Re: [Caml-list] A way to avoid "WARNING: myocamlbuild.cmi occurs in several directories"?

[Anthony Tavener <anthony.tavener@gmail.com>]

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The benefit is editing library code as freely as application code. If I
have to do a separate build/install, and then build/install up the
hierarchy, this becomes a significant pain if it's a bit of code which I'm
doing a edit/test cycle with.

For example, say I have some procedural noise function (in noiselib) which
I'm enhancing, with respect to a particular application (app), and we have
this dependency: app > texturelib > noiselib. I'd rather not have this
process to iterate with:

<noiselib> make; make install_local
<noiselib> cd ../texturelib
<texturelib> make clean; make; make install_local
<texturelib> cd ../app
<app> make clean; make

Also note the "install_local" as opposed to "install" -- this would be a
minor ugliness too. I have applications which rely on more stable versions
of the libraries installed system-wide, and infrequently updated. If I'm
needing a special install process anyway, why install at all? Seems better
to use it in-place.

Creating an "app-local" version of the function in question (extending
modules via include) can work, and I do this, but sometimes the changes are
more complex or pervasive than a single function -- and you don't always
realize the changes are going to escape their initial scope.

I regularly develop libraries in parallel with application code. This was
also the case in the large studios I've worked in (games). Typically there
are a few tiers of library code -- where a library is common code, rather
than rigid code. In practice the library code doesn't change much because
other code depends on it and has fixed the interfaces, but when you do work
with library code, it's in the context of application and needs the benefit
of easy edit/test iteration. I think another view of libraries is much more
standalone, with unit-tests to determine correct behavior. Again, this can
apply in some cases, but perhaps it's less common with an interactive artsy
application like games -- where correctness is more a matter of end-result
behavior, rather than something you can build good unit-tests for.

Thank-you for asking, Gabriel... it helped me sort some of this out for
myself too! The stumbling blocks I'm encountering have made me feel a bit
uncertain -- there's an impedance mismatch which might indicate I'm doing
something inappropriate. Now I think I might just be working with a
slightly different bias: library as shared code, moreso than rigid code...
which might be the assumption the OCaml build ecosystem is working with.
I'm not developing/changing library code in a vacuum -- it's with respect
to higher level usage and results.

A reflection of the distinction between library use... the ossified
libraries (rarely changed, system-wide) are used as packages, while
libraries under active development as part of several apps are... not
installed, and are included by "use_xxx" of ocamlbuild.

Does this make sense?


On Thu, Dec 12, 2013 at 3:33 PM, Gabriel Scherer
<gabriel.scherer@gmail.com>wrote:

> I'm not trying to dismiss your workflow, it's new¹ to me and interesting.
> But is there really such a benefit to the "install-less" part of your
> setup? On the project I've worked on, installation always took a time
> neglectible when compared to compilation or (even more so) unit-testing.
> When you say "immediate use", is there any reason other than speed for
> avoiding a local install? Did you measure the speed difference?
>
> ¹: we've been aware of "huge monolithic builds" used in some OCaml-using
> companies, but they generally use a single build system to direct all the
> build, instead of several separate-but-connected islands of libraries. I
> also use Stog, a static blog engine by Maxence Guesdon, that allows plugin
> and has built-in support for finding them through ocamlfind. In my periods
> of Stog hacking I've always frequently modified and rebuild the plugins, in
> synchronization with evolution Stog's code itself; but then I re-install
> each of them separately and never felt that to be a problem.
>
>
> On Thu, Dec 12, 2013 at 10:47 PM, Anthony Tavener <
> anthony.tavener@gmail.com> wrote:
>
>> (Or a better structure to my build process?)
>>
>> I've recently switched to OPAM and ocamlfind (from manual management and
>> makefiles).
>>
>> I have some libraries which undergo frequent changes -- as frequent as
>> application code. For these, I don't "install" after every change; instead
>> I refer to the _build directory.
>>
>>   ocaml_lib ~extern:true ~dir:"/home/anthony/src/gui/_build" "gui";
>>
>> Now that I'm using ocamlfind (with ocamlbuild) these _build directories
>> are included in a more general sense... causing multiple myocamlbuild.cmi's
>> to be seen -- resulting in "findlib: [WARNING] Interface myocamlbuild.cmi
>> occurs in several directories"
>>
>> Does someone know a way to avoid the inclusion of these spurious
>> myocamlbuild.cmi's, or to suppress the warning, or have another suggestion?
>>
>> The obvious thing is adding an install step which dumps the interesting
>> library files in a local lib dir. But then I'd have two kinds of install: a
>> "package" install (using ocamlfind, and OPAM-friendly), and this
>> immediate-use local install. Yuck, I say.
>>
>>
>> Ultimately what I strive for is install-less build, and build dependency
>> on local library changes. For example:
>>
>> (unit : dependencies)
>>  App1 : Lib2 Lib3
>>  App2 : Lib1 Lib2
>>  Lib1 : -
>>  Lib2 : -
>>  Lib3 : Lib1
>>
>> <~/Lib1> touch lib1file.ml
>> <~/App1> make
>>   Build Lib2
>>   Build Lib1
>>   Build Lib3
>>   Build App1
>>
>> No "install", as these are all in flux. The libraries are just like the
>> app-code but shared. Like they used to be before the world of package
>> management. ;) I'm sure others must still do this for internal development
>> too? Or does everyone work with libraries as explicitly built and
>> separately installed units? (Note: I do have some slowly-evolving libraries
>> which I install as packages via OPAM.)
>>
>> To rephrase: Am I doing it all wrong? :D
>>
>> I haven't figured out how to get ocamlbuild to handle library dependency
>> like this yet. The tools, or at least the examples of how to use them, seem
>> very geared toward usage of infrequently-changed packages. So any tips on
>> an example of using ocamlbuild in this manner would be great too!
>>
>> I'm always hesitant to pester the mailing list, but it generally follows
>> days of frustration on my part, and I don't know any other OCaml people, so
>> thank-you!
>>
>>  -Tony
>>
>>
>

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