Gdbdump

Print C level and Ruby level backtrace of living process using gdb

Installation

$ gem install gdbdump

Requirements

• run with sudo.
• on Linux.

I verified that this gem works with ruby executables built by rbenv/ruby-build.

Example

With living ruby process of pid 1897,

$ sudo gdbdump 1897

You will see C and Ruby level backtrace on STDERR of the target process of pid 1897 as:

== c backtrace ==
/home/ubuntu/.rbenv/versions/2.4.1/bin/ruby(rb_print_backtrace+0x15) [0x7fd23062c115] vm_dump.c:684
[0x7ffc98c378af]
== ruby backtrace ==
        from loop.rb:3:in `<main>'
        from loop.rb:3:in `loop'
        from loop.rb:5:in `block in <main>'
        from loop.rb:5:in `sleep'

Usage

Usage: gdbdump [options] [pid|prog pid]
    -d, --[no-]debug                 print debug log (default: false)

How this work

Attach to the ruby process with gdb, and call rb_print_backtrace() (C level backtrace) and rb_backtrace() (Ruby level backtrace). That's it.

The path of ruby executable is found by /proc/[PID]/exe as default.

ToDo

• Want to print backtrace on STDOUT of gdbdump process.
  • To do it, we need another version of rb_print_backtrace and rb_backtrace to print results into a file in CRuby itself.
  • If they are available, gdbdump can dump to a file and, then read and print into STDOUT of gdbdump process.

Comparisons

• gdb
  • You can get C level backtrace with raw gdb, of course.
• sigdump
  • You can get ruby level backtrace with sigdump gem, but your ruby application must pre-install sigdump and require 'sigdump/setup'. gdbdump does not require it.

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/sonots/gdbdump. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

License

The gem is available as open source under the terms of the MIT License.

Code of Conduct

Everyone interacting in the Gdbdump project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.