I ran a dtrace script on the MacRuby samples to print all the info provided to the method_entry probe. The sourcefile was always either empty or "core" and the linenumber was always 0. Do I have to execute the script in some particular way for this information to be received? SCRIPT: ------------- #!/usr/sbin/dtrace -s #pragma D option quiet BEGIN { printf("Target pid: %d\n\n", $target); } macruby$target:::method-entry { printf("Class name: %s, Method name %s, Source file %s, Line number %d\n", copyinstr(arg0), copyinstr(arg1), copyinstr(arg2), arg3); } COMMAND: ------------- sudo dtrace -s call_info.d -c ../build/AnimatingViews.app/Contents/MacOS/AnimatingViews OUTPUT: ------------- Class name: DemoView, Method name randf:, Source file , Line number 0 Class name: DemoView, Method name rand:, Source file , Line number 0 Class name: Float, Method name to_int, Source file core, Line number 0 Class name: Class, Method name new:, Source file , Line number 0 Class name: CGPoint, Method name x, Source file , Line number 0 Class name: CGPoint, Method name y, Source file , Line number 0 Class name: Fixnum, Method name to_i, Source file , Line number 0 Thanks, Gabriel Ayuso