Debugger - Rubinius
Author: Less Than Three. <3. http://less.thanthree.com
Description: Rubinius is an implementation of the Ruby programming language. The Rubinius bytecode virtual machine is written in C++. The bytecode compiler is written in pure Ruby. The vast majority of the core library is also written in Ruby, with some supporting primitives that interact with the VM directly.

1.2.3

## Debugger

Rubinius zawiera referencyjny debugger na poziomie kodu źródłowego.

## Wywołanie debuggera

Debugger można wywołać z poziomu kodu źródłowego programu wykonując Rubinius::Debugger.start

Biorąc za przykład kod z app.rb

    class Toast
      attr_accessor :setting
      def initialize
        require 'rubinius/debugger'
        Rubinius::Debugger.start
        @setting = :brown
      end
    end

    p Toast.new.setting

Wykonanie powyższego kodu w Rubiniusie spowoduje:

    $ rbx app.rb

    | Breakpoint: Toast#initialize at app.rb:5 (15)
    | 5:     Rubinius::Debugger.start
    debug> help
                    help: Show information about debugger commands
           b, break, brk: Set a breakpoint at a point in a method
        tb, tbreak, tbrk: Set a temporary breakpoint
               d, delete: Delete a breakpoint
                 n, next: Move to the next line or conditional branch
                 s, step: Step into next method call or to next line
               ni, nexti: Move to the next bytecode instruction
                f, frame: Make a specific frame in the call stack the current frame
       c, cont, continue: Continue running the target thread
           bt, backtrace: Show the current call stack
                 p, eval: Run code in the current context
        dis, disassemble: Show the bytecode for the current method
                 i, info: Show information about things
                     set: Set a debugger config variable
                    show: Display the value of a variable or variables
    debug> bt
    | Backtrace:
    |    0 Toast#initialize at app.rb:5 (15)
    |    1 main.__script__ at app.rb:11 (46)
    |    2 Rubinius::CodeLoader#load_script(debug) at kernel/delta/codeloader.rb:67 (44)
    |    3 Rubinius::CodeLoader.load_script(name) at kernel/delta/codeloader.rb:91 (40)
    |    4 Rubinius::Loader#script at kernel/loader.rb:460 (79)
    |    5 Rubinius::Loader#main at kernel/loader.rb:571 (64)
    |    6 Rubinius::Loader.main at kernel/loader.rb:609 (33)
    |    7 Object#__script__ at kernel/loader.rb:621 (60)
    debug> n

    | Breakpoint: Toast#initialize at app.rb:6 (16)
    | 6:     @setting = :brown
    debug> n

    | Breakpoint: Toast#initialize at app.rb:7 (21)
    | 7:     @kind = :rye
    debug> p @setting = :light_brown
    $d0 = :light_brown
    debug> c
    :light_brown

Opis wszystkich komend uzyskamy wpisując `help` w konsoli debuggera.

## Wywołanie debuggera z linii poleceń

Debugger można wywołać z linii poleceń. Debugowanie rozpocznie się od pierwszej linii kodu wywoływanego skryptu.

Zakładając poniższy kod w skrypcie bug.rb:

    def problem_code
      puts "I have a problem"
      a = 1 + 2
      puts "a math problem" unless a == 4
    end

    problem_code

Aby zdebugować powyższy kod uruchom Rubiniusa z opcją `-Xdebug`.

    $ rbx -Xdebug bug.rb

    | Breakpoint: Rubinius::Loader#debugger at kernel/loader.rb:424 (34)
    | 424:         Rubinius::Debugger.start
    debug> b Object#problem_code:2
    * Unable to find method 'problem_code' in Object
    | Would you like to defer this breakpoint to later? [y/n] y
    | Defered breakpoint created.
    debug> c
    | Resolved breakpoint for Object#problem_code
    | Set breakpoint 2: bug.rb:2 (+0)

    | Breakpoint: Object#problem_code at bug.rb:2 (0)
    | 2:   puts "I have a problem"
    debug> n
    I have a problem

    | Breakpoint: Object#problem_code at bug.rb:3 (9)
    | 3:   a = 1 + 2
    debug> n

    | Breakpoint: Object#problem_code at bug.rb:4 (16)
    | 4:   puts "a math problem" unless a == 4
    debug> p a = 4
    $d0 = 4
    debug> n

    | Breakpoint: main.__script__ at bug.rb:7 (17)
    | 7: problem_code
    debug> c

Jak widać, wywołanie `p a = 4` w debugerze zmienia wartość zmiennej lokalnej `a` oraz wpływa na wykonywany program.