made it possibly to actually override the C++ standard in CMake (#677)

Author: firewave

.clang-tidy

@@ -31,10 +31,15 @@ Checks: >
         -modernize-avoid-c-arrays,
         -modernize-loop-convert,
         -modernize-pass-by-value,
+        -modernize-use-auto,
+        -modernize-use-designated-initializers,
         -modernize-use-nodiscard,
+        -modernize-use-ranges,
+        -modernize-use-starts-ends-with,
         -modernize-use-trailing-return-type,
         -readability-avoid-nested-conditional-operator,
         -readability-braces-around-statements,
+        -readability-container-contains,
         -readability-function-cognitive-complexity,
         -readability-function-size,
         -readability-implicit-bool-conversion,

CMakeLists.txt

@@ -1,9 +1,13 @@
 cmake_minimum_required (VERSION 3.10)
 project (simplecpp LANGUAGES CXX)
 
-set(CMAKE_CXX_STANDARD 11)
+set(CMAKE_CXX_STANDARD 11 CACHE STRING "C++ standard to use")
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
+if(CMAKE_CXX_STANDARD LESS 11)
+    message(FATAL_ERROR "C++ standard was set to ${CMAKE_CXX_STANDARD} but 11 is required as a minimum")
+endif()
+
 include(CheckCXXCompilerFlag)
 
 if (WIN32)

test.cpp

@@ -18,6 +18,10 @@
 #include <utility>
 #include <vector>
 
+#ifdef __cpp_lib_string_view
+#include <string_view>
+#endif
+
 #ifndef SIMPLECPP_TEST_SOURCE_DIR
 #error "SIMPLECPP_TEST_SOURCE_DIR is not defined."
 #endif