X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=m4%2Froundf.m4;h=a105760d2b52cdce4dc02500d4d0de03fff2e761;hb=6892ce27efe6c361326a4e478ee564f59579f7d2;hp=650311e3cc333c1b055361176d9d9a8fc462d161;hpb=13314b446d38305438b86c5baafe72395376e310;p=gnulib.git

diff --git a/m4/roundf.m4 b/m4/roundf.m4
index 650311e3c..a105760d2 100644
--- a/m4/roundf.m4
+++ b/m4/roundf.m4
@@ -1,5 +1,5 @@
-# roundf.m4 serial 4
-dnl Copyright (C) 2007 Free Software Foundation, Inc.
+# roundf.m4 serial 9
+dnl Copyright (C) 2007-2010 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.
@@ -12,9 +12,48 @@ AC_DEFUN([gl_FUNC_ROUNDF],
   AC_CHECK_DECLS([roundf], , , [#include <math.h>])
   if test "$ac_cv_have_decl_roundf" = yes; then
     gl_CHECK_MATH_LIB([ROUNDF_LIBM], [x = roundf (x);])
+    if test "$ROUNDF_LIBM" != missing; then
+      dnl Test whether roundf() produces correct results. On mingw, for
+      dnl x = 1/2 - 2^-25, the system's roundf() returns a wrong result.
+      AC_REQUIRE([AC_PROG_CC])
+      AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
+      AC_CACHE_CHECK([whether roundf works], [gl_cv_func_roundf_works],
+        [
+          save_LIBS="$LIBS"
+          LIBS="$LIBS $ROUNDF_LIBM"
+          AC_RUN_IFELSE([AC_LANG_SOURCE([[
+#include <float.h>
+#include <math.h>
+int main()
+{
+  /* 2^FLT_MANT_DIG.  */
+  static const float TWO_MANT_DIG =
+    /* Assume FLT_MANT_DIG <= 3 * 31.
+       Use the identity  n = floor(n/3) + floor((n+1)/3) + floor((n+2)/3).  */
+    (float) (1U << (FLT_MANT_DIG / 3))
+    * (float) (1U << ((FLT_MANT_DIG + 1) / 3))
+    * (float) (1U << ((FLT_MANT_DIG + 2) / 3));
+  volatile float x = 0.5f - 0.5f / TWO_MANT_DIG;
+  exit (x < 0.5f && roundf (x) != 0.0f);
+}]])], [gl_cv_func_roundf_works=yes], [gl_cv_func_roundf_works=no],
+          [case "$host_os" in
+             mingw*) gl_cv_func_roundf_works="guessing no";;
+             *)      gl_cv_func_roundf_works="guessing yes";;
+           esac
+          ])
+          LIBS="$save_LIBS"
+        ])
+      case "$gl_cv_func_roundf_works" in
+        *no) ROUNDF_LIBM=missing ;;
+      esac
+    fi
+    if test "$ROUNDF_LIBM" = missing; then
+      REPLACE_ROUNDF=1
+    fi
+  else
+    HAVE_DECL_ROUNDF=0
   fi
-  if test "$ac_cv_have_decl_roundf" != yes || test "$ROUNDF_LIBM" = missing; then
-    REPLACE_ROUNDF=1
+  if test $HAVE_DECL_ROUNDF = 0 || test $REPLACE_ROUNDF = 1; then
     AC_LIBOBJ([roundf])
     AC_CHECK_DECLS([ceilf, floorf], , , [#include <math.h>])
     if test "$ac_cv_have_decl_floorf" = yes \
@@ -22,9 +61,19 @@ AC_DEFUN([gl_FUNC_ROUNDF],
       gl_FUNC_FLOORF_LIBS
       gl_FUNC_CEILF_LIBS
       if test "$FLOORF_LIBM" != '?' && test "$CEILF_LIBM" != '?'; then
-        AC_DEFINE([HAVE_FLOORF_AND_CEILF], 1,
+        AC_DEFINE([HAVE_FLOORF_AND_CEILF], [1],
           [Define if the both the floorf() and ceilf() functions exist.])
-        ROUNDF_LIBM="$FLOORF_LIBM $CEILF_LIBM"
+        ROUNDF_LIBM=
+        dnl Append $FLOORF_LIBM to ROUNDF_LIBM, avoiding gratuitous duplicates.
+        case " $ROUNDF_LIBM " in
+          *" $FLOORF_LIBM "*) ;;
+          *) ROUNDF_LIBM="$ROUNDF_LIBM $FLOORF_LIBM" ;;
+        esac
+        dnl Append $CEILF_LIBM to ROUNDF_LIBM, avoiding gratuitous duplicates.
+        case " $ROUNDF_LIBM " in
+          *" $CEILF_LIBM "*) ;;
+          *) ROUNDF_LIBM="$ROUNDF_LIBM $CEILF_LIBM" ;;
+        esac
       else
         ROUNDF_LIBM=
       fi