rjmccall added a comment.
In https://reviews.llvm.org/D44536#1054929, @rsmith wrote:
> It seems that we have two options: either we valiantly try to support this:
>
> - we keep a list of types for which we've tried to form a
> //delete-expression//, but found that the type was incomplete
> - when such a type is completed, we mark the destructor as used, triggering
> its synthesis or instantiation if necessary, and likewise for the `operator
> delete`
> - we change our `CXXDeleteExpr` representation so that we don't store any
> information that might be changed by completing the class on the expression,
> such as the selected `OperatorDelete` function and whether we're performing a
> sized delete
Yeah, this is probably unworkable. (Of course I'm brainstorming ways we could
do it — we could have a global entry for late-realized destructor information.
But it just seems like a terrible idea.)
> ... or we say that we're not interested in calling the destructor for code
> like this that has undefined behavior. The latter is certainly my preference;
> it seems hard to justify the complexity required to get this "right",
> especially since we still won't get it right in cases where we choose to emit
> some function definitions before the end of the TU.
I agree.
> I agree with John that tracking that we're in the "delete of incomplete class
> type" case (or some equivalent state, such as a "need to run a cleanup" flag)
> on the `CXXDeleteExpr` seems best. We should be careful to ensure that we
> rebuild the expression in template instantiation when the "delete of
> incomplete class type" flag is set, even if the expression is non-dependent,
> though. That is, I think this should work:
>
> struct X { ~X(); };
> struct A;
> A *get();
> template<int> void f() { delete (&get)(); }
> struct A { X x; };
> A *get() { return new A; }
> void g() { f<0>(); }
>
>
> ... even though we first form a (non-dependent) //delete-expression// for an
> `A` at a point where `A` is incomplete.
Good point. I agree that we should allow incomplete deletes to work as long as
they've been completed by instantiation time.
Repository:
rC Clang
https://reviews.llvm.org/D44536
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