[m-dev.] sourcing foreign code

[Julien Fischer]

Hi Peter,

On Wed, 26 Feb 2014, Peter Wang wrote:

> Hi,
>
> Writing foreign code inside foreign_code is a bit painful (no syntax
> highlighting, need to escape quotes and backslashes).
> When the amount of foreign code is significant, I would like to keep
> it in a separate file and reference it from the Mercury file.  This is
> possible using the C preprocessor but not ideal:
>
>    * mmc --make does not know about the dependency so you must manually
>      touch the relevant .m file.  Imagine if you switch branches in a
>      workspace and the .c file is touched but not the .m file.
>
>    * you must tell the C compiler where to find the .c file,
>      e.g. with --c-include-dir in Mercury.options
>
>    * only works for C backends
>
> A solution might be to extend pragma foreign_decl/foreign_code like so:
>
>    :- pragma foreign_code("C", source_file("<path>")).
>
> where <path> is _relative to the .m file_, or else an absolute path.

<path> is the (possibly directory qualified) name of the .c file to
include?

> I have not looked into how much work it would be to modify mmc --make,
> but what do you think?

In principle it seems like a worthwhile addition.  I wonder if
include_file might not be a better name than source_file.  Also,
if the .c file has some supporting header files associated with
it how would you handle them in terms of dependencies?

Cheers,
Julien.