From: Aston <blackapache512-ticket@...>
Date: 2010-07-03T00:37:56+09:00
Subject: Ruby/DL problem

Hello,

I have very little experience with dl. But I want to use it to 
call SetEnvironmentVariable() from Win32. I could use FFI but cannot, since this 
script will be supplied to a customer where it is difficult to install.

SetEnvironmentVariable on 
MSDN http://msdn.microsoft.com/en-us/library/ms686206(v=VS.85).aspx

reading sparse, old, and cryptic documentation I came up with this snippet, 
which of course does not work

require 'dl/import'

module Win32
extend DL::Importer
extern "int SetEnvironmentVariableA( char* lpName, char* lpValue)"
extern "int GetEnvironmentVariableA( char* lpName, char* lpValue, int size)"
end

buff = Array.new( 256, 0).pack("c*")
Win32.GetEnvironmentVariableA( "ENV_VAR", buff, 255)
puts buff.unpack("a*")

this is the error i get
D:/ruby/usr/lib/ruby/1.9.1/dl/import.rb:194:in `import_function': undefined 
method `sym' for nil:NilClass (NoMethodError)
        from D:/ruby/usr/lib/ruby/1.9.1/dl/import.rb:118:in `extern'
        from test.rb:5:in `<module:Win32>'
        from test.rb:3:in `<main>'

machine is WinXP
ruby 1.9.1 (2008-10-28 revision 19983) [i386-mswin32_80]

can anybody suggest a better signature ?

Aston