Re: [C++ Patch / RFC] PR 33067

[Paolo Carlini]

On 10/11/2011 03:04 AM, Jason Merrill wrote:

On 10/10/2011 12:40 PM, Paolo Carlini wrote:

+ // The fraction 643/2136 approximates log10(2) to 7 significant digits.

+  int max_digits10 = 2 + (is_decimal ? fmt->p : fmt->p * 643L / 2136);

Please cite N1822 in the comment and convert it to C syntax. OK with that change.

Thanks. The below is what I actually applied.

Paolo.

/////////////////

2011-10-11  Paolo Carlini  <paolo.carl...@oracle.com>

        PR c++/33067
        * c-family/c-pretty-print.c (pp_c_floating_constant): Output
        max_digits10 (in the ISO C++ WG N1822 sense) decimal digits.

Index: c-family/c-pretty-print.c
===================================================================
--- c-family/c-pretty-print.c   (revision 179792)
+++ c-family/c-pretty-print.c   (working copy)
@@ -1018,8 +1018,20 @@ pp_c_enumeration_constant (c_pretty_printer *pp, t
 static void
 pp_c_floating_constant (c_pretty_printer *pp, tree r)
 {
+  const struct real_format *fmt
+    = REAL_MODE_FORMAT (TYPE_MODE (TREE_TYPE (r)));
+
+  REAL_VALUE_TYPE floating_cst = TREE_REAL_CST (r);
+  bool is_decimal = floating_cst.decimal;
+
+  /* See ISO C++ WG N1822.  Note: The fraction 643/2136 approximates
+     log10(2) to 7 significant digits.  */
+  int max_digits10 = 2 + (is_decimal ? fmt->p : fmt->p * 643L / 2136);
+
   real_to_decimal (pp_buffer (pp)->digit_buffer, &TREE_REAL_CST (r),
-                  sizeof (pp_buffer (pp)->digit_buffer), 0, 1);
+                  sizeof (pp_buffer (pp)->digit_buffer),
+                  max_digits10, 1);
+
   pp_string (pp, pp_buffer(pp)->digit_buffer);
   if (TREE_TYPE (r) == float_type_node)
     pp_character (pp, 'f');