Do Ruby objects have a size limit?

Question

I\'m building some large strings which have a short lifetime within the application. Will the String objects grow arbitrarily large up to the physical limits of the ruby instan

Answer 1

There is a limit. A String can be 2**31 - 1 (and accordingly 2**63 - 1 on 64 bit ruby). You can see the limit with:

>> s = String.new("1" * (2**32))
RangeError: bignum too big to convert into `long'
    from (irb):3:in `*'
    from (irb):3
>> s = String.new("1" * (2**31))
RangeError: bignum too big to convert into `long'
    from (irb):4:in `*'
    from (irb):4

Having said that, while you could try to allocate a string that big it will likely fail (at least on a 32 bit system as typically the maximum amount of memory a process can allocate is between 2.5 and 3GB and a 2**31 - 1 length string is nearly 2GB by itself.) As seen:

>> "1" * (2**30)
NoMemoryError: failed to allocate memory
    from /usr/lib/ruby/1.8/irb.rb:310:in `inspect'
    from /usr/lib/ruby/1.8/irb.rb:310:in `output_value'
    from /usr/lib/ruby/1.8/irb.rb:159:in `eval_input'
    from /usr/lib/ruby/1.8/irb.rb:271:in `signal_status'
    from /usr/lib/ruby/1.8/irb.rb:155:in `eval_input'
    from /usr/lib/ruby/1.8/irb/ruby-lex.rb:244:in `each_top_level_statement'
    from /usr/lib/ruby/1.8/irb/ruby-lex.rb:230:in `loop'
    from /usr/lib/ruby/1.8/irb/ruby-lex.rb:230:in `each_top_level_statement'
    from /usr/lib/ruby/1.8/irb/ruby-lex.rb:229:in `catch'
    from /usr/lib/ruby/1.8/irb/ruby-lex.rb:229:in `each_top_level_statement'
    from /usr/lib/ruby/1.8/irb.rb:154:in `eval_input'
    from /usr/lib/ruby/1.8/irb.rb:71:in `start'
    from /usr/lib/ruby/1.8/irb.rb:70:in `catch'
    from /usr/lib/ruby/1.8/irb.rb:70:in `start'
    from /usr/bin/irb:13
Maybe IRB bug!!

I don't believe there is any way to catch the NoMemoryError.

Updated to reflect the comment from sepp2k