Re: macro FIXNUM_OVERFLOW_P in lisp.h is valid ?

[Toru TSUNEYOSHI <t_tuneyosi@hotmail.com>]

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Thanks for your checking.

From: Eli Zaretskii <eliz@gnu.org>

> OK, but please make your patch compare against MOST_POSITIVE_FIXNUM,
> instead of using INT_MAX or LONG_MAX.  Also, if you know that the
> value does not overflow an EMACS_INT, you can simply call make_number,
> instead of make_fixnum_or_float.

I revised the patch as you wrote.
Would you like to check it?

;; supplement
;; check list (with results on 32-bit platforms)

(string-to-number "268435455")		; 2^28 - 1
=>		   268435455
(string-to-number "268435456")		; 2^28
=>		   268435456.0
(string-to-number "268435457")		; 2^28 + 1
=>		   268435457.0
(string-to-number "-268435456")		; - 2^28
=>		   -268435456
(string-to-number "-268435457")		; - 2^28 - 1
=>		   -268435457.0
(string-to-number "536870911")		; 2^29 - 1
=>		   536870911.0
(string-to-number "1073741822")		; 2^30 - 1
=>		   1073741822.0
(string-to-number "2147483647")		; 2^31 - 1
=>		   2147483647.0
(string-to-number "1152921504606846975") ; 2^60 - 1
=>		  1.1529215046068467e+018
(string-to-number "1152921504606846976") ; 2^60
=>		  1.1529215046068467e+018
(string-to-number "1152921504606846977") ; 2^60 + 1
=>		  1.1529215046068467e+018
(string-to-number "-1152921504606846976") ; - 2^60
=>		  -1.1529215046068467e+018
(string-to-number "-1152921504606846977") ; - 2^60 - 1
=>		  -1.1529215046068467e+018
(string-to-number "9223372036854775807") ; 2^63 - 1
=>		  9.223372036854778e+018

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--- data.c.orig	2009-06-21 13:38:14.000000000 +0900
+++ data.c	2009-10-25 03:35:54.414697700 +0900
@@ -2392,17 +2392,43 @@
     val = make_float (sign * atof (p));
   else
     {
-      double v = 0;
+      unsigned char *old_p = p;
+      EMACS_INT most_fixnum, chknum, v = 0;
+      int overflow = 0;		/* most_fixnum overflow */
 
-      while (1)
+      most_fixnum = sign > 0 ? MOST_POSITIVE_FIXNUM : MOST_NEGATIVE_FIXNUM * -1;
+      chknum = most_fixnum / b;
+
+      while (v >= 0)
 	{
 	  int digit = digit_to_number (*p++, b);
 	  if (digit < 0)
 	    break;
+	  if (chknum < v / b)
+	    {
+	      overflow = 1;
+	      break;
+	    }
 	  v = v * b + digit;
 	}
 
-      val = make_fixnum_or_float (sign * v);
+      if (!overflow && v <= most_fixnum && v >= 0)
+	val = make_number (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_float (sign * w);
+	}
     }
 
   return val;