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[perl #116589] open2 acts very strange when STDOUT is redirected.

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From:
Xungeng Lee
Date:
January 30, 2013 07:07
Subject:
[perl #116589] open2 acts very strange when STDOUT is redirected.
Message ID:
rt-3.6.HEAD-27190-1359527894-1895.116589-75-0@perl.org
# New Ticket Created by  Xungeng Lee 
# Please include the string:  [perl #116589]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org:443/rt3/Ticket/Display.html?id=116589 >


This is a bug report for perl from xungeng@gmail.com,
generated with the help of perlbug 1.39 running under perl 5.14.2.


-----------------------------------------------------------------
[Please describe your issue here]

see this example:
xungeng@debian:~/work/test/test$ cat foo
#!/usr/bin/perl
use FileHandle;
use IPC::Open2;
use IO::Handle;

#*STDOUT = IO::Handle->new;

for (1..3) {
        print STDERR "Loop: $_\n";
        $pid = open2( \*Reader, \*Writer, "cat" );
        Writer->autoflush(); # default here, actually
        print Writer "stuff\n";
        $got = <Reader>;
        print STDERR $got;
}
xungeng@debian:~/work/test/test$ cat bar
#!/usr/bin/perl
use FileHandle;
use IPC::Open2;
use IO::Handle;

*STDOUT = IO::Handle->new;

for (1..3) {
        print STDERR "Loop: $_\n";
        $pid = open2( \*Reader, \*Writer, "cat" );
        Writer->autoflush(); # default here, actually
        print Writer "stuff\n";
        $got = <Reader>;
        print STDERR $got;
}
xungeng@debian:~/work/test/test$ ./foo > /dev/null
Loop: 1
stuff
Loop: 2
stuff
Loop: 3
stuff
xungeng@debian:~/work/test/test$ ./bar > /dev/null
Loop: 1
Loop: 2
Loop: 3

the difference between foo and bar is only that STDOUT redirected or not.

when STDOUT is redirected, open2 make the child process write to the old
STDOUT,
not the child_out handler (\*Reader in this example).




[Please do not change anything below this line]
-----------------------------------------------------------------
---
Flags:
    category=library
    severity=high
    module=IPC::Open2
---
Site configuration information for perl 5.14.2:

Configured by Debian Project at Mon Dec 10 13:17:22 UTC 2012.

Summary of my perl5 (revision 5 version 14 subversion 2) configuration:

  Platform:
    osname=linux, osvers=3.2.0-4-686-pae,
archname=i486-linux-gnu-thread-multi-64int
    uname='linux callisto 3.2.0-4-686-pae #1 smp debian 3.2.32-1 i686
gnulinux '
    config_args='-Dusethreads -Duselargefiles -Dccflags=-DDEBIAN
-D_FORTIFY_SOURCE=2 -g -O2 -fstack-protector --param=ssp-buffer-size=4
-Wformat -Werror=format-security -Dldflags= -Wl,-z,relro
-Dlddlflags=-shared -Wl,-z,relro -Dcccdlflags=-fPIC
-Darchname=i486-linux-gnu -Dprefix=/usr -Dprivlib=/usr/share/perl/5.14
-Darchlib=/usr/lib/perl/5.14 -Dvendorprefix=/usr
-Dvendorlib=/usr/share/perl5 -Dvendorarch=/usr/lib/perl5
-Dsiteprefix=/usr/local -Dsitelib=/usr/local/share/perl/5.14.2
-Dsitearch=/usr/local/lib/perl/5.14.2 -Dman1dir=/usr/share/man/man1
-Dman3dir=/usr/share/man/man3 -Dsiteman1dir=/usr/local/man/man1
-Dsiteman3dir=/usr/local/man/man3 -Duse64bitint -Dman1ext=1 -Dman3ext=3perl
-Dpager=/usr/bin/sensible-pager -Uafs -Ud_csh -Ud_ualarm -Uusesfio -Uusenm
-Ui_libutil -DDEBUGGING=-g -Doptimize=-O2 -Duseshrplib
-Dlibperl=libperl.so.5.14.2 -des'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=define, usemultiplicity=define
    useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef
    use64bitint=define, use64bitall=undef, uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='cc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN
-fstack-protector -fno-strict-aliasing -pipe -I/usr/local/include
-D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
    optimize='-O2 -g',
    cppflags='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN -fstack-protector
-fno-strict-aliasing -pipe -I/usr/local/include'
    ccversion='', gccversion='4.7.2', gccosandvers=''
    intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=12345678
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12
    ivtype='long long', ivsize=8, nvtype='double', nvsize=8, Off_t='off_t',
lseeksize=8
    alignbytes=4, prototype=define
  Linker and Libraries:
    ld='cc', ldflags =' -fstack-protector -L/usr/local/lib'
    libpth=/usr/local/lib /lib/i386-linux-gnu /lib/../lib
/usr/lib/i386-linux-gnu /usr/lib/../lib /lib /usr/lib
    libs=-lgdbm -lgdbm_compat -ldb -ldl -lm -lpthread -lc -lcrypt
    perllibs=-ldl -lm -lpthread -lc -lcrypt
    libc=, so=so, useshrplib=true, libperl=libperl.so.5.14.2
    gnulibc_version='2.13'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
    cccdlflags='-fPIC', lddlflags='-shared -L/usr/local/lib
-fstack-protector'

Locally applied patches:


---
@INC for perl 5.14.2:
    /etc/perl
    /usr/local/lib/perl/5.14.2
    /usr/local/share/perl/5.14.2
    /usr/lib/perl5
    /usr/share/perl5
    /usr/lib/perl/5.14
    /usr/share/perl/5.14
    /usr/local/lib/site_perl
    .

---
Environment for perl 5.14.2:
    HOME=/home/xungeng
    LANG=en_US.UTF-8
    LANGUAGE=en_US:en
    LD_LIBRARY_PATH=/usr/local/lib/
    LOGDIR (unset)

PATH=/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games:/home/xungeng/bin:/usr/local/go/bin
    PERL_BADLANG (unset)
    SHELL=/bin/bash

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