Issue #21501 has been updated by mame (Yusuke Endoh). Let me clarify why the current behavior is generally preferred. The underlying premise is that a bug is far more likely to be in the user's Ruby code than in the C extensions. Therefore, a line like: ``` native-filenames-example.rb:6:in 'BigDecimal.save_rounding_mode': ... error ``` ...concisely points to the most relevant location for the user to inspect first. In most cases, debugging simply involves fixing the code at or around this exact location. If the backtrace instead pointed to a line in `.../bigdecimal.so` or `.../bigdecimal.c`, the user would have to scan down the trace to find the first line corresponding to their own `.rb` file. This adds an unnecessary step and cognitive cost to the daily debugging process. In short, the current behavior is optimized for the most common use case: efficiently debugging the frequent, simple bugs in one's own application code. To justify changing this, we would need a strong and clear reason that outweighs this benefit. ---------------------------------------- Feature #21501: Include native filenames in backtraces as sources for native methods https://bugs.ruby-lang.org/issues/21501#change-114000 * Author: ivoanjo (Ivo Anjo) * Status: Open ---------------------------------------- Consider this example: ```ruby require 'bigdecimal' BigDecimal.singleton_class.prepend( Module.new do def save_rounding_mode super end end ) [:example].each do BigDecimal.save_rounding_mode do puts caller sleep 1 end end ``` which Ruby will print as (from 3.4, since https://bugs.ruby-lang.org/issues/19117): ``` native-filenames-example.rb:6:in 'BigDecimal.save_rounding_mode' native-filenames-example.rb:6:in 'save_rounding_mode' native-filenames-example.rb:12:in 'block in <main>' native-filenames-example.rb:11:in 'Array#each' native-filenames-example.rb:11:in '<main>' ``` Having the class names helps, but I think this behavior can still be confusing. Without looking at the code, and understanding that `Array#each` and `BigDecimal.save_rounding_mode` are written in native code, it can be confusing to see them be assigned to `native-filenames-example.rb` in the backtrace. I would like to propose that, whenever possible (see notes below), Ruby shows the name of the native filename where a method was defined. This would result on the backtrace becoming: ``` /rvm/gems/ruby-3.4.4/gems/bigdecimal-3.2.2/lib/bigdecimal.so:0:in 'BigDecimal.save_rounding_mode' native-filenames-example.rb:6:in 'save_rounding_mode' native-filenames-example.rb:12:in 'block in <main>' /rvm/rubies/ruby-3.4.4/lib/libruby.so.3.4:0:in 'Array#each' native-filenames-example.rb:11:in '<main>' ``` or, alternatively, this mechanism could be applied only to extensions, not to libruby/the ruby binary (it's not particularly hard to detect and exclude it): ``` /rvm/gems/ruby-3.4.4/gems/bigdecimal-3.2.2/lib/bigdecimal.so:0:in 'BigDecimal.save_rounding_mode' native-filenames-example.rb:6:in 'save_rounding_mode' native-filenames-example.rb:12:in 'block in <main>' native-filenames-example.rb:11:in 'Array#each' # Don't touch array ;) native-filenames-example.rb:11:in '<main>' ``` This would make it even easier to understand what's coming from where, and I believe it's a great complement to showing the class names. Furthermore, displaying the actual native libraries matches really well with the semantics we get for regular Ruby files: if I were to look on my machine, I would see `/rvm/gems/ruby-3.4.4/gems/bigdecimal-3.2.2/lib/bigdecimal.so` and `/rvm/rubies/ruby-3.4.4/lib/libruby.so.3.4`. And if I moved them, or overrode them, and loaded them from a different path, I would see the difference. (I say this because in the past I've thought about displaying the actual source .c files and lines, but that a) requires debug information; and b) the files often no longer exist in the filesystem; c) is much harder to implement cross-os). Edit: This also matches with `$LOADED_FEATURES`, which also include the `.so` files as well. --- The extra cool thing is that this is really, really easy to implement! I actually created a [micro gem to show this off](https://github.com/ivoanjo/native-filenames/blob/main/ext/native_filenames_e...) as [well as added this as a feature to the Datadog Ruby profiler](https://github.com/DataDog/dd-trace-rb/pull/4745). Other than checking for headers and whatnot, fetching the info can be implemented in 41 lines of C: https://github.com/ivoanjo/native-filenames/blob/main/ext/native_filenames_e... and works in Linux, macOS and Windows! The way it works is, we can use the function pointer passed to `rb_define_method`, looking it put using `dladdr` (or some of the other variants shown in the code). Then, given just the function pointer, we can get a path back. It's as simple as that -- it can be added transparently as part of storing the cfunc. And if for some reason the path is not available, we could fall back to the current behavior. I'd be very happy to contribute a PR to make this change, but I decided to start with a proposal first as I realize not everyone may be as excited about this idea as I am ;) -- https://bugs.ruby-lang.org/