Class: TracePoint

Inherits:
Object show all
Defined in:
vm_trace.c,
vm_trace.c

Overview

A class that provides the functionality of Kernel#set_trace_func in a nice Object-Oriented API.

Example

We can use TracePoint to gather information specifically for exceptions:

trace = TracePoint.new(:raise) do |tp|

p [tp.lineno, tp.event, tp.raised_exception]

end
#=> #<TracePoint:disabled>

trace.enable
#=> false

0 / 0
#=> [5, :raise, #<ZeroDivisionError: divided by 0>]

Events

If you don't specify the type of events you want to listen for, TracePoint will include all available events.

Note do not depend on current event set, as this list is subject to change. Instead, it is recommended you specify the type of events you want to use.

To filter what is traced, you can pass any of the following as events:

:line

execute code on a new line

:class

start a class or module definition

:end

finish a class or module definition

:call

call a Ruby method

:return

return from a Ruby method

:c_call

call a C-language routine

:c_return

return from a C-language routine

:raise

raise an exception

:b_call

event hook at block entry

:b_return

event hook at block ending

:thread_begin

event hook at thread beginning

:thread_end

event hook at thread ending

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.newObject

TracePoint.new(*events) { |obj| block } -> obj

Returns a new TracePoint object, not enabled by default.

Next, in order to activate the trace, you must use TracePoint.enable

trace = TracePoint.new(:call) do |tp|

p [tp.lineno, tp.defined_class, tp.method_id, tp.event]

end #=> #<TracePoint:disabled>

trace.enable #=> false

puts “Hello, TracePoint!” # … # [48, IRB::Notifier::AbstractNotifier, :printf, :call] # …

When you want to deactivate the trace, you must use TracePoint.disable

trace.disable

See [email protected] for possible events and more information.

A block must be given, otherwise a ThreadError is raised.

If the trace method isn't included in the given events filter, a RuntimeError is raised.

TracePoint.trace(:line) do |tp|

p tp.raised_exception

end #=> RuntimeError: 'raised_exception' not supported by this event

If the trace method is called outside block, a RuntimeError is raised.

TracePoint.trace(:line) do |tp|
  $tp = tp
end
$tp.line #=> access from outside (RuntimeError)

Access from other threads is also forbidden.


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# File 'vm_trace.c', line 1234

static VALUE
tracepoint_new_s(int argc, VALUE *argv, VALUE self)
{
    rb_event_flag_t events = 0;
    int i;

    if (argc > 0) {
	for (i=0; i<argc; i++) {
	    events |= symbol2event_flag(argv[i]);
	}
    }
    else {
	events = RUBY_EVENT_TRACEPOINT_ALL;
    }

    if (!rb_block_given_p()) {
	rb_raise(rb_eThreadError, "must be called with a block");
    }

    return tracepoint_new(self, 0, events, 0, 0, rb_block_proc());
}

.traceObject

call-seq: TracePoint.trace(*events) { |obj| block } -> obj

A convenience method for TracePoint.new, that activates the trace
automatically.

   trace = TracePoint.trace(:call) { |tp| [tp.lineno, tp.event] }
   #=> #<TracePoint:enabled>

   trace.enabled? #=> true

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# File 'vm_trace.c', line 1256

static VALUE
tracepoint_trace_s(int argc, VALUE *argv, VALUE self)
{
    VALUE trace = tracepoint_new_s(argc, argv, self);
    rb_tracepoint_enable(trace);
    return trace;
}

Instance Method Details

#bindingObject

Return the generated binding object from event


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# File 'vm_trace.c', line 955

static VALUE
tracepoint_attr_binding(VALUE tpval)
{
    return rb_tracearg_binding(get_trace_arg());
}

#defined_classObject

Return class or module of the method being called.

class C; def foo; end; end trace = TracePoint.new(:call) do |tp| p tp.defined_class #=> C end.enable do C.new.foo end

If method is defined by a module, then that module is returned.

module M; def foo; end; end class C; include M; end; trace = TracePoint.new(:call) do |tp| p tp.defined_class #=> M end.enable do C.new.foo end

Note: #defined_class returns singleton class.

6th block parameter of Kernel#set_trace_func passes original class of attached by singleton class.

This is a difference between Kernel#set_trace_func and TracePoint.

class C; def self.foo; end; end trace = TracePoint.new(:call) do |tp| p tp.defined_class #=> #<Class:C> end.enable do C.foo end


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# File 'vm_trace.c', line 946

static VALUE
tracepoint_attr_defined_class(VALUE tpval)
{
    return rb_tracearg_defined_class(get_trace_arg());
}

#disableObject

trace.disable -> true or false trace.disable { block } -> obj

Deactivates the trace

Return true if trace was enabled. Return false if trace was disabled.

trace.enabled? #=> true trace.disable #=> false (previous status) trace.enabled? #=> false trace.disable #=> false

If a block is given, the trace will only be disable within the scope of the block.

trace.enabled? #=> true

trace.disable do

trace.enabled?
# only disabled for this block

end

trace.enabled? #=> true

Note: You cannot access event hooks within the block.

trace.disable { p tp.lineno } #=> RuntimeError: access from outside


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# File 'vm_trace.c', line 1128

static VALUE
tracepoint_disable_m(VALUE tpval)
{
    rb_tp_t *tp = tpptr(tpval);
    int previous_tracing = tp->tracing;
    rb_tracepoint_disable(tpval);

    if (rb_block_given_p()) {
	return rb_ensure(rb_yield, Qnil,
			 previous_tracing ? rb_tracepoint_enable : rb_tracepoint_disable,
			 tpval);
    }
    else {
	return previous_tracing ? Qtrue : Qfalse;
    }
}

#enableObject

trace.enable -> true or false trace.enable { block } -> obj

Activates the trace

Return true if trace was enabled. Return false if trace was disabled.

trace.enabled? #=> false trace.enable #=> false (previous state)

#   trace is enabled

trace.enabled? #=> true trace.enable #=> true (previous state)

#   trace is still enabled

If a block is given, the trace will only be enabled within the scope of the block.

trace.enabled? #=> false

trace.enable do

trace.enabled?
# only enabled for this block

end

trace.enabled? #=> false

Note: You cannot access event hooks within the block.

trace.enable { p tp.lineno } #=> RuntimeError: access from outside


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# File 'vm_trace.c', line 1077

static VALUE
tracepoint_enable_m(VALUE tpval)
{
    rb_tp_t *tp = tpptr(tpval);
    int previous_tracing = tp->tracing;
    rb_tracepoint_enable(tpval);

    if (rb_block_given_p()) {
	return rb_ensure(rb_yield, Qnil,
			 previous_tracing ? rb_tracepoint_enable : rb_tracepoint_disable,
			 tpval);
    }
    else {
	return previous_tracing ? Qtrue : Qfalse;
    }
}

#enabled?Boolean

trace.enabled? -> true or false

The current status of the trace

Returns:

  • (Boolean)

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# File 'vm_trace.c', line 1151

VALUE
rb_tracepoint_enabled_p(VALUE tpval)
{
    rb_tp_t *tp = tpptr(tpval);
    return tp->tracing ? Qtrue : Qfalse;
}

#eventObject

Type of event

See [email protected] for more information.


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# File 'vm_trace.c', line 879

static VALUE
tracepoint_attr_event(VALUE tpval)
{
    return rb_tracearg_event(get_trace_arg());
}

#inspectString

Return a string containing a human-readable TracePoint status.

Returns:


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# File 'vm_trace.c', line 1272

static VALUE
tracepoint_inspect(VALUE self)
{
    rb_tp_t *tp = tpptr(self);
    rb_trace_arg_t *trace_arg = GET_THREAD()->trace_arg;

    if (trace_arg) {
	switch (trace_arg->event) {
	  case RUBY_EVENT_LINE:
	  case RUBY_EVENT_SPECIFIED_LINE:
	    {
		VALUE sym = rb_tracearg_method_id(trace_arg);
		if (NIL_P(sym))
		  goto default_inspect;
		return rb_sprintf("#<TracePoint:%"PRIsVALUE"@%"PRIsVALUE":%d in `%"PRIsVALUE"'>",
				  rb_tracearg_event(trace_arg),
				  rb_tracearg_path(trace_arg),
				  FIX2INT(rb_tracearg_lineno(trace_arg)),
				  sym);
	    }
	  case RUBY_EVENT_CALL:
	  case RUBY_EVENT_C_CALL:
	  case RUBY_EVENT_RETURN:
	  case RUBY_EVENT_C_RETURN:
	    return rb_sprintf("#<TracePoint:%"PRIsVALUE" `%"PRIsVALUE"'@%"PRIsVALUE":%d>",
			      rb_tracearg_event(trace_arg),
			      rb_tracearg_method_id(trace_arg),
			      rb_tracearg_path(trace_arg),
			      FIX2INT(rb_tracearg_lineno(trace_arg)));
	  case RUBY_EVENT_THREAD_BEGIN:
	  case RUBY_EVENT_THREAD_END:
	    return rb_sprintf("#<TracePoint:%"PRIsVALUE" %"PRIsVALUE">",
			      rb_tracearg_event(trace_arg),
			      rb_tracearg_self(trace_arg));
	  default:
	  default_inspect:
	    return rb_sprintf("#<TracePoint:%"PRIsVALUE"@%"PRIsVALUE":%d>",
			      rb_tracearg_event(trace_arg),
			      rb_tracearg_path(trace_arg),
			      FIX2INT(rb_tracearg_lineno(trace_arg)));
	}
    }
    else {
	return rb_sprintf("#<TracePoint:%s>", tp->tracing ? "enabled" : "disabled");
    }
}

#linenoObject

Line number of the event


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# File 'vm_trace.c', line 888

static VALUE
tracepoint_attr_lineno(VALUE tpval)
{
    return rb_tracearg_lineno(get_trace_arg());
}

#method_idObject

Return the name of the method being called


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# File 'vm_trace.c', line 906

static VALUE
tracepoint_attr_method_id(VALUE tpval)
{
    return rb_tracearg_method_id(get_trace_arg());
}

#pathObject

Path of the file being run


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# File 'vm_trace.c', line 897

static VALUE
tracepoint_attr_path(VALUE tpval)
{
    return rb_tracearg_path(get_trace_arg());
}

#raised_exceptionObject

Value from exception raised on the :raise event


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# File 'vm_trace.c', line 985

static VALUE
tracepoint_attr_raised_exception(VALUE tpval)
{
    return rb_tracearg_raised_exception(get_trace_arg());
}

#return_valueObject

Return value from :return, c_return, and b_return event


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# File 'vm_trace.c', line 976

static VALUE
tracepoint_attr_return_value(VALUE tpval)
{
    return rb_tracearg_return_value(get_trace_arg());
}

#selfObject

Return the trace object during event

Same as TracePoint#binding: trace.binding.eval('self')


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# File 'vm_trace.c', line 967

static VALUE
tracepoint_attr_self(VALUE tpval)
{
    return rb_tracearg_self(get_trace_arg());
}