Bug #1883

REXML hash sometimes computes a value that is too large

Added by Ryan Riley over 2 years ago. Updated 7 months ago.

[ruby-core:24754]
Status:Open Start date:08/05/2009
Priority:Normal Due date:
Assignee:- % Done:

0%
Category:-
Target version:-
ruby -v:1.8.6p287

Description

The hash method sometimes computes a value that is too large. This is a rare occurrence in MRI, but this is causing problems for IronRuby. The following patch is suggested for computing smaller hashes:

edit: c:/ruby/libs/ruby/1.8/rexml/attribute.rb;C908357
File: attribute.rb
===================================================================
--- c:/ruby/libs/ruby/1.8/rexml/attribute.rb;C908357  (server)    6/23/2009 1:24 PM
+++ c:/ruby/libs/ruby/1.8/rexml/attribute.rb
@@ -93,7 +93,7 @@

 		# Creates (and returns) a hash from both the name and value
 		def hash
-			name.hash + value.hash
+			name.hash ^ value.hash
 		end

 		# Returns this attribute out as XML source, expanding the name
===================================================================

rexml-hash.patch - REXML hash patch (576 Bytes) Ryan Riley, 08/05/2009 03:24 am

History

#1
Updated by Nobuyoshi Nakada over 2 years ago

Hi,

At Wed, 5 Aug 2009 03:24:49 +0900,
Ryan Riley wrote in [ruby-core:24754]:
> The hash method sometimes computes a value that is too
> large. This is a rare occurrence in MRI, but this is causing
> problems for IronRuby. The following patch is suggested for
> computing smaller hashes:

What problems?

-- 
Nobu Nakada

#2
Updated by Tomas Matousek over 2 years ago

This is potential problem for MRI as well since Array#hash blows up if any item's hash is not a Fixnum:

class C
  def hash
    100000000000000000000
  end
end

[C.new].hash  # => in `hash': bignum too big to convert into `long' (RangeError)

#3
Updated by Nobuyoshi Nakada over 2 years ago

Hi,

At Wed, 5 Aug 2009 04:43:31 +0900,
Tomas Matousek wrote in [ruby-core:24758]:
> This is potential problem for MRI as well since Array#hash blows up if any item's hash is not a Fixnum:

> [C.new].hash  # => in `hash': bignum too big to convert into `long' (RangeError)

It's been fixed in r22308, and should be backported to 1.8.

-- 
Nobu Nakada

[ruby-core:35406]#4
Updated by Ryan Davis 11 months ago

I believe this patch was backported to ruby 1.8... so shouldn't this ticket be closed?

[ruby-core:38366]#5
Updated by Charles Nutter 7 months ago

This does not appear to have been backported to ruby_1_8_7 branch, so we have gotten recent reports about it being a bug in JRuby. Is it possible to get this tiny patch backported to ruby_1_8_7, so we can pull the change into our patched stdlib at https://github.com/jruby/ruby/tree/jruby-ruby_1_8_7 ? I'd rather not apply the patch unilaterally, but this is a visible bug that needs fixing.

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