From: Stefan Mahlitz <stefan@...>
Date: 2006-12-05T18:45:25+09:00
Subject: Re: Integer#to_s(2) works on x86, fails on x86_64

Paul Lutus wrote:
> It's way too large to fit into an old-style integer of 32 bits, but it fits
> with two bits to spare in a 64-bit integer. Also, in Ruby, normally an
> integer too large for the Fixnum class is automatically converted to a
> Bignum, so this error should not have happened.
> 
> Try this test:
> 
> 32.upto(128) do |p|
>   puts 2 ** p
> end
> 
> See what happens on both platforms. BTW I am thinking this is an error in
> the x86_64 Ruby code.

The same Exception is thrown on my machine.

From cpuinfo:
processor       : 0
vendor_id       : AuthenticAMD
cpu family      : 15
model           : 47
model name      : AMD Athlon(tm) 64 Processor 3000+
stepping        : 2

Operating System is Ubuntu 6.06 LTS.

Ruby version (installed via OS package manager): ruby 1.8.4 (2005-12-24)
[x86_64-linux].

16.upto(128) do |p|
  n = 2 ** p
  puts("#{p}: #{n}: #{n.class}")
end

shows a conversion at

  61: 2305843009213693952: Fixnum
  62: 4611686018427387904: Bignum

where to_s(2) fails at p == 31

16.upto(128) do |p|
  n = 2 ** p
  puts("#{p}: #{n}: #{n.class}")
  puts(n.to_s(2))
end

  31: 2147483648: Fixnum
  RangeError: integer 2147483648 too big to convert to `int'

Stefan