Pleased to announce the first public release of the backtracer gem (0.5)
It mission:
to output higher quality backtraces if an unhandled exception occurs.
If you've ever seen
...24 levels...
and disliked it, this is the gem for you.
If you've ever wished the exception trace would display the code of each
line (a la Python), this gem is also for you.
It displays the full back trace (no ...'s), along with the code from
each line! It can even display local variables at each level of the
call stack, if desired.
Examples:
a script that once output:
$ ruby crash.rb
crash.rb:2:in `go2': unhandled exception
from crash.rb:6:in `go'
from crash.rb:9
Now outputs:
$ backtracer crash.rb
RuntimeError
crash.rb:2:in `go2'
raise
crash.rb:7:in `go'
go2(a, 55)
crash.rb:10
go '3'
(Now has the code lines, and if there had been ...'s, would have ovecome
them).
or use the --locals option
$ backtracer --locals crash.rb
unhandled exception: crash.rb:2: raise
locals: {"a"=>"3", "b"=>55}
from:
crash.rb:1 go2(a=>3, b=>55)
locals: {"a"=>"3", "b"=>55}
crash.rb:5 go(a=>3)
locals: {"a"=>"3"}
(displays locals, parameters as current value)
Also included are several other options. One is --ping, which
periodically dumps current threads' backtrace(s) (quite useful for
profiling to see where you code is spending a lot of its time (thanks
xray gem!)). There is also an option that will print out thread dumps
whenever you hit ctrl+c.
To see all possible backtrace options run
$ backtracer -h
or
$ backtracer --help
More examples can be found here:
== Installation ==
== 1.8.x ==
$ gem install ruby-debug # only necessary for the --locals option
$ gem install jeweler && jeweler tumble # if necessary
$ gem install backtracer
now run like
$ backtracer script_name.rb
$ backtracer --locals script_name.rb arg1 arg2
== 1.9.1 ==
$ gem install ruby-debug19 # only necessary for the --locals option
$ gem install jeweler && jeweler tumble # if necessary
$ gem install backtracer
run as above (backtracer executable), or as a ruby require:
$ ruby -rbacktracer script_name
$ ruby -rbacktracer_locals script_name
== Other ==
Note that you can load backtracing capability within a script itself by:
require 'backtracer'
which will cause it to output a coded backtrace at exit time, if an
unhandled exception occurs. Backtracer default and backtracer_simple
don't cause runtime slowdown, so sometimes you just want to add this by
default. If so, then add it to your RUBYOPT variable. (Once I did
this, I wondered why I would ever want anything else). Here's how:
1.9:
$ export RUBYOPT=-rbacktracer
or
$ export RUBYOPT=-rbacktracer_simple # or whichever one you want
1.8:
you'll need to install a helper gem since rubygems can't load both
itself and a gem on the command line for some reason.
$ sudo gem install faster_rubygems # the helper--installs
faster_rubygems.rb and some other files to your site_ruby dir
$ export RUBYOPT='-rfaster_rubygems -rbacktracer'
or
$ export RUBYOPT='-rfaster_rubygems -rbacktracer_simple'
Enjoy.
== Other related projects ==
unroller, http://eigenclass.org/hiki/method+arguments+via+introspection,
liveconsole, ruby-debug (thanks guys!)
Comments welcome.
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