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Re: [perl #32032] defined may incorrectly returns true in 5.8.X
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From:
Nick Ing-Simmons
Date:
October 19, 2004 06:21
Subject:
Re: [perl #32032] defined may incorrectly returns true in 5.8.X
Message ID:
20041019132110.5043.2@llama.elixent.com
Austin Schutz <perl5-porters@perl.org> writes:
># New Ticket Created by Austin Schutz
># Please include the string: [perl #32032]
># in the subject line of all future correspondence about this issue.
># <URL: http://rt.perl.org:80/rt3/Ticket/Display.html?id=32032 >
>
>
> Included is a message I sent to the Expect.pm list regarding the
>behavior of IO::Tty. What I discovered while debugging the error was very
>strange behavior of defined(). I was able to recreate this error using both
>perl 5.8.0 and 5.8.4, so I suspect it is a bug endemic to the 5.8 series.
>
> In order to recreate the bug, TIOCSCTTY must not be defined. This
>may be accomplished by using a system which doesn't define this constant
>or by commenting out or undefining it.
>
> After building IO::Tty, make test will warn "warning: TIOCSCTTY failed"
>because the test if(defined TIOCSCTTY) at line 118 succeeds even though
>TIOCSCTTY is set to undef, and is clearly set as such by the module.
If TIOSCTTY isn't a constant sub it is a bareword i.e. a string.
So that is like writing
if (defined("TIOSCTTY"))
ands strings are always defined.
I think it should be written as
if (defined(&TIOSCTTY) && TIOSCTTY())
>
> IO::Tty version was 1.02, I've recreated this on a couple systems
>verying both by perl version and OS, so I'm not including my perl -V
>information here.
>
> Please let me know if there is anything I can do to help fix
>this bug or provide more relevant information.
>
> Thanks muchly,
>
> Austin
>
>----- Forwarded message from Austin Schutz <tex@off.org> -----
>
>> Date: Fri, 8 Oct 2004 13:48:13 -0700
>> From: Austin Schutz <tex@off.org>
>> To: Roland Giersig <RGiersig@cpan.org>
>> Cc: Austin Schutz <tex@off.org>, Zhisong Jin <jjin@dynaccsys.com>,
>> expectperl-discuss@lists.sourceforge.net
>> Subject: Re: [Expectperl-discuss] re: building Expect.pm on solaris 9
>>
>> On Fri, Oct 08, 2004 at 11:28:37AM +0200, Roland Giersig wrote:
>> >
>> > Hmm, in the 'perl Makefile.PL' step I'm trying to figure out what
>> > constants are defined by compiling test progs for each constant. Austin,
>> > as you seem to have a solaris machine on your hands, could you look into
>> > that and see why it gets defined?
>> >
>>
>> On my solaris machine I'm not able to replicate the issue because
>> I'm running an old perl: 5.00503, which doesn't exhibit this problem and
>> I can't get 5.8.4 to compile.
>> However, I _was_ able to replicate this on my home linux workstation
>> by commenting out #define TIOCSCTTY in /usr/include/asm/ioctls.h.
>>
>> I'm not sure why the code in question is being executed. Running
>> it in the debugger I still couldn't figure it out (output follows). It looks
>> to me like a perl bug. However, I was able to work around it by changing line
>> 118 to:
>>
>> if (defined TIOCSCTTY && TIOCSCTTY) {
>>
>> which _should_ be valid - I doubt any vendor defines TIOCSCTTY as 0.
>>
>> Austin
>>
>> DB<5> p defined TIOCSCTTY
>>
>> DB<6> l
>> 118==> if (defined TIOCSCTTY) {
>> 119: if (not defined ioctl( ${*$self}{'io_pty_slave'}, TIOCSCTTY, 0 )) {
>> 120: warn "warning: TIOCSCTTY failed, slave might not be set as control
>> ling terminal: $!" if $^W;
>> 121 }
>> 122 } elsif (defined TCSETCTTY) {
>> 123: if (not defined ioctl( ${*$self}{'io_pty_slave'}, TCSETCTTY, 0 )) {
>> 124: warn "warning: TCSETCTTY failed, slave might not be set as control
>> ling terminal: $!" if $^W;
>> 125 }
>> 126 }
>> 127
>> DB<6> s
>> IO::Pty::make_slave_controlling_terminal(/root/.cpan/build/IO-Tty-1.02/blib/lib/
>> IO/Pty.pm:119):
>> 119: if (not defined ioctl( ${*$self}{'io_pty_slave'}, TIOCSCTTY, 0 )) {
>> DB<6> p defined TIOCSCTTY
>>
>> DB<7> p defined TIOCSCTTY
>>
>> DB<8> if(defined TIOCSCTTY) { print "defined\n"; }
>>
>> DB<9> n
>> IO::Pty::make_slave_controlling_terminal(/root/.cpan/build/IO-Tty-1.02/blib/lib/IO/Pty.pm:119):
>> 119: if (not defined ioctl( ${*$self}{'io_pty_slave'}, TIOCSCTTY, 0 )) {
>> DB<9> n
>> Use of uninitialized value in ioctl at /root/.cpan/build/IO-Tty-1.02/blib/lib/IO/Pty.pm line 119, <XT> line 1.
>> IO::Pty::make_slave_controlling_terminal('IO::Pty=GLOB(0x8171f8c)') called at test.pl line 66
>> IO::Pty::make_slave_controlling_terminal(/root/.cpan/build/IO-Tty-1.02/blib/lib/IO/Pty.pm:120):
>> 120: warn "warning: TIOCSCTTY failed, slave might not be set as controlling terminal: $!" if $^W;
>
>----- End forwarded message -----
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