build: Fallback to C++11

This required minor syntactic fixes and replacing std::optional
with a 3rd party implementation (by Andrzej Krzemienski). The
selection of `optional` is done on the basis of C++ standard
version, e.g.:

cmake -DCASS_CPP_STANDARD=17 ..

will use std::optional, while `-DCASS_CPP_STANDARD=11` will fall
back to 3rd party impl.

Author: jul-stas

CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 2.8.12)
+cmake_minimum_required(VERSION 3.1)
 project(cassandra C CXX)
 
 set(CASS_ROOT_DIR ${CMAKE_CURRENT_SOURCE_DIR})
@@ -43,10 +43,12 @@ option(CASS_USE_KERBEROS "Use Kerberos" OFF)
 option(CASS_USE_LIBSSH2 "Use libssh2 for integration tests" OFF)
 option(CASS_USE_OPENSSL "Use OpenSSL" ON)
 option(CASS_USE_STATIC_LIBS "Link static libraries when building executables" OFF)
-option(CASS_USE_STD_ATOMIC "Use C++11 atomics library" ON)
+option(CASS_USE_STD_ATOMIC "Use std::atomic library" ON)
 option(CASS_USE_ZLIB "Use zlib" ON)
 option(CASS_USE_TIMERFD "Use timerfd (Linux only)" ON)
 
+set(CASS_CPP_STANDARD "11" CACHE STRING "C++ standard (11, 14, 17, etc.)")
+
 # Handle testing dependencies
 if(CASS_BUILD_TESTS)
   # Enable integration and unit tests
@@ -161,10 +163,10 @@ endif()
 # Top-level compiler flags
 #------------------------
 
+set (CMAKE_CXX_STANDARD ${CASS_CPP_STANDARD})
+
 if("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang" OR
    "${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
-  # Enable C++17 support by default
-  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++17")
 
   # OpenSSL is deprecated on later versions of Mac OS X. The long-term solution
   # is to provide a CommonCryto implementation.
@@ -191,9 +193,6 @@ if("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang" OR
 elseif("${CMAKE_CXX_COMPILER_ID}" STREQUAL "MSVC")
   add_definitions(/we4800)
 
-  # Enable C++17 support by default
-  add_definitions(/std:c++17)
-
   # Determine if multicore compilation should be enabled
   if(CASS_MULTICORE_COMPILATION)
     # Default multicore compilation with effective processors (see https://msdn.microsoft.com/en-us/library/bb385193.aspx)

driver_config.hpp.in

@@ -4,6 +4,7 @@
 #cmakedefine HAVE_KERBEROS
 #cmakedefine HAVE_OPENSSL
 #cmakedefine HAVE_STD_ATOMIC
+#cmakedefine CASS_CPP_STANDARD @CASS_CPP_STANDARD@
 #cmakedefine HAVE_BOOST_ATOMIC
 #cmakedefine HAVE_NOSIGPIPE
 #cmakedefine HAVE_SIGTIMEDWAIT

LICENSE.txt renamed to examples/licenses/apache-2.0.txt

@@ -0,0 +1,23 @@
+Boost Software License - Version 1.0 - August 17th, 2003
+
+Permission is hereby granted, free of charge, to any person or organization
+obtaining a copy of the software and accompanying documentation covered by
+this license (the "Software") to use, reproduce, display, distribute,
+execute, and transmit the Software, and to prepare derivative works of the
+Software, and to permit third-parties to whom the Software is furnished to
+do so, all subject to the following:
+
+The copyright notices in the Software and this entire statement, including
+the above license grant, this restriction and the following disclaimer,
+must be included in all copies of the Software, in whole or in part, and
+all derivative works of the Software, unless such copies or derivative
+works are solely in the form of machine-executable object code generated by
+a source language processor.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
+SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
+FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
+ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.

examples/licenses/boost-1.0.txt

@@ -36,6 +36,15 @@ else()
   endif()
 endif()
 
+# Determine `optional` library to include
+if(CMAKE_CXX_STANDARD LESS 17)
+  message(STATUS "Using akrzemi's `optional` implementation")
+  list(APPEND SOURCES optional/optional_akrzemi.hpp)
+else()
+  message(STATUS "Using std::optional library")
+  list(APPEND SOURCES optional/optional_std.hpp)
+endif()
+
 add_subdirectory(third_party/curl)
 add_subdirectory(third_party/hdr_histogram)
 add_subdirectory(third_party/http-parser)

src/CMakeLists.txt

@@ -22,7 +22,7 @@
 #include "socket.hpp"
 #include "stream_manager.hpp"
 
-#include <optional>
+#include "optional.hpp"
 
 namespace datastax { namespace internal { namespace core {
 
@@ -197,7 +197,7 @@ class Connection : public RefCounted<Connection> {
    */
   void set_listener(ConnectionListener* listener = NULL);
 
-  std::optional<int32_t> shard_id() const { return shard_id_opt_; }
+  CassOptional<int32_t> shard_id() const { return shard_id_opt_; }
   void set_shard_id(int32_t shard_id) {
     shard_id_opt_ = shard_id;
   }
@@ -248,7 +248,7 @@ class Connection : public RefCounted<Connection> {
   ProtocolVersion protocol_version_;
   String keyspace_;
 
-  std::optional<int32_t> shard_id_opt_;
+  CassOptional<int32_t> shard_id_opt_;
 
   unsigned int idle_timeout_secs_;
   unsigned int heartbeat_interval_secs_;

src/connection.hpp

@@ -33,7 +33,7 @@
 
 #include <math.h>
 #include <stdint.h>
-#include <optional>
+#include "optional.hpp"
 
 namespace datastax { namespace internal { namespace core {
 
@@ -126,7 +126,7 @@ class Host : public RefCounted<Host> {
     dc_id_ = dc_id;
   }
 
-  std::optional<ShardingInfo> sharding_info() const { return sharding_info_opt_; }
+  CassOptional<ShardingInfo> sharding_info() const { return sharding_info_opt_; }
   void set_sharding_info(ShardingInfo si) {
     sharding_info_opt_ = std::move(si);
   }
@@ -219,7 +219,7 @@ class Host : public RefCounted<Host> {
   Vector<String> tokens_;
   Atomic<int32_t> connection_count_;
   Atomic<int32_t> inflight_request_count_;
-  std::optional<ShardingInfo> sharding_info_opt_;
+  CassOptional<ShardingInfo> sharding_info_opt_;
 
   ScopedPtr<LatencyTracker> latency_tracker_;
 

src/host.hpp

@@ -0,0 +1,31 @@
+/*
+ * Copyright (C) 2020 ScyllaDB 
+ *
+ * This file is part of Scylla.
+ *
+ * Scylla is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Scylla 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Scylla.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef DATASTAX_INTERNAL_OPTIONAL_HPP
+#define DATASTAX_INTERNAL_OPTIONAL_HPP
+
+#include "driver_config.hpp"
+
+#if CASS_CPP_STANDARD >= 17
+  #include "optional/optional_std.hpp"
+#else
+  #include "optional/optional_akrzemi.hpp"
+#endif
+
+#endif /* DATASTAX_INTERNAL_OPTIONAL_HPP */