build: ns3 and CMake fixes

- fix scratch shortcut transformation to build target and binary
- scan scratch files for a main function to use them as the target name
- fix CMake generator parsing
- update the -- separator message
- use -- separator to forward CMake flags from ns3
- add --vis option to ns3
- embedded version fixes
    Fix NS3_VERSION_PATCH and NS3_VERSION_RELEASE_CANDIDATE default values.
    Add check-version target to CMake.
    Add --enable-build-version to ns3.
    Add --check-profile and --check-version options to ns3.
- process each scratch subdirectory as a single target
- forward ns3 arguments after -- separator to the program to run
- fix escape sequence in command-template help string
- handle modules with very long names

scratch/CMakeLists.txt

@@ -1,36 +1,78 @@
-file(GLOB_RECURSE scratches ${CMAKE_CURRENT_SOURCE_DIR}/*.cc)
-
-set(DONT_BUILD)
 set(target_prefix scratch_)
 
-foreach(scratch_src ${scratches})
-  # Get source filename without path or extension
-  get_filename_component(scratch_name ${scratch_src} NAME)
-  string(REGEX REPLACE "\\.[^.]*$" "" scratch_name ${scratch_name})
+function(create_scratch source_files)
+  # Return early if no sources in the subdirectory
+  list(LENGTH source_files number_sources)
+  if(number_sources EQUAL 0)
+    return()
+  endif()
+
+  # If the scratch has more than a source file, we need
+  # to find the source with the main function
+  unset(scratch_src)
+  foreach(source_file ${source_files})
+      file(READ ${source_file} source_file_contents)
+      string(REGEX MATCHALL "main[(| (]" main_position "${source_file_contents}")
+      if(CMAKE_MATCH_0)
+        set(scratch_src ${source_file})
+      endif()
+  endforeach()
+
+  # Get parent directory name
+  get_filename_component(scratch_dirname ${scratch_src} DIRECTORY)
+  string(REPLACE "${CMAKE_CURRENT_SOURCE_DIR}/" "" scratch_dirname
+                 ${scratch_dirname}
+  )
+  # Get source name
+  get_filename_component(scratch_name ${scratch_src} NAME_WE)
+
+  set(target_prefix scratch_)
+  if(${scratch_dirname})
+    # Join the names together if dirname is not the scratch folder
+    set(target_prefix scratch_${scratch_dirname}_)
+  endif()
 
   # Get source absolute path and transform into relative path
   get_filename_component(scratch_absolute_directory ${scratch_src} DIRECTORY)
   string(REPLACE "${PROJECT_SOURCE_DIR}" "${CMAKE_OUTPUT_DIRECTORY}"
                  scratch_directory ${scratch_absolute_directory}
   )
-
-  # Build scratch if not listed as a DONT_BUILD
-  string(FIND "${DONT_BUILD}" "${scratch_name}" res)
-  if(res LESS 0)
-    add_executable(${target_prefix}${scratch_name} "${scratch_src}")
-    if(${NS3_STATIC})
-      target_link_libraries(
-        ${target_prefix}${scratch_name} ${LIB_AS_NEEDED_PRE_STATIC}
-        ${lib-ns3-static}
-      )
-    else()
-      target_link_libraries(
-        ${target_prefix}${scratch_name} "${ns3-libs}" "${ns3-contrib-libs}"
-        "${ns3-external-libs}"
-      )
-    endif()
-    set_runtime_outputdirectory(
-      ${scratch_name} ${scratch_directory}/ ${target_prefix}
+  add_executable(${target_prefix}${scratch_name} "${source_files}")
+  if(${NS3_STATIC})
+    target_link_libraries(
+      ${target_prefix}${scratch_name} ${LIB_AS_NEEDED_PRE_STATIC}
+      ${lib-ns3-static}
+    )
+  else()
+    target_link_libraries(
+      ${target_prefix}${scratch_name} "${ns3-libs}" "${ns3-contrib-libs}"
+      "${ns3-external-libs}"
     )
   endif()
+  set_runtime_outputdirectory(
+    ${scratch_name} ${scratch_directory}/ ${target_prefix}
+  )
+endfunction()
+
+# Scan *.cc files in ns-3-dev/scratch and build a target for each
+file(GLOB single_source_file_scratches ${CMAKE_CURRENT_SOURCE_DIR}/*.cc)
+foreach(scratch_src ${single_source_file_scratches})
+  create_scratch(${scratch_src})
+endforeach()
+
+# Scan *.cc files in ns-3-dev/scratch subdirectories and build a target for each
+# subdirectory
+file(GLOB_RECURSE scratch_subdirectories LIST_DIRECTORIES true
+     ${CMAKE_CURRENT_SOURCE_DIR}/**
+)
+# Filter out files
+foreach(entry ${scratch_subdirectories})
+  if(NOT (IS_DIRECTORY ${entry}))
+    list(REMOVE_ITEM scratch_subdirectories ${entry})
+  endif()
+endforeach()
+
+foreach(subdir ${scratch_subdirectories})
+  file(GLOB scratch_sources ${subdir}/*.cc)
+  create_scratch("${scratch_sources}")
 endforeach()