From: "David A. Black" <dblack@...>
Date: 2005-11-26T13:56:27+09:00
Subject: Re: Marshal.dump(obj) as String bug?

Hi --

On Sat, 26 Nov 2005, Hampton wrote:

> Alright, so I've been scratching my head about this along with some
> folks over at #ruby-lang.
>
> This may be a known problem, but after spending a few minutes
> searching, I can't find any reference... so I'll document it here.
>
> If you take some object and marshal it, then try and concat that
> string, it produces some funny results.
>
> Here is the test case that I've discovered. I'm thinking this is
> happening because Marshal sends back some weird characters that are
> screwing up the string methods. But, I would still classify that as a
> bug, because when an object returns a string, that should always be a
> fairly safe string to handle or it should be returning something else.
> That would be an invalid or misformed string if you can't even use the
> regular expressions on it.
>
> Any help would be greatly appreciated.
>
> #I'm running ruby 1.8.3 on ubuntu
> #email hcatlin at gmail.com with any help
>
>
> 	class MyObject
> 		def initialize
> 			@name = "testvar"
> 			@array = Array.new
> 		end
>  end
>
> 	test = MyObject.new
> 	dumpresult = Marshal.dump(test)
> 	puts 'Result: ' << dumpresult # Expected: "Result: MYOBJECTDUMP"
> 	puts 'Result=' << Marshal.dump(test) #Expected "Result=MYOBJECTDUMP"
> 	puts 'Result: ' + dumpresult # Expected: "Result: MYOBJECTDUMP"
> 	puts 'Result=' + Marshal.dump(test) #Expected "Result=MYOBJECTDUMP"
> 	puts "U=" << Marshal.dump(test) # Expected "U=MYOBJECTDUMP"
>
>
> 	#My result is this code below.
>
> #MyObject:
> #         @array[:
> #@name"
> #testvar
> #MyObject:
> #         @array[:
> #@name"
> #testvar
> #MyObject:
> #         @array[:
> #@name"
> #testvar
> #MyObject:
> #         @array[:
> #@name"
> #testvar
> #MyObject:
> #         @array[:
> #@name"
> #testvar

If you use p instead of puts you'll see what's going on:

"Result: \004\010o:\rMyObject\a:\v@array[\000:\n@name\"\ftestvar"

Note the \r, which does a carriage return.  Then what follows
overwrites what came before (when you do a puts).

You can work around this by doing:

   puts "Result:\n" << dumpresult


David

-- 
David A. Black
dblack@wobblini.net