From: Reginald Tan <lists@...>
Date: 2012-07-03T15:05:09+09:00
Subject: Re: Using binding + set trace func to capture execution state

>
> To achieve your goal you'd need to copy the state of variables at each
> tracefunc invocation. Even worse, as the objects themselves may change,
> you will need to do a deep copy each time (otherwise you'll pluck into
> exactly the same problem with object instance variables). I would
> suggest
> marshalling the objects and writing them to something like tmpfs, then
> using a special tool to navigate the captured information.
>
> This is going to consume a lot of memory. I repeat: a lot. Like tens
> of gigabytes for a complex thing like... Sinatra. And probably
> terabytes
> for Rails.

Hmm, you're right, it would not be efficient at all to store all those 
variables especially in a large program.

I guess another possible approach is to rerun the program every time i 
want to inspect a variable.  Since I know which file and line the 
variable is, I can use that as a condition on set_trace_func handler on 
when to output that variable.

set_trace_func proc { |event, file, line, id, binding, classname|
  if event == "line" && file == "myfile.rb" && line == 4
    puts eval("@myvar", binding)
  end
}

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