From d28ee4eee8b777b75eb103b95bf0ed18ef26a124 Mon Sep 17 00:00:00 2001
From: arvidn <arvid@libtorrent.org>
Date: Thu, 24 Aug 2023 16:34:21 +0200
Subject: [PATCH] rely on RVO in C++20

---
 bindings/python/src/entry.cpp | 4 ++--
 include/libtorrent/config.hpp | 6 ++++++
 src/alert.cpp                 | 6 +++---
 src/session_stats.cpp         | 2 +-
 src/torrent_handle.cpp        | 4 ++--
 5 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/bindings/python/src/entry.cpp b/bindings/python/src/entry.cpp
index 6e0ee74aadb..e4c55aa14a3 100644
--- a/bindings/python/src/entry.cpp
+++ b/bindings/python/src/entry.cpp
@@ -20,7 +20,7 @@ struct entry_to_python
             result.append(*i);
         }
 
-        return std::move(result);
+        return TORRENT_RVO(result);
     }
 
     static object convert(entry::dictionary_type const& d)
@@ -30,7 +30,7 @@ struct entry_to_python
         for (entry::dictionary_type::const_iterator i(d.begin()), e(d.end()); i != e; ++i)
             result[bytes(i->first)] = i->second;
 
-        return std::move(result);
+        return TORRENT_RVO(result);
     }
 
     static object convert0(entry const& e)
diff --git a/include/libtorrent/config.hpp b/include/libtorrent/config.hpp
index 84e2b845575..76091984dcf 100644
--- a/include/libtorrent/config.hpp
+++ b/include/libtorrent/config.hpp
@@ -579,6 +579,12 @@ constexpr std::size_t TORRENT_WRITE_HANDLER_MAX_SIZE = 400;
 #define __has_builtin(x) 0  // for non-clang compilers
 #endif
 
+#if __cplusplus >= 202002L
+#define TORRENT_RVO(x) x
+#else
+#define TORRENT_RVO(x) std::move(x)
+#endif
+
 #if (TORRENT_HAS_SSE && defined __GNUC__)
 #	define TORRENT_HAS_BUILTIN_CLZ 1
 #elif (TORRENT_HAS_ARM && defined __GNUC__ && !defined __clang__)
diff --git a/src/alert.cpp b/src/alert.cpp
index 0ac87588906..1e24a4d9e22 100644
--- a/src/alert.cpp
+++ b/src/alert.cpp
@@ -2531,7 +2531,7 @@ namespace {
 		for (int i = 0; i < m_v6_num_peers; i++)
 			peers.push_back(detail::read_v6_endpoint<tcp::endpoint>(v6_ptr));
 
-		return std::move(peers);
+		return TORRENT_RVO(peers);
 	}
 
 	dht_direct_response_alert::dht_direct_response_alert(
@@ -2771,7 +2771,7 @@ namespace {
 			nodes.emplace_back(ih, detail::read_v6_endpoint<udp::endpoint>(v6_ptr));
 		}
 
-		return std::move(nodes);
+		return TORRENT_RVO(nodes);
 	}
 	}
 
@@ -2881,7 +2881,7 @@ namespace {
 		char const* ptr = m_alloc.get().ptr(m_samples_idx);
 		std::memcpy(samples.data(), ptr, samples.size() * 20);
 
-		return std::move(samples);
+		return TORRENT_RVO(samples);
 	}
 
 	int dht_sample_infohashes_alert::num_nodes() const
diff --git a/src/session_stats.cpp b/src/session_stats.cpp
index 7a96fa9b1d2..147cd7e29b8 100644
--- a/src/session_stats.cpp
+++ b/src/session_stats.cpp
@@ -585,7 +585,7 @@ namespace {
 			stats[i].type = metrics[i].value_index >= counters::num_stats_counters
 				? metric_type_t::gauge : metric_type_t::counter;
 		}
-		return std::move(stats);
+		return TORRENT_RVO(stats);
 	}
 
 	int find_metric_idx(string_view name)
diff --git a/src/torrent_handle.cpp b/src/torrent_handle.cpp
index 0b856439d11..82e26f70206 100644
--- a/src/torrent_handle.cpp
+++ b/src/torrent_handle.cpp
@@ -487,7 +487,7 @@ namespace libtorrent {
 		aux::vector<download_priority_t, piece_index_t> ret;
 		auto retp = &ret;
 		sync_call(&torrent::piece_priorities, retp);
-		return std::move(ret);
+		return TORRENT_RVO(ret);
 	}
 
 #if TORRENT_ABI_VERSION == 1
@@ -543,7 +543,7 @@ namespace libtorrent {
 		aux::vector<download_priority_t, file_index_t> ret;
 		auto retp = &ret;
 		sync_call(&torrent::file_priorities, retp);
-		return std::move(ret);
+		return TORRENT_RVO(ret);
 	}
 
 #if TORRENT_ABI_VERSION == 1