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my emacs version is 24.3.1.

i understand i have to put the ob-C.el (available from here) in a path where Emacs can read it.

i first copy-pasted the code from that .el file to my .emacs file and restarted emacs. then i went to a C code block (within an org file) and tried to execute it (using C-c C-c). the minibuffer said 'no org-babel-execute function for C'. the same story played out with trying to execute a C++ code block. note that R and python evaluate perfectly from within my org files. the problems seems to be only with these compiled languages.

i then tried putting this ob-C.el inside the ~/.emacs.d directory to see if that helped matters. restarted emacs and checked. it didn't work.

then i tried putting it into a directory ~/.emacs.d/lisp and added the following lines to my .emacs file

(add-to-list 'load-path "~/.emacs.d/lisp/")
(load "ob-C.el")
(require 'ob-C)

after restarting emacs, evaluating the C or C++ code blocks from within an org file still doesn't work. i keep getting the same error "no org-babel-execute function for C" or "no org-babel-execute function for C++".

Update

i upgraded my emacs version to 24.5, deleted all the previous elpa and melpa subdirectories in my ~/.emacs.d directory. suspecting that it had to do with the order in which i placed my 

(custom-set-variables

'(org-babel-load-languages
(quote
((emacs-lisp . t)
 (C . t)
 (css . t)
 (sh . t)
 (awk . t)
 (R . t))))

and 

;; load the pathnames to custom lisp files
(add-to-list 'load-path "~/.emacs.d/lisp/")
(load "ob-C.el")
(require 'ob-C)

code blocks, i put the load "ob-C.el" before the org-babel-load-languages thing. i then executed the c++ code block multiple times. no luck.

then i removed everything (cleaned out the custom-set-variables block in the .emacs file) and now my .emacs file looks like 

;; load the pathnames to custom lisp files
(add-to-list 'load-path "~/.emacs.d/lisp/")
(load "ob-C.el")
(require 'ob-C)

;; load the languages that are needed
(org-babel-do-load-languages
'org-babel-load-languages '((C . t)))

Its still not working.

The code that i am trying to evaluate in an orgmode buffer is : 

#+BEGIN_SRC c
printf("Hello world");
#+END_SRC

My Messages buffer looks like this after restarting emacs and attempting to execute the above code block : 

Loading /home/taeten/.emacs.d/lisp/ob-C.el (source)...done
Wrote /home/taeten/.emacs.d/.emacs.desktop.lock
Desktop: 1 frame, 0 buffers restored.
For information about GNU Emacs and the GNU system, type C-h C-a.
Quit [2 times]
Making completion list... [3 times]
org-babel-execute-src-block: No org-babel-execute function for c! [5   
times]
Ignoring unknown mode `elisp-mode'
File local-variables error: (void-function elisp-mode)
byte-code: Beginning of buffer [6 times]
byte-code: Beginning of buffer
Arjun J Rao
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    You really don't need the `load` and `require` bits. `require` does loading (in case the file has a `provide` statement, which in this case it does), but you also don't need the `require` because this is handled by `org-babel-do-load-languages`, you do need to make sure to require `org` before any of that happens. Also, I think it's `C` not `c`, did you try that? – wvxvw Oct 30 '15 at 16:43
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    ohh damn... it worked ! C (not c) and C++ (not c++) inside the #+BEGIN_SRC block was what it took after having done all the 'load' statements in the right order. Thanks a lot man ! – Arjun J Rao Oct 31 '15 at 01:46

2 Answers2

33

You really only need this bit in your init file:

(org-babel-do-load-languages
 'org-babel-load-languages '((C . t)))

Note it's a capital C. This enables Babel to process C, C++ and D source blocks.

wvxvw
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    Its not working still. I tried removing the earlier ob-c.el crap too. Still not working. Same error message "No org-babel-execute function for c++" – Arjun J Rao Oct 27 '15 at 13:25
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    @ArjunJRao did you evaluate the code after adding it? (It's ok to evaluate it multiple times). The error message technically means that it couldn't find `org-babel-execute:c++` function, which would be defined in `ob-C.el`, but the way to tell Babel that it needs to load `ob-C.el` is to call `org-babel-do-load-languages`. – wvxvw Oct 27 '15 at 14:30
  • i updated my question. – Arjun J Rao Oct 29 '15 at 05:06
  • I've just bumped into this myself, the issue is that you been "#+begin_src C" with a capital C as well as all capital C in the configuration as mentioned prior. It provides C syntax highlighting without the lower c, making it hard to realize – syntaxError Sep 30 '20 at 19:20
0

It should be a capital 'C' not a lower case 'c' for the name of the source code block.

#+BEGIN_SRC C
#+END_SRC

After solving this independently, I noticed @syntaxError also posted this solution above in the comments for @wvxvw's answer. I am submitting it here as an answer because it might be hard to see in a comment on an answer.

Chase Minor
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  • Thanks. Yes, Q&A needs to be in the Q&A. Comments aren't searchable, and they can be deleted at any time. – Drew Nov 14 '20 at 05:42