The Find Unused Code script

Overview

This script reads the tags file (which can be generated using ctags -R .) and uses it to search for unused identifiers (functions, macros, etc.) via git grep (note that the git grep command is executed for every identifier in the tags file).

It provides the following functions:

• parse_ctags_file(use_cnt: int) - Read the ./tags file and load the found info into global dictionaries. Call this function before the very first one; the others are meaningless without it.

  • @use_cnt - all identifiers appearing more frequently than use_cnt are not loaded. Default 1

• get_identifiers(identifier_type: str, count: int) - get an array of string containing identifiers.

  • @identifier_type - identifier type, single letter string - 'f', 'd'; Default '?' - combine all identifiers; '!dfs' - include evrything, except 'd', 'f', 's'.
  • @count - return identifiers that appear exactly count times. Default 1.

• print_identifiers(cnt: int) - display the total number of identifiers in group.

  • cnt - print identifiers that appear exactly count times. Default 1, "unused".

Types of identifiers (from ctags):

- 'd' - macro
- 'f' - function
- 's' - structure name
- 'u' - unuion name
- 'm' - struct/union member
- 't' - typedef
- 'e' - enumerators (values inside an enum)
- 'g' - enumeration (enum names)
- 'h' - included header
- 'v' - variable

Integration with Vim

I originally planned to use it from Vim, so here is a part of my ~/.vimrc file:

py3file ~/scripts/uc/fuc.py

let g:fuc_info = []
let g:fuc_index = 0
function FucParse()
    :py3 parse_ctags_file()
    echo "Success"
endfunction
":call FucLoad('d') - load unused macros
function FucLoad(identifier_type)
    let cmd = printf('get_identifiers("%s", %s)', a:identifier_type, a:use_count)

    let g:fuc_info = py3eval(cmd)
    let g:fuc_index = 0
    echo len(g:fuc_info) . " identifiers found"
endfunction

function FucJumpToNext()
    execute "tag " . g:fuc_info[g:fuc_index]
    let g:fuc_index += 1
endfunction

function FucShowUnused()
	echo py3eval("print_identifiers()")
endfunction


nnoremap <F6> :call FucJumpToNext() <CR>

Thus, usage boils down to opening the required file, calling FucParse() and FucLoad(), and then simply pressing F6:

$ vim hal/hal_com.c
(vim) :call FucParse()
    ... wait a few seconds ...
(vim) :call FucLoad('d')
(vim) <F6>, <F6>...
(vim) <C-t>, <C-t>...
(vim) :tabnew ...

Execution from the terminal

Run the script with the --check_code flag to check the C source code in the current directory and output brief statistics using print_identifiers():

python ./path/to/fuc.py --check-code ./

Running the script without parameters has no effect; it is intended for correct loading from ~/.vimrc