The vim code base is around 300K lines of C code.

I found this hard to believe, so I ran it through cloc:

  ----------------------------------------------------
  Language      files      blank    comment       code
  ----------------------------------------------------
  C               113      33366      61819     285817
  vim script     1186      22871      32599     145700
  C/C++ Header     63       3175       4626      19735

Slightly more than 300k, but still mightily impressive.