Class: Tracer

Inherits:
Object
  • Object
show all
Defined in:
lib/tracer.rb

Overview

Outputs a source level execution trace of a Ruby program.

It does this by registering an event handler with Kernel#set_trace_func for processing incoming events. It also provides methods for filtering unwanted trace output (see Tracer.add_filter, Tracer.on, and Tracer.off).

Example

Consider the following Ruby script

class A
  def square(a)
    return a*a
  end
end

a = A.new
a.square(5)

Running the above script using ruby -r tracer example.rb will output the following trace to STDOUT (Note you can also explicitly require 'tracer')

#0:<internal:lib/rubygems/custom_require>:38:Kernel:<: -
#0:example.rb:3::-: class A
#0:example.rb:3::C: class A
#0:example.rb:4::-:   def square(a)
#0:example.rb:7::E: end
#0:example.rb:9::-: a = A.new
#0:example.rb:10::-: a.square(5)
#0:example.rb:4:A:>:   def square(a)
#0:example.rb:5:A:-:     return a*a
#0:example.rb:6:A:<:   end
 |  |         | |  |
 |  |         | |   ---------------------+ event
 |  |         |  ------------------------+ class
 |  |          --------------------------+ line
 |   ------------------------------------+ filename
  ---------------------------------------+ thread

Symbol table used for displaying incoming events:

}

call a C-language routine

{

return from a C-language routine

>

call a Ruby method

C

start a class or module definition

E

finish a class or module definition

-

execute code on a new line

^

raise an exception

<

return from a Ruby method

by Keiju ISHITSUKA([email protected])

Constant Summary collapse

EVENT_SYMBOL =

Symbol table used for displaying trace information

{
  "line" => "-",
  "call" => ">",
  "return" => "<",
  "class" => "C",
  "end" => "E",
  "raise" => "^",
  "c-call" => "}",
  "c-return" => "{",
  "unknown" => "?"
}
Single =

Reference to singleton instance of Tracer

new

Class Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initializeTracer

:nodoc:


109
110
111
112
113
114
115
116
117
118
119
120
# File 'lib/tracer.rb', line 109

def initialize # :nodoc:
  @threads = Hash.new
  if defined? Thread.main
    @threads[Thread.main.object_id] = 0
  else
    @threads[Thread.current.object_id] = 0
  end

  @get_line_procs = {}

  @filters = []
end

Class Attribute Details

.display_c_callObject Also known as: display_c_call?

display C-routine calls in trace output (defaults to false)


84
85
86
# File 'lib/tracer.rb', line 84

def display_c_call
  @display_c_call
end

.display_process_idObject Also known as: display_process_id?

display process id in trace output (defaults to false)


76
77
78
# File 'lib/tracer.rb', line 76

def display_process_id
  @display_process_id
end

.display_thread_idObject Also known as: display_thread_id?

display thread id in trace output (defaults to true)


80
81
82
# File 'lib/tracer.rb', line 80

def display_thread_id
  @display_thread_id
end

.stdoutObject

output stream used to output trace (defaults to STDOUT)


70
71
72
# File 'lib/tracer.rb', line 70

def stdout
  @stdout
end

.stdout_mutexObject (readonly)

mutex lock used by tracer for displaying trace output


73
74
75
# File 'lib/tracer.rb', line 73

def stdout_mutex
  @stdout_mutex
end

.verboseObject Also known as: verbose?

display additional debug information (defaults to false)


66
67
68
# File 'lib/tracer.rb', line 66

def verbose
  @verbose
end

Class Method Details

.add_filter(p = nil, &b) ⇒ Object

Used to filter unwanted trace output

Example which only outputs lines of code executed within the Kernel class:

Tracer.add_filter do |event, file, line, id, binding, klass, *rest|
  "Kernel" == klass.to_s
end

267
268
269
270
# File 'lib/tracer.rb', line 267

def Tracer.add_filter(p = nil, &b)
  p ||= b
  Single.add_filter(p)
end

.offObject

Disable tracing


239
240
241
# File 'lib/tracer.rb', line 239

def Tracer.off
  Single.off
end

.onObject

Start tracing

Example

Tracer.on
# code to trace here
Tracer.off

You can also pass a block:

Tracer.on {
  # trace everything in this block
}

228
229
230
231
232
233
234
# File 'lib/tracer.rb', line 228

def Tracer.on
  if block_given?
    Single.on{yield}
  else
    Single.on
  end
end

.set_get_line_procs(file_name, p = nil, &b) ⇒ Object

Register an event handler p which is called every time a line in file_name is executed.

Example:

Tracer.set_get_line_procs("example.rb", lambda { |line|
  puts "line number executed is #{line}"
})

253
254
255
256
# File 'lib/tracer.rb', line 253

def Tracer.set_get_line_procs(file_name, p = nil, &b)
  p ||= b
  Single.set_get_line_procs(file_name, p)
end

Instance Method Details

#add_filter(p = nil, &b) ⇒ Object

:nodoc:


145
146
147
148
# File 'lib/tracer.rb', line 145

def add_filter(p = nil, &b) # :nodoc:
  p ||= b
  @filters.push p
end

#get_line(file, line) ⇒ Object

:nodoc:


155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
# File 'lib/tracer.rb', line 155

def get_line(file, line) # :nodoc:
  if p = @get_line_procs[file]
    return p.call(line)
  end

  unless list = SCRIPT_LINES__[file]
    list = File.readlines(file) rescue []
    SCRIPT_LINES__[file] = list
  end

  if l = list[line - 1]
    l
  else
    "-\n"
  end
end

#get_thread_noObject

:nodoc:


172
173
174
175
176
177
178
# File 'lib/tracer.rb', line 172

def get_thread_no # :nodoc:
  if no = @threads[Thread.current.object_id]
    no
  else
    @threads[Thread.current.object_id] = @threads.size
  end
end

#offObject

:nodoc:


140
141
142
143
# File 'lib/tracer.rb', line 140

def off # :nodoc:
  set_trace_func nil
  stdout.print "Trace off\n" if Tracer.verbose?
end

#onObject

:nodoc:


126
127
128
129
130
131
132
133
134
135
136
137
138
# File 'lib/tracer.rb', line 126

def on # :nodoc:
  if block_given?
    on
    begin
      yield
    ensure
      off
    end
  else
    set_trace_func method(:trace_func).to_proc
    stdout.print "Trace on\n" if Tracer.verbose?
  end
end

#set_get_line_procs(file, p = nil, &b) ⇒ Object

:nodoc:


150
151
152
153
# File 'lib/tracer.rb', line 150

def set_get_line_procs(file, p = nil, &b) # :nodoc:
  p ||= b
  @get_line_procs[file] = p
end

#stdoutObject

:nodoc:


122
123
124
# File 'lib/tracer.rb', line 122

def stdout # :nodoc:
  Tracer.stdout
end

#trace_func(event, file, line, id, binding, klass) ⇒ Object

:nodoc:


180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
# File 'lib/tracer.rb', line 180

def trace_func(event, file, line, id, binding, klass, *) # :nodoc:
  return if file == __FILE__

  for p in @filters
    return unless p.call event, file, line, id, binding, klass
  end

  return unless Tracer::display_c_call? or
    event != "c-call" && event != "c-return"

  Tracer::stdout_mutex.synchronize do
    if EVENT_SYMBOL[event]
      stdout.printf("<%d>", $$) if Tracer::display_process_id?
      stdout.printf("#%d:", get_thread_no) if Tracer::display_thread_id?
      if line == 0
        source = "?\n"
      else
        source = get_line(file, line)
      end
      stdout.printf("%s:%d:%s:%s: %s",
             file,
             line,
             klass || '',
             EVENT_SYMBOL[event],
             source)
    end
  end

end