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

[Tim Shen]

On Mon, Sep 19, 2016 at 1:06 PM, Tim Shen <timshen@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.


-- 
Regards,
Tim Shen
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