setting up YCM

Setting up YCM

Prerequisites:

install pyenv and virtual environment as mentioned here.

YCM is a vim plugin , install Vundle first and and then install YCM,

set up Vundle: git clone https://github.com/VundleVim/Vundle.vim.git ~/.vim/bundle/Vundle.vim
Update/create the ~/.vimrc file with following lines. There are detailed instructions here

below here is an example

set nocompatible
filetype off
 
set rtp+=~/.vim/bundle/Vundle.vim
call vundle#begin()
 
" let Vundle manage Vundle, required
Plugin 'VundleVim/Vundle.vim'
Plugin 'Valloric/YouCompleteMe'
 
"All of your Plugins must be added before the following line
call vundle#end()            " required

"Not really needed because of "shared" option when building python
"let g:ycm_path_to_python_interpreter = '$HOME/.pyenv/shims/python'
let g:ycm_clangd_binary_path="/usr/bin/clangd-12"

filetype plugin indent on    " required
"To ignore plugin indent changes, instead use:
"filetype plugin on
"
" Brief help
" :PluginList       - lists configured plugins
" :PluginInstall    - installs plugins; append `!` to update or just :PluginUpdate
" :PluginSearch foo - searches for foo; append `!` to refresh local cache
" :PluginClean      - confirms removal of unused plugins; append `!` to auto-approve removal
"
" see :h vundle for more details or wiki for FAQ
" Put your non-Plugin stuff after this line
 
" :W sudo saves the file when the file is open in readonly mode.
 
"command W w !sudo tee % > /dev/null
 
" ***********  Line **********
" show line numbets
"
set number
 
 
" ********** Indents *********
"replace tabs with spaces
"
set expandtab
" 1 tab =  2 spaces
"
set tabstop=2 shiftwidth=2

" when deleting whitespaces at the begining of a line, delete 1 tab worth of
" spaces
"
set smarttab
 
" when creating a new line, copy the indentation from the line above
"
set autoindent
 
" ********* Search **********
" ignorecase 

set ignorecase
set smartcase
 
" highlight search results 
"
set hlsearch
 
" highlight all pattern matches 
"
set incsearch
 
" ************ Code stuff  *****
"
set showmatch
"set cursorline 

Now install the plugin by launching vim and running :PluginInstall

You may need to update cmake or GCC or LLVM

note that in the above listing I’ve used let g:ycm_clangd_binary_path="/usr/bin/clangd-12" to point to the clangd server.

Configuring projects

The following is taken from the YCM readme and the wiki

If you are using CMake add -DCMAKE_EXPORT_COMPILE_COMMANDS=ON when configuring or add set(CMAKE_EXPORT_COMPILE_COMMANDS ON ) to CMakeLists.txt and copy or symlink the database to the root pf the project.

the second method is having a ycm_extra_conf.py in the project dir (in or above the source dir as it searches upward until it finds a command file or a extra config python file) check this example provided by YCM developers.

def Settings(**kwargs):
  return { 'flags': list_of_compiler_flags,
           'override_filename': path_to_actually_compiled_file }

Note: [Clangd for arm64 can be downloaded(/via apt) here.

for clangd to find the compile_commands.json we need it to be in a top-level directory relative to the source directory.

Note: sadly for this to work you need to run cmake twice (otherwise it won’t see the file)

IF(EXISTS "${CMAKE_CURRENT_BINARY_DIR}/compile_commands.json")
  EXECUTE_PROCESS(COMMAND ${CMAKE_COMMAND} -E create_symlink "${CMAKE_CURRENT_BINARY_DIR}/compile_commands.json" "${PROJECT_SOURCE_DIR}/compile_commands.json")
message(STATUS "******* symlinks generated *******")
ENDIF()

Note: read this blog post for more info