A warning about warnings

[Damien Doligez <damien.doligez@inria.fr>]

Hello World,

I've been compiling OCaml programs and libraries lately, and I've seen
this kind of things in make output:

    ocamlc -w A -warn-error A ....

or even:

    ocamlc -w Ael -warn-error Ael ....


You should not do that, because it means your build will break with
the next version of OCaml that adds a new warning, even if that
warning is disabled by default for compatibility reasons, as soon
as your code triggers the new warning (which it will do, due to
Murphy's law).

What you should do instead:

    ocamlc -w ELZ -warn-error A ....

and

    ocamlc -w Z -warn-error A ....

Or completely refrain from using -warn-error A and only activate
the error option on explicit sets of warnings.

Better yet, you could remove the -warn-error option from your
released Makefiles, and reserve it for development.

Happy hacking,

-- Damien