Update: Using C++26 with contracts enabled

CMakeLists.txt

@@ -12,6 +12,22 @@ set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_CXX_EXTENSIONS OFF)
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 
+if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
+    if(CMAKE_CXX_COMPILER_VERSION VERSION_LESS 16)
+        message(
+            FATAL_ERROR
+            "GCC 16+ is required (found ${CMAKE_CXX_COMPILER_VERSION}). "
+            "Use the 'default' CMake preset or cmake/toolchains/gcc-16.cmake."
+        )
+    endif()
+else()
+    message(
+        FATAL_ERROR
+        "This project requires GCC 16+. Found compiler: ${CMAKE_CXX_COMPILER_ID}. "
+        "Select the GCC 16 toolchain / default CMake preset in CLion."
+    )
+endif()
+
 option(COURSE_BUILD_TESTS "Build Google Test exercise targets" ON)
 option(COURSE_WARNINGS_AS_ERRORS "Treat compiler warnings as errors" OFF)
 option(COURSE_ENABLE_CONTRACTS "Enable C++26 contracts on GCC 16+" ON)
@@ -37,3 +53,6 @@ if(COURSE_BUILD_TESTS)
 endif()
 
 add_subdirectory(modules)
+
+include(Cppcheck)
+course_add_cppcheck_targets()