Re: [C++ PATCH] Compare binfo types directly

[Gabriel Dos Reis <gdr at cs dot tamu dot edu>]

Mark Mitchell <mark@codesourcery.com> writes:

| Nathan Sidwell wrote:
| 
| > Mark,
| > this patch replaces 'same_type_p (BINFO_TYPE (b), t)' with
| > 'BINFO_TYPE (b) == t'. I know you've expressed reservations about
| > omitting
| > same_type_p calls in this way, so I'm running this by you for comment
| > before committing.
| 
| I guess the big question I have is not "does this work at the moment?"
| but "should it always work in the future?"
| 
| For example, if the user writes:
| 
|   struct A {};
|   typedef A T;
|   struct B : public T {};
| 
| should the BINFO for A-in-B actually be for T-in-B?  In general, we've
| tried to preserve the type that the user used for better error
| messages, potentially better debug messages, and (ikn the distant
| future) better behavior when using the G++ front end independent of
| the GCC back end.

I strongly concur on all points you raised.
The ability for g++ to accurately represent C++ programs at their most
abstract/generic forms is crucial for both diagnostics and use of the
front-end to build other development tools.

Interestingly, we've been through the above tradeoffs in our
forthcoming paper "Representing C++ Directly, Completely and Efficiently".
I hope to make a draft available by the committee meeting (next week).

-- Gaby