# Getting gdb backtrace from ruby exception **URL:** \ **Category:** ruby-talk\ **Created:** [12 July 2007 14:10 UTC](https://rubytalk.org/t/getting-gdb-backtrace-from-ruby-exception/39038 "2007-07-12T14:10:01Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![Alex\_Fenton](https://avatars.discourse-cdn.com/v4/letter/a/ecccb3/32.png) [@Alex\_Fenton](https://rubytalk.org/u/Alex_Fenton)\ **Post date:** [12 July 2007 14:10 UTC](https://rubytalk.org/t/getting-gdb-backtrace-from-ruby-exception/39038/1 "2007-07-12T14:10:01Z")
Hi I'm working on a C extension and somewhere in itsomething is raising a NoMethodError. The exception is reported with the line of ruby code that triggered the bad call in the C extension. As the C code is large and complex (it's a big SWIG project), I'm having trouble finding the problem in the C code. I would use gdb or Microsoft's debugger to look at the stack if it was a C error - but when a Ruby exception is raised, the process exits and there's no stack to inspect. Ruby's debugger isn't helpful because it only knows about ruby written in ruby. Is there any way I can get at the C stack at the point of ruby 'raise' from a C extension? Thanks alex ---
**Author:** ![Jan\_Svitok](https://avatars.discourse-cdn.com/v4/letter/j/cab0a1/32.png) [@Jan\_Svitok](https://rubytalk.org/u/Jan_Svitok)\ **Post date:** [12 July 2007 14:26 UTC](https://rubytalk.org/t/getting-gdb-backtrace-from-ruby-exception/39038/2 "2007-07-12T14:26:34Z")
There was a way how to run ruby under gdb with the ability to debug at "ruby level" while still having the "C view" at hand. [http://eigenclass.org/hiki.rb?ruby+live+process+introspection](http://eigenclass.org/hiki.rb?ruby+live+process+introspection) [http://weblog.jamisbuck.org/2006/9/25/gdb-wrapper-for-ruby](http://weblog.jamisbuck.org/2006/9/25/gdb-wrapper-for-ruby) [http://redhanded.hobix.com/inspect/theRubyGdbArmsRaceNowAtAStandoff.html](http://redhanded.hobix.com/inspect/theRubyGdbArmsRaceNowAtAStandoff.html) J. > **···** > > On 7/12/07, Alex Fenton \ wrote: > > > Hi > > > > I'm working on a C extension and somewhere in itsomething is raising a > > NoMethodError. The exception is reported with the line of ruby code that > > triggered the bad call in the C extension. > > > > As the C code is large and complex (it's a big SWIG project), I'm having > > trouble finding the problem in the C code. I would use gdb or > > Microsoft's debugger to look at the stack if it was a C error - but when > > a Ruby exception is raised, the process exits and there's no stack to > > inspect. > > > > Ruby's debugger isn't helpful because it only knows about ruby written > > in ruby. > > > > Is there any way I can get at the C stack at the point of ruby 'raise' > > from a C extension? > > > > Thanks > > alex ---
**Author:** ![Detlef\_Reichl](https://avatars.discourse-cdn.com/v4/letter/d/439d5e/32.png) [@Detlef\_Reichl](https://rubytalk.org/u/Detlef_Reichl)\ **Post date:** [12 July 2007 14:27 UTC](https://rubytalk.org/t/getting-gdb-backtrace-from-ruby-exception/39038/3 "2007-07-12T14:27:29Z")
Hi, i don't know how to build stack traces, but you can start ruby in gdb. first call gdb with ruby as argument. On liux it looks like:   det@datengrab:~/Desktop$ gdb /usr/bin/ruby and then in gdb start your ruby program with "run"   (gdb) run ./my-prg.rb Cheers detlef > **···** > > Am Donnerstag, den 12.07.2007, 23:10 +0900 schrieb Alex Fenton: > > > Hi > > > > I'm working on a C extension and somewhere in itsomething is raising a > > NoMethodError. The exception is reported with the line of ruby code that > > triggered the bad call in the C extension. > > > > As the C code is large and complex (it's a big SWIG project), I'm having > > trouble finding the problem in the C code. I would use gdb or > > Microsoft's debugger to look at the stack if it was a C error - but when > > a Ruby exception is raised, the process exits and there's no stack to > > inspect. > > > > Ruby's debugger isn't helpful because it only knows about ruby written > > in ruby. > > > > Is there any way I can get at the C stack at the point of ruby 'raise' > > \>from a C extension? > > > > Thanks > > alex ---
**Author:** ![a11](https://yyz1.discourse-cdn.com/flex029/user_avatar/rubytalk.org/a11/32/8169_2.png) [@a11](https://rubytalk.org/u/a11)\ **Post date:** [12 July 2007 21:00 UTC](https://rubytalk.org/t/getting-gdb-backtrace-from-ruby-exception/39038/4 "2007-07-12T21:00:42Z")
cfp:~ \> cat core.rb BEGIN{ at\_exit{ Process.kill 'SIGSEGV', Process.pid if $! } } cfp:~ \> cat a.rb #! /usr/bin/env ruby require 'core' p 42 cfp:~ \> ruby a.rb 42 cfp:~ \> cat b.rb #! /usr/bin/env ruby require 'core' raise cfp:~ \> ruby b.rb ./core.rb:1: [BUG] Segmentation fault ruby 1.8.6 (2007-03-13) [i686-darwin8.9.1] Abort trap (core dumped) -a > **···** > > On Jul 12, 2007, at 8:10 AM, Alex Fenton wrote: > > > Hi > > > > I'm working on a C extension and somewhere in itsomething is raising a NoMethodError. The exception is reported with the line of ruby code that triggered the bad call in the C extension. > > > > As the C code is large and complex (it's a big SWIG project), I'm having trouble finding the problem in the C code. I would use gdb or Microsoft's debugger to look at the stack if it was a C error - but when a Ruby exception is raised, the process exits and there's no stack to inspect. > > > > Ruby's debugger isn't helpful because it only knows about ruby written in ruby. > > > > Is there any way I can get at the C stack at the point of ruby 'raise' from a C extension? > > > > Thanks > > alex > > -- > we can deny everything, except that we have the possibility of being better. simply reflect on that. > h.h. the 14th dalai lama ---
**Author:** ![Alex\_Fenton2](https://avatars.discourse-cdn.com/v4/letter/a/7ab992/32.png) [@Alex\_Fenton2](https://rubytalk.org/u/Alex_Fenton2)\ **Post date:** [12 July 2007 20:15 UTC](https://rubytalk.org/t/getting-gdb-backtrace-from-ruby-exception/39038/5 "2007-07-12T20:15:00Z")
Jano Svitok wrote: > > Is there any way I can get at the C stack at the point of ruby 'raise' > > from a C extension? > There was a way how to run ruby under gdb with the ability to debug at > "ruby level" while still having the "C view" at hand. > > [http://eigenclass.org/hiki.rb?ruby+live+process+introspection](http://eigenclass.org/hiki.rb?ruby+live+process+introspection) > [Buckblog: GDB wrapper for Ruby](http://weblog.jamisbuck.org/2006/9/25/gdb-wrapper-for-ruby) > [http://redhanded.hobix.com/inspect/theRubyGdbArmsRaceNowAtAStandoff.html](http://redhanded.hobix.com/inspect/theRubyGdbArmsRaceNowAtAStandoff.html) Thanks for the pointer - that's really interesting stuff. I got round it a bit more prosaically by simply setting a breakpoint in gdb where ruby calls the exception raising class (gdb) b rb\_exc\_raise Breakpoint 1, rb\_exc\_raise (mesg=3057353380) at eval.c:4583 4583 rb\_longjmp(TAG\_RAISE, mesg); (gdb) whe .... tasty stacktrace cheers alex > **···** > > > On 7/12/07, Alex Fenton \ wrote: ---
**Author:** ![Joel\_VanderWerf1](https://avatars.discourse-cdn.com/v4/letter/j/94ad74/32.png) [@Joel\_VanderWerf1](https://rubytalk.org/u/Joel_VanderWerf1)\ **Post date:** [12 July 2007 22:25 UTC](https://rubytalk.org/t/getting-gdb-backtrace-from-ruby-exception/39038/6 "2007-07-12T22:25:40Z")
ara.t.howard wrote: > > Hi > > > > I'm working on a C extension and somewhere in itsomething is raising a NoMethodError. The exception is reported with the line of ruby code that triggered the bad call in the C extension. > > > > As the C code is large and complex (it's a big SWIG project), I'm having trouble finding the problem in the C code. I would use gdb or Microsoft's debugger to look at the stack if it was a C error - but when a Ruby exception is raised, the process exits and there's no stack to inspect. > > > > Ruby's debugger isn't helpful because it only knows about ruby written in ruby. > > > > Is there any way I can get at the C stack at the point of ruby 'raise' from a C extension? > > > > Thanks > > alex > > cfp:~ \> cat core.rb > BEGIN{ at\_exit{ Process.kill 'SIGSEGV', Process.pid if $! } } > > cfp:~ \> cat a.rb > #! /usr/bin/env ruby > require 'core' > p 42 > cfp:~ \> ruby a.rb > 42 > > cfp:~ \> cat b.rb > #! /usr/bin/env ruby > require 'core' > raise > > cfp:~ \> ruby b.rb > ./core.rb:1: [BUG] Segmentation fault > ruby 1.8.6 (2007-03-13) [i686-darwin8.9.1] > > Abort trap (core dumped) Doesn't that only give you the C stack at the time the ruby process exits, not at the time the exception is raised? > **···** > > > On Jul 12, 2007, at 8:10 AM, Alex Fenton wrote: > > -- >        vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407 ---
**Author:** ![a11](https://yyz1.discourse-cdn.com/flex029/user_avatar/rubytalk.org/a11/32/8169_2.png) [@a11](https://rubytalk.org/u/a11)\ **Post date:** [12 July 2007 23:31 UTC](https://rubytalk.org/t/getting-gdb-backtrace-from-ruby-exception/39038/7 "2007-07-12T23:31:27Z")
yeah - it's a short leap though... -a > **···** > > On Jul 12, 2007, at 4:25 PM, Joel VanderWerf wrote: > > > Doesn't that only give you the C stack at the time the ruby process exits, not at the time the exception is raised? > > -- > we can deny everything, except that we have the possibility of being better. simply reflect on that. > h.h. the 14th dalai lama