Macro expansion C/C++

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created April 10, 2014 · complexity basic · author TTRh · version 7.0

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This tip shows a function to expand a C/C++ macro using the gcc compiler.

The function expands a specific line in a preview window as the gcc compiler sees it. Normally this function deals with severals tab/buffer/windows.

Macro expansion with gcc

Here is the function :

function! ExpandCMacro()
  "get current info
  let l:macro_file_name = "__macroexpand__" . tabpagenr()
  let l:file_row = line(".")
  let l:file_name = expand("%")
  let l:file_window = winnr()
  "create mark
  execute "normal! Oint " . l:macro_file_name . ";"
  execute "w"
  "open tiny window ... check if we have already an open buffer for macro
  if bufwinnr( l:macro_file_name ) != -1
    execute bufwinnr( l:macro_file_name) . "wincmd w"
    setlocal modifiable
    execute "normal! ggdG"
  else
    execute "bot 10split " . l:macro_file_name
    execute "setlocal filetype=cpp"
    execute "setlocal buftype=nofile"
    nnoremap <buffer> q :q!<CR>
  endif
  "read file with gcc
  silent! execute "r!gcc -E " . l:file_name
  "keep specific macro line
  execute "normal! ggV/int " . l:macro_file_name . ";$\<CR>d"
  execute "normal! jdG"
  "indent
  execute "%!indent -st -kr"
  execute "normal! gg=G"
  "resize window
  execute "normal! G"
  let l:macro_end_row = line(".")
  execute "resize " . l:macro_end_row
  execute "normal! gg"
  "no modifiable
  setlocal nomodifiable
  "return to origin place
  execute l:file_window . "wincmd w"
  execute l:file_row
  execute "normal!u"
  execute "w"
  "highlight origin line
  let @/ = getline('.')
endfunction

A useful mapping to call the function is:

autocmd FileType cpp nnoremap <leader>m :call ExpandCMacro()<CR>

The function depends on the gnu program indent which could be replaced by some tricky search/replace operations.

Preview

1/2

Comments

Any ideas about the preview? It shows nothing for me, presumably because I don't have all scripts enabled. JohnBeckett (talk) 06:17, April 11, 2014 (UTC)