[ruby-core:126092] [Ruby Bug#22197] Backtraces show methods which do not exist
Issue #22197 has been reported by Eregon (Benoit Daloze). ---------------------------------------- Bug #22197: Backtraces show methods which do not exist https://bugs.ruby-lang.org/issues/22197 * Author: Eregon (Benoit Daloze) * Status: Open * ruby -v: ruby 4.0.3 (2026-04-21 revision 85ddef263a) +PRISM [arm64-darwin25] * Backport: 3.3: DONTNEED, 3.4: UNKNOWN, 4.0: UNKNOWN ---------------------------------------- ```ruby class Parent def original puts caller_locations(0), nil end end class Child < Parent alias_method :alias, :original end Child.new.alias module Original def original puts caller_locations(0) end end class A define_method(:a, Original.instance_method(:original)) end A.new.a ``` gives: ``` $ ruby -v backtrace_alias.rb ruby 4.0.3 (2026-04-21 revision 85ddef263a) +PRISM [arm64-darwin25] backtrace_alias.rb:3:in 'Child#original' backtrace_alias.rb:11:in '<main>' backtrace_alias.rb:15:in 'A#original' backtrace_alias.rb:23:in '<main>' ``` But this seems clearly incorrect: * there is no `Child#original`, there is only `Parent#original` and `Child#alias`. * there is no `A#original`, there is only `Original#original` and `A#a`. This behavior exists since Ruby 3.4 which added the module name in backtraces (#19117). So the issue is that backtraces show the "original method name from the definition" with the "method owner of the actually-called method". It should be consistent to avoid showing methods which don't exist. And it should be the original method from the definition, because we show the file and line of that, so we should also show the original name (already the case) and the original module (not the case yet, the bug). FWIW TruffleRuby already behaves like that: ``` $ truffleruby 34.0.1 (2026-04-26), like ruby 3.4.9, Oracle GraalVM Native [arm64-darwin23] backtrace_alias.rb:3:in 'Parent#original' backtrace_alias.rb:11:in '<main>' backtrace_alias.rb:15:in 'Original#original' backtrace_alias.rb:23:in '<main>' ``` In #19117 there was some discussion about this, notably: https://bugs.ruby-lang.org/issues/19117#note-17 @byroot
My suggestion is for the owner. Simply put because it matches the path and other existing method representations.
But actually the owner isn't that, what is described here is the original module of the method definition, same as the expected from this issue. https://bugs.ruby-lang.org/issues/19117#note-18 @eregon
It must be the owner, anything else would be very confusing. I believe nobody wants String#then (there is no such method), they want to see Kernel#then.
Where I was wrong about owner being the only thing. I was also expressing we should show where the method is defined, but I overlooked the "originally" part (aliases, define_method, etc). Also CC @mame who implemented the change. I think this is worth fixing for Ruby 4.1 (not sure if worth backporting). -- https://bugs.ruby-lang.org/
Issue #22197 has been updated by Eregon (Benoit Daloze). In CRuby implementation terms we'd get the original method module with something like: ```c const rb_callable_method_entry_t *me = cme; // (1) unwrap an explicit alias entry, if present while (me->def->type == VM_METHOD_TYPE_ALIAS) { me = me->def->body.alias.original_me; // cf. original_method_definition(), vm_method.c:2737 } // (2) defined_class -> real module VALUE dc = me->defined_class; VALUE mod = RB_TYPE_P(dc, T_ICLASS) ? RBASIC_CLASS(dc) : dc; // + prepend-origin guard (4156-4158) ``` I'll attempt to make a PR for it soon. ---------------------------------------- Bug #22197: Backtraces show methods which do not exist https://bugs.ruby-lang.org/issues/22197#change-118098 * Author: Eregon (Benoit Daloze) * Status: Open * ruby -v: ruby 4.0.3 (2026-04-21 revision 85ddef263a) +PRISM [arm64-darwin25] * Backport: 3.3: DONTNEED, 3.4: UNKNOWN, 4.0: UNKNOWN ---------------------------------------- ```ruby class Parent def original puts caller_locations(0), nil end end class Child < Parent alias_method :alias, :original end Child.new.alias module Original def original puts caller_locations(0) end end class A define_method(:a, Original.instance_method(:original)) end A.new.a ``` gives: ``` $ ruby -v backtrace_alias.rb ruby 4.0.3 (2026-04-21 revision 85ddef263a) +PRISM [arm64-darwin25] backtrace_alias.rb:3:in 'Child#original' backtrace_alias.rb:11:in '<main>' backtrace_alias.rb:15:in 'A#original' backtrace_alias.rb:23:in '<main>' ``` But this seems clearly incorrect: * there is no `Child#original`, there is only `Parent#original` and `Child#alias`. * there is no `A#original`, there is only `Original#original` and `A#a`. This behavior exists since Ruby 3.4 which added the module name in backtraces (#19117). So the issue is that backtraces show the "original method name from the definition" with the "method owner of the actually-called method". It should be consistent to avoid showing methods which don't exist. And it should be the original method from the definition, because we show the file and line of that, so we should also show the original name (already the case) and the original module (not the case yet, the bug). FWIW TruffleRuby already behaves like that: ``` $ truffleruby 34.0.1 (2026-04-26), like ruby 3.4.9, Oracle GraalVM Native [arm64-darwin23] backtrace_alias.rb:3:in 'Parent#original' backtrace_alias.rb:11:in '<main>' backtrace_alias.rb:15:in 'Original#original' backtrace_alias.rb:23:in '<main>' ``` In #19117 there was some discussion about this, notably: https://bugs.ruby-lang.org/issues/19117#note-17 @byroot
My suggestion is for the owner. Simply put because it matches the path and other existing method representations.
But actually the owner isn't that, what is described here is the original module of the method definition, same as the expected from this issue. https://bugs.ruby-lang.org/issues/19117#note-18 @eregon
It must be the owner, anything else would be very confusing. I believe nobody wants String#then (there is no such method), they want to see Kernel#then.
Where I was wrong about owner being the only thing. I was also expressing we should show where the method is defined, but I overlooked the "originally" part (aliases, define_method, etc). Also CC @mame who implemented the change. I think this is worth fixing for Ruby 4.1 (not sure if worth backporting). -- https://bugs.ruby-lang.org/
Issue #22197 has been updated by sophiathedev (Nguyen Thang). Eregon (Benoit Daloze) wrote in #note-1:
In CRuby implementation terms we'd get the original method module with something like: ```c const rb_callable_method_entry_t *me = cme; // (1) unwrap an explicit alias entry, if present while (me->def->type == VM_METHOD_TYPE_ALIAS) { me = me->def->body.alias.original_me; // cf. original_method_definition(), vm_method.c:2737 } // (2) defined_class -> real module VALUE dc = me->defined_class; VALUE mod = RB_TYPE_P(dc, T_ICLASS) ? RBASIC_CLASS(dc) : dc; // + prepend-origin guard (4156-4158) ```
I'll attempt to make a PR for it soon.
Hi everyone. This is my first time attempting to contribute to Ruby core, and I'm very excited to be part of this! I have opened a Pull Request to address this issue based on the suggestions provided: https://github.com/ruby/ruby/pull/17978 Thank you, @Eregon, for reporting this bug and providing the very helpful notes on the implementation details! :goat: Any feedback or guidance on the PR would be highly appreciated. ---------------------------------------- Bug #22197: Backtraces show methods which do not exist https://bugs.ruby-lang.org/issues/22197#change-118124 * Author: Eregon (Benoit Daloze) * Status: Open * ruby -v: ruby 4.0.3 (2026-04-21 revision 85ddef263a) +PRISM [arm64-darwin25] * Backport: 3.3: DONTNEED, 3.4: UNKNOWN, 4.0: UNKNOWN ---------------------------------------- ```ruby class Parent def original puts caller_locations(0), nil end end class Child < Parent alias_method :alias, :original end Child.new.alias module Original def original puts caller_locations(0) end end class A define_method(:a, Original.instance_method(:original)) end A.new.a ``` gives: ``` $ ruby -v backtrace_alias.rb ruby 4.0.3 (2026-04-21 revision 85ddef263a) +PRISM [arm64-darwin25] backtrace_alias.rb:3:in 'Child#original' backtrace_alias.rb:11:in '<main>' backtrace_alias.rb:15:in 'A#original' backtrace_alias.rb:23:in '<main>' ``` But this seems clearly incorrect: * there is no `Child#original`, there is only `Parent#original` and `Child#alias`. * there is no `A#original`, there is only `Original#original` and `A#a`. This behavior exists since Ruby 3.4 which added the module name in backtraces (#19117). So the issue is that backtraces show the "original method name from the definition" with the "method owner of the actually-called method". It should be consistent to avoid showing methods which don't exist. And it should be the original method from the definition, because we show the file and line of that, so we should also show the original name (already the case) and the original module (not the case yet, the bug). FWIW TruffleRuby already behaves like that: ``` $ truffleruby 34.0.1 (2026-04-26), like ruby 3.4.9, Oracle GraalVM Native [arm64-darwin23] backtrace_alias.rb:3:in 'Parent#original' backtrace_alias.rb:11:in '<main>' backtrace_alias.rb:15:in 'Original#original' backtrace_alias.rb:23:in '<main>' ``` In #19117 there was some discussion about this, notably: https://bugs.ruby-lang.org/issues/19117#note-17 @byroot
My suggestion is for the owner. Simply put because it matches the path and other existing method representations.
But actually the owner isn't that, what is described here is the original module of the method definition, same as the expected from this issue. https://bugs.ruby-lang.org/issues/19117#note-18 @eregon
It must be the owner, anything else would be very confusing. I believe nobody wants String#then (there is no such method), they want to see Kernel#then.
Where I was wrong about owner being the only thing. I was also expressing we should show where the method is defined, but I overlooked the "originally" part (aliases, define_method, etc). Also CC @mame who implemented the change. I think this is worth fixing for Ruby 4.1 (not sure if worth backporting). -- https://bugs.ruby-lang.org/
Issue #22197 has been updated by Eregon (Benoit Daloze). PR is ready: https://github.com/ruby/ruby/pull/17963 Would appreciate some reviews :) --- sophiathedev (Nguyen Thang) wrote in #note-2:
This is my first time contributing to Ruby core. I've submitted a PR to fix this issue here: [https://github.com/ruby/ruby/pull/17978](https://github.com/ruby/ruby/pull/17978)
Thank you for your PR, I think this is quite a difficult fix for a first PR though. I took a look and your PR fixes one case but not the other cases (I commented there). ---------------------------------------- Bug #22197: Backtraces show methods which do not exist https://bugs.ruby-lang.org/issues/22197#change-118214 * Author: Eregon (Benoit Daloze) * Status: Open * ruby -v: ruby 4.0.3 (2026-04-21 revision 85ddef263a) +PRISM [arm64-darwin25] * Backport: 3.3: DONTNEED, 3.4: UNKNOWN, 4.0: UNKNOWN ---------------------------------------- ```ruby class Parent def original puts caller_locations(0), nil end end class Child < Parent alias_method :alias, :original end Child.new.alias module Original def original puts caller_locations(0) end end class A define_method(:a, Original.instance_method(:original)) end A.new.a ``` gives: ``` $ ruby -v backtrace_alias.rb ruby 4.0.3 (2026-04-21 revision 85ddef263a) +PRISM [arm64-darwin25] backtrace_alias.rb:3:in 'Child#original' backtrace_alias.rb:11:in '<main>' backtrace_alias.rb:15:in 'A#original' backtrace_alias.rb:23:in '<main>' ``` But this seems clearly incorrect: * there is no `Child#original`, there is only `Parent#original` and `Child#alias`. * there is no `A#original`, there is only `Original#original` and `A#a`. This behavior exists since Ruby 3.4 which added the module name in backtraces (#19117). So the issue is that backtraces show the "original method name from the definition" with the "method owner of the actually-called method". It should be consistent to avoid showing methods which don't exist. And it should be the original method from the definition, because we show the file and line of that, so we should also show the original name (already the case) and the original module (not the case yet, the bug). FWIW TruffleRuby already behaves like that: ``` $ truffleruby 34.0.1 (2026-04-26), like ruby 3.4.9, Oracle GraalVM Native [arm64-darwin23] backtrace_alias.rb:3:in 'Parent#original' backtrace_alias.rb:11:in '<main>' backtrace_alias.rb:15:in 'Original#original' backtrace_alias.rb:23:in '<main>' ``` In #19117 there was some discussion about this, notably: https://bugs.ruby-lang.org/issues/19117#note-17 @byroot
My suggestion is for the owner. Simply put because it matches the path and other existing method representations.
But actually the owner isn't that, what is described here is the original module of the method definition, same as the expected from this issue. https://bugs.ruby-lang.org/issues/19117#note-18 @eregon
It must be the owner, anything else would be very confusing. I believe nobody wants String#then (there is no such method), they want to see Kernel#then.
Where I was wrong about owner being the only thing. I was also expressing we should show where the method is defined, but I overlooked the "originally" part (aliases, define_method, etc). Also CC @mame who implemented the change. I think this is worth fixing for Ruby 4.1 (not sure if worth backporting). -- https://bugs.ruby-lang.org/
Issue #22197 has been updated by matz (Yukihiro Matsumoto). This is a bug and should be fixed. The file and line we print are those of the original definition, so the module must come from that same definition. Mixing it with the run-time owner produces a name for a method that does not exist, which is worse than either choice alone. Please fix it in 4.1. It changes backtrace output, so I lean against not backporting, but I leave that to the branch maintainers. Matz. ---------------------------------------- Bug #22197: Backtraces show methods which do not exist https://bugs.ruby-lang.org/issues/22197#change-118392 * Author: Eregon (Benoit Daloze) * Status: Open * ruby -v: ruby 4.0.3 (2026-04-21 revision 85ddef263a) +PRISM [arm64-darwin25] * Backport: 3.3: DONTNEED, 3.4: UNKNOWN, 4.0: UNKNOWN ---------------------------------------- ```ruby class Parent def original puts caller_locations(0), nil end end class Child < Parent alias_method :alias, :original end Child.new.alias module Original def original puts caller_locations(0) end end class A define_method(:a, Original.instance_method(:original)) end A.new.a ``` gives: ``` $ ruby -v backtrace_alias.rb ruby 4.0.3 (2026-04-21 revision 85ddef263a) +PRISM [arm64-darwin25] backtrace_alias.rb:3:in 'Child#original' backtrace_alias.rb:11:in '<main>' backtrace_alias.rb:15:in 'A#original' backtrace_alias.rb:23:in '<main>' ``` But this seems clearly incorrect: * there is no `Child#original`, there is only `Parent#original` and `Child#alias`. * there is no `A#original`, there is only `Original#original` and `A#a`. This behavior exists since Ruby 3.4 which added the module name in backtraces (#19117). So the issue is that backtraces show the "original method name from the definition" with the "method owner of the actually-called method". It should be consistent to avoid showing methods which don't exist. And it should be the original method from the definition, because we show the file and line of that, so we should also show the original name (already the case) and the original module (not the case yet, the bug). FWIW TruffleRuby already behaves like that: ``` $ truffleruby 34.0.1 (2026-04-26), like ruby 3.4.9, Oracle GraalVM Native [arm64-darwin23] backtrace_alias.rb:3:in 'Parent#original' backtrace_alias.rb:11:in '<main>' backtrace_alias.rb:15:in 'Original#original' backtrace_alias.rb:23:in '<main>' ``` In #19117 there was some discussion about this, notably: https://bugs.ruby-lang.org/issues/19117#note-17 @byroot
My suggestion is for the owner. Simply put because it matches the path and other existing method representations.
But actually the owner isn't that, what is described here is the original module of the method definition, same as the expected from this issue. https://bugs.ruby-lang.org/issues/19117#note-18 @eregon
It must be the owner, anything else would be very confusing. I believe nobody wants String#then (there is no such method), they want to see Kernel#then.
Where I was wrong about owner being the only thing. I was also expressing we should show where the method is defined, but I overlooked the "originally" part (aliases, define_method, etc). Also CC @mame who implemented the change. I think this is worth fixing for Ruby 4.1 (not sure if worth backporting). PR: https://github.com/ruby/ruby/pull/17963 -- https://bugs.ruby-lang.org/
participants (3)
-
Eregon (Benoit Daloze) -
matz (Yukihiro Matsumoto)
-
sophiathedev (Nguyen Thang)