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+##### http://autoconf-archive.cryp.to/ax_c_arithmetic_rshift.html
+#
+# SYNOPSIS
+#
+# AX_C_ARITHMETIC_RSHIFT
+#
+# DESCRIPTION
+#
+# Checks if the right shift operation is arithmetic.
+#
+# This macro uses compile-time detection and so is cross-compile
+# ready.
+#
+# LAST MODIFICATION
+#
+# 2006-12-12
+#
+# COPYLEFT
+#
+# Copyright (c) 2006 YAMAMOTO Kengo <yamaken AT bp.iij4u.or.jp>
+#
+# Copying and distribution of this file, with or without
+# modification, are permitted in any medium without royalty provided
+# the copyright notice and this notice are preserved.
+
+AC_DEFUN([AX_C_ARITHMETIC_RSHIFT], [
+ AC_CACHE_CHECK([whether right shift operation is arithmetic],
+ [ax_cv_c_arithmetic_rshift],
+ [AC_COMPILE_IFELSE([[int dummy[((-1 >> 1) < 0) ? 1 : -1];]],
+ [ax_cv_c_arithmetic_rshift=yes],
+ [ax_cv_c_arithmetic_rshift=no])])
+ if test "x$ax_cv_c_arithmetic_rshift" = xyes; then
+ AC_DEFINE([HAVE_ARITHMETIC_RSHIFT], [1],
+ [Define to 1 if the right shift operation is arithmetic.])
+ fi
+])