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Re: [PATCH 0/6] Conversion of gimple types to C++ inheritance (v3)


On 11/06/13 04:31, Richard Biener wrote:
On Wed, Nov 6, 2013 at 12:02 PM, Bernd Schmidt <bernds@codesourcery.com> wrote:
On 11/06/2013 10:31 AM, Richard Biener wrote:
We decided to move to C++.  As part of a later discussion we decided
to go with a single general dynamic-casting style, mimicing the "real"
C++ variant which is dynamic_cast < ... >.  Which resulted in
is-a.h.

So yes, we've decided to go C++ so we have to live with certain
uglinesses of that decisions (and maybe over time those uglinesses
will fade away and we get used to it and like it).

Thus, there isn't another option besides using the is-a.h machinery
and enabling and using RTTI.  Sticking to C for gimple doesn't seem
to be consistent with the decision to move to C++.

Oh, I'm not saying I'm a big fan of as_a / is_a or C++ in general
as it plays out right now.  But well, we've had the discussion and
had a decision.

Maybe we need to revisit it? As one of those who were not in favour of
the C++ move, can I ask you guys to step back for a moment and think
about - what do all of these changes buy us, exactly? Imagine the state
at the end, where everything is converted and supposedly the temporary
ugliness is gone, what have we gained over the code as it is now?

as_a gains us less runtime checking and more static type checking
which is good.
Absolutely.

That I agree to.  Instead of fixing the less than optimal separation / boundary
between frontends and the middle-end, or fixing several other long-standing
issues with GCC we spend a lot of time refactoring things to be C++.
But that was kind of part of the decision (though I remember that we
mainly wanted to convert containters and isolated stuff, not gimple
or trees (I bet that'll be next)).
That's a reasonable bet given what's already been said on this list WRT gimple.



Of course I don't see contributors of "changes that improve gcc for its users"
now wasting their time with converting code to C++.  That conversion
may slow down those people, but only so much.  It'll get more interesting
with branch maintainance ...
True. But that's probabl more of an artifact of the engineers involved. David (who's by far the most gung-ho on the C++ front) is fairly new to GCC and isn't really in a position right now to drive much user visible stuff. So he's doing what he can right now.

jeff


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