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Subject: Re: Problem with new acl code and cdrtools
From: Warren Young <wyml AT etr-usa DOT com>
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Date: Mon, 8 Feb 2016 21:14:10 -0700
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On Feb 8, 2016, at 9:59 AM, Ismail Donmez <ismail AT i10z DOT com> wrote:
> 
> On Mon, Feb 8, 2016 at 6:29 PM, Peter Rosin <peda AT lysator DOT liu DOT se> wrote:
>> On 2016-02-08 14:31, Ismail Donmez wrote:
>>> This is a generic code so I don't want to add a cygwin specific
>>> dependency there. Is there a preprocessor definition for cygwin
>>> version? I could use that to disable HAVE_SUN_ACL for cygwin 2.5+
>> 
>> Pardon me for butting in, but isn't adding a Cygwin version check
>> about as non-generic as it gets?
>> 
>> Wouldn't something like this work:
>> 
>> .../configure ac_cv_func_aclfromtext=no
> 
> Thats a hack :)

I don’t know if that smiley means you’re joking or if you’re just trying to soften a negative judgement, but Peter’s proposal is as far from a hack as it gets.

He is proposing that you write an autoconf test that determines if the platform has this new ACL behavior.  Then in your C code:

   #include <config.h>
   #if HAVE_FUNC_ACLFROMTEXT
   #  include <cygwin/acl.h>
   #endif

Now you’re not dependent on Cygwin header file #defines that don’t exist yet, and will continue to not exist on older Cygwin installs.  You only include the Cygwin header if your autoconf test determines that this is necessary.

This is standard Autoconf practice: check for features, not for platforms or platform versions.  This practice comes from 40+ years of Unix portability experience, which is that platform and version tests often break, but feature tests rarely do.
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