Use C++14 by default when building on systems that support it. (#16972)

This is needed to properly support the latest versions of Protobuf.

CMakeLists.txt

@@ -60,7 +60,13 @@ project(netdata
 find_package(PkgConfig REQUIRED)
 
 set(CMAKE_C_STANDARD 11)
-set(CMAKE_CXX_STANDARD 11)
+set(CMAKE_CXX_STANDARD 14)
+
+option(USE_CXX_11 "use C++11 instead of C++14" False)
+
+if(USE_CXX_11)
+    set(CMAKE_CXX_STANDARD 11)
+endif()
 
 set(CMAKE_C_STANDARD_REQUIRED On)
 set(CMAKE_CXX_STANDARD_REQUIRED On)

netdata-installer.sh

@@ -209,6 +209,7 @@ USAGE: ${PROGRAM} [options]
   --disable-ebpf             Disable eBPF Kernel plugin. Default: enabled.
   --disable-cloud            Disable all Netdata Cloud functionality.
   --require-cloud            Fail the install if it can't build Netdata Cloud support.
+  --force-legacy-cxx         Force usage of an older C++ standard to allow building on older systems. This will usually be autodetected.
   --enable-plugin-freeipmi   Enable the FreeIPMI plugin. Default: enable it when libipmimonitoring is available.
   --disable-plugin-freeipmi  Explicitly disable the FreeIPMI plugin.
   --disable-https            Explicitly disable TLS support.
@@ -257,6 +258,7 @@ ENABLE_H2O=1
 ENABLE_CLOUD=1
 ENABLE_LOGS_MANAGEMENT=1
 ENABLE_LOGS_MANAGEMENT_TESTS=0
+FORCE_LEGACY_CXX=0
 NETDATA_CMAKE_OPTIONS="${NETDATA_CMAKE_OPTIONS-}"
 
 RELEASE_CHANNEL="nightly" # valid values are 'nightly' and 'stable'
@@ -273,6 +275,7 @@ while [ -n "${1}" ]; do
     "--auto-update-type") ;;
     "--stable-channel") RELEASE_CHANNEL="stable" ;;
     "--nightly-channel") RELEASE_CHANNEL="nightly" ;;
+    "--force-legacy-cxx") FORCE_LEGACY_CXX=1 ;;
     "--enable-plugin-freeipmi") ENABLE_FREEIPMI=1 ;;
     "--disable-plugin-freeipmi") ENABLE_FREEIPMI=0 ;;
     "--disable-https")

netdata.spec.in

@@ -352,6 +352,11 @@ make download
 # Conf step
 %cmake -G Ninja \
 	-DCMAKE_INSTALL_PREFIX=/ \
+	%if 0%{?centos_ver:1}
+	%if %{centos_ver} < 8
+	-DUSE_CXX_11=On \
+	%endif
+	%endif
 	%if %{_have_cups}
 	-DENABLE_PLUGIN_CUPS=On \
 	%else

packaging/installer/functions.sh

@@ -235,6 +235,28 @@ check_for_feature() {
 prepare_cmake_options() {
   NETDATA_CMAKE_OPTIONS="-S ./ -B ${NETDATA_BUILD_DIR} ${CMAKE_OPTS} ${NETDATA_PREFIX+-DCMAKE_INSTALL_PREFIX="${NETDATA_PREFIX}"} ${NETDATA_USER:+-DNETDATA_USER=${NETDATA_USER}} ${NETDATA_CMAKE_OPTIONS} "
 
+  NEED_OLD_CXX=0
+
+  if [ "${FORCE_LEGACY_CXX:-0}" -eq 1 ]; then
+    NEED_OLD_CXX=1
+  else
+    if command -v gcc >/dev/null 2>&1; then
+      if [ "$(gcc --version | head -n 1 | sed 's/(.*) //' | cut -f 2 -d ' ' | cut -f 1 -d '.')" -lt 5 ]; then
+        NEED_OLD_CXX=1
+      fi
+    fi
+
+    if command -v clang >/dev/null 2>&1; then
+      if [ "$(clang --version | head -n 1 | cut -f 3 -d ' ' | cut -f 1 -d '.')" -lt 4 ]; then
+        NEED_OLD_CXX=1
+      fi
+    fi
+  fi
+
+  if [ "${NEED_OLD_CXX}" -eq 1 ]; then
+    NETDATA_CMAKE_OPTIONS="${NETDATA_CMAKE_OPTIONS} -DUSE_CXX_11=On"
+  fi
+
   if [ "${USE_SYSTEM_PROTOBUF:-1}" -eq 1 ]; then
     enable_feature BUNDLED_PROTOBUF 0
   else