[m-dev.] warning suppression pragmas

[Peter Wang]

On Mon, 27 May 2013 15:11:33 +1000 (EST), Julien Fischer <jfischer at opturion.com> wrote:
> 
> Hi all,
> 
> The following concerns the first of the changes listed in this diff
> of Zoltan's:
> 
>      <http://lists.mercurylang.org/pipermail/reviews/2011-April/015128.html>
> 
> along with my (unaddressed) review comments concerning it:
> 
>      <http://lists.mercurylang.org/pipermail/reviews/2011-April/015129.html>
> 
> Zoltan's diff introduced the pragma `no_determinism_warning' that can be used
> to suppress the warning that the compiler emits if a predicate's determinism
> declaration is too lax.  The original change was committed but never
> documented.
> 
> In my review comments, I suggest generalising this mechanism so that other
> per-predicate warnings can be suppressed,
> 
>      :- pragma suppress_warnings(<pred>/<arity>, [<warnings>])
> 
> where <warnings> is one of: `lax_determinism' or `inferred_erroneous'.
> There are a few others that would be useful to disable in some circumstances
> as well, for example `unknown_format_calls'.
> 

`pragma no_warn' would match command-line options and `pragma no_inline'.

> A modification of this proposal is to add another pragma that suppresses
> module level warnings.
> 
>      :- pragma suppress_module_warnings([<module warnings>]).
> 

Module-level warnings can already be handled by Mercury.options.

> Under this proposal the original, suppress_warnings/2 pragma would become:
> 
>      :- pragma suppress_pred_warnings(<pred>/<arity>, [<pred warnings>])
> 
> I am looking for feedback about whether either of my proposed generalisations
> should be implemented.  (Or indeed any other feedback regarding the original
> diff.)

I prefer we added as few such things as possible.  I haven't really
needed either your suggestions, I think.

Sometimes I would like to suppress the warnings about dead procedures
related to a mutable, when I used some but not all of the procedures
that it generated (don't have an example at hand).  But maybe the dead
procs pass should just be smarter.

Peter