CMake buildsystem

Hi,

I'm not sure on the demand for this, but using CMake enables basically all IDEs through Xcode/Visual Studio/Makefiles/Ninja projects (CLion, Code::Blocks, Visual Studio, Xcode, Eclipse, etc). Those are great for developing, but especially for profiling and debugging. It has been working for the last few years, but it was not in a presentable state.

Tried to make it as a drop-in replacement for waf, with very few changes to upstream code. The changes to upstream code are mostly in test.py to accept executables without ns3ver- and -buildProfileSuffix (which I could reproduce, but choose not to do so for now), a missing header in dhcp-example.cc, a gitignore file and the CI file.

The current version should be able to build most of the ns-3 project without issues and run ./test.py with --nowaf flag. It should also work fine for MinGW/Msys2 with the patches from !437 (merged).

What is missing?

1. Doxygen
2. A code coverage option
3. Python bindings (it is kind of working, but failing for a fd-net-device)
4. Sphinx docs
5. Contribution scripts (still not exactly the same, but closer to the waf version)
6. All-in-one/Bake integration
7. Newer fd-net-devices added in 3.32
8. Linking to boost libraries
9. Examples-as-tests-suites are broken due to waf dependency
10. NSC examples
11. Click
12. MPI
13. Planetlab dependencies
14. Visualizer

What is working but currently not included?

1. Static builds
2. Vcpkg library/dependencies installation
3. Libtorch support (nobody asked for these two, so I'm not including them)
4. Netanim
5. Openflow
6. Brite

How to use?

From the command line (directly)

1. Create a cmake cache folder (e.g. mkdir cmake_cache && cd cmake_cache)
2. Call cmake to generate the build system files and copy headers to ns-3-dev/build/ns3

• (e.g. cmake -DCMAKE_BUILD_TYPE=debug -G"Ninja" -DNS3_TESTS=ON -DNS3_EXAMPLES=ON ..)
• All flag options like NS3_TESTS|NS3_EXAMPLES are located in the CMakeLists.txt file in ns-3-dev.

3. Call the build system (e.g. ninja)

• Not that different from waf , except for the fact the header copy isn't triggered every time you try to rebuild things.

From the command line (via waf-like wrapper)

1. If you run ./ns3 configure, the CMake project will be configured with the default settings
2. If you run ./ns3 build, the entire project will be built. If you specify a target to be built (either a module or an executable), it will get built along with its dependencies (e.g. ./ns3waf build wifi)
3. If you run ./ns3 --run example, it will refresh the CMake cache, then build and then run the example
4. If you run ./ns3 --gdb|--valgrind --run example, it will execute all the previous steps but execute the program through gdb|valgrind
5. If you run ./ns3 configure -G Ninja, the CMake project will be configured to use the specified generator (in this case Ninja)

From IDEs that do not support CMake projects (e.g. Code::Blocks)

Same instructions for command line, but choosing "Unix Makefiles" or "MinGW Makefiles" as the CMake generator (-G). Then open the IDE and load the Makefile in the cmake cache folder. Targets to build/run/debug should be available for libraries/tests/examples/docs if enabled.

From IDEs that support CMake projects (e.g. CLion and Visual Studio)

Just open the ns-3-dev folder, right click the CMakeLists file and click to load the CMake project. It will automatically generate the cache and load the targets to build/run/debug.

I've more details at https://gabrielcarvfer.github.io/NS3/installation. I can rewrite the docs properly depending on the demand/feedback.

EDIT: Adding a list of supported switches and their mapping to CMake.

Main wscript option switches

--enable-gcov and --lcov-report : NS3_COVERAGE=ON|OFF
--lcov-zerocounters: NS3_COVERAGE_ZERO_COUNTERS=ON|OFF
--no-task-lines: depend on the buildsystem, not sure CMake can silence this. Supported in ns3waf.py --no-task-lines.
--run, --run-no-build, --visualize, --gdb, --valgrind: ns3waf.py --run|--run-no-build|--visualize|--gdb|--valgrind
--command-template, --pyrun and --pyrun-no-build: in the works for ns3waf.
--doxygen-no-build, --docset: probably require two targets per command, one depending on the libraries/executables and other not depending on them
--enable-sudo: not implemented. Assuming running `sudo ninja|make|etc` would do the trick
--enable-tests/--disable-tests: NS3_TESTS=ON|OFF
--enable-examples/--disable-examples: NS3_EXAMPLES=ON|OFF  
--enable-static: NS3_STATIC=ON|OFF
--enable-mpi: NS3_MPI=ON|OFF
--enable-des-metrics: NS3_DES_METRICS=ON|OFF
--enable-cxx-standard: CMAKE_CXX_STANDARD=11|14|...
--enable-asserts: NS3_ASSERT=ON|OFF
--enable-logs: NS3_LOG=ON|OFF

src/wscript option switches

--enable-rpath: enabled by default
--enable-modules: currently not implemented. Assumed it was not needed since only the necessary libraries are built for a selected target. Brite, click, mpi, openflow, visualizer and tap-bridge are only built if NS3_BRITE, NS3_CLICK, NS3_MPI, NS3_OPENFLOW, NS3_PYTHON_BINDINGS and NS3_TAP are enabled.