[ruby-talk:12105] Re: RCR: replacing 'caller'

Robert,

Nice... this is, of course, exactly what we needed to be able to play with
dispatchers in pure ruby.
  
However, it needs some error checking:

class Foo
	define_method(:x) {puts call_stack[0]}
end

Foo.new.x #=> SEGFAULT

I can work around it for new by using call_stack(2)...


On Tue, 6 Mar 2001, Robert Feldt wrote:

> Hi,
> 
> IMHO, 'caller' would be much more useful if you could know/access the
> method and object that called you. Therefore I submit this RCR:
> 
> Replace 'caller' with 'call_stack' returning an array of arrays each with
> the format:
> 
> [object_called, method_called_id, args, file_with_call, line_for_call]
> 
> 'call_stack' takes a level parameter (almost) in the same way as 'caller'. 
> 
> Example:
> def m(a,b)
>   puts call_stack.inspect
> end
> def m2(a,b)
>   m(a,b)
> end
> 
> m2(1,true)
> 
> would print
> [[main, :m, [1, true], "../call_stack/t2.rb", 5], [main, :m2, [1, true],
> "../call_stack/t2.rb", 8]]
> 
> It might also be useful to add any blocks associated with calls (I'm
> skeptical if this adds enough value for the added complexity).
> 
> Maybe there's a risk in including the args. I'm not sure... Probably
> there's a risk in any of this since Matz hasn't previously included it?
> 
> Below is the diff to eval.c in latest snapshot implementing
> call_stack.
> 
> Regards,
> 
> Robert
> 
> 
> 
> --- eval.c.orig	Tue Mar  6 06:00:04 2001
> +++ eval.c	Tue Mar  6 07:52:24 2001
> @@ -4687,6 +4687,54 @@
>  }
>  
>  static VALUE
> +call_stack(lev)
> +    int lev;
> +{
> +    struct FRAME *frame = ruby_frame;
> +    VALUE ary = rb_ary_new();
> +    VALUE inner_ary;
> +
> +    while (lev-- > 0) {
> +      frame = frame->prev;
> +      if (!frame) {
> +	ary = Qnil;
> +	break;
> +      }
> +    }
> +    while (frame && frame->file) {
> +      inner_ary = rb_ary_new();
> +      rb_ary_push(inner_ary, frame->self);
> +      rb_ary_push(inner_ary, ID2SYM(frame->last_func));
> +      rb_ary_push(inner_ary, rb_ary_new4(frame->argc, frame->argv));
> +      rb_ary_push(inner_ary, rb_str_new2(frame->file));
> +      rb_ary_push(inner_ary, INT2FIX(frame->line));
> +      // Add block if block_given? ie. check iter stack and traverse
> block
> +      // stack accordingly...
> +      rb_ary_push(ary, inner_ary);
> +      frame = frame->prev;
> +    }
> +
> +    return ary;
> +}
> +
> +static VALUE
> +rb_f_call_stack(argc, argv)
> +    int argc;
> +    VALUE *argv;
> +{
> +    VALUE level;
> +    int lev;
> +
> +    rb_scan_args(argc, argv, "01", &level);
> +
> +    if (NIL_P(level)) lev = 1;
> +    else lev = NUM2INT(level);
> +    if (lev < 0) rb_raise(rb_eArgError, "negative level(%d)", lev);
> +
> +    return call_stack(lev);
> +}
> +
> +static VALUE
>  rb_f_caller(argc, argv)
>      int argc;
>      VALUE *argv;
> @@ -5869,6 +5917,7 @@
>      rb_define_global_function("fail", rb_f_raise, -1);
>  
>      rb_define_global_function("caller", rb_f_caller, -1);
> +    rb_define_global_function("call_stack", rb_f_call_stack, -1);
>  
>      rb_define_global_function("exit", rb_f_exit, -1);
>      rb_define_global_function("abort", rb_f_abort, 0);
> 
>