Feature #15473: TracePoint#enable(target_thread:) to specify a Thread

• Status: Closed
• Assignee: ko1 (Koichi Sasada)
• Target version: -

[ko1 (Koichi Sasada)]

We introduced TracePoint#enable(target:, target_line:) keyword.
How about to introduce target_thread: keyword which specify enabling threads?

TracePoint.new(:line){|tp| p tp}.enable(target_thread: Thread.current) do
  p 1
  Thread.new{
    p 10
    p 12
  }.join
  p 2
end

#<TracePoint:line@/home/ko1/src/ruby/trunk/test.rb:3>
1
#<TracePoint:line@/home/ko1/src/ruby/trunk/test.rb:4>
10
12
#<TracePoint:line@/home/ko1/src/ruby/trunk/test.rb:8>
2

Maybe Thread.current is frequent pattern, so accepting :current` symbol is reasonable for me.

TracePoint.new(:line){|tp| p tp}.enable(target_thread: :current) do
  p 1
  Thread.new{
    p 10
    p 12
  }.join
  p 2
end

# same result

This is a patch.

Index: prelude.rb
===================================================================
--- prelude.rb	(revision 66594)
+++ prelude.rb	(working copy)
@@ -133,8 +133,8 @@ class IO
 end
 
 class TracePoint
-  def enable target: nil, target_line: nil, &blk
-    self.__enable target, target_line, &blk
+  def enable target: nil, target_line: nil, target_thread: nil, &blk
+    self.__enable target, target_line, target_thread, &blk
   end
 end
 
Index: vm_trace.c
===================================================================
--- vm_trace.c	(revision 66594)
+++ vm_trace.c	(working copy)
@@ -1398,11 +1398,26 @@ rb_hook_list_remove_tracepoint(rb_hook_l
  *
  */
 static VALUE
-tracepoint_enable_m(VALUE tpval, VALUE target, VALUE target_line)
+tracepoint_enable_m(VALUE tpval, VALUE target, VALUE target_line, VALUE target_thread)
 {
     rb_tp_t *tp = tpptr(tpval);
     int previous_tracing = tp->tracing;
 
+    if (RTEST(target_thread)) {
+        static VALUE sym_current = 0;
+        if (sym_current == 0) sym_current = rb_id2sym(rb_intern("current"));
+
+        if (target_thread == sym_current) {
+            tp->target_th = GET_THREAD();
+        }
+        else {
+            tp->target_th = rb_thread_ptr(target_thread);
+        }
+    }
+    else {
+        tp->target_th = NULL;
+    }
+
     if (NIL_P(target)) {
         if (!NIL_P(target_line)) {
             rb_raise(rb_eArgError, "only target_line is specified");
@@ -1801,7 +1816,7 @@ Init_vm_trace(void)
      */
     rb_define_singleton_method(rb_cTracePoint, "trace", tracepoint_trace_s, -1);
 
-    rb_define_method(rb_cTracePoint, "__enable", tracepoint_enable_m, 2);
+    rb_define_method(rb_cTracePoint, "__enable", tracepoint_enable_m, 3);
     rb_define_method(rb_cTracePoint, "disable", tracepoint_disable_m, 0);
     rb_define_method(rb_cTracePoint, "enabled?", rb_tracepoint_enabled_p, 0);
 

This is a similar feature proposed at https://bugs.ruby-lang.org/issues/13483 but no compatibility issue.

[shevegen (Robert A. Heiler)]

To me personally the proposal seems fine. I like the shortcut :current for Thread.current
which makes sense (to me), as Thread.current already exists as name, so it appears intuitive
to me.

For sake of completion, I would recommend showing how/if we can target other threads too,
and how it would look like. Unless I overlooked something, I believe we have only examples
for Thread.current / :current so far.

[Eregon (Benoit Daloze)]

ko1 (Koichi Sasada) wrote:

Maybe Thread.current is frequent pattern, so accepting :current` symbol is reasonable for me.

I think it's not needed, and that passing Thread.current is clearer and simpler, so I would propose to not add this special shortcut.

The feature seems useful and good to me, and clearer (more explicit & compatible) than #13483.

BTW, I noticed ri TracePoint#enable doesn't show any documentation (because it's attached as __enable), and that target: and target_line: are not documented.

[ko1 (Koichi Sasada)]

Thank you for your comments.

For sake of completion, I would recommend showing how/if we can target other threads too, and how it would look like.

I don't have good example, but there is a Thread#set_trace_func to specify the thread.

For example, a debugger running on one dedicated thread and it monitors a thread?

Eregon (Benoit Daloze) wrote:

I think it's not needed, and that passing Thread.current is clearer and simpler, so I would propose to not add this special shortcut.

I can agree it. Or introduce other keywords like current_thread: true (maybe not a good name).
Anyway, I'll introduce target_thraed: soon without :current shortcut if there are no other objections.

BTW, I noticed ri TracePoint#enable doesn't show any documentation (because it's attached as __enable), and that target: and target_line: are not documented.

:(

[ko1 (Koichi Sasada)]

• Status changed from Open to Closed

Applied in changeset trunk|r66640.

---

TracePoint#enable(target_thraed:) [Feature #15473]

• vm_trace.c (tracepoint_enable_m): TracePoint#enable supports
  target_thread: keyword to filter a target thread.
  [Feature #15473]