Hello,
the below patch ports the -var-info-path-expression MI command from Apple
version. It allows on get expression corresponding to any variable object,
in language-specific syntax, which can be used, for example, to set
watchpoint  on that expression.

Top-level changelog entry:

2006-03-17  Vladimir Prus <ghost@cs.msu.su>, 
   port of changes on Apple branch: 
   2002-03-28  James Ingham <jingham@apple.com>

        * varobj.c 
        (child_exists): Take child index, not child name, for performance.
        (get_type_deref): Pass out whether the original was a pointer or
         not.
        (path_expr_of_variable): New function.  This returns the full path
        expression to a variable.  The intent here is that you could use
        this to make a new root varobj corresponding to the child varobj
        whose path expression you are getting.
        (varobj_get_path_expr): New function.  External wrapper for
        path_expr_of_variable.
        (c_path_expr_of_child, cplus_path_expr_of_child,
        java_path_expr_of_child): New functions, return the path expr of a
        child in its parent.  Also caches the expr for later use.
        (is_root_p): New convenience function, returns whether a variable is
        a root. Then I changed all the uses of var->name to use
        name_of_variable, and the test
        for is this a root were changed to use is_root_p.

        * varobj.h: (varobj_get_path_expr): New function definition.


MI changelog entry:

2006-03-17  Vladimir Prus <ghost@cs.msu.su>, 
   port of changes on Apple branch: 
   2002-03-28  James Ingham <jingham@apple.com>


        * mi-cmds.h: Added def'n of mi_cmd_var_info_path_expression.
        * mi-cmds.c: Added var-info-path-expression to command list.
        * mi-cmd-var.c (mi_cmd_var_info_path_expression) New function,
        the MI interface to varobj_get_path_expression.