Re: [PATCH] libstdc++/77641 fix std::variant for literal types

[Jonathan Wakely]

On 20/09/16 11:03 -0700, Tim Shen wrote:

On Mon, Sep 19, 2016 at 1:06 PM, Tim Shen <tims...@google.com> wrote:

I believe that it's a "typo" from me - it should be
is_trivially_destructible, not is_default_constructible (so that we
can avoid using aligned_storage in the corresponding specialization).
is_literal_type works, since literal types are trivially destructible.

Sorry I misunderstood your patch.

The underlying problem is that _Variant_storage wasn't always default
constructible, but it should be.

Jon, your fix doesn't fix the following constexpr variation of your test case:
 struct X {
   constexpr X() { }
 };

 constexpr std::variant<X> v1 = X{};

So I have a patch here to make _Variant_storage's internal union
default constructible.

Tested on x86_64-linux-gnu.

THanks, OK for trunk.