m * sizeof (double));
            p->d[0] = 0.0;
            m = p->d != (double *) NULL;
            free (p);
            return m;]])],
       [ac_cv_c_flexmember=yes],
       [ac_cv_c_flexmember=no])])
  if test $ac_cv_c_flexmember = yes; then
    AC_DEFINE([FLEXIBLE_ARRAY_MEMBER], [],
      [Define to nothing if C supports flexible array members, and to
       1 if it does not.  That way, with a declaration like 'struct s
       { int n; double d@<:@FLEXIBLE_ARRAY_MEMBER@:>@; };', the struct hack
       can be used with pre-C99 compilers.
       When computing the size of such an object, don't use 'sizeof (struct s)'
       as it overestimates the size.  Use 'offsetof (struct s, d)' instead.
       Don't use 'offsetof (struct s, d@<:@0@:>@)', as this doesn't work with
       MSVC and with C++ compilers.])
  else
    AC_DEFINE([FLEXIBLE_ARRAY_MEMBER], 1)
  fi
])


# AC_C_VARARRAYS
# --------------
# Check whether the C compiler supports variable-length arrays.
AC_DEFUN([AC_C_VARARRAYS],
[
  AC_CACHE_CHECK([for variable-length arrays],
    ac_cv_c_vararrays,
    [AC_COMPILE_IFELSE([AC_LANG_SOURCE(
[[      #ifndef __STDC_NO_VLA__
        #error __STDC_NO_VLA__ not defined
        #endif
]])],
       [ac_cv_c_vararrays='no: __STDC_NO_VLA__ is defined'],
       [AC_COMPILE_IFELSE(
          [AC_LANG_PROGRAM(
             [[/* Test for VLA support.  This test is partly inspired
                  from examples in the C standard.  Use at least two VLA
                  functions to detect the GCC 3.4.3 bug described in:
                  https://lists.gnu.org/archive/html/bug-gnulib/2014-08/msg00014.html
                  */
               #ifdef __STDC_NO_VLA__
                syntax error;
               #else
                 extern int n;
                 int B[100];
                 int fvla (int m, int C[m][m]);

                 int
                 simple (int count, int all[static count])
                 {
                   return all[count - 1];
                 }

                 int
                 fvla (int m, int C[m][m])
                 {
                   typedef int VLA[m][m];
                   VLA x;
                   int D[m];
                   static int (*q)[m] = &B;
                   int (*s)[n] = q;
                   return C && &x[0][0] == &D[0] && &D[0] == s[0];
                 }
               #endif
               ]])],
          [ac_cv_c_vararrays=yes],
          [ac_cv_c_vararrays=no])])])
  if test "$ac_cv_c_vararrays" = yes; then
    dnl This is for compatibility with Autoconf 2.61-2.69.
    AC_DEFINE([HAVE_C_VARARRAYS], 1,
      [Define to 1 if C supports variable-length arrays.])
  elif test "$ac_cv_c_vararrays" = no; then
    AC_DEFINE([__STDC_NO_VLA__], 1,
      [Define to 1 if C does not support variable-length arrays, and
       if the compiler does not already define this.])
  fi
])


# AC_C_TYPEOF
# -----------
# Check if the C compiler supports GCC's typeof syntax.
# The test case provokes incompatibilities in the Sun C compilers
# (both Solaris 8 and Solaris 10).
AC_DEFUN([AC_C_TYPEOF],
[
  AC_CACHE_CHECK([for typeof syntax and keyword spelling], ac_cv_c_typeof,
    [ac_cv_c_typeof=no
     for ac_kw in typeof __typeof__ no; do
       test $ac_kw = no && break
       AC_COMPILE_IFELSE([AC_LANG_PROGRAM([],
         [[
           int value;
           typedef struct {
                   char a [1
                           + ! (($ac_kw (value))
                                (($ac_kw (value)) 0 < ($ac_kw (value)) -1
                                 ? ($ac_kw (value)) - 1
                                 : ~ (~ ($ac_kw (value)) 0
                                      << sizeof ($ac_kw (value)))))]; }
              ac__typeof_type_;
           return
             (! ((void) ((ac__typeof_type_ *) 0), 0));
         ]])],
         [ac_cv_c_typeof=$ac_kw])
       test $ac_cv_c_typeof != no && break
     done])
  if test $ac_cv_c_typeof != no; then
    AC_DEFINE([HAVE_TYPEOF], 1,
      [Define to 1 if typeof works with your compiler.])
    if test $ac_cv_c_typeof != typeof; then
      AC_DEFINE_UNQUOTED([typeof], [$ac_cv_c_typeof],
        [Define to __typeof__ if your compiler spells it that way.])
    fi
  fi
])


# _AC_LANG_OPENMP
# ---------------
# Expands to some language dependent source code for testing the presence of
# OpenMP.
AC_DEFUN([_AC_LANG_OPENMP],
[AC_LANG_SOURCE([_AC_LANG_DISPATCH([$0], _AC_LANG, $@)])])

# _AC_LANG_OPENMP(C)
# ------------------
m4_define([_AC_LANG_OPENMP(C)],
[
#ifndef _OPENMP
#error "OpenMP not supported"
#endif
#include <omp.h>
int main (void) { return omp_get_num_threads (); }
])

# _AC_LANG_OPENMP(C++)
# --------------------
m4_copy([_AC_LANG_OPENMP(C)], [_AC_LANG_OPENMP(C++)])

# _AC_LANG_OPENMP(Fortran 77)
# ---------------------------
m4_define([_AC_LANG_OPENMP(Fortran 77)],
[
      program main
      implicit none
!\$    integer tid
      tid = 42
      call omp_set_num_threads(2)
      end
])

# _AC_LANG_OPENMP(Fortran)
# ------------------------
m4_copy([_AC_LANG_OPENMP(Fortran 77)], [_AC_LANG_OPENMP(Fortran)])

# AC_OPENMP
# ---------
# Check which options need to be passed to the C compiler to support OpenMP.
# Set the OPENMP_CFLAGS / OPENMP_CXXFLAGS / OPENMP_FFLAGS variable to these
# options.
# The options are necessary at compile time (so the #pragmas are understood)
# and at link time (so the appropriate library is linked with).
# This macro takes care to not produce redundant options if $CC $CFLAGS already
# supports OpenMP.
#
# For each candidate option, we do a compile test first, then a link test;
# if the compile test succeeds but the link test fails, that means we have
# found the correct option but it doesn't work because the libraries are
# broken.  (This can happen, for instance, with SunPRO C and a bad combination
# of operating system patches.)
#
# Several of the options in our candidate list can be misinterpreted by
# compilers that don't use them to activate OpenMP support; for example,
# many compilers understand "-openmp" to mean "write output to a file
# named 'penmp'" rather than "enable OpenMP".  We can't completely avoid
# the possibility of clobbering files named 'penmp' or 'mp' in configure's
# working directory; therefore, this macro will bomb out if any such file
# already exists when it's invoked.
AC_DEFUN([AC_OPENMP],
[AC_REQUIRE([_AC_OPENMP_SAFE_WD])]dnl
[AC_ARG_ENABLE([openmp],
   [AS_HELP_STRING([--disable-openmp], [do not use OpenMP])])]dnl
[
  OPENMP_[]_AC_LANG_PREFIX[]FLAGS=
  if test "$enable_openmp" != no; then
    AC_CACHE_CHECK([for $[]_AC_CC[] option to support OpenMP],
      [ac_cv_prog_[]_AC_LANG_ABBREV[]_openmp],
      [ac_cv_prog_[]_AC_LANG_ABBREV[]_openmp='not found'
      dnl Try these flags:
      dnl   (on by default)      ''
      dnl   GCC >= 4.2           -fopenmp
      dnl   SunPRO C             -xopenmp
      dnl   Intel C              -openmp
      dnl   SGI C, PGI C         -mp
      dnl   Tru64 Compaq C       -omp
      dnl   IBM XL C (AIX, Linux) -qsmp=omp
      dnl   Cray CCE             -homp
      dnl   NEC SX               -Popenmp
      dnl   Lahey Fortran (Linux)  --openmp
      for ac_option in '' -fopenmp -xopenmp -openmp -mp -omp -qsmp=omp -homp \
                       -Popenmp --openmp; do

        ac_save_[]_AC_LANG_PREFIX[]FLAGS=$[]_AC_LANG_PREFIX[]FLAGS
        _AC_LANG_PREFIX[]FLAGS="$[]_AC_LANG_PREFIX[]FLAGS $ac_option"
        AC_COMPILE_IFELSE([_AC_LANG_OPENMP],
          [AC_LINK_IFELSE([_AC_LANG_OPENMP],
            [ac_cv_prog_[]_AC_LANG_ABBREV[]_openmp=$ac_option],
            [ac_cv_prog_[]_AC_LANG_ABBREV[]_openmp='unsupported'])])
        _AC_LANG_PREFIX[]FLAGS=$ac_save_[]_AC_LANG_PREFIX[]FLAGS

        if test "$ac_cv_prog_[]_AC_LANG_ABBREV[]_openmp" != 'not found'; then
          break
        fi
      done
      if test "$ac_cv_prog_[]_AC_LANG_ABBREV[]_openmp" = 'not found'; then
        ac_cv_prog_[]_AC_LANG_ABBREV[]_openmp='unsupported'
      elif test "$ac_cv_prog_[]_AC_LANG_ABBREV[]_openmp" = ''; then
        ac_cv_prog_[]_AC_LANG_ABBREV[]_openmp='none needed'
      fi
      dnl _AC_OPENMP_SAFE_WD checked that these files did not exist before we
      dnl started probing for OpenMP support, so if they exist now, they were
      dnl created by the probe loop and it's safe to delete them.
      rm -f penmp mp])
    if test "$ac_cv_prog_[]_AC_LANG_ABBREV[]_openmp" != 'unsupported' && \
       test "$ac_cv_prog_[]_AC_LANG_ABBREV[]_openmp" != 'none needed'; then
      OPENMP_[]_AC_LANG_PREFIX[]FLAGS="$ac_cv_prog_[]_AC_LANG_ABBREV[]_openmp"
    fi
  fi
  AC_SUBST([OPENMP_]_AC_LANG_PREFIX[FLAGS])
])

# _AC_OPENMP_SAFE_WD
# ------------------
# AC_REQUIREd by AC_OPENMP.  Checks both at autoconf time and at
# configure time for files that AC_OPENMP clobbers.
AC_DEFUN([_AC_OPENMP_SAFE_WD],
[m4_syscmd([test ! -e penmp && test ! -e mp])]dnl
[m4_if(sysval, [0], [], [m4_fatal(m4_normalize(
  [AC_OPENMP clobbers files named 'mp' and 'penmp'.
   To use AC_OPENMP you must not have either of these files
   at the top level of your source tree.]))])]dnl
[if test -e penmp || test -e mp; then
  AC_MSG_ERROR(m4_normalize(
    [AC@&t@_OPENMP clobbers files named 'mp' and 'penmp'.
     Aborting configure because one of these files already exists.]))
fi])