build: add STANDALONE option to build_exec and fix static builds

build-support/cmake-format-modules.txt

@@ -1,6 +1,6 @@
 additional_commands:
     build_exec:
-        flags: [IGNORE_PCH]
+        flags: [IGNORE_PCH, STANDALONE]
         kwargs:
             EXECNAME : '1'
             EXECNAME_PREFIX : '1'

build-support/cmake-format.txt

@@ -1,6 +1,6 @@
 additional_commands:
     build_exec:
-        flags: [IGNORE_PCH]
+        flags: [IGNORE_PCH, STANDALONE]
         kwargs:
             EXECNAME : '1'
             EXECNAME_PREFIX : '1'

build-support/custom-modules/ns3-compiler-workarounds.cmake

@@ -70,6 +70,3 @@ check_cxx_source_compiles(
   "
   FILESYSTEM_LIBRARY_IS_LINKED
 )
-if(NOT FILESYSTEM_LIBRARY_IS_LINKED)
-  link_libraries(-lstdc++fs)
-endif()

build-support/custom-modules/ns3-module-macros.cmake

@@ -98,6 +98,10 @@ function(build_lib)
       )
     endif()
 
+    if(NOT FILESYSTEM_LIBRARY_IS_LINKED)
+      list(APPEND BLIB_LIBRARIES_TO_LINK -lstdc++fs)
+    endif()
+
     # Enable examples as tests suites
     if(${ENABLE_EXAMPLES} AND ${ENABLE_TESTS})
       if(NOT ${XCODE})

build-support/macros-and-definitions.cmake

@@ -1058,7 +1058,9 @@ macro(process_options)
     mark_as_advanced(MAKE)
     find_program(MAKE NAMES make mingw32-make)
     if(${MAKE} STREQUAL "MAKE-NOTFOUND")
-      message(FATAL_ERROR "Make was not found but it is required by Sphinx docs")
+      message(
+        FATAL_ERROR "Make was not found but it is required by Sphinx docs"
+      )
     elseif(${MAKE} MATCHES "mingw32-make")
       # This is a super wild hack for MinGW
       #
@@ -1253,7 +1255,10 @@ macro(process_options)
   set(PRECOMPILE_HEADERS_ENABLED OFF)
   if(${NS3_PRECOMPILE_HEADERS})
     if(${NS3_CLANG_TIDY})
-      message(${HIGHLIGHTED_STATUS} "Clang-tidy is incompatible with precompiled headers. Continuing without them.")
+      message(
+        ${HIGHLIGHTED_STATUS}
+        "Clang-tidy is incompatible with precompiled headers. Continuing without them."
+      )
     elseif(${CMAKE_VERSION} VERSION_GREATER_EQUAL "3.16.0")
       set(PRECOMPILE_HEADERS_ENABLED ON)
       message(STATUS "Precompiled headers were enabled")
@@ -1395,7 +1400,7 @@ endfunction(set_runtime_outputdirectory)
 
 function(build_exec)
   # Argument parsing
-  set(options IGNORE_PCH)
+  set(options IGNORE_PCH STANDALONE)
   set(oneValueArgs EXECNAME EXECNAME_PREFIX EXECUTABLE_DIRECTORY_PATH
                    INSTALL_DIRECTORY_PATH
   )
@@ -1418,12 +1423,12 @@ function(build_exec)
     )
   endif()
 
-  if(${NS3_STATIC})
+  if(${NS3_STATIC} AND (NOT BEXEC_STANDALONE))
     target_link_libraries(
       ${BEXEC_EXECNAME_PREFIX}${BEXEC_EXECNAME} ${LIB_AS_NEEDED_PRE_STATIC}
       ${lib-ns3-static}
     )
-  elseif(${NS3_MONOLIB})
+  elseif(${NS3_MONOLIB} AND (NOT BEXEC_STANDALONE))
     target_link_libraries(
       ${BEXEC_EXECNAME_PREFIX}${BEXEC_EXECNAME} ${LIB_AS_NEEDED_PRE}
       ${lib-ns3-monolib} ${LIB_AS_NEEDED_POST}

doc/manual/source/working-with-cmake.rst

@@ -1535,6 +1535,13 @@ The path is relative to the ``CMAKE_INSTALL_PREFIX`` (e.g. /usr).
 To set custom compiler defines for that specific executable, defines can be passed
 to the ``DEFINITIONS`` argument.
 
+Add the ``STANDALONE`` option to prevent linking the ns-3 static library
+(``NS3_STATIC``) and single shared library (``NS3_MONOLIB``) to the executable.
+This may be necessary in case the executable redefine symbols which are part
+of the ns-3 library. This is the case for the fd-net-device creators and the tap-creator,
+which include the source file ``encode-decode.cc``, which is also part of fd-net-device module
+and tap-bridge module, respectively.
+
 Finally, to ignore precompiled headers, include ``IGNORE_PCH`` to the list of parameters.
 You can find more information about ``IGNORE_PCH`` at the `PCH side-effects`_ section.
 
@@ -1551,6 +1558,7 @@ You can find more information about ``IGNORE_PCH`` at the `PCH side-effects`_ se
      EXECNAME_PREFIX scratch_subdir_prefix_ # target name = scratch_subdir_prefix_example
      INSTALL_DIRECTORY_PATH ${CMAKE_INSTALL_BIN}/   # e.g. /usr/bin/ns3.37-scratch_subdir_prefix_example-debug
      DEFINITIONS -DHAVE_FEATURE=1           # defines for this specific target
+     [STANDALONE]                           # set in case you don't want the executable to be linked to ns3-static/ns3-monolib
      IGNORE_PCH
    )
 

src/fd-net-device/CMakeLists.txt

@@ -163,6 +163,7 @@ if(${ENABLE_FDNETDEV})
       EXECUTABLE_DIRECTORY_PATH
         ${CMAKE_RUNTIME_OUTPUT_DIRECTORY}/src/fd-net-device/
       INSTALL_DIRECTORY_PATH ${CMAKE_INSTALL_LIBEXECDIR}/ns3
+      STANDALONE
     )
 
     list(
@@ -198,6 +199,7 @@ if(${ENABLE_FDNETDEV})
       EXECUTABLE_DIRECTORY_PATH
         ${CMAKE_RUNTIME_OUTPUT_DIRECTORY}/src/fd-net-device/
       INSTALL_DIRECTORY_PATH ${CMAKE_INSTALL_LIBEXECDIR}/ns3
+      STANDALONE
     )
 
     list(
@@ -235,6 +237,7 @@ if(${ENABLE_FDNETDEV})
       EXECUTABLE_DIRECTORY_PATH
         ${CMAKE_RUNTIME_OUTPUT_DIRECTORY}/src/fd-net-device/
       INSTALL_DIRECTORY_PATH ${CMAKE_INSTALL_LIBEXECDIR}/ns3
+      STANDALONE
     )
 
     list(

src/tap-bridge/CMakeLists.txt

@@ -43,4 +43,5 @@ build_exec(
                model/tap-encode-decode.cc
   EXECUTABLE_DIRECTORY_PATH ${CMAKE_RUNTIME_OUTPUT_DIRECTORY}/src/tap-bridge/
   INSTALL_DIRECTORY_PATH ${CMAKE_INSTALL_LIBEXECDIR}/ns3
+  STANDALONE
 )

utils/tests/test-ns3.py

@@ -1280,7 +1280,12 @@ class NS3ConfigureTestCase(NS3BaseTestCase):
                 self.assertIn("Invalid library name: %s" % invalid_or_nonexistent_library, stderr)
             elif invalid_or_nonexistent_library in ["gsd", "libfi", "calibre"]:
                 self.assertEqual(return_code, 2)  # should fail due to missing library
-                self.assertIn("cannot find -l%s" % invalid_or_nonexistent_library, stderr)
+                # GCC's LD says cannot find
+                # LLVM's LLD says unable to find
+                if "lld" in stdout + stderr:
+                    self.assertIn("unable to find library -l%s" % invalid_or_nonexistent_library, stderr)
+                else:
+                    self.assertIn("cannot find -l%s" % invalid_or_nonexistent_library, stderr)
             else:
                 pass
 
@@ -1611,8 +1616,8 @@ class NS3ConfigureTestCase(NS3BaseTestCase):
             # Delete mold leftovers
             os.remove("./mold-1.4.2-x86_64-linux.tar.gz")
 
-        # Reconfigure to clean leftovers before the next test
-        NS3ConfigureTestCase.cleaned_once = False
+        # Clean leftovers before proceeding
+        run_ns3("clean")
 
 
 class NS3BuildBaseTestCase(NS3BaseTestCase):