From 05260ace94833685c9f1966ef37e85a227f7983c Mon Sep 17 00:00:00 2001
From: Gioacchino Mazzurco <gio@eigenlab.org>
Date: Wed, 30 Oct 2019 14:24:19 +0100
Subject: [PATCH] Backport as_const C++17 helper

This is expecially useful to use const_iterator without giving up on
  using auto keyword
---
 libretroshare/src/libretroshare.pro       |  1 +
 libretroshare/src/util/cxx17retrocompat.h | 35 +++++++++++++++++++++++
 2 files changed, 36 insertions(+)
 create mode 100644 libretroshare/src/util/cxx17retrocompat.h

diff --git a/libretroshare/src/libretroshare.pro b/libretroshare/src/libretroshare.pro
index 01cbc8852..360eb4ab8 100644
--- a/libretroshare/src/libretroshare.pro
+++ b/libretroshare/src/libretroshare.pro
@@ -503,6 +503,7 @@ HEADERS +=	util/folderiterator.h \
             util/stacktrace.h \
             util/rsdeprecate.h \
             util/cxx11retrocompat.h \
+    util/cxx17retrocompat.h \
             util/rsurl.h
 
 SOURCES +=	ft/ftchunkmap.cc \
diff --git a/libretroshare/src/util/cxx17retrocompat.h b/libretroshare/src/util/cxx17retrocompat.h
new file mode 100644
index 000000000..58cdfe84c
--- /dev/null
+++ b/libretroshare/src/util/cxx17retrocompat.h
@@ -0,0 +1,35 @@
+/*******************************************************************************
+ * libretroshare/src/util: cxx17retrocompat.h                                  *
+ *                                                                             *
+ * libretroshare: retroshare core library                                      *
+ *                                                                             *
+ * Copyright (C) 2019  Gioacchino Mazzurco <gio@eigenlab.org>                  *
+ *                                                                             *
+ * This program is free software: you can redistribute it and/or modify        *
+ * it under the terms of the GNU Lesser General Public License as              *
+ * published by the Free Software Foundation, either version 3 of the          *
+ * License, or (at your option) any later version.                             *
+ *                                                                             *
+ * This program is distributed in the hope that it will be useful,             *
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of              *
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the                *
+ * GNU Lesser General Public License for more details.                         *
+ *                                                                             *
+ * You should have received a copy of the GNU Lesser General Public License    *
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.       *
+ *                                                                             *
+ *******************************************************************************/
+#pragma once
+
+#if __cplusplus < 201703L
+
+#include <type_traits>
+
+namespace std
+{
+using namespace std;
+template <class T> constexpr typename add_const<T>::type& as_const(T& t) noexcept
+{ return t; }
+template <class T> void as_const(const T&&) = delete;
+}
+#endif // __cplusplus < 201703L