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[perl #114878] Regular Expression matching in signal handler causes side-effects

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From:
tim @ electronghost . co . uk
Date:
September 13, 2012 10:28
Subject:
[perl #114878] Regular Expression matching in signal handler causes side-effects
Message ID:
rt-3.6.HEAD-11172-1347527342-287.114878-75-0@perl.org
# New Ticket Created by  tim@electronghost.co.uk 
# Please include the string:  [perl #114878]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org:443/rt3/Ticket/Display.html?id=114878 >



This is a bug report for perl from tim@electronghost.co.uk,
generated with the help of perlbug 1.39 running under perl 5.14.2.


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

Using Safe signals...
If a signal arrives while a regular expression is being processed, and the
signal handler contains an RE itself, then the original RE is silently not
executed, causing bugs which appear "impossible".

Here is a test case:

====== CUT HERE ======
#!/usr/bin/env perl

sub sighup {
    my $bar="This-Has-Dashes-HUP";
    $bar=~s/.*-//;
    print "$bar\n";
    
}

$SIG{'HUP'}=\&sighup;

while (1) {
    my $foo="This:Has:Colons";
    $foo=~s/.*://;
    if ($foo=~m/:/) {
        print "BUG!!: $foo\n";
    }
}
====== CUT HERE ======

Run this endless loop and arrange to send it a SIGHUP once per second.

On PERL 5.14 (and, presumably, later versions) you see the following output:

bash$ perl ./t.pl
HUP
HUP
HUP
HUP
BUG!!: This:Has:Colons
HUP
HUP
BUG!!: This:Has:Colons
HUP
BUG!!: This:Has:Colons
HUP
BUG!!: This:Has:Colons
HUP
HUP
BUG!!: This:Has:Colons
HUP
BUG!!: This:Has:Colons
HUP
HUP
BUG!!: This:Has:Colons
HUP
HUP
HUP
BUG!!: This:Has:Colons

On PERL 5.12 and earlier, you see correct output:

bash$ perl ./t.pl
HUP
HUP
HUP
HUP
HUP
HUP
HUP
HUP
HUP
HUP
HUP
HUP
HUP
HUP
HUP

Silently failing to execute code seems like a critical failure, so marking
this critical :-)


[Please do not change anything below this line]
-----------------------------------------------------------------
---
Flags:
    category=core
    severity=critical
---
This perlbug was built using Perl 5.14.2 in the Fedora build system.
It is being executed now by Perl 5.14.2 - Wed May 30 14:55:10 UTC 2012.

Site configuration information for perl 5.14.2:

Configured by Red Hat, Inc. at Wed May 30 14:55:10 UTC 2012.

Summary of my perl5 (revision 5 version 14 subversion 2) configuration:
   
  Platform:
    osname=linux, osvers=2.6.32-220.4.1.el6.x86_64, archname=x86_64-linux-thread-multi
    uname='linux x86-14.phx2.fedoraproject.org 2.6.32-220.4.1.el6.x86_64 #1 smp thu jan 19 14:50:54 est 2012 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 -Dccdlflags=-Wl,--enable-new-dtags -Dlddlflags=-shared -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4  -m64 -mtune=generic -Wl,-z,relro  -DDEBUGGING=-g -Dversion=5.14.2 -Dmyhostname=localhost -Dperladmin=root@localhost -Dcc=gcc -Dcf_by=Red Hat, Inc. -Dprefix=/usr -Dvendorprefix=/usr -Dsiteprefix=/usr/local -Dsitelib=/usr/local/share/perl5 -Dsitearch=/usr/local/lib64/perl5 -Dprivlib=/usr/share/perl5 -Dvendorlib=/usr/share/perl5/vendor_perl -Darchlib=/usr/lib64/perl5 -Dvendorarch=/usr/lib64/perl5/vendor_perl -Darchname=x86_64-linux-thread-multi -Dlibpth=/usr/local/lib64 /lib64 /usr/lib64 -Duseshrplib -Dusethreads -Duseithreads -Dusedtrace=/usr/bin/dtrace -Duselargefiles -Dd_semctl_semun -Di_db -Ui_ndbm -Di_gdbm -Di_shadow -Di_syslog -Dman3ext=3pm -Duseperlio -Dinstallusrbin!
 perl=n -Ubincompat5005 -Uversiononly -Dpager=/usr/bin/less -isr -Dd_gethostent_r_proto -Ud_endhostent_r_proto -Ud_sethostent_r_proto -Ud_endprotoent_r_proto -Ud_setprotoent_r_proto -Ud_endservent_r_proto -Ud_setservent_r_proto -Dscriptdir=/usr/bin'
    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='gcc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
    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 -fstack-protector -I/usr/local/include'
    ccversion='', gccversion='4.7.0 20120507 (Red Hat 4.7.0-5)', 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 =' -fstack-protector'
    libpth=/usr/local/lib64 /lib64 /usr/lib64
    libs=-lresolv -lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lpthread -lc -lgdbm_compat
    perllibs=-lresolv -lnsl -ldl -lm -lcrypt -lutil -lpthread -lc
    libc=, so=so, useshrplib=true, libperl=libperl.so
    gnulibc_version='2.15'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,--enable-new-dtags -Wl,-rpath,/usr/lib64/perl5/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 -Wl,-z,relro '

Locally applied patches:
    

---
@INC for perl 5.14.2:
    /usr/local/lib64/perl5
    /usr/local/share/perl5
    /usr/lib64/perl5/vendor_perl
    /usr/share/perl5/vendor_perl
    /usr/lib64/perl5
    /usr/share/perl5
    .

---
Environment for perl 5.14.2:
    HOME=/home/tim
    LANG=en_US.UTF-8
    LANGUAGE=
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/usr/lib64/qt-3.3/bin:/usr/local/bin:/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/sbin:/usr/sbin:/home/tim/bin
    PERL_BADLANG (unset)
    SHELL=/bin/bash


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