build: switch from RULE_LAUNCH_COMPILE to CXX_COMPILER_LAUNCHER

CMakeLists.txt

@@ -106,7 +106,7 @@ if(${NS3_CCACHE})
   find_program(CCACHE ccache)
   if(NOT ("${CCACHE}" STREQUAL "CCACHE-NOTFOUND"))
     message(STATUS "CCache is enabled.")
-    set_property(GLOBAL PROPERTY RULE_LAUNCH_COMPILE ${CCACHE})
+    set(CMAKE_CXX_COMPILER_LAUNCHER ${CCACHE})
     execute_process(
       COMMAND
         ${CCACHE} --set-config

build-support/3rd-party/colored-messages.cmake

@@ -71,25 +71,25 @@ if(${NS3_COLORED_OUTPUT} OR "$ENV{CLICOLOR}")
   # Replace the default message macro with a custom colored one
   function(message)
     list(GET ARGV 0 MessageType)
+    list(REMOVE_AT ARGV 0)
+
+    # Transform list of arguments into a single line.
+    string(REPLACE ";" " " ARGV "${ARGV}")
+
     if((${MessageType} STREQUAL FATAL_ERROR) OR (${MessageType} STREQUAL
                                                  SEND_ERROR)
     )
-      list(REMOVE_AT ARGV 0)
       _message(${MessageType} "${BoldRed}${ARGV}${ColourReset}")
     elseif(MessageType STREQUAL WARNING)
-      list(REMOVE_AT ARGV 0)
       _message(${MessageType} "${Yellow}${ARGV}${ColourReset}")
     elseif(MessageType STREQUAL AUTHOR_WARNING)
-      list(REMOVE_AT ARGV 0)
       _message(${MessageType} "${BoldCyan}${ARGV}${ColourReset}")
     elseif(MessageType STREQUAL HIGHLIGHTED_STATUS) # Custom message type
-      list(REMOVE_AT ARGV 0)
       _message(STATUS "${Yellow}${ARGV}${ColourReset}")
     elseif(MessageType STREQUAL STATUS)
-      list(REMOVE_AT ARGV 0)
       _message(${MessageType} "${ARGV}")
     else()
-      _message(${ARGV})
+      _message(${MessageType} "${ARGV}")
     endif()
   endfunction()
 endif()

build-support/macros-and-definitions.cmake

@@ -478,6 +478,18 @@ macro(process_options)
     if("${CLANG_TIDY}" STREQUAL "CLANG_TIDY-NOTFOUND")
       message(FATAL_ERROR "Clang-tidy was not found")
     else()
+      if((${CMAKE_VERSION} VERSION_LESS "3.12.0") AND ${NS3_CCACHE}
+         AND (NOT ("${CCACHE}" STREQUAL "CCACHE-NOTFOUND"))
+      )
+        # CMake <3.12 puts CMAKE_CXX_COMPILER_LAUNCHER in the incorrect place
+        # and CCache ends up being unable to cache anything if calling
+        # clang-tidy https://gitlab.kitware.com/cmake/cmake/-/issues/18266
+        message(
+          FATAL_ERROR
+            "The current CMake ${CMAKE_VERSION} won't ccache objects correctly when running with clang-tidy."
+            "Update CMake to at least version 3.12, or disable either ccache or clang-tidy to continue."
+        )
+      endif()
       set(CMAKE_CXX_CLANG_TIDY "${CLANG_TIDY}")
     endif()
   else()