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[perl #133391] Bad "Use of uninitialized value within @socks inref-to-glob cast"

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From:
" Ulrich Windl "
Date:
July 18, 2018 10:35
Subject:
[perl #133391] Bad "Use of uninitialized value within @socks inref-to-glob cast"
Message ID:
rt-4.0.24-30587-1531910128-1700.133391-75-0@perl.org
# New Ticket Created by  "Ulrich Windl" 
# Please include the string:  [perl #133391]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/Ticket/Display.html?id=133391 >


This is a bug report for perl from Ulrich.Windl@rz.uni-regensburg.de,
generated with the help of perlbug 1.36 running under perl 5.10.0.


-----------------------------------------------------------------
I wrote a simple test program to send some random UDP packets to a 
specific address, simulating multiple senders, like this:

---
require 5.010;
use strict;

use Socket;

sub x($$)
{
    my ($addr, $proto) = @_;
    my $socket;

    $proto = (getprotobyname($proto))[2];
    die unless ($proto);
    if (socket($socket, PF_INET, SOCK_DGRAM, $proto)) {
        my $port = 0;
        my $my_addr = sockaddr_in($port, $addr);
        unless (bind($socket, $my_addr)) {
            my ($l_port, $l_addr) = sockaddr_in(getsockname($socket));
            die sprintf("bind socket to address %s port %u: %s",
                        inet_ntoa($l_addr), $l_port, $!);
        }
    } else {
        print "socket(): $!\n";
    }
    return $socket;
}

my @socks;
my $d_naddr = inet_aton('some_local_host_name');
my $d_taddr = sockaddr_in(10123, $d_naddr);

$#socks = 9;
while (1) {
    my $i = int(rand(10));
    my $msg = ('A'..'Z', '0'..'9')[rand(36)] x rand(50);
    print "sock $i\n";
    unless ($socks[$i] || int(rand(10)) == 0) {
        if (my $s = x($d_naddr, 'udp')) {
            if ($socks[$i]) {
                print "close sock $i\n";
                close($socks[$i]) or die $!;
            }
            $socks[$i] = $s;
            print "new sock $i\n";
        } else {
            print "new sock $i failed: $!\n";
            next unless ($socks[$i]);
            print "old sock $i\n";
        }
    }
    print "msg $msg\n";
    unless (send($socks[$i], $msg, 0, $d_taddr)) {
        print "send(): $!\n";
    }
    sleep(3);
}
---

However I see errors I (and strace) cannot explain. Like this (partial
strace):

---
sock 9
socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP) = 3
bind(3, {sa_family=AF_INET, sin_port=htons(0), sin_addr=inet_addr("172.20.16.35")}, 16) = 0
new sock 9
msg 777777777777777777777
sendto(3, "777777777777777777777", 21, 0, {sa_family=AF_INET, sin_port=htons(10123), sin_addr=inet_addr("172.20.16.35")}, 16) = 21
sock 0
msg KKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKK
Use of uninitialized value within @socks in ref-to-glob cast at ./tester.pl line 64.
Use of uninitialized value within @socks in ref-to-glob cast at ./tester.pl line 64.
send() on unopened socket at ./tester.pl line 64.
send(): Bad file descriptor
---

So the socket to use is 3, and the send seems successful. Sometimes it takes
quite some time until this error appears. For example:

---
sock 6
new sock 6
msg 4444444444444444
sock 3
new sock 3
msg
send():
sock 9
new sock 9
msg SSSSSSSSSSS
sock 1
new sock 1
msg GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG
sock 4
new sock 4
msg WWWWWWWWWWWWWWWWWWWWWWW
sock 0
new sock 0
msg JJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJ
sock 8
new sock 8
msg GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG
sock 5
new sock 5
msg JJJJJJJJJJJJJ
sock 2
new sock 2
msg AAAAAAAAAAAAAAAA
sock 0
msg UUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU
sock 5
msg TTTTTTTTTTTTTTTTTTTTTTTTTTTTTT
sock 9
msg HHHHHHHHHHHHHHHHHHHHHHH
sock 0
msg LLLLLLLLLLLLLLLLLLLLLLLLLLL
sock 3
msg NNNNNNNNNNN
sock 8
msg VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVV
sock 7
msg QQQQQQQQ
Use of uninitialized value within @socks in ref-to-glob cast at ./tester.pl line 64.
Use of uninitialized value within @socks in ref-to-glob cast at ./tester.pl line 64.
send() on unopened socket at ./tester.pl line 64.
send(): Bad file descriptor
sock 1
msg 7
sock 4
msg VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVV
^C
---

Thus I suspect some obscure error in the Socket module...
Maybe I should add for completeness that the packets being sent are
expected to be returned to the same socket, but I'm not receiving those
yet...


[Please do not change anything below this line]
-----------------------------------------------------------------
---
Flags:
    category=library
    severity=medium
---
This perlbug was built using Perl 5.10.0 - Tue Apr  3 07:43:33 UTC 2018
It is being executed now by  Perl 5.10.0 - Tue Apr  3 07:39:46 UTC 2018.

Site configuration information for perl 5.10.0:

Configured by abuild at Tue Apr  3 07:39:46 UTC 2018.

Summary of my perl5 (revision 5 version 10 subversion 0) configuration:
  Platform:
    osname=linux, osvers=2.6.32, archname=x86_64-linux-thread-multi
    uname='linux sheep58 2.6.32 #1 smp fri jun 14 08:21:43 utc 2013 (ccab990) x86_64 x86_64 x86_64 gnulinux '
    config_args='-ds -e -Dprefix=/usr -Dvendorprefix=/usr -Dinstallusrbinperl -Dusethreads -Di_db -Di_dbm -Di_ndbm -Di_gdbm -Duseshrplib=true -Doptimize=-fmessage-length=0 -O2 -Wall -D_FORTIFY_SOURCE=2 -fstack-protector -funwind-tables -fasynchronous-unwind-tables -g -Wall -pipe -Accflags=-DPERL_USE_SAFE_PUTENV'
    hint=recommended, useposix=true, d_sigaction=define
    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='cc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -DPERL_USE_SAFE_PUTENV -DDEBUGGING -fno-strict-aliasing -pipe -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
    optimize='-fmessage-length=0 -O2 -Wall -D_FORTIFY_SOURCE=2 -fstack-protector -funwind-tables -fasynchronous-unwind-tables -g -Wall -pipe',
    cppflags='-D_REENTRANT -D_GNU_SOURCE -DPERL_USE_SAFE_PUTENV -DDEBUGGING -fno-strict-aliasing -pipe'
    ccversion='', gccversion='4.3.4 [gcc-4_3-branch revision 152973]', 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='cc', ldflags =' -L/usr/local/lib64'
    libpth=/lib64 /usr/lib64 /usr/local/lib64
    libs=-lm -ldl -lcrypt -lpthread
    perllibs=-lm -ldl -lcrypt -lpthread
    libc=/lib64/libc-2.11.3.so, so=so, useshrplib=true, libperl=libperl.so
    gnulibc_version='2.11.3'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E -Wl,-rpath,/usr/lib/perl5/5.10.0/x86_64-linux-thread-multi/CORE'
    cccdlflags='-fPIC', lddlflags='-shared -L/usr/local/lib64'

Locally applied patches:
    

---
@INC for perl 5.10.0:
    /usr/lib/perl5/5.10.0/x86_64-linux-thread-multi
    /usr/lib/perl5/5.10.0
    /usr/lib/perl5/site_perl/5.10.0/x86_64-linux-thread-multi
    /usr/lib/perl5/site_perl/5.10.0
    /usr/lib/perl5/vendor_perl/5.10.0/x86_64-linux-thread-multi
    /usr/lib/perl5/vendor_perl/5.10.0
    /usr/lib/perl5/vendor_perl

---
Environment for perl 5.10.0:
    HOME=/home/windl
    LANG=en_US.UTF-8
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/home/windl/bin:/usr/local/bin:/usr/bin:/bin:/usr/bin/X11:/usr/X11R6/bin:/usr/games:/usr/lib/mit/bin:/usr/lib/mit/sbin
    PERL_BADLANG (unset)
    SHELL=/bin/bash


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