From: Ulrich Drepper <drepper@redhat.com>
Date: Wed, 28 Jul 1999 22:40:32 +0000 (+0000)
Subject: Use IEEE 854 formula to compute the number of digits to print.
X-Git-Tag: cvs/glibc_2-1-2~201
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=0eb7585e82e55b744f5d0e1d91fba216e86ce356;p=thirdparty%2Fglibc.git

Use IEEE 854 formula to compute the number of digits to print.
---

diff --git a/misc/efgcvt.c b/misc/efgcvt.c
index 9348914ff2b..dc711c63dcd 100644
--- a/misc/efgcvt.c
+++ b/misc/efgcvt.c
@@ -17,6 +17,7 @@
    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
    Boston, MA 02111-1307, USA.  */
 
+#include <math.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <sys/param.h>
@@ -29,8 +30,13 @@
 # define FLOAT_FMT_FLAG
 /* Actually we have to write (DBL_DIG + log10 (DBL_MAX_10_EXP)) but we
    don't have log10 available in the preprocessor.  */
-# define MAXDIG (DBL_DIG + 3)
-# define NDIGIT_MAX DBL_DIG
+# define MAXDIG (NDIGIT_MAX + 3)
+# if DBL_MANT_DIG == 53
+#  define NDIGIT_MAX 17
+# else
+/* See IEEE 854 5.6, table 2 for this formula.  */
+#  define NDIGIT_MAX (lrint (ceil (M_LN2 / M_LN10 * DBL_MANT_DIG + 1.0)))
+# endif
 #endif
 
 #define APPEND(a, b) APPEND2 (a, b)
diff --git a/misc/efgcvt_r.c b/misc/efgcvt_r.c
index 944fe4cc984..d73fd22f70f 100644
--- a/misc/efgcvt_r.c
+++ b/misc/efgcvt_r.c
@@ -30,7 +30,12 @@
 # define FUNC_PREFIX
 # define FLOAT_FMT_FLAG
 # define FLOAT_NAME_EXT
-# define NDIGIT_MAX DBL_DIG
+# if DBL_MANT_DIG == 53
+#  define NDIGIT_MAX 17
+# else
+/* See IEEE 854 5.6, table 2 for this formula.  */
+#  define NDIGIT_MAX (lrint (ceil (M_LN2 / M_LN10 * DBL_MANT_DIG + 1.0)))
+# endif
 #endif
 
 #define APPEND(a, b) APPEND2 (a, b)
diff --git a/misc/qefgcvt.c b/misc/qefgcvt.c
index af65fc1688e..faf788aa5d4 100644
--- a/misc/qefgcvt.c
+++ b/misc/qefgcvt.c
@@ -17,13 +17,20 @@
    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
    Boston, MA 02111-1307, USA.  */
 
+#include <float.h>
+
 #define FLOAT_TYPE long double
 #define FUNC_PREFIX q
 #define FLOAT_FMT_FLAG "L"
 /* Actually we have to write (LDBL_DIG + log10 (LDBL_MAX_10_EXP)) but
    we don't have log10 available in the preprocessor.  Since we cannot
    assume anything on the used `long double' format be generous.  */
-#define MAXDIG (LDBL_DIG + 12)
-#define NDIGIT_MAX LDBL_DIG
+#define MAXDIG (NDIGIT_MAX + 12)
+#if LDBL_MANT_DIG == 64
+# define NDIGIT_MAX 21
+#else
+/* See IEEE 854 5.6, table 2 for this formula.  */
+# define NDIGIT_MAX (lrint (ceil (M_LN2 / M_LN10 * LDBL_MANT_DIG + 1.0)))
+#endif
 
 #include "efgcvt.c"
diff --git a/misc/qefgcvt_r.c b/misc/qefgcvt_r.c
index 012ab54acc4..5ff8110e3bb 100644
--- a/misc/qefgcvt_r.c
+++ b/misc/qefgcvt_r.c
@@ -18,10 +18,17 @@
    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
    Boston, MA 02111-1307, USA.  */
 
+#include <float.h>
+
 #define FLOAT_TYPE long double
 #define FUNC_PREFIX q
 #define FLOAT_FMT_FLAG "L"
 #define FLOAT_NAME_EXT l
-# define NDIGIT_MAX LDBL_DIG
+#if LDBL_MANT_DIG == 64
+# define NDIGIT_MAX 21
+#else
+/* See IEEE 854 5.6, table 2 for this formula.  */
+# define NDIGIT_MAX (lrint (ceil (M_LN2 / M_LN10 * LDBL_MANT_DIG + 1.0)))
+#endif
 
 #include "efgcvt_r.c"