Merge pull request #1441 from iwanders/support-cmake-older-than-3-8-with-if

Use C++11 features supported by CMake 3.1.

CMakeLists.txt

@@ -46,7 +46,11 @@ endif()
 ##
 add_library(${NLOHMANN_JSON_TARGET_NAME} INTERFACE)
 add_library(${PROJECT_NAME}::${NLOHMANN_JSON_TARGET_NAME} ALIAS ${NLOHMANN_JSON_TARGET_NAME})
-target_compile_features(${NLOHMANN_JSON_TARGET_NAME} INTERFACE cxx_std_11)
+if (${CMAKE_VERSION} VERSION_LESS "3.8.0") 
+    target_compile_features(${NLOHMANN_JSON_TARGET_NAME} INTERFACE cxx_range_for)
+else()
+    target_compile_features(${NLOHMANN_JSON_TARGET_NAME} INTERFACE cxx_std_11)
+endif()
 
 target_include_directories(
     ${NLOHMANN_JSON_TARGET_NAME}

benchmarks/CMakeLists.txt

-cmake_minimum_required(VERSION 3.1)
+cmake_minimum_required(VERSION 3.8)
 project(JSON_Benchmarks LANGUAGES CXX)
 
 # set compiler flags

test/CMakeLists.txt

@@ -64,7 +64,11 @@ set_target_properties(catch_main PROPERTIES
     COMPILE_DEFINITIONS "$<$<CXX_COMPILER_ID:MSVC>:_SCL_SECURE_NO_WARNINGS>"
     COMPILE_OPTIONS "$<$<CXX_COMPILER_ID:MSVC>:/EHsc;$<$<CONFIG:Release>:/Od>>"
 )
-target_compile_features(catch_main PUBLIC cxx_std_11)
+if (${CMAKE_VERSION} VERSION_LESS "3.8.0") 
+    target_compile_features(catch_main PUBLIC cxx_range_for)
+else()
+    target_compile_features(catch_main PUBLIC cxx_std_11)
+endif()
 target_include_directories(catch_main PRIVATE "thirdparty/catch")
 
 # https://stackoverflow.com/questions/2368811/how-to-set-warning-level-in-cmake