When programming in C and C++ you usually split your function prototypes and actual functions into a .h/.hpp and .c/.cpp file. Sadly it's very tedious to transfer the function prototypes from one file to another, and requires opening both files at the same time (or a good memory), as well as a lot of unnecessary typing, especially when changes to the arguments or member names are made.



int someFunction(int someArgument);

class someClass

     int anotherFunction(int anotherArgument);


#include "foo.hpp"

int someFunction(int someArgument)
    // Code goes here

    // Code goes here

    // Code goes here   

int someClass::anotherFunction(int anotherArgument)
    // Code goes here


Is there a way to automatically create and update the functions in foo.cpp using the definitions and prototypes in foo.hpp?

2 Answers 2


Whew, this one was fun!

:g/.*\n^{/yank A<cr>:bn<cr>pkdd:%s/$/;/<cr>:g/::/d B<cr>A<cr><cr>class <cr>{<cr>};<esc>"BP:%s/[^ ]\+:://<cr>j%jyt(kk$p=ipjA<cr>public:<esc>

You can go ahead and map that to a single keystroke in your .vimrc:

nnoremap <C-b> :g/.*\n^{/yank A<cr>:bn<cr>pkdd:%s/$/;/<cr>:g/::/d B<cr>A<cr><cr>class <cr>{<cr>};<esc>"BP:%s/[^ ]\+:://<cr>j%jyt(kk$p=ipjA<cr>public:<esc>

Note that this assumes that the constructor is the first class method to appear. (I could fix that, but I'd rather keep it simple. Please do mention in a comment if you need that fixed.)

This also assumes that your header file buffer is empty and located directly after your source file buffer.

Step-by-step explanation:

:g/.*\n^{/yank A<cr>            Yank all the function definitions (power of g!)
:bn<cr>                         Move to the header file buffer
pkdd                            Put in the function definitions
:%s/$/;/<cr>                    Add semicolons
:g/::/d B<cr>                   Grab the class methods and put them in register B
A<cr><cr>class <cr>{<cr>};<esc> Self-explanatory, add class skeleton
"BP                             Put the class methods in the class
:%s/[^ ]\+:://<cr>              Remove someClass::
j%jyt(kk$p                      Add the actual class name
=ip                             Fix indentation
jA<cr>public:<esc>              Add the `public:' modifier
  • 1
    While this is impressive (I'm rather new to vim, so I'm discovering new things every day!), I'm afraid this isn't at all what I need. Maybe I should look into making my own plugin? It seems like a fun thing to do.
    – Lukas
    Feb 6, 2015 at 3:31
  • 2
    @Lukas In what way doesn't a mapping in your .vimrc solve the problem? Simply hitting Ctrl-B will then automatically fill out the header file for you. (I should probably make it clear the header file before replacing it with an updated version, but I have to sleep so I might do that later.) A plugin does sound interesting; keep me updated if you decide to make one. And thanks for the interesting challenge to sharpen up my Vim skills! ;)
    – Doorknob
    Feb 6, 2015 at 3:52
  • 2
    This seems to work in the opposite direction from the request: it creates a header file from the .cpp file. Feb 6, 2015 at 18:51
  • ... which would also be nice, actually, but I think there are some things that can't be known from the definition: e.g., is the declaration supposed to be inline? Are there default arguments? Should the argument names be elided? Aug 26, 2015 at 17:52
  • @200_success Ah, you're right (I don't know why I didn't reply to your comment earlier). When I have time, I'll try to edit my answer to go the other way.
    – Doorknob
    Aug 26, 2015 at 18:59

The :GOTOIMPL command from lh-cpp is able to jump to a function definition from its declaration, or to provide a default empty definition in the case none was found.

Some features I can think of:

  • The command already understands comments, exception specifications, keywords that shall not be copied (but possibly copied within comments)(virtual, static, ...).
  • The current scope of the function is decoded (namespaces::classes::...) and correctly reported (i.e. it won't prefix with ns:: if we are within namespace ns{ or a using namespace ns; context.


  • Templates are not (yet) understood.
  • Function body are to be built manually one after the other -- i.e. I haven't yet took the time to execute :GOTOIMPL on all function declarations that ctags could points me.

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