Segmentation fault with Containers::RBTreeMap

bench_rbtree.rb

require 'benchmark'
#require 'rbtree'
require 'algorithms'

Benchmark.bm(20) do |r|
  data = nil
  r.report('shuffling') { data = (0..1_000_000).to_a.shuffle }

  { :hash      => Hash.new,
#    :classic   => RBTree.new,
    :container => Containers::RBTreeMap.new }.each do |kind,tree|

      r.report( "write #{kind}" ) { data.each { |d| tree[d] = "foo" } }
      r.report( "read  #{kind}" ) { data.each { |d| tree[d] } }

      if kind == :container then
        r.report( "drain #{kind}" ) { tree.delete_min until tree.empty? }
      else
        r.report( "drain #{kind}" ) { tree.shift until tree.empty? }
      end

    end
end

output.txt

                           user     system      total        real
shuffling              0.090000   0.010000   0.100000 (  0.092279)
write hash             0.850000   0.050000   0.900000 (  0.919895)
read  hash             0.420000   0.010000   0.430000 (  0.419167)
drain hash             0.570000   0.020000   0.590000 (  0.599493)
write container      bench_rbtree.rb:16: [BUG] Segmentation fault at 0x007fff584bcfe4
ruby 2.1.2p95 (2014-05-08 revision 45877) [x86_64-darwin12.0]

-- Crash Report log information --------------------------------------------
   See Crash Report log file under the one of following:
     * ~/Library/Logs/CrashReporter
     * /Library/Logs/CrashReporter
     * ~/Library/Logs/DiagnosticReports
     * /Library/Logs/DiagnosticReports
   for more details.

-- Control frame information -----------------------------------------------
c:0013 p:---- s:0061 e:000060 CFUNC  :push
c:0012 p:0016 s:0056 e:000054 BLOCK  bench_rbtree.rb:16 [FINISH]
c:0011 p:---- s:0052 e:000051 CFUNC  :each
c:0010 p:0009 s:0049 e:000048 BLOCK  bench_rbtree.rb:16
c:0009 p:0034 s:0047 e:000046 METHOD /opt/rubies/ruby-2.1.2/lib/ruby/2.1.0/benchmark.rb:279
c:0008 p:0039 s:0039 e:000037 METHOD /opt/rubies/ruby-2.1.2/lib/ruby/2.1.0/benchmark.rb:361
c:0007 p:0015 s:0031 E:000a58 BLOCK  bench_rbtree.rb:16 [FINISH]
c:0006 p:---- s:0027 e:000026 CFUNC  :each
c:0005 p:0050 s:0024 E:001e58 BLOCK  bench_rbtree.rb:14
c:0004 p:0133 s:0020 e:000019 METHOD /opt/rubies/ruby-2.1.2/lib/ruby/2.1.0/benchmark.rb:172
c:0003 p:0030 s:0010 e:000009 METHOD /opt/rubies/ruby-2.1.2/lib/ruby/2.1.0/benchmark.rb:204
c:0002 p:0029 s:0004 E:0010a8 EVAL   bench_rbtree.rb:5 [FINISH]
c:0001 p:0000 s:0002 E:000cf8 TOP    [FINISH]

bench_rbtree.rb:5:in `<main>'
/opt/rubies/ruby-2.1.2/lib/ruby/2.1.0/benchmark.rb:204:in `bm'
/opt/rubies/ruby-2.1.2/lib/ruby/2.1.0/benchmark.rb:172:in `benchmark'
bench_rbtree.rb:14:in `block in <main>'
bench_rbtree.rb:14:in `each'
bench_rbtree.rb:16:in `block (2 levels) in <main>'
/opt/rubies/ruby-2.1.2/lib/ruby/2.1.0/benchmark.rb:361:in `item'
/opt/rubies/ruby-2.1.2/lib/ruby/2.1.0/benchmark.rb:279:in `measure'
bench_rbtree.rb:16:in `block (3 levels) in <main>'
bench_rbtree.rb:16:in `each'
bench_rbtree.rb:16:in `block (4 levels) in <main>'
bench_rbtree.rb:16:in `push'

-- C level backtrace information -------------------------------------------
Segmentation fault: 11