strtod: make it more-accurate typically, and don't require libm

[gnulib.git] / m4 / roundf.m4

diff --git a/m4/roundf.m4 b/m4/roundf.m4
index 57778a8..a105760 100644 (file)
--- a/m4/roundf.m4
+++ b/m4/roundf.m4
@@ -1,5 +1,5 @@
-# roundf.m4 serial 1
-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.
@@ -9,14 +9,77 @@ AC_DEFUN([gl_FUNC_ROUNDF],
   AC_REQUIRE([gl_MATH_H_DEFAULTS])
   dnl Persuade glibc <math.h> to declare roundf().
   AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
-  dnl Test whether roundf() is declared.
-  gl_CHECK_LIBM_FUNC([roundf], [x = roundf(x);], [], [
-    dnl No.  Are both floorf() and ceilf() available?  If so then we can use
-    dnl them to implement roundf(), on the assumption that they're fast.
-    gl_CHECK_LIBM_FUNC([floorf], [x = floorf(x);], [
-      AC_CHECK_DECL([ceilf], 
-        [dnl Yes.  Both are declared.  Link against the necessary library.
-         ROUNDF_LIBM="$FLOORF_LIBM"],
-        [: dnl No. We will use an implementation that doesn't need them.
-], [#include <math.h>
-])])])])
+  AC_CHECK_DECLS([roundf], , , [#include <math.h>])
+  if test "$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 $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 \
+       && test "$ac_cv_have_decl_ceilf" = yes; then
+      gl_FUNC_FLOORF_LIBS
+      gl_FUNC_CEILF_LIBS
+      if test "$FLOORF_LIBM" != '?' && test "$CEILF_LIBM" != '?'; then
+        AC_DEFINE([HAVE_FLOORF_AND_CEILF], [1],
+          [Define if the both the floorf() and ceilf() functions exist.])
+        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
+    else
+      ROUNDF_LIBM=
+    fi
+  fi
+  AC_SUBST([ROUNDF_LIBM])
+])