# P(65536\*\*(1\<\<29)) stalls

**URL:** <https://www.ruby-forum.com/t/p-65536-1-29-stalls/109646>\
**Category:** Development\
**Created:** [July 17, 2007, 3:33pm UTC](https://www.ruby-forum.com/t/p-65536-1-29-stalls/109646 "2007-07-17T15:33:22Z")\
**Posts on this page:** 6\
**Page:** 1

<div class="post-metadata">

**Author:** ![Yusuke\_ENDOH](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/c89c15/32.png) [@Yusuke\_ENDOH](https://www.ruby-forum.com/u/Yusuke_ENDOH)\
**Post date:** [July 17, 2007, 3:33pm UTC](https://www.ruby-forum.com/t/p-65536-1-29-stalls/109646/1 "2007-07-17T15:33:22Z")

</div>

e$B1sF#$H?=$7$^$9!#e(B

e$B0J2\<$N$h$&$K$9$k$HH?1~$,$J$/$J$j$^$9!#e(BCtrl+C  
e$B$G$b;\_$a$i$l$^$;$s!#e(B

$ ./ruby -ve ‘p(65536\*\*(1\<\<29))’  
ruby 1.8.6 (2007-07-17 patchlevel 5000) [i686-linux]

$ ./ruby -ve ‘p(65536\*\*(1\<\<29))’  
ruby 1.9.0 (2007-07-17 patchlevel 0) [i686-linux]

bignum e$B$NBg$-$5$N%A%’%C%/$Ge(B integer overflow  
e$B$7$F$$$k$N$,860x$N$h$&$G$9!#e(B  
1.8 e$B$G$N1~5^A\<CV$G$9!#e(B

# Index: bignum.c

— bignum.c (revision 12809)  
+++ bignum.c (working copy)  
@@ -1755,8 +1755,13 @@  
if (yy \> 0) {  
VALUE z = 0;  
long mask;

- 

```
      VALUE f = 1, t1 = RBIGNUM(x)->len * SIZEOF_BDIGITS;

```

- 

```
      if (t1 / SIZEOF_BDIGITS == RBIGNUM(x)->len && t1 %

```

SIZEOF\_BDIGITS == 0) {

- 

```
          VALUE t2 = t1 * yy;

```

- 

```
          if (t2 / yy == t1 && t2 % yy == 0 && t2 <= 1024*1024) f 

```

= 0;

- 

```
      }

```

- 

```
      if (RBIGNUM(x)->len * SIZEOF_BDIGITS * yy > 1024*1024) {

```

- 

```
      if (f) {
          rb_warn("in a**b, b may be too big");
          d = (double)yy;
          break;

```

1024\*1024 e$B$,B(CM$GKd$a9~$^$l$F$$$k$N$,5$;}$A0-$$$s$G$9$,!"e(B  
bignum e$B$N:GBgCM$C$F$A$c$s$H7h$^$C$F$J$$$s$G$7$g$&$+!#e(B

e$B$D$$$G$K!"=EH"$N6y$G$9$,!"0J2\<$N;EMMJQ99$O0U?^$5$l$?$b$N$G$7$g$&$+!#e(B

$ ./ruby -ve ‘p(0\*\*(1\<\<30))’  
ruby 1.8.6 (2007-06-07 patchlevel 36) [i686-linux]  
-e:1: warning: in a\*\*b, b may be too big  
0.0

$ ./ruby -ve ‘p(0\*\*(1\<\<30))’  
ruby 1.8.6 (2007-07-17 patchlevel 5000) [i686-linux]  
0

---

<div class="post-metadata">

**Author:** ![Yusuke\_ENDOH](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/c89c15/32.png) [@Yusuke\_ENDOH](https://www.ruby-forum.com/u/Yusuke_ENDOH)\
**Post date:** [July 18, 2007, 10:06am UTC](https://www.ruby-forum.com/t/p-65536-1-29-stalls/109646/2 "2007-07-18T10:06:57Z")

</div>

e$B$J$+$@$G$9!#e(B

At Tue, 17 Jul 2007 22:30:38 +0900,  
Yusuke ENDOH wrote in [ruby-dev:31242]:

> bignum e$B$NBg$-$5$N%A%’%C%/$Ge(B integer overflow e$B$7$F$$$k$N$,860x$N$h$&$G$9!#e(B  
> 1.8 e$B$G$N1~5^A\<CV$G$9!#e(B

e$B$"$j$,$H$&$4$6$$$^$9!#$A$g$C$H0c$&7A$G$9$,!"%A%’%C%/$rD\>$7$^$7$?!#e(B

> 1024\*1024 e$B$,B(CM$GKd$a9~$^$l$F$$$k$N$,5$;}$A0-$$$s$G$9$,!"e(B  
> bignum e$B$N:GBgCM$C$F$A$c$s$H7h$^$C$F$J$$$s$G$7$g$&$+!#e(B

e$B$H$/$K7h$^$C$F$J$$$G$9!#:#$N$H$3$m!V%a%b%j$N5v$98B$j!W$H$$$&@)e(B  
e$B8B$@$1$J$s$G$9$,!"$I$3$+$KL@\<(E\*$J@~0z$-$r$7$?$[$&$,$$$$$G$7$ge(B  
e$B$&$+$M$’!#e(B

> e$B$D$$$G$K!"=EH"$N6y$G$9$,!"0J2\<$N;EMMJQ99$O0U?^$5$l$?$b$N$G$7$g$&$+!#e(B
> 
> $ ./ruby -ve ‘p(0\*\*(1\<\<30))’  
> ruby 1.8.6 (2007-06-07 patchlevel 36) [i686-linux]  
> -e:1: warning: in a\*\*b, b may be too big  
> 0.0
> 
> $ ./ruby -ve ‘p(0\*\*(1\<\<30))’  
> ruby 1.8.6 (2007-07-17 patchlevel 5000) [i686-linux]  
> 0

0\*\*((1\<\<30)-1)e$B$^$G$Oe(BFixnume$B$,JV$C$FMh$F$$$k$N$G!“F1$8e(B0e$B$,JV$k$[$&e(B  
e$B$,0l4S@-$O$”$k$H;W$$$^$9$,!#e(B

---

<div class="post-metadata">

**Author:** ![Yusuke\_ENDOH](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/c89c15/32.png) [@Yusuke\_ENDOH](https://www.ruby-forum.com/u/Yusuke_ENDOH)\
**Post date:** [July 18, 2007, 1:59pm UTC](https://www.ruby-forum.com/t/p-65536-1-29-stalls/109646/3 "2007-07-18T13:59:41Z")

</div>

e$B1sF#$G$9!#e(B

> e$B$A$g$C$H0c$&7A$G$9$,!"%A%’%C%/$rD\>$7$^$7$?!#e(B

e$B=$@53NG’$7$^$7$?!#$J$k$[$I$=$&D\>$;$P$$$$$N$+!D!D!#e(B

> > 1024\*1024 e$B$,B(CM$GKd$a9~$^$l$F$$$k$N$,5$;}$A0-$$$s$G$9$,!"e(B  
> > bignum e$B$N:GBgCM$C$F$A$c$s$H7h$^$C$F$J$$$s$G$7$g$&$+!#e(B
> 
> e$B$H$/$K7h$^$C$F$J$$$G$9!#:#$N$H$3$m!V%a%b%j$N5v$98B$j!W$H$$$&@)e(B  
> e$B8B$@$1$J$s$G$9$,!"$I$3$+$KL@\<(E\*$J@~0z$-$r$7$?$[$&$,$$$$$G$7$ge(B  
> e$B$&$+$M$’!#e(B

e$B;d$b!V%a%b%j$N5v$98B$j!W$@$H;W$C$F$$$?$N$G!"Bg$-$9$.$ke(B Bignum  
e$B$,e(B  
Float e$B$K$J$k$HCN$C$F6C$-$^$7$?!#$I$3$+$K=q$$$F$^$7$?$C$1!#e(B

> 0\*\*((1\<\<30)-1)e$B$^$G$Oe(BFixnume$B$,JV$C$FMh$F$$$k$N$G!“F1$8e(B0e$B$,JV$k$[$&e(B  
> e$B$,0l4S@-$O$”$k$H;W$$$^$9$,!#e(B

e$B$=$l$r8@$&$J$i!"!Ve(Bn\*\*(1\<\<30) e$B$Oe(B 0 e$B$He(B 1 e$B0J30$Ne(B n  
e$B$KBP$7$Fe(B Float e$B$rJV$9e(B  
e$B$N$G!“e(B0 e$B$He(B 1 e$B$be(B Float  
e$B$rJV$9$[$&$,0l4S@-$,$”$k!W$H$$$&5DO@$b@.$jN)$De(B  
e$B5$$,$7$^$9!#$1$l$I!"$3$N5sF0$K0MB8$9$k%3!\<%I$r=q$/;v$O$J$5$=$&$G$9$7!“e(B  
e$B8D?ME\*$K$bFC$K$3$@$o$j$O$J$$$N$G!”%(%s%P%0$G$J$$$J$i$=$l$G$$$$$G$9!#e(B

---

<div class="post-metadata">

**Author:** ![Yusuke\_ENDOH](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/c89c15/32.png) [@Yusuke\_ENDOH](https://www.ruby-forum.com/u/Yusuke_ENDOH)\
**Post date:** [July 18, 2007, 3:19pm UTC](https://www.ruby-forum.com/t/p-65536-1-29-stalls/109646/4 "2007-07-18T15:19:53Z")

</div>

e$B1sF#$G$9!#e(B

07/07/18 e$B$Ke(B U.Nakamura[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
e$B$5$s$O=q$-$^$7$?e(B:

> |  
> | e$B;d$b!V%a%b%j$N5v$98B$j!W$@$H;W$C$F$$$?$N$G!"Bg$-$9$.$ke(B Bignum e$B$,e(B  
> | Float e$B$K$J$k$HCN$C$F6C$-$^$7$?!#$I$3$+$K=q$$$F$^$7$?$C$1!#e(B
> 
> e$BBg$-$9$.$ke(BBignume$B$,e(BFloate$B$K$J$k!“$o$1$8$c$J$/$F!“e(BBignum#\*\*e$B$N5se(B  
> e$BF0$H$7$F7k2L$,e(BFloate$B$K$J$k$3$H$b$”$k$h!”$H$$$&$3$H$@$H;W$$$^$9!#e(B

e$B$J$k$[$I!"0lHLE\*$J%]%j%7!\<$G$O$J$/e(B Bignum#\*\*  
e$B8GM-$N;EMM$J$s$G$9$M!#e(B

> e$B7k2L$,e(BFloate$B$K$J$j$&$k$3$H$Oe(Brdoce$B$K=q$$$F$"$j$^$9$M!#e(B

[http://www.ruby-lang.org/ja/man/index.cgi?cmd=view;name=Integer](http://www.ruby-lang.org/ja/man/index.cgi?cmd=view;name=Integer)  
e$B$Ne(B self \*\* other e$B$N$H$3$@$18+$F$^$7$?!#e(B

[http://ruby-doc.org/core/classes/Bignum.html#M001127](http://ruby-doc.org/core/classes/Bignum.html#M001127)

> The result may be a Fixnum, Bignum, or Float  
> e$B$N$3$H$G$7$g$&$+!#3N$+$K=q$$$F$“$k$C$A$c$”$j$^$9$,!“Nc$r$”$o$;8+$F!"e(B  
> e$B!Ve(BBignum \*\* Bignum e$B$G$be(B Float  
> e$B$K$J$j$&$k!W$H8+H4$/$N$O87$7$$$+$b!#e(B  
> e$B$;$a$F!"e(B

123456789 \*\* 123456789 #=\> Infinity

e$B$rDI2C$7$F$b$i$($l$P!D!De(B (e$B$+$($C$F:.Mp$7$=$&e(B) e$B!#e(B

---

<div class="post-metadata">

**Author:** ![Yusuke\_ENDOH](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/c89c15/32.png) [@Yusuke\_ENDOH](https://www.ruby-forum.com/u/Yusuke_ENDOH)\
**Post date:** [July 18, 2007, 4:57pm UTC](https://www.ruby-forum.com/t/p-65536-1-29-stalls/109646/5 "2007-07-18T16:57:16Z")

</div>

e$B$^$D$b$He(B e$B$f$-$R$m$G$9e(B

In message “Re: [ruby-dev:31242] p(65536\*\*(1\<\<29)) stalls”  
on Tue, 17 Jul 2007 22:30:38 +0900, “Yusuke ENDOH” [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
writes:

|1024\*1024 e$B$,B(CM$GKd$a9~$^$l$F$$$k$N$,5$;}$A0-$$$s$G$9$,!"e(B  
|bignum e$B$N:GBgCM$C$F$A$c$s$H7h$^$C$F$J$$$s$G$7$g$&$+!#e(B

e$BCfED$5$s$+$i$b$“$j$^$7$?$,!”%a%b%j$,5v$98B$j$NBg$-$5$N?tCM$re(B  
e$B5v$9$H$$$&$N$,0l1~$N;EMM$G$9!#$Y$-\>h$N7W;;$N\>l9g!“$”$kDxEY0Je(B  
e$B\>eBg$-$$?t$OIbF0\>.?tE@1i;;$G6a;w$9$k$H$$$&\<j$r;H$C$F$$$^$9!#e(B  
e$B$9$0$Ke(BInfinitye$B$K$J$C$A$c$$$^$9$,!#e(B

|e$B$D$$$G$K!“=EH”$N6y$G$9$,!"0J2\<$N;EMMJQ99$O0U?^$5$l$?$b$N$G$7$g$&$+!#e(B  
|  
|$ ./ruby -ve ‘p(0\*\*(1\<\<30))’  
|ruby 1.8.6 (2007-06-07 patchlevel 36) [i686-linux]  
|-e:1: warning: in a**b, b may be too big  
|0.0  
|  
|$ ./ruby -ve 'p(0**(1\<\<30))’  
|ruby 1.8.6 (2007-07-17 patchlevel 5000) [i686-linux]  
|0

e$B$O$$!#$^$:$$%1!\<%9$,$"$l$P65$($F$/$@$5$$!#e(B

---

<div class="post-metadata">

**Author:** ![Yusuke\_ENDOH](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/c89c15/32.png) [@Yusuke\_ENDOH](https://www.ruby-forum.com/u/Yusuke_ENDOH)\
**Post date:** [July 18, 2007, 2:13pm UTC](https://www.ruby-forum.com/t/p-65536-1-29-stalls/109646/6 "2007-07-18T14:13:44Z")

</div>

e$B$3$s$K$A$O!"$J$+$`$ie(B(e$B$&e(B)e$B$G$9!#e(B

In message “[ruby-dev:31250] Re: p(65536\*\*(1\<\<29)) stalls”  
on Jul.18,2007 20:57:30, [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:  
| \> \> 1024_1024 e$B$,B(CM$GKd$a9~$^$l$F$$$k$N$,5$;}$A0-$$$s$G$9$,!“e(B  
| \> \> bignum e$B$N:GBgCM$C$F$A$c$s$H7h$^$C$F$J$$$s$G$7$g$&$+!#e(B  
| \>  
| \> e$B$H$/$K7h$^$C$F$J$$$G$9!#:#$N$H$3$m!V%a%b%j$N5v$98B$j!W$H$$$&@)e(B  
| \> e$B8B$@$1$J$s$G$9$,!”$I$3$+$KL@\<(E_$J@~0z$-$r$7$?$[$&$,$$$$$G$7$ge(B  
| \> e$B$&$+$M$'!#e(B  
|  
| e$B;d$b!V%a%b%j$N5v$98B$j!W$@$H;W$C$F$$$?$N$G!"Bg$-$9$.$ke(B Bignum e$B$,e(B  
| Float e$B$K$J$k$HCN$C$F6C$-$^$7$?!#$I$3$+$K=q$$$F$^$7$?$C$1!#e(B

e$BBg$-$9$.$ke(BBignume$B$,e(BFloate$B$K$J$k!“$o$1$8$c$J$/$F!“e(BBignum#\*\*e$B$N5se(B  
e$BF0$H$7$F7k2L$,e(BFloate$B$K$J$k$3$H$b$”$k$h!”$H$$$&$3$H$@$H;W$$$^$9!#e(B  
e$B7k2L$,e(BFloate$B$K$J$j$&$k$3$H$Oe(Brdoce$B$K=q$$$F$"$j$^$9$M!#e(B

e$B$I$&$$$&4p=`$Ge(BFloate$B$K$J$k$+!“$H$$$&$N$O$”$C$F$b$$$$$N$+$b$7$le(B  
e$B$J$$$H$O;W$$$^$9!#e(B

e$B$=$l$G$O!#e(B