Use Vundle.vim to install this plugin
Plugin 'yongzhy/vim-cflags'
Only one global veriable is required, g:c_define_file points to the file has all global defines.
let g:c_define_file="f:/flags.h"
Example of the define file:
#define _HELLO_ 1
#define _WORLD_ 0
cflags#SynUpdate() will update current buffer to gray out those inactive code blocks cflags#PrintDefine() will display the flag value under cursor
nnoremap <leader>bu :call cflags#SynUpdate()<cr>
nnoremap <leader>fv :call cflags#PrintDefine()<cr>