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Re: macro FIXNUM_OVERFLOW_P in lisp.h is valid ?
From: |
Toru TSUNEYOSHI |
Subject: |
Re: macro FIXNUM_OVERFLOW_P in lisp.h is valid ? |
Date: |
Sun, 25 Oct 2009 03:45:39 +0900 |
Thanks for your checking.
From: Eli Zaretskii <address@hidden>
> 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
--- 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;
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Re: macro FIXNUM_OVERFLOW_P in lisp.h is valid ?, Andreas Schwab, 2009/10/23