Re: macro FIXNUM_OVERFLOW_P in lisp.h is valid ?

[Toru TSUNEYOSHI <t_tuneyosi@hotmail.com>]

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> So in 64-bit platforms, casting `double' to `int' causes lack of
> precision already (because a double does not have 64 bits in the
> mantissa), doesn't it?

So I make a patch for keep the precision.
It tries to deal with the number in type `int' possibly, otherwise it
deals with the number in type `double'.

Would you like to check it ?

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--- data.c.original	2009-06-21 13:38:14.000000000 +0900
+++ data.c	2009-10-24 14:31:43.356164300 +0900
@@ -22,6 +22,7 @@
 #include <config.h>
 #include <signal.h>
 #include <stdio.h>
+#include <limits.h>
 #include "lisp.h"
 #include "puresize.h"
 #include "character.h"
@@ -2392,17 +2393,42 @@
     val = make_float (sign * atof (p));
   else
     {
-      double v = 0;
+      unsigned char *old_p = p;
+      int v = 0;
+      int overflow = 0;
 
-      while (1)
+      while (v >= 0)
 	{
 	  int digit = digit_to_number (*p++, b);
 	  if (digit < 0)
 	    break;
+	  if (v > INT_MAX / b)
+	    {
+	      overflow = 1;
+	      break;
+	    }
 	  v = v * b + digit;
 	}
 
-      val = make_fixnum_or_float (sign * v);
+      if (!overflow && v >= 0)
+	{
+	  val = make_fixnum_or_float (sign * v);
+	}
+      else
+	{
+	  double w = 0;
+	  p = old_p;
+
+	  while (1)
+	    {
+	      int digit = digit_to_number (*p++, b);
+	      if (digit < 0)
+		break;
+	      w = w * b + digit;
+	    }
+
+	  val = make_fixnum_or_float (sign * w);
+	}
     }
 
   return val;