TracePoint return event location is incorrect for methods defined with define_method
ruby-2.4.1-p111 (x86_64-linux) tracepoint_bug_ext.rb:4 call to_s tracepoint_bug_ext.rb:5 c_call to_s tracepoint_bug_ext.rb:5 c_return to_s racepoint_bug.rb:12 return to_s
Why the call event on to_s is in file tracepoint_bug_ext.rb and the return event in file tracepoint_bug.rb? I think it's a bug. In jruby, for example, the call and the return event are both fired in the tracepoint_bug_ext.rb file.
Updated by jeremyevans0 (Jeremy Evans) over 2 years ago
- Subject changed from TracePoint doesn't work correct with monkey patches / aliased methods to TracePoint return event location is incorrect for methods defined with define_method
This isn't an issue specific to monkey patches or aliased methods. This is a general issue with the :return event handling of bmethods (methods defined using blocks instead of with
def). The return event handling occurs after the related VM frame has been popped instead of before, which is why the return event for bmethods shows the caller location instead of the return location in the callee. I've submitted a pull request to fix this: https://github.com/ruby/ruby/pull/4588
Updated by alanwu (Alan Wu) almost 2 years ago
- Status changed from Open to Closed
Applied in changeset git|9121e57a5f50bc91bae48b3b91edb283bf96cb6b.
Rework tracing for blocks running as methods
The main impetus for this change is to fix [Bug #13392]. Previously, we
fired the "return" TracePoint event after popping the stack frame for
the block running as method (BMETHOD). This gave undesirable source
location outputs as the return event normally fires right before the
frame going away.
The iseq for each block can run both as a block and as a method. To
accommodate that, this commit makes vm_trace() fire call/return events for
instructions that have b_call/b_return events attached when the iseq is
running as a BMETHOD. The logic for rewriting to "trace_*" instruction
is tweaked so that when the user listens to call/return events,
instructions with b_call/b_return become trace variants.
To continue to provide the return value for non-local returns done using
the "return" or "break" keyword inside BMETHODs, the stack unwinding
code is tweaked. b_return events now provide the same return value as
return events for these non-local cases. A pre-existing test deemed not
providing a return value for these b_return events as a limitation.
This commit removes the checks for call/return TracePoint events that
happen when calling into BMETHODs when no TracePoints are active.
Technically, migrating just the return event is enough to fix the bug,
but migrating both call and return removes our reliance on
VM_FRAME_FLAG_FINISH and re-entering the interpreter when the caller
is already in the interpreter.