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Bug #3841

Updated by ko1 (Koichi Sasada) almost 8 years ago

 =begin 
  I have been playing with the concept of caching compiled Ruby instruction sequences and reloading them later. For now the simplest way to do it is to use RubyVM::InstructionSequence.to_a() and Marshal.dump() to convert the resulting array to a smaller binary byte sequence. While testing this, I found that some Ruby scripts worked fine when an instruction sequence was reloaded, but others broke. 
 
  As a test, I decided to try compiling irb.rb and its dependencies. When I try to reload the compiled sequences, the first file that breaks is irb/extend-command.rb. I tracked it down to the way "for <vars> in <list>" code block and parameters are handled, but I am not sure how to fix it. When I converted each "for <vars> in <list>" loop to "<list>.each {|<vars>|", it started working perfectly. Here's an example of how the disassembly differs between the two loops: 
 

 ``` 
  
 
  def self.install_extend_commands 
    @EXTEND_COMMANDS.each {|args| 
      def_extend_command(*args) 
    } 
  end 
  == disasm: <RubyVM::InstructionSequence:block in install_extend_commands@irb/extend-command.rb> 
  == catch table 
  | catch type: redo     st: 0000 ed: 0012 sp: 0000 cont: 0000 
  | catch type: next     st: 0000 ed: 0012 sp: 0000 cont: 0012 
  |------------------------------------------------------------------------ 
  local table (size: 2, argc: 1 [opts: 0, rest: -1, post: 0, block: -1] s3) 
  [ 2] args<Arg>   
  0000 trace              1                                                 ( 110) 
  0002 putnil            
  0003 getdynamic         args, 0 
  0006 send               :def_extend_command, 1, nil, 10, <ic:0> 
  0012 leave             
 
  def self.install_extend_commands 
    for args in @EXTEND_COMMANDS 
      def_extend_command(*args) 
    end 
  end 
  == disasm: <RubyVM::InstructionSequence:block in install_extend_commands@irb/extend-command.rb> 
  == catch table 
  | catch type: redo     st: 0005 ed: 0016 sp: 0000 cont: 0005 
  | catch type: next     st: 0005 ed: 0016 sp: 0000 cont: 0016 
  |------------------------------------------------------------------------ 
  local table (size: 2, argc: 1 [opts: 0, rest: -1, post: 0, block: -1] s3) 
  [ 2] ?<Arg>      
  0000 getdynamic         *, 0                                              ( 206) 
  0003 setlocal           args                                              ( 204) 
  0005 trace              1                                                 ( 205) 
  0007 putnil            
  0008 getlocal           args 
  0010 send               :def_extend_command, 1, nil, 10, <ic:0> 
  0016 leave             
 ``` 
 
              
 
  In this example, rb_id2name() returns NULL for the name of the argument passed to the code block. That is why it puts a "?" in the local table and a "*" in the getdynamic command. The to_a() method has a similar problem, and it appears to put a number there instead. When I use the load() method to convert the array back into an instruction sequence and try to execute it, the code block ends up receiving a number as a parameter instead of the entry in the list it is supposed to get. 
 
  I imagine this is not a high priority for the Ruby core team, and I don't mind putting in some work to fix it. However, it looks like it would take me a while to figure out, so I would appreciate any tips you could give me to point me in the right direction. 
 
  Thank you, 
  Sean O'Neil 
 =end 

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