Re: [PR c++/20103] failure to gimplify constructors for addressabletypes

[Mark Mitchell <mark at codesourcery dot com>]

Alexandre Oliva wrote:

> > Then you should tsubst the INITIAL first, and unconditionally copy the
> > type to the TARGET_EXPR when you use build3.
>
>
> But what if the TARGET_EXPR had been created for different purposes,
> and did have a different type than that of the initializer?  Say, a
> Base& being bound to a Derived TARGET_EXPR?  That's why I'm performing
> the tests the way I am.

Are you sure that we can use TARGET_EXPR as a type-conversion node?  I 
would think in that case that the INITIAL for the TARGET_EXPR would be a 
call to the derived class constructor.  Hmm.  I suppose the type of such 
 a constructor is "void", so it may indeed be the case that there's 
really no relationship between the types.  Good point.

> Yeah, I know we'd like to do that, but we can't.  At that point we
> have no clue what that TARGET_EXPR or the CONSTRUCTOR in its initial
> came from.  We'd have to create a new tree node type for compound
> literals to be able to call finish_compound_literal at that point.

Then we really should do that.  We could have COMPOUND_LITERAL_EXPR 
whose type would be the type in the (syntactic) cast, and whose argument 
would be the CONSTRUCTOR for the brace-enclosed initializer.  We'd 
create one of these things if the TYPE, or any of the initializers, was 
dependent.

The games that you want to play with type-equality are just too fragile.

--
Mark Mitchell
CodeSourcery, LLC
mark@codesourcery.com
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