Forum: Ruby not swallowed levels of the backtrace on unrescued exception

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Roger P. (Guest)
on 2009-02-07 17:52
Currently ruby [at least versions 1.8.6 and greater]
swallows the "middle" of backtraces if the thrown error was
"SystemStackError":
ex:

>cat bad.rb
def go
 go2
end

def go2
 go
end
go

>ruby bad.rb
bad.rb:5:in `go2': stack level too deep (SystemStackError)
        from bad.rb:2:in `go'
        from bad.rb:5:in `go2'
        from bad.rb:2:in `go'
        from bad.rb:5:in `go2'
        from bad.rb:2:in `go'
        from bad.rb:5:in `go2'
        from bad.rb:2:in `go'
        from bad.rb:5:in `go2'
         ... 22112 levels...
        from bad.rb:2:in `go'
        from bad.rb:5:in `go2'
        from bad.rb:2:in `go'
        from bad.rb:8


However, this has the unfortunate side effect of preventinf useful parts
of the backtrace from being displayed in certain other cases, here's an
example I ran into just recently:

C:/dev/ruby-benchmark-suite/rails/substruct/vendor/plugins/attachment_fu_fixtures/lib/attachment_fu_fixtures.rb:53:in
`include?': stack level too deep (SystemStackError)
        from
C:/dev/ruby-benchmark-suite/rails/substruct/vendor/plugins/attachment_fu_fixtures/lib/attachment_fu_fixtures.rb:53:in
`attachment_model?'
        from
C:/dev/ruby-benchmark-suite/rails/substruct/vendor/plugins/attachment_fu_fixtures/lib/attachment_fu_fixtures.rb:10:in
`insert_fixture_without_attachment'
        from
C:/dev/ruby-benchmark-suite/rails/substruct/vendor/plugins/attachment_fu_fixtures/lib/attachment_fu_fixtures.rb:28:in
`insert_fixture'
        from
C:/dev/ruby-benchmark-suite/rails/substruct/vendor/rails/activerecord/lib/active_record/fixtures.rb:639:in
`insert_fixtures'
        from
C:/dev/ruby-benchmark-suite/rails/substruct/vendor/rails/activerecord/lib/active_record/fixtures.rb:576:in
`each'
        from
C:/dev/ruby-benchmark-suite/rails/substruct/vendor/rails/activerecord/lib/active_record/fixtures.rb:576:in
`insert_fixtures'
        from
C:/dev/ruby-benchmark-suite/rails/substruct/vendor/rails/activerecord/lib/active_record/fixtures.rb:520:in
`create_fixtures'
        from
C:/dev/ruby-benchmark-suite/rails/substruct/vendor/rails/activerecord/lib/active_record/fixtures.rb:520:in
`each'
         ... 24 levels...
        from
c:/ruby18/lib/ruby/gems/1.8/gems/rake-0.8.3/lib/rake.rb:564:in `invoke'
        from ./substruct_start_and_bootstrap_if_necessary.rb:15
        from bm_substruct_request_root_100x.rb:8:in `require'
        from bm_substruct_request_root_100x.rb:8


So my question is:
What would be a better way to handle this in core [I want to submit a
patch, but am unsure what would be better].
some possibilities: if $VERBOSE is set then output all levels.
Have it output "100 lines" of backtrace each time--probably enough.

Thoughts?
-=r
Ken B. (Guest)
on 2009-02-08 20:41
(Received via mailing list)
On Sat, 07 Feb 2009 10:51:23 -0500, Roger P. wrote:

> def go
>  go2
> end
>
> def go2
>  go
> end
> go

def go
 go2
end

def go2
 go
end

begin
  go
rescue StandardError => e
  require 'pp'
  pp e.backtrace
end

will print all the levels, so what you should probably do is submit a
patch to Rails or Rake to explicitly catch the exception and customize
the output (possibly by grepping out things internal to rails and rake,
or by printing more levels there.)

--Ken
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