Mail Archives: cygwin/2002/02/04/10:10:28
Gerrit P. Haase wrote:
>Hmmm, I'm still confused a little. Isn't '010' as TRUE as '011'?
Yes, 010 is as true as 011. However, the $^S returns 0 or 1. The example
snippet shows the output of 3 separate reads of $^S. I print the output as
a string of zero's and ones just for simplicity -- it was just an easy way
to show what the values of $^S were.
perl -e 'print $^S || 0;eval {print $^S || 0}; print $^S || 0;' decomposes
to 3 statements:
1: print $^S || 0;
2: eval { print $^S || 0};
3: print $^S || 0;
= 3 separate times I print 1 or 0. The only reason I did "|| 0" was in case
$^S was undef I wanted to print 0 (perl prints nothing for an undef value)
-- I really shouldn't have done that since in fact it masked another bug --
see statement below. The reason perl is buggy for this example is that after
the eval (statement #2 above) $^S should have a value of 0 but instead it
has a value of 1. $^S should be 1 ONLY inside an eval. Also, I didn't
catch it (because I had the || 0 above) but the first read of $^S is also
buggy -- it returns undef when it should be 0. On Cygwin perl 5.6.1:
$ perl -e 'print "undef" if not defined $^S'
undef
$^S should be 0 not undef in that example.
So, the effect of having $^S be 1 outside an eval is that a custom DIE or
WARN handler cannot determine if it's inside an eval or not and this is
important to know.
Hope that helps. Regards,
--Rhet
----Original Message Follows----
From: "Gerrit P. Haase" <gerrit AT familiehaase DOT de>
Reply-To: gerrit AT familiehaase DOT de
To: "Rhet Turnbull" <RhetTbull AT hotmail DOT com>,
<cygwin AT cygwin DOT com>
Subject: Re: bug in Cygwin perl 5.6.1?
Date: Sun, 3 Feb 2002 22:03:36 +0100
Am 2 Feb 2002 um 17:58 hat Rhet Turnbull geschrieben:
>Gerrit P. Haase wrote:
>> Why? Where is docu about this?
>
>The perl documentation for $^S in the perlvar manpage states:
>
>$^S Current state of the interpreter. Undefined if
> parsing of the current module/eval is not finished
> (may happen in $SIG{__DIE__} and $SIG{__WARN__}
> handlers). True if inside an eval(), otherwise
> false.
>
>The "True if inside an eval(), otherwise false" is what I was getting at.
I
Previous mail:
>>>There seems to be a bug in Cygwin's perl (5.6.1). The
>>>following code:
>>>
>>>perl -e 'print $^S || 0;eval {print $^S || 0}; print
>>>$^S || 0;'
>>>
>>>should produce '010'
>ran into this since I was writing a custom SIG{__DIE__} handler (which
needs
>to know if you're inside an eval where die is an exception catching
>mechanism or in normal code where die means to exit with error.) The bug
is
>that after executing an eval(), $^S stays true even though it should be
>false outside the scope of the eval.
Hmmm, I'm still confused a little. Isn't '010' as TRUE as '011'?
>I reported this to perlbug and they've acknowledged that it's a known bug
>that will be fixed in next release.
Thanks,
Gerrit--
=^..^=
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