not swallowed levels of the backtrace on unrescued exception

R

Roger Pack

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
 
K

Ken Bloom

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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