Re: [PATCH] ob-C.el compile-only header argument, was Re: How to use mpirun with C or C++ Org-babel?

[Ihor Radchenko]

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

>> #+begin_src C :compile-only t :file foo :includes "stdio.h"
>> printf("This is test");
>> #+end_src
>
> It should be "yes" not "t".

I tested with :compile-only yes, but it did not change the observed
issue.

>> , executing should yield file link, even though it is not explicitly
>> specified.
>
> Ok. But, isn't it a responsibility of org-babel to ensure that if :file
> is set and :results is not, then the parameter list that is passed to
> org-babel-*-execute includes a correctly set :result-params field
> (i.e. it includes "file")? I mean, the docs say [1]:
>
> ‘file’                                                                  
>      Interpret as a filename.  Save the results of execution of the code
>      block to that file, then insert a link to it.  
>
> I would prefer not to fiddle in ob-*.el to implement a policy that
> should be implemented at a higher level.
>
> [1] (info "(org) Results of Evaluation"):

No, it is not the responsibility of ob-core. Simply because :file "name"
may imply multiple things that only the backend can determine.

:results value :file foo.txt means "execute src block, take its return
value, and save it to file foo.txt"

:results file link :file foo.txt means a completely different thing -
"execute src block for side effect, and insert link to file specified in
:file argument; assume that the file is created by the side effect"

So, when :results is not specified, ob-core leaves it up to the backend
to decide what kind of output to produce.

>> Basically, Org babel promises DWIM behavior when :results type is not
>> explicitly stated.
>
> I am happy to modify the patch to make ob-C.el conform to the stated (or
> implied) Org policies. But, "dwim" hurts my head.

May you please elaborate why "dwim" is a problem?

>> And when you have compilation error,
>>
>> #+begin_src C :compile-only t :file foo :includes "stdio.h"
>> printf("This is test")
>> #+end_src
>>
>> the result may be empty - buffer displayed by `org-babel-eval' is
>> probably enough.
>
> Can you tell me what behaviour you expect? No #+RESULTS: ?

No. The purpose of this example was to illustrate that the same set of
header arguments should _not_ yield [[file:foo]] link in the results, in
contrast to when no compilation error is produced.

-- 
Ihor Radchenko // yantar92,
Org mode contributor,
Learn more about Org mode at <https://orgmode.org/>.
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