warnigns pragma and -w (solved: Re: Constant subroutine __USE_POSIX undefined (problem with p2ph?))

[Florian Hinzmann <f.hinzmann@mcs-cityline.net>]

Hello Kurt!

Thanks for your answer. 


On Thu, 14 Nov 2002 12:47:53 -0500
"Kurt D. Starsinic" <kstar@cpan.org> wrote:

> On Nov 14, Florian Hinzmann wrote:
> > I do get lines like this when running a perl script:
> > 
> > > Constant subroutine __USE_POSIX undefined at /usr/lib/perl/5.8.0/features.ph line 6.
> > > Constant subroutine __USE_POSIX2 undefined at /usr/lib/perl/5.8.0/features.ph line 7.
> > > Constant subroutine __USE_POSIX199309 undefined at /usr/lib/perl/5.8.0/features.ph line 8.
> > > Constant subroutine __USE_POSIX199506 undefined at /usr/lib/perl/5.8.0/features.ph line 9.
> > > Constant subroutine __USE_XOPEN undefined at /usr/lib/perl/5.8.0/features.ph line 10.

> 
>     I'm the upstream guy.  You're seeing all of those useless warnings
> because you're executing features.ph with warnings turned on.  They can
> be silenced thusly:
> 
>         {
>             no warnings;
>             require "features.ph";
>         }

This did not work. The following did:
{
  local ($^W) = 0;
  #no warnings;
  require "sys/ioctl.ph";
}

(Note: sys/ioctl.ph 'requires' features.ph)

I have learned something about this by reading perllexwarn(1). This
is how far I got:
The warnings above are compile time warnings triggered by running perl
with "-w". "use warnings" does not enable compile time warnings, but 
using "-w" does. 

Writing "no warnings" inside a block did not turn them off, but 
"local ($^W) = 0" did. This solved my problem for now, but left
me confused.

As far as I understand perllexwarn(1) "-w" is kind of depreciated
and the "warnings" pragma should be used instead. But the pragma
does not give me compile time warnings like "-w". I have no idea
currently if this is bad, that is which kind of errors compile time
warnings will catch.


perllexwarn(1) says about the warning pragma:
'It also means that the pragma setting will not leak across files (via "use",
 "require" or "do").'
Is this the reason your proposed solution did not work?


This whole issue isn't very pressing for my any longer as I can
continue programming without warnings. But would really like 
to understand the implications of different warning settings as
I don't write perl scripts without warnings turned on.
Therefore I would be thankful for anyone who is able to
bring some light into this issues.


  Regards
     Florian



-- 
  Florian Hinzmann
  mailto:f.hinzmann@mcs-cityline.net
  http://www.mcs-cityline.net