Feature #15289


Accept "target" keyword on `TracePoint#enable`

Added by ko1 (Koichi Sasada) over 5 years ago. Updated almost 5 years ago.

Target version:



To enable TracePoint for specific location, I propose new keyword argument target: to TracePoint#enable for specific events (line, call, return, class, end).


line_trace ={|tp|
  p tp

def foo
  p 1

line_trace.enable(target: method(:foo)) do

In this case, a line trace is enable only on the method foo.

target: keyword accepts Method, UnboundMethod, Proc and RubyVM::InstructionSequence (ISeq for short) . All of objects can pull ISeq objects.

Further more, I propose target_lines: keyword too, which specify effective line(s).

These features can improve "break point" feature and so on.


If we want to insert break point in Ruby's source code, we can use TracePoint (line event, for example). However, it enables all locations. It hurt performance.

This proposal overcomes this performance penalty.


Now basic design are completed in my mind :p


line or lines

For breakpoint purpose, we only need to specify a line. Specifying lines is needed?

no events on lines

It is not clear that if line is specified (for example: 10) and there are no line event (for example, empty line).

Possible options:

  • (1) raise an exception
  • (2) adjust before/after effective event
  • (3) ignore

I prefer (1).

no events in Proc

Similar to last topic, if we specify call event on Proc object, there are no call event. What happens?

recursive or not

If method foo refers other blocks, I think we need to enable recursively.

how to get File target?

Sometimes we want to specify breakponit to the location specified by "file:line". How to get the lines? provides the feature to collect all of ISeqs. debugger can collects all of them and debugger can filter with path name.

Also [Feature #15287] will help to hook not loaded locations.

enable w/ keywords or other method name?

I have no strong opinion, but TracePoint#enable_on(target, lines: ...) is another idea?



This implementation is based on trace_ insn.

Updated by shevegen (Robert A. Heiler) over 5 years ago

Sounds nice. Please do not forget documentation when/if approved/added. :)

I have no particular opinion on the API/name(s) as such, but I would recommend
to try to keep it simple and "logical" if possible. A Hash would probably make
the most sense, and the names for the parameters should ideally be the same, e. g.
if "lines:" is used, to also keep the same names whenever possible (both for
TracePoint, but also perhaps elsewhere in ruby if that is necessary; a bit
like how recently :exception was added to Kernel#system and other methods
there, like in the news entry for the upcoming 2.6.x xmas-release.

That is not necessarily an endorsement of the name "lines:" as such, mind
you; just more a general comment.

(I think the name "lines:" may not always be ideal, e. g. in the cases where
a ruby user may only want to add one breakpoint to a single line - but this
is mostly a detail, IMO. I am sure any fitting name can be derived when we
have some examples of how this is used. Ideally a short name if possible.)

Updated by ko1 (Koichi Sasada) over 5 years ago

I got Matz's approval.
I'll implement it and commit soon before ruby 2.6 rc1.

Now, I finished most of features, except handling at exception.

Actions #3

Updated by ko1 (Koichi Sasada) over 5 years ago

  • Status changed from Open to Closed

Applied in changeset trunk|r66003.

Support targetting TracePoint [Feature #15289]

  • vm_trace.c (rb_tracepoint_enable_for_target): support targetting
    TracePoint. [Feature #15289]

    Tragetting TracePoint is only enabled on specified method, proc
    and so on, example: tp.enable(target: code).

    code should be consisted of InstructionSeuqnece (iseq)
    (RubyVM::InstructionSeuqnece.of(code) should not return nil)
    If code is a tree of iseq, TracePoint is enabled on all of
    iseqs in a tree.

    Enabled tragetting TracePoints can not enabled again with
    and without target.

  • vm_core.h (rb_iseq_t): introduce rb_iseq_t::local_hooks
    to store local hooks.
    rb_iseq_t::aux::trace_events is renamed to
    global_trace_events to contrast with local_hooks.

  • vm_core.h (rb_hook_list_t): add rb_hook_list_t::running
    to represent how many Threads/Fibers are used this list.
    If this field is 0, nobody using this hooks and we can
    delete it.

    This is why we can remove code from cont.c.

  • vm_core.h (rb_vm_t): because of above change, we can eliminate
    rb_vm_t::trace_running field.
    Also renamed from rb_vm_t::event_hooks to global_hooks.

  • vm_core.h, vm.c (ruby_vm_event_enabled_global_flags): renamed
    from `ruby_vm_event_enabled_flags.

  • vm_core.h, vm.c (ruby_vm_event_local_num): added to count
    enabled targetting TracePoints.

  • vm_core.h, vm_trace.c (rb_exec_event_hooks): accepts
    hook list.

  • vm_core.h (rb_vm_global_hooks): added for convinience.

  • method.h (rb_method_bmethod_t): added to maintain Proc
    and rb_hook_list_t for bmethod (defined by define_method).

  • prelude.rb (TracePoint#enable): extracet a keyword parameter
    (because it is easy than writing in C).
    It calls TracePoint#__enable internal method written in C.

  • vm_insnhelper.c (vm_trace): check also iseq->local_hooks.

  • vm.c (invoke_bmethod): check def->body.bmethod.hooks.

  • vm.c (hook_before_rewind): check iseq->local_hooks
    and def->body.bmethod.hooks before rewind by exception.

Updated by k0kubun (Takashi Kokubun) over 5 years ago

  • Status changed from Closed to Assigned

I reopen this ticket as a reminder to fix MinGW test failure by this. Please close this ticket once AppVeyor becomes green with r66062 reverted.

Updated by k0kubun (Takashi Kokubun) over 5 years ago

  • Status changed from Assigned to Closed

The above issue was fixed in r66087. Thank you.

Actions #6

Updated by nobu (Nobuyoshi Nakada) almost 5 years ago

  • Description updated (diff)

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