[ruby-core:119278] [Ruby master Feature#20757] Make rb_tracearg_(parameters|eval_script|instruction_sequence) public C-API

Issue #20757 has been updated by richardboehme (Richard B=F6hme).


Actually it seems like retrieving the method object using the `method_id` d=
oes not work well for super-calls. See this example:

``` ruby
TracePoint.new(:call) do  |tp|
  p tp.self
end.enable

class A
  def test
  end
end

class B < A
  def test =3D super
end

B.new.test
```

`TracePoint#self` will return the instance of B twice, which makes it hard =
to get the parameters of `A#test` without being able to call `TracePoint#pa=
rameters`. In general this makes it hard to track down the location of the =
method behind `TracePoint#method_id`, but this is another issue.

----------------------------------------
Feature #20757: Make rb_tracearg_(parameters|eval_script|instruction_sequen=
ce) public C-API
https://bugs.ruby-lang.org/issues/20757#change-109886

* Author: richardboehme (Richard B=F6hme)
* Status: Open
----------------------------------------
**Abstract**
As a C-extension developer when using tracepoints I include "ruby/debug.h".=
 This includes most of TracePoint's API but it seems like the C-equivalents=
 for TracePoint#parameters, TracePoint#eval_script and TracePoint#instructi=
on_sequence are missing/not being exported in the header.
=20
**Background**
Most APIs like rb_tracearg_return_value are exported in "ruby/debug.h". If =
I understand correctly, the implementations for those methods are located i=
n "ruby/vm_trace.c". The following methods implemented in "ruby/vm_trace.c"=
 are missing in "ruby/debug.h":
* rb_tracearg_parameters
* rb_tracearg_eval_script
* rb_tracearg_instruction_sequence
 =20
**Proposal**
I propose to add those methods to "ruby/debug.h". From my limiting understa=
nding the change should be simple and not break backward compatibility, bec=
ause we'd only need to add those function declarations to "ruby/debug.h".

I'd be open to contribute this change if it was approved.

**Use cases**
I'm implementing a method call tracer for Ruby using the C-extension API. I=
 wanted to get information about the parameters that the called method rece=
ives. When writing in Ruby this can be done using the TracePoint#parameters=
 method, but I could not find the equivalent C-API. A workaround is to retr=
ieve the method object (using the method_id) and check the method parameter=
s. =20

**See also**

* Implementation of TracePoint#parameters in #14694=20
* Implementation of TracePoint#eval_script and TracePoint#instruction_seque=
nce in #15287=20



--=20
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