From: "Klaus Kämpf" <redmine@...>
Date: 2010-05-15T04:10:24+09:00
Subject: [ruby-core:30246] [Bug #3297] [patch] Array#pack("i_") is broken in big endian 64bit systems

Bug #3297: [patch] Array#pack("i_") is broken in big endian 64bit systems
http://redmine.ruby-lang.org/issues/show/3297

Author: Klaus K��mpf
Status: Open, Priority: Normal
Category: core
ruby -v: ruby 1.8.7 (2008-08-11 patchlevel 72) [powerpc64-linux] 

See also http://redmine.ruby-lang.org/issues/show/1131 for a similar issue (String#unpack("V"))

Array#pack("i_") is broken in big endian 64 bit systems

irb> [1].pack("i_")
=> "\000\000\000\000"


The root cause is similar to the one of issue 1131, use of a wrong offset in a 64bit long.
But the fix is a bit simpler and is probably correct for all other architectures too.

According to the documentation, the "i" format of pack/unpack uses a fixed-size (32bit) integer, while adding "_" uses the system-size.
However, the implementation of Array#pack uses a 'long' type (64bit !) to store an intermediate value, thus breaking OFF() in accessing the wrong 4 bytes of the value.

Fix: Use 'int' to store the intermediate value (use of int is correct for the fixed-size as well as the system-size case) and don't use OFF()

With this patch, the pack_spec and unpack_spec tests of rubyspec.org run without issues.


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