If doom is your favorite editor and you want to work on ns-3 with doom then follow these steps:

• Have doom emacs and ns-3 installed.

• Make sure your init.el file has cc with lsp enabled:
  

(cc +lsp)

• You will need to generate a file called compile_commands.json.

• Depending on your version of ns-3 you might use waf or cmake for that.

• on cmake, add the following to your cmake compilation command:
  

cmake -DCMAKE_EXPORT_COMPILE_COMMANDS=ON ...

• on waf, the document is automatically generated inside the build folder.

• Move the compile_commands.json file to the root of your ns3 folder.

• Enjoy your autocompletion:

• You can use g d to jump to the definition of an identifier.