Re: Modifies vs. Replaces

[Michael Eager <eager at eagercon dot com>]

David Weatherford wrote:
> 
> Ron 603-884-2088 wrote:
> >
> > Michael Eager wrote:
> > >The Dwarf spec doesn't specify what a compiler should generate, nor
> > >does it specify what a debugger should do with the data generated.
> > >We continually leave the job of determining what action to take
> > >given a specific Dwarf description to the debugger.
> >
> > Wow, these assertions leave me incredulous. Our job is to specify
> > what descriptions mean. Surely we expect that a compiler will generate
> > a description whose interpretation/meaning is consistent with the
> > program and how it was compiled. And surely we expect that a debugger
> > will take actions that are consistent with the specified interpretation
> > of the description it encounters. While we don't specify "actions"
> > as such, actions that are inconsistent with the DWARF specified
> > interpretations are bugs...
> 
> [Mike, please correct me if I'm misrepresenting your intent....]
> 
> Mike was saying that the DWARF document describes a format which may
> be used by DWARF producers (typically compilers) to communicate certain
> aspects of the structure of some piece of a program to any interested
> comsumers (typically debuggers).  As such, the spec describes logical
> contents and physical file format for several "sections" (typically
> ELF file sections) along with certain conventions for using the tags
> and attributes defined by the spec.  It does *not* contain a set of
> rules that a producer must follow given a certain input.  That would
> be the job of a language bindings document for a given language, none
> of which has been written (to date), as far as I know.
> 
> Now, we all have in our heads typical (?) language bindings for the
> languages that we are most familiar with, and we each try to make the
> DWARF spec sufficiently flexible to support those bindings efficiently.
> This is good.  But those bindings are not part of the spec.  The spec
> describes mechanism, and has only a few italicized hints concerning
> policy (i.e., bindings).  Thus it is descriptive, but not proscriptive.
> 
> Did that make sense?

Yes.

Dwarf provides a structure for representing programs.  We permit 
people to use as much or as little of this structure as they see
fit.  Our only "demand" is that when a producer uses a certain
part of Dwarf, that they use it as described in the specification.


-- 
Michael Eager	 Eager Consulting     eager@eagercon.com
1960 Park Blvd., Palo Alto, CA 94306  650-325-8077