Ruby

I'll try before preview-2.

JRuby already has a implementation and tests?

This issue was solved with changeset r44170.
Charles, thank you for reporting this issue.
Your contribution to Ruby is greatly appreciated.
May Ruby be with you.

• error.c: add Exception#backtrace_locations.
  Now, there are no setter and independent from Exception#backtrace.
  [Feature #8960]
• eval.c (setup_exception): set backtrace locations for `bt_location'
  special attribute.
• vm_backtrace.c (rb_backtrace_to_location_ary): added.
• internal.h: ditto.
• test/ruby/test_backtrace.rb: add a test for
  Exception#backtrace_locations.

Now, I implemented half-baked feature (read-only backtrace locations).

How about to continue how to change it?

Is there any way to re-raise an exception and propagate backtrace_locations? When I want to trap an exception and provide a different exception class and error message, I'm used to doing something like:

rescue => e
  raise MyCustomException, "Error details", e.backtrace

But this is calling set_backtrace, leaving the resulting exception's backtrace_locations nil (on MRI 2.3.1) or and empty array (on jruby 9.1.2.0).

If only some exceptions will have a valid backtrace_locations array (matching the information in backtrace), it is difficult to write code that takes advantage of this feature.