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[perl #54198] readlink() returns result along with garbage

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From:
Denis Melnikov
Date:
May 15, 2008 09:48
Subject:
[perl #54198] readlink() returns result along with garbage
Message ID:
rt-3.6.HEAD-11257-1210851465-1428.54198-75-0@perl.org
# New Ticket Created by  "Denis Melnikov" 
# Please include the string:  [perl #54198]
# in the subject line of all future correspondence about this issue. 
# <URL: http://rt.perl.org/rt3/Ticket/Display.html?id=54198 >


To: perlbug@perl.org
Subject: readlink() returns result along with garbage
Reply-To: dmelnik@regent.ru
Message-Id: <5.8.8_16640_1210847066@hq-data.msk.regent.ru>

This is a bug report for perl from dmelnik@regent.ru,
generated with the help of perlbug 1.35 running under perl v5.8.8.


-----------------------------------------------------------------
[Please enter your report here]
Hi,
There's a problem with readlink().

print readlink("/proc/13917/exe");
results in:
/usr/sbin/squidr.pyo (deleted)

While it should be '/usr/sbin/squid'.
Actually there are \0's in the resulting string:

00000000  2f 75 73 72 2f 73 62 69  6e 2f 73 71 75 69 64 00  |/usr/sbin/squid.|
00000010  72 2e 70 79 6f 00 00 00  00 00 00 00 00 00 00 00  |r.pyo...........|
00000020  20 28 64 65 6c 65 74 65  64 29                    | (deleted)|

As far as I understand, C's readlink() and shell's readlink(1) work
fine 'cause they see \0 termination, while Perl doesn't use it.

The problem has appeared today, yesterday the code worked fine.

[Please do not change anything below this line]
-----------------------------------------------------------------
---
Flags:
    category=core
    severity=medium
---
This perlbug was built using Perl v5.8.8 in the Red Hat build system.
It is being executed now by Perl v5.8.8 - Wed Jan  9 11:30:38 CST 2008.

Site configuration information for perl v5.8.8:

Configured by Red Hat, Inc. at Wed Jan  9 11:30:38 CST 2008.

Summary of my perl5 (revision 5 version 8 subversion 8) configuration:
  Platform:
    osname=linux, osvers=2.6.18-8.1.15.el5, archname=x86_64-linux-thread-multi
    uname='linux linux55.fnal.gov 2.6.18-8.1.15.el5 #1 smp mon oct 22 09:47:50 edt 2007 x86_64 x86_64 x86_64 gnulinux '
    config_args='-des -Doptimize=-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic -Dversion=5.8.8 -Dmyhostname=localhost -Dperladmin=root@localhost -Dcc=gcc -Dcf_by=Red Hat, Inc. -Dinstallprefix=/usr -Dprefix=/usr -Dlibpth=/usr/local/lib64 /lib64 /usr/lib64 -Dprivlib=/usr/lib/perl5/5.8.8 -Dsitelib=/usr/lib/perl5/site_perl/5.8.8 -Dvendorlib=/usr/lib/perl5/vendor_perl/5.8.8 -Darchlib=/usr/lib64/perl5/5.8.8/x86_64-linux-thread-multi -Dsitearch=/usr/lib64/perl5/site_perl/5.8.8/x86_64-linux-thread-multi -Dvendorarch=/usr/lib64/perl5/vendor_perl/5.8.8/x86_64-linux-thread-multi -Darchname=x86_64-linux -Dvendorprefix=/usr -Dsiteprefix=/usr -Duseshrplib -Dusethreads -Duseithreads -Duselargefiles -Dd_dosuid -Dd_semctl_semun -Di_db -Ui_ndbm -Di_gdbm -Di_shadow -Di_syslog -Dman3ext=3pm -Duseperlio -Dinstallusrbinperl=n -Ubincompat5005 -Uversiononly -Dpager=/usr/bin/less -isr -Dd_gethostent_r_proto -Ud_endhostent_r_pro
 to -Ud_sethostent_r_proto -Ud_endprotoent_r_proto -Ud_setprotoent_r_proto -Ud_endservent_r_proto -Ud_setservent_r_proto -Dinc_version_list=5.8.7 5.8.6 5.8.5 -Dscriptdir=/usr/bin'
    hint=recommended, useposix=true, d_sigaction=define
    usethreads=define use5005threads=undef useithreads=define usemultiplicity=define
    useperlio=define d_sfio=undef uselargefiles=define usesocks=undef
    use64bitint=define use64bitall=define uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='gcc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -fno-strict-aliasing -pipe -Wdeclaration-after-statement -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -I/usr/include/gdbm',
    optimize='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic',
    cppflags='-D_REENTRANT -D_GNU_SOURCE -fno-strict-aliasing -pipe -Wdeclaration-after-statement -I/usr/local/include -I/usr/include/gdbm'
    ccversion='', gccversion='4.1.1 20070105 (Red Hat 4.1.1-52)', gccosandvers=''
    intsize=4, longsize=8, ptrsize=8, doublesize=8, byteorder=12345678
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=16
    ivtype='long', ivsize=8, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8
    alignbytes=8, prototype=define
  Linker and Libraries:
    ld='gcc', ldflags =''
    libpth=/usr/local/lib64 /lib64 /usr/lib64
    libs=-lresolv -lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lpthread -lc
    perllibs=-lresolv -lnsl -ldl -lm -lcrypt -lutil -lpthread -lc
    libc=/lib/libc-2.5.so, so=so, useshrplib=true, libperl=libperl.so
    gnulibc_version='2.5'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E -Wl,-rpath,/usr/lib64/perl5/5.8.8/x86_64-linux-thread-multi/CORE'
    cccdlflags='-fPIC', lddlflags='-shared -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic'

Locally applied patches:
    

---
@INC for perl v5.8.8:
    /usr/lib64/perl5/site_perl/5.8.8/x86_64-linux-thread-multi
    /usr/lib64/perl5/site_perl/5.8.7/x86_64-linux-thread-multi
    /usr/lib64/perl5/site_perl/5.8.6/x86_64-linux-thread-multi
    /usr/lib64/perl5/site_perl/5.8.5/x86_64-linux-thread-multi
    /usr/lib/perl5/site_perl/5.8.8
    /usr/lib/perl5/site_perl/5.8.7
    /usr/lib/perl5/site_perl/5.8.6
    /usr/lib/perl5/site_perl/5.8.5
    /usr/lib/perl5/site_perl
    /usr/lib64/perl5/vendor_perl/5.8.8/x86_64-linux-thread-multi
    /usr/lib64/perl5/vendor_perl/5.8.7/x86_64-linux-thread-multi
    /usr/lib64/perl5/vendor_perl/5.8.6/x86_64-linux-thread-multi
    /usr/lib64/perl5/vendor_perl/5.8.5/x86_64-linux-thread-multi
    /usr/lib/perl5/vendor_perl/5.8.8
    /usr/lib/perl5/vendor_perl/5.8.7
    /usr/lib/perl5/vendor_perl/5.8.6
    /usr/lib/perl5/vendor_perl/5.8.5
    /usr/lib/perl5/vendor_perl
    /usr/lib64/perl5/5.8.8/x86_64-linux-thread-multi
    /usr/lib/perl5/5.8.8
    .

---
Environment for perl v5.8.8:
    HOME=/root
    LANG=en_US.UTF-8
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/usr/kerberos/sbin:/usr/kerberos/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin
    PERL_BADLANG (unset)
    SHELL=/bin/bash


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