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Re: "unused parameter" warnings


From: Jim Meyering
Subject: Re: "unused parameter" warnings
Date: Sat, 18 Oct 2008 21:29:36 +0200

Bruno Haible <address@hidden> wrote:
> Jim Meyering wrote:
>> However, it would be good to accept patches (at least for gnulib's .h
>> files) that mark each unused parameter with __attribute__ ((__unused__)).
>> Then, a project that requires use of -Wunused-parameter can use gnulib's
>> headers without having to relax their standards.
>
> I agree regarding gnulib's public .h files. I'll handle unistr.h.
>
>> although I admit to disliking the seemingly necessary duplication of
>> the snippet to define __attribute__.
>
> One could define __attribute__, or a special-purpose macro, in an extra
> module. But then keeping track of the module dependency is some work.
> It's easier to define it in generated config.h always.
>
> I propose this. A special-purpose macro called _UNUSED_PARAMETER_ is as
> understandable as is __attribute__ ((__unused__)), and may accomodate other
> compilers (whereas #defining __attribute__ is gcc specific).

It's a trade off.
"stand-alone" usability (i.e., outside of gnulib context)
vs. maintainability.  I've learned that as gnulib matures,
the value of the former is diminishing.

> gcc 2.7.2.3 already supported __attribute__ ((__unused__)), as far as I can
> see.
>
> 2008-10-18  Bruno Haible  <address@hidden>
>
>       Avoid -Wunused-parameter warnings in public gnulib header files.
>       * m4/gnulib-common.m4 (gl_COMMON_BODY): Define _UNUSED_PARAMETER_ as a
>       macro.
>       * lib/unistr.h (u32_mbtouc_unsafe, u32_mbtouc): Use it.

This is a good change.

Whether to replace all existing __attribute__ ((__attribute__))
uses with _UNUSED_PARAMETER_ is a harder call.




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