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From: "Dave Korn" <dave DOT korn AT artimi DOT com>
To: <cygwin AT cygwin DOT com>
Subject: RE: Define _POSIX_SOURCE in cygwin's features.h?
Date: Thu, 12 Jan 2006 18:13:16 -0000
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Christopher Faylor wrote:
> On Thu, Jan 12, 2006 at 05:40:35PM -0000, Dave Korn wrote:
>> Christopher Faylor wrote:
>>> Someone on the cygwin irc channel had a problem building a package
>>> which would have been solved if Cygwin defined _POSIX_SOURCE.
>>> 
>>> I know that Cygwin is not fully POSIX compliant (I really really do)
>>> but I'm wondering if setting _POSIX_SOURCE in the cygwin headers
>>> wouldn't solve more porting problems than it creates.

>> As far as I can tell by googling, _POSIX_SOURCE, despite the leading
>> underscore, is in fact a user-land feature test macro that it is up to
>> each individual application to decide whether to switch it on or not
>> according to whether the application itself is compliant or not.
> 
> No need to use google.  Just grep for it in /usr/include on linux.

  Um, I know all about the -A/-B/-C switches that get grep to show you the
context around the search match, but I don't know what option switch you pass
to grep to get  it to show you the semantic meaning of the matched text....

> _POSIX_SOURCE is defined in features.h on linux under control of the
> _GNU_SOURCE macro.
>
>   /* If _GNU_SOURCE was defined by the user, turn on all the other
>   features.  */ #ifdef _GNU_SOURCE

... which is equally something that belongs to and is under control of the
user's application, and is a way for the user's application to specify (to the
compiler, C runtime, and whoever else) that it's compliant and requires/copes
with POSIX compliant source in the system header files.

> So, let me clarify.  Should we define _POSIX_SOURCE similarly to the way
> that linux does it?  This may mean that we have to define _GNU_SOURCE
> also and maybe that's not a good idea but, again, it might solve more
> problems than it causes.

  I think it means that whoever you were talking to in the IRC channel should
have defined _POSIX_SOURCE in their application, and the bug is that they
didn't when they should have.

    cheers,
      DaveK
-- 
Can't think of a witty .sigline today....


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