This is the mail archive of the libstdc++@gcc.gnu.org mailing list for the libstdc++ project.

Index Nav:	[Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav:	[Date Prev] [Date Next]	[Thread Prev] [Thread Next]
Other format:	[Raw text]

Re: [v3 PATCH] Use single-visitation in variant assignment and swap.

From: Paolo Carlini <paolo dot carlini at oracle dot com>
To: Ville Voutilainen <ville dot voutilainen at gmail dot com>, libstdc++ <libstdc++ at gcc dot gnu dot org>, gcc-patches List <gcc-patches at gcc dot gnu dot org>
Date: Mon, 1 Apr 2019 10:29:58 +0200
Subject: Re: [v3 PATCH] Use single-visitation in variant assignment and swap.
References: <CAFk2RUZ-RvZyqWcUnyAHFRqc9VoPW9+qdWdXQCUGb5i5757wXQ@mail.gmail.com>

Hi

On 30/03/19 19:00, Ville Voutilainen wrote:

-  template<typename _Visitor, typename... _Variants>
+  template<bool __use_index, typename _Visitor, typename... _Variants>
+    decltype(auto)
+    __visitor_result_type(_Visitor&& __visitor, _Variants&&... __variants)
+    {
+      if constexpr(__use_index)
+        return __detail::__variant::__variant_idx_cookie{};
+      else
+	return std::forward<_Visitor>(__visitor)(
+	  std::get<0>(std::forward<_Variants>(__variants))...);
+    }

If I'm not misreading something, the new function will be usuallycompiled/optimized to something very small and isn't constexpr thusnormally should be explicitly marked inline. Or the problem is themissing constexpr? (sorry, I didn't really study the new code)


Paolo.

Follow-Ups:
- Re: [v3 PATCH] Use single-visitation in variant assignment and swap.
  - From: Ville Voutilainen

Index Nav:	[Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav:	[Date Prev] [Date Next]	[Thread Prev] [Thread Next]