RE: [Caml-list] Interface(.mli) location

[David Allsopp <dra-news@metastack.com>]

moosotc@gmail.com wrote:
> David Allsopp <dra-news@metastack.com> writes:
> > moosotc@gmail.com wrote:
> >> David Allsopp <dra-news@metastack.com> writes:
> >> > moosotc@gmail.com wrote:
> >> >> Gabriel Scherer <gabriel.scherer@gmail.com> writes:
> >> >>
> >> >> > It is correct that ocamldep assumes that the .ml and .mli of a
> >> >> > given module are at the same place, but this is not the case for
> >> >> > the rest of the compilation chain, which is either concerned
> >> >> > with single source files (a .ml file or a .mli file) or with
> >> >> > "compilation units" (a .cmo and .cmi files passed together,
> >> >> > independently of where their source files were). In particular,
> >> >> > all type-checking tools do look in -I directories to find .cmi
> >> >> > files for the dependencies of the module being compiled (and at
> >> >> > this stage
> >> they do not care for .mli files).
> >> >>
> >> >> But the script seems to (somewhat) contradict this, i.e. after
> >> >> `ocamlc -I d -c a.ml' ocamlc ignores the presence of .mli inside
> >> >> subdirectory d/, producing both .cmi/.cmo when when compiling a.ml.
> >> >
> >> > The -I option specifies extra directories for compiled files only,
> >> > so it's correct that the compiler ignores d/a.mli.
> >>
> >> After sending the first post I've realized that: ocamlc -c d/a.mli
> >> was forgotten, but even after adding that to the script things do not
> >> change, i.e. following compilation of a.ml with -I d where d contains
> >> a.cmi still produces both a.cmo and a.cmi in the top-level directory.
> >
> > Indeed - but that's the correct documented behaviour, even if not
> > necessarily the ideal. There are various things you can do:
> >
> > a) Delete ./a.cmi as part of your build procedure. This isn't ideal,
> > though, because you lose the type-checking against d/a.cmi
> > b) Have an empty ./a.mli but never compile it - the compiler will then
> > unify ./a.cmo against d/a.cmi. This isn't ideal because having a
> > source file which you don't expect to compile will confuse dependency
> > generators and automatic build rules.
> > c) Implement a new option in the compiler driver which suppresses the
> > automatic generation of .cmi files (e.g. ocamlc -c -I d -no-cmi a.ml)
> 
> d) Make the compiler skip generation of .cmi if it sees one in the -I
>    directories?

No - I think the use-case is too niche to justify breaking backwards compatibility. That's potentially a very subtle way to break someone else's existing build system. The existing behaviour is precisely documented in the manual (even if it's not necessarily the best approach).


David