+# FP_COMPUTE_INT(EXPRESSION, VARIABLE, INCLUDES, IF-FAILS)
+# --------------------------------------------------------
+# Assign VARIABLE the value of the compile-time EXPRESSION using INCLUDES for
+# compilation. Execute IF-FAILS when unable to determine the value. Works for
+# cross-compilation, too.
+#
+# Implementation note: We are lazy and use an internal autoconf macro, but it
+# is supported in autoconf versions 2.50 up to the actual 2.57, so there is
+# little risk.
+AC_DEFUN([FP_COMPUTE_INT],
+[_AC_COMPUTE_INT([$1], [$2], [$3], [$4])[]dnl
+])# FP_COMPUTE_INT
+
+
+# FP_CHECK_CONST(EXPRESSION, [INCLUDES = DEFAULT-INCLUDES], [VALUE-IF-FAIL = -1])
+# -------------------------------------------------------------------------------
+# Defines CONST_EXPRESSION to the value of the compile-time EXPRESSION, using
+# INCLUDES. If the value cannot be determined, use VALUE-IF-FAIL.
+AC_DEFUN([FP_CHECK_CONST],
+[AS_VAR_PUSHDEF([fp_Cache], [fp_cv_const_$1])[]dnl
+AC_CACHE_CHECK([value of $1], fp_Cache,
+[FP_COMPUTE_INT([$1], fp_check_const_result, [AC_INCLUDES_DEFAULT([$2])],
+ [fp_check_const_result=m4_default([$3], ['-1'])])
+AS_VAR_SET(fp_Cache, [$fp_check_const_result])])[]dnl
+AC_DEFINE_UNQUOTED(AS_TR_CPP([CONST_$1]), AS_VAR_GET(fp_Cache), [The value of $1.])[]dnl
+AS_VAR_POPDEF([fp_Cache])[]dnl
+])# FP_CHECK_CONST
+
+
+# FP_CHECK_CONSTS_TEMPLATE(EXPRESSION...)
+# ---------------------------------------
+# autoheader helper for FP_CHECK_CONSTS
+m4_define([FP_CHECK_CONSTS_TEMPLATE],
+[AC_FOREACH([fp_Const], [$1],
+ [AH_TEMPLATE(AS_TR_CPP(CONST_[]fp_Const),
+ [The value of ]fp_Const[.])])[]dnl
+])# FP_CHECK_CONSTS_TEMPLATE
+
+
+# FP_CHECK_CONSTS(EXPRESSION..., [INCLUDES = DEFAULT-INCLUDES], [VALUE-IF-FAIL = -1])
+# -----------------------------------------------------------------------------------
+# List version of FP_CHECK_CONST
+AC_DEFUN([FP_CHECK_CONSTS],
+[FP_CHECK_CONSTS_TEMPLATE([$1])dnl
+for fp_const_name in $1
+do
+FP_CHECK_CONST([$fp_const_name], [$2], [$3])
+done
+])# FP_CHECK_CONSTS
+
+
+dnl ** Map an arithmetic C type to a Haskell type.
+dnl Based on autconf's AC_CHECK_SIZEOF.
+
+dnl FPTOOLS_CHECK_HTYPE(TYPE [, DEFAULT_VALUE, [, VALUE-FOR-CROSS-COMPILATION])
+AC_DEFUN([FPTOOLS_CHECK_HTYPE],
+[changequote(<<, >>)dnl
+dnl The name to #define.
+define(<<AC_TYPE_NAME>>, translit(htype_$1, [a-z *], [A-Z_P]))dnl
+dnl The cache variable name.
+define(<<AC_CV_NAME>>, translit(fptools_cv_htype_$1, [ *], [_p]))dnl
+define(<<AC_CV_NAME_supported>>, translit(fptools_cv_htype_sup_$1, [ *], [_p]))dnl
+changequote([, ])dnl
+AC_MSG_CHECKING(Haskell type for $1)
+AC_CACHE_VAL(AC_CV_NAME,
+[AC_CV_NAME_supported=yes
+fp_check_htype_save_cppflags="$CPPFLAGS"
+CPPFLAGS="$CPPFLAGS $X_CFLAGS"
+AC_RUN_IFELSE([AC_LANG_SOURCE([[#include <stdio.h>
+#include <stddef.h>
+
+#if HAVE_SYS_TYPES_H
+# include <sys/types.h>
+#endif
+
+#if HAVE_UNISTD_H
+# include <unistd.h>
+#endif
+
+#if HAVE_SYS_STAT_H
+# include <sys/stat.h>
+#endif
+
+#if HAVE_FCNTL_H
+# include <fcntl.h>
+#endif
+
+#if HAVE_SIGNAL_H
+# include <signal.h>
+#endif
+
+#if HAVE_TIME_H
+# include <time.h>
+#endif
+
+#if HAVE_TERMIOS_H
+# include <termios.h>
+#endif
+
+#if HAVE_STRING_H
+# include <string.h>
+#endif
+
+#if HAVE_CTYPE_H
+# include <ctype.h>
+#endif
+
+#if HAVE_INTTYPES_H
+# include <inttypes.h>