[Rubycocoa-talk] Do you use GDB with RubyCocoa programs?

[Brian M. <ma...@ex...>]

I'm writing some text about how to debug RubyCocoa programs. In  
particular, I'm trying to help people who've done something wrong that  
leads to a blowup down in some NSClass. For example, suppose I use  
textfield.intValue to set text in some NSTextView, rather than  
textfield.stringValue. That leads to this error:

2008-04-08 08:46:46.314 Flat Fenestration[27099:10b] *** -[NSCFNumber  
length]: unrecognized selector sent to instance 0x730db0
2008-04-08 08:46:46.330 Flat Fenestration[27099:10b]  
FenestrationController#chooseWebapp: OSX::OCException:  
NSInvalidArgumentException - *** -[NSCFNumber length]: unrecognized  
selector sent to instance 0x730db0

The problem is that somewhere something is trying to take the length  
of an integer object. GDB 'backtrace' produces a trace of ObjC message  
sends that could be, in theory, useful. In this case, it isn't. But it  
might be if I could get descriptions of the args. I can't do that with  
the standard libraries:

(gdb) frame 20
#20 0x946d81a8 in -[NSView interpretKeyEvents:] ()
(gdb) info args
No symbol table info available.

I was hoping I would get more information if I used the _debug  
versions of the frameworks (as set in the executable's General Info  
pane under "Use ______ suffix when loading frameworks" but all that  
produces is a flood of these messages:

warning: Could not find object file "/var/tmp/Libm/Libm-287.1~6/ 
Libm.build/Libm_debug.a.build/Objects-normal/i386/xmm_arcsincostan.o"  
- no debug information available for "/SourceCache/Libm/Libm-287.1/ 
Source/Intel/xmm_arcsincostan.c".

... and the same lack of symbol table information.

I am wondering if it's worth continuing to try to dig for useful  
things you can do with GDB. Are there any?

-----
Brian Marick, independent consultant
Mostly on agile methods with a testing slant
www.exampler.com, www.exampler.com/blog, www.twitter.com/marick