-# log2.m4 serial 1
+# log2.m4 serial 2
dnl Copyright (C) 2010-2012 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
AC_DEFUN([gl_FUNC_LOG2],
[
+ m4_divert_text([DEFAULTS], [gl_log2_required=plain])
AC_REQUIRE([gl_MATH_H_DEFAULTS])
dnl Persuade glibc <math.h> to declare log2().
*yes) ;;
*) REPLACE_LOG2=1 ;;
esac
+
+ m4_ifdef([gl_FUNC_LOG2_IEEE], [
+ if test $gl_log2_required = ieee && test $REPLACE_LOG2 = 0; then
+ AC_CACHE_CHECK([whether log2 works according to ISO C 99 with IEC 60559],
+ [gl_cv_func_log2_ieee],
+ [
+ save_LIBS="$LIBS"
+ LIBS="$LIBS $LOG2_LIBM"
+ AC_RUN_IFELSE(
+ [AC_LANG_SOURCE([[
+#ifndef __NO_MATH_INLINES
+# define __NO_MATH_INLINES 1 /* for glibc */
+#endif
+#include <math.h>
+#ifndef log2 /* for Cygwin 1.7.x */
+extern
+#ifdef __cplusplus
+"C"
+#endif
+double log2 (double);
+#endif
+/* Compare two numbers with ==.
+ This is a separate function because IRIX 6.5 "cc -O" miscompiles an
+ 'x == x' test. */
+static int
+numeric_equal (double x, double y)
+{
+ return x == y;
+}
+static double dummy (double x) { return 0; }
+int main (int argc, char *argv[])
+{
+ double (*my_log2) (double) = argc ? log2 : dummy;
+ /* Test log2(negative).
+ This test fails on NetBSD 5.1 and Solaris 11 2011-11. */
+ double y = my_log2 (-1.0);
+ if (numeric_equal (y, y))
+ return 1;
+ return 0;
+}
+ ]])],
+ [gl_cv_func_log2_ieee=yes],
+ [gl_cv_func_log2_ieee=no],
+ [gl_cv_func_log2_ieee="guessing no"])
+ LIBS="$save_LIBS"
+ ])
+ case "$gl_cv_func_log2_ieee" in
+ *yes) ;;
+ *) REPLACE_LOG2=1 ;;
+ esac
+ fi
+ ])
else
HAVE_LOG2=0
HAVE_DECL_LOG2=0