maint.mk: avoid sc_prohibit_always-defined_macros failure in coreutils

[gnulib.git] / m4 / round.m4

diff --git a/m4/round.m4 b/m4/round.m4
index 44c05ca..9f6691f 100644 (file)
--- a/m4/round.m4
+++ b/m4/round.m4
@@ -1,23 +1,113 @@
-# round.m4 serial 4
-dnl Copyright (C) 2007 Free Software Foundation, Inc.
+# round.m4 serial 12
+dnl Copyright (C) 2007, 2009-2011 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
 
 AC_DEFUN([gl_FUNC_ROUND],
 [
+  m4_divert_text([DEFAULTS], [gl_round_required=plain])
   AC_REQUIRE([gl_MATH_H_DEFAULTS])
   dnl Persuade glibc <math.h> to declare round().
   AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
   AC_CHECK_DECLS([round], , , [#include <math.h>])
   if test "$ac_cv_have_decl_round" = yes; then
     gl_CHECK_MATH_LIB([ROUND_LIBM], [x = round (x);])
+    if test "$ROUND_LIBM" != missing; then
+      dnl Test whether round() produces correct results. On NetBSD 3.0, for
+      dnl x = 1/2 - 2^-54, the system's round() returns a wrong result.
+      AC_REQUIRE([AC_PROG_CC])
+      AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
+      AC_CACHE_CHECK([whether round works], [gl_cv_func_round_works],
+        [
+          save_LIBS="$LIBS"
+          LIBS="$LIBS $ROUND_LIBM"
+          AC_RUN_IFELSE([AC_LANG_SOURCE([[
+#include <float.h>
+#include <math.h>
+int main()
+{
+  /* 2^DBL_MANT_DIG.  */
+  static const double TWO_MANT_DIG =
+    /* Assume DBL_MANT_DIG <= 5 * 31.
+       Use the identity
+       n = floor(n/5) + floor((n+1)/5) + ... + floor((n+4)/5).  */
+    (double) (1U << (DBL_MANT_DIG / 5))
+    * (double) (1U << ((DBL_MANT_DIG + 1) / 5))
+    * (double) (1U << ((DBL_MANT_DIG + 2) / 5))
+    * (double) (1U << ((DBL_MANT_DIG + 3) / 5))
+    * (double) (1U << ((DBL_MANT_DIG + 4) / 5));
+  volatile double x = 0.5 - 0.5 / TWO_MANT_DIG;
+  exit (x < 0.5 && round (x) != 0.0);
+}]])], [gl_cv_func_round_works=yes], [gl_cv_func_round_works=no],
+          [case "$host_os" in
+             netbsd* | aix*) gl_cv_func_round_works="guessing no";;
+             *)              gl_cv_func_round_works="guessing yes";;
+           esac
+          ])
+          LIBS="$save_LIBS"
+        ])
+      case "$gl_cv_func_round_works" in
+        *no) ROUND_LIBM=missing ;;
+      esac
+    fi
+    if test "$ROUND_LIBM" = missing; then
+      REPLACE_ROUND=1
+    fi
+    m4_ifdef([gl_FUNC_ROUND_IEEE], [
+      if test $gl_round_required = ieee && test $REPLACE_ROUND = 0; then
+        AC_CACHE_CHECK([whether round works according to ISO C 99 with IEC 60559],
+          [gl_cv_func_round_ieee],
+          [
+            save_LIBS="$LIBS"
+            LIBS="$LIBS $ROUND_LIBM"
+            AC_RUN_IFELSE(
+              [AC_LANG_SOURCE([[
+#ifndef __NO_MATH_INLINES
+# define __NO_MATH_INLINES 1 /* for glibc */
+#endif
+#include <math.h>
+]gl_DOUBLE_MINUS_ZERO_CODE[
+]gl_DOUBLE_SIGNBIT_CODE[
+static double dummy (double f) { return 0; }
+int main (int argc, char *argv[])
+{
+  double (*my_round) (double) = argc ? round : dummy;
+  /* Test whether round (-0.0) is -0.0.  */
+  if (signbitd (minus_zerod) && !signbitd (my_round (minus_zerod)))
+    return 1;
+  return 0;
+}
+              ]])],
+              [gl_cv_func_round_ieee=yes],
+              [gl_cv_func_round_ieee=no],
+              [gl_cv_func_round_ieee="guessing no"])
+            LIBS="$save_LIBS"
+          ])
+        case "$gl_cv_func_round_ieee" in
+          *yes) ;;
+          *) REPLACE_ROUND=1 ;;
+        esac
+      fi
+    ])
+  else
+    HAVE_DECL_ROUND=0
   fi
-  if test "$ac_cv_have_decl_round" != yes || test "$ROUND_LIBM" = missing; then
-    REPLACE_ROUND=1
-    AC_LIBOBJ([round])
+  if test $HAVE_DECL_ROUND = 0 || test $REPLACE_ROUND = 1; then
+    dnl Find libraries needed to link lib/round.c.
     gl_FUNC_FLOOR_LIBS
     gl_FUNC_CEIL_LIBS
-    ROUND_LIBM="$FLOOR_LIBM $CEIL_LIBM"
+    ROUND_LIBM=
+    dnl Append $FLOOR_LIBM to ROUND_LIBM, avoiding gratuitous duplicates.
+    case " $ROUND_LIBM " in
+      *" $FLOOR_LIBM "*) ;;
+      *) ROUND_LIBM="$ROUND_LIBM $FLOOR_LIBM" ;;
+    esac
+    dnl Append $CEIL_LIBM to ROUND_LIBM, avoiding gratuitous duplicates.
+    case " $ROUND_LIBM " in
+      *" $CEIL_LIBM "*) ;;
+      *) ROUND_LIBM="$ROUND_LIBM $CEIL_LIBM" ;;
+    esac
   fi
-  AC_SUBST([ROUND_LIBM])])
+  AC_SUBST([ROUND_LIBM])
+])