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Re: [PATCH 06/13] Installed header hygiene (BZ#20366): Macros used in #if without checking whether they are defined.

From: Carlos O'Donell <carlos at redhat dot com>
To: Paul Eggert <eggert at cs dot ucla dot edu>, Joseph Myers <joseph at codesourcery dot com>
Cc: Zack Weinberg <zackw at panix dot com>, libc-alpha at sourceware dot org
Date: Wed, 21 Sep 2016 15:09:43 -0400
Subject: Re: [PATCH 06/13] Installed header hygiene (BZ#20366): Macros used in #if without checking whether they are defined.
Authentication-results: sourceware.org; auth=none
References: <20160830011645.25769-1-zackw@panix.com> <20160830011645.25769-2-zackw@panix.com> <20160830011645.25769-3-zackw@panix.com> <20160830011645.25769-4-zackw@panix.com> <20160830011645.25769-5-zackw@panix.com> <20160830011645.25769-6-zackw@panix.com> <20160830011645.25769-7-zackw@panix.com> <670d128e-b21a-b26c-8c5f-bc64bf68527e@redhat.com> <alpine.DEB.2.20.1609211803480.12978@digraph.polyomino.org.uk> <da47bda6-0db1-23e8-faae-5fce33390f70@redhat.com> <462e9837-ef26-3790-7e90-97fbf853a805@cs.ucla.edu>

On 09/21/2016 02:46 PM, Paul Eggert wrote:
> On 09/21/2016 11:40 AM, Carlos O'Donell wrote:
>> Isn't that just a normal coordination issue with gnulib?
> 
> I think so. Gnulib could readily change to follow whatever _LIBC
> practice is thought to be convenient for libc itself.

Thanks for confirming.

Best practice for macro APIs, where possible, is to always define the
macro e.g. set it to 0 or 1, and then enable the use of -Wundef to catch
any mistakes.

This isn't always possible with defines coming from other projects or
the compiler itself (where behaviour is standardized), but in our own
GNU projects I think we could adopt the less error prone usages.

I'm not suggesting Zack tackle this now.

-- 
Cheers,
Carlos.

References:
- Re: [PATCH 06/13] Installed header hygiene (BZ#20366): Macros used in #if without checking whether they are defined.
  - From: Carlos O'Donell
- Re: [PATCH 06/13] Installed header hygiene (BZ#20366): Macros used in #if without checking whether they are defined.
  - From: Joseph Myers
- Re: [PATCH 06/13] Installed header hygiene (BZ#20366): Macros used in #if without checking whether they are defined.
  - From: Carlos O'Donell
- Re: [PATCH 06/13] Installed header hygiene (BZ#20366): Macros used in #if without checking whether they are defined.
  - From: Paul Eggert

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