Feature #8960: Add Exception#backtrace_locations

• Status: Assigned
• Priority: Normal
• Assignee: ko1 (Koichi Sasada)
• Target version: -

[headius (Charles Nutter)]

All parties agreed this would be useful to add in https://bugs.ruby-lang.org/issues/7895 and ko1 suggested I file a feature against ruby-trunk. So here it is.

I might be able to come up with a patch, but I'm not sure when. Help wanted.

Can we agree this will go into 2.1?

[ko1 (Koichi Sasada)]

• Category set to core
• Assignee set to ko1 (Koichi Sasada)
• Target version set to 2.1.0

I'll try before preview-2.

JRuby already has a implementation and tests?

[headius (Charles Nutter)]

JRuby has implementation but no tests. The test should look pretty much like Thread#backtrace_locations tests, though.

I can work on some tests if you work on impl for MRI.

[nobu (Nobuyoshi Nakada)]

What will be returned from an exception set by Exception#set_backtrace in JRuby?

[ko1 (Koichi Sasada)]

• Status changed from Open to Closed
• % Done changed from 0 to 100

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.

[ko1 (Koichi Sasada)]

• Status changed from Closed to Feedback
• Target version changed from 2.1.0 to 2.6
• % Done changed from 100 to 0

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

How about to continue how to change it?

[headius (Charles Nutter)]

ko1: I have no problem whatsoever with backtrace_locations being read-only now and forever. I'm glad to see this made it into 2.1 as at least a basic feature.

[ryannevell (Ryan Nevell)]

• Assignee changed from ko1 (Koichi Sasada) to headius (Charles Nutter)

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.

[nobu (Nobuyoshi Nakada)]

Ryan Nevell wrote:

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:

Nothing right now.

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.

Agree.

[shyouhei (Shyouhei Urabe)]

• Assignee changed from headius (Charles Nutter) to ko1 (Koichi Sasada)
• Status changed from Feedback to Assigned

[shyouhei (Shyouhei Urabe)]

We looked at this issue today. It turned out that ruby do not fully implement what was needed originally now. Reopened the ticket to assign ko1.