json/ext 1.5.0 on 32-bit ree-1.8.7 sometimes produces garbage output on Bignums

[redterror]

Here's a sample program that exhibits the problem:

ree-1.8.7@jsonbug1 steinbergd@davedev:~/dev/timing-bug$ cat test1.rb
require 'rubygems'
require 'json/ext'

puts "JSON Version: #{JSON::VERSION}"
1000000.times do |i|
s = 12345678900000.to_json
puts s
end
ree-1.8.7@jsonbug1 steinbergd@davedev:/dev/timing-bug$ ruby test1.rb | sort | uniq -c
2 �ï¿5678900000
999461 12345678900000
1 �ï¿5678900000
533 ï¿5678900000
3 @ï¿5678900000
1 JSON Version: 1.5.0
ree-1.8.7@jsonbug1 steinbergd@davedev:/dev/timing-bug$ uname -a

Linux davedev 2.6.32-24-generic #41-Ubuntu SMP Thu Aug 19 01:12:52 UTC 2010 i686 GNU/Linux

Also on pastebin: http://pastebin.com/fpxF5Tzd

Switching the test program to json/pure fixes it. In addition, monkey patching Bignum.to_s like so:

class Bignum
def to_json
return self.to_s
end
end

also seems to fix it.

[redterror]

Forgot to mention - the problem doesn't seem to exist on 64-bit machines. Or maybe it does and we just need a much bigger number!

[gilltots]

we're seeing this in script/console in a rails 2.3.8 app on 32-bit machines.

slightly easier repro steps are to run this in script/console from a rails app:
$ script/console production
Loading production environment (Rails 2.3.8)
ree-1.8.7-2010.02 > 10000.times{|i| s = 1234567890.to_json; puts s unless s == "1234567890"}
?L(567890?'P
567890
`?e
567890
PS8
567890
S8
567890
??c
567890
=> 10000

[jfahrenkrug]

I see the same issue. I found out that it's connected to the garbage collector. See:

a = {:x => 1309471200} # that's a Bignum
10000.times {|i| puts i; JSON.parse(a.to_json)}

if you run this multiple times, it always creates corrupt bignum-json on iteration 1554. That was a clear indication for a GC problem. So I tried it and alas, this works:

GC.disable
a = {:x => 1309471200} # that's a Bignum
10000.times {|i| puts i; JSON.parse(a.to_json)}
GC.enable

So it looks as if the GC in REE 1.8.7 p330 is somehow corrupt?

[nocode]

I've posted a fix for this at http://redmine.ruby-lang.org/issues/5173

[nocode]

I ported my changes against Ruby to the standalone Gem repo.
You can also pull in my changes for the json repo directly:

git pull git://bogomips.org/ruby-json.git master

There's also a second patch in there found by nobu.

Patches individually downloadable at:

http://bogomips.org/ruby-json.git/patch/?id=8a82bffe927e8928e304b96
http://bogomips.org/ruby-json.git/patch/?id=40869aa9fc8ab194813b850

nobu had another bug in the aforementioned redmine ticket I don't have time to
fix right now.

[flori]

I applied your patch, it's in master now.

[nocode]

flori reply@reply.github.com wrote:

I applied your patch, it's in master now.

Thanks, I'd really like to get this in the next Ruby 1.9.3 RC, too.

[nurse]

I merged 2149f41 in r33122 (trunk) and r33123 (ruby_1_9_3), thanks!
So this will be included in 1.9.3.

[jfahrenkrug]

Great, thanks!