On Wed, Feb 2, 2011 at 10:47 AM, Yusuke = ENDOH <mame@tsg.ne.j= p> wrote:

Hi,

2011/2/2 James M. Lawrence <red= mine@ruby-lang.org>:
> Thank you for that detailed explanation. The problem for me is the
> connection to source_location, which should be usable by tools.

What kind of tools are you talking about?
Even if a binding location is discarded, we can still fake __FILE__
and __LINE__ without using a binding:

=A0eval <<-END, nil, "/etc/passwd", 1
=A0 =A0def foo
=A0 =A0end
=A0END
=A0p method(:foo).source_location =A0#=3D> ["/etc/passwd", 1]=

So, source_location user should know and accept the fact that the
information is not trustable.

Sigh. The= main use of setting the file and line in an eval() call is to get around t= he fact that the location is not what folks expect.

In fact, that's why you yourself used that form to suggest how to re= write the code to do what James M. Lawrence seems to want.=A0

See also http://ola-bini.blogspot.com/2008/01/ruby-anti= pattern-using-eval-without.html. It is called an "anti-pattern&quo= t; there which I guess is used in a derogatory fashion.

A place where setting the file and line is used is in t= emplate systems like merb or erb =A0where the file the user works on is not= a Ruby file but a template file that expands to a Ruby file. In that situa= tion, disregarding the expanded Ruby file is convenient since there can onl= y be one location attached in the Ruby implementation.

However I don't see why a templating system couldn&= #39;t also provide an expanded Ruby file for debugging problems much as one= can get the C-preprocessed output for a C program when one wants.

In the trepanning debuggers (http://github.com/rocky/rb-trepanning and http://github.com/rbx-trepanning) I allow similar types of filename remapping to go on in the debugger. Bu= t in reporting a location I always try to report both locations; and it is = done automatically in showing an eval location.

But shouldn't we try to address the location proble= m head on in the Ruby implementation? I suspect it too late to try to chang= e Ruby MRI 1.x, but perhaps in Ruby 2.x some thought could be given to how = to address.=A0

If the fact that source_location is not trustable is a = a concern, then perhaps setting the file and line parameters on eval can be= disallowed at some level greater than 0 and less than 4 which is where eva= l() is disallowed totally.=A0

=A0

Why do you think only a binding location as a problem?

--
Yusuke Endoh <mame@tsg.ne.jp>