Re: How to use mpirun with C or C++ Org-babel?

[Ihor Radchenko <yantar92@posteo.net>]

Leo Butler <Leo.Butler@umanitoba.ca> writes:

> From 7d8e406bc4a92e2e2eab772b2671dcd72ca8c202 Mon Sep 17 00:00:00 2001
> From: Leo Butler <leo.butler@umanitoba.ca>
> Date: Tue, 12 Dec 2023 12:32:41 -0600
> Subject: [PATCH] lisp/ob-C.el: add :compile-only header to compile to a named
>  target

Thanks for the patch!

> * lisp/ob-C.el (org-babel-C-execute): The new header argument,
> `:compile-only', causes source and compiled binary files to be named
> using the `:file' header argument.  When `:compile-only' is set,
> execution of source block ends at compilation.  The naming of source
> and binary filenames is factored out to `org-babel-C-src/bin-file'.

What will happen if we have something like :results value or :results
output instead of :results file link?

> * lisp/ob-C.el (org-babel-C-src/bin-file): A new function that factors
> out the setting of source and binary filenames.  It also signals an
> error if `:compile-only' is set, but `:file' is not.
> * testing/examples/ob-C-test.org: Add three example that exercise the
> `:compile-only' header argument, including one that causes an error.
> * testing/lisp/test-ob-C.el: Add three tests of the `:compile-only'
> header argument.  New tests: ob-C/set-src+bin-file-name-{1,2,3}.

You should also announce the new feature in ORG-NEWS and document it in
WORG.

> +                                    (compile-only . (nil no t yes)))

Why nil/t? No other header argument allow "nil" or "t". Just yes/no.

> +(defun org-babel-C-src/bin-file (params src? compile-only?)
> +  "Return the src or bin filename to `org-babel-C-execute'.
> +
> +If `SRC?' is T, a file extension is added to the filename.  By

Just SRC?. You should only quote Elisp symbols and upcase the function
arguments. See
https://www.gnu.org/software/emacs/manual/html_node/elisp/Documentation-Tips.html

Also, why upcase "T"?

> +default, the filename is created by `org-babel-temp-file'. If
> +`COMPILE-ONLY?' is T, the filename is taken from the `:file'

I think quoting :file is not necessary.

> +field in `PARAMS'; if that is NIL, an error occurs."

No need to upcase NIL.
Also, "if that is nil, throw an error" - this is more common style
(saying what function does).

> +  (let ((f (cdr (assq :file params))))

Please avoid short variable names - they are harder to understand and
search in code.

> +    (when (and compile-only? (null f))
> +      (error "Error: When COMPILE-ONLY is T or YES, output FILE needs to be set"))

t or "yes". Also, what does "output FILE" refer to? Upcasing implies
function argument, but you are referring to :file header argument in PARAMS.

> +    (let* ((file (cond (compile-only? f) (src? "C-src-") (t "C-bin-")))
> +           (ext (if src? (pcase org-babel-c-variant
> +	                   (`c ".c") (`cpp ".cpp") (`d ".d"))

We usually split `cond' and `case' into multiple lines for readability.
Otherwise, it is confusing, especially in `let' forms where one can
confuse `cond' forms with `let' bindings.

> +    (unless compile-only?
> +      (let ((results
> +	     (org-babel-eval
> ...

No return value at all? I'd expect file link to be returned, as we
discussed in another thread. Also, see the above considerations about
:results value/output. We might want return the compiler output for
:results output. Or maybe even arrange `org-babel-eval-error-notify' to
display compile-mode window when there are compilation warnings.

> --- a/testing/examples/ob-C-test.org
> +++ b/testing/examples/ob-C-test.org
> @@ -174,3 +174,29 @@ std::cout << "\"line 1\"\n";
>  std::cout << "\"line 2\"\n";
>  std::cout << "\"line 3\"\n";
>  #+end_src

If you can, please avoid adding tests as Org files where possible.
Instead, we prefer using `org-test-with-temp-text' or
`org-test-with-temp-text-in-file' when the Org fragment for the test is
not too long.

-- 
Ihor Radchenko // yantar92,
Org mode contributor,
Learn more about Org mode at <https://orgmode.org/>.
Support Org development at <https://liberapay.com/org-mode>,
or support my work at <https://liberapay.com/yantar92>