[perl #24423] ignoring SIGCHLD corrupts system() return value

# New Ticket Created by  dbarmann@brick.net 
# Please include the string:  [perl #24423]
# in the subject line of all future correspondence about this issue. 
# <URL: http://rt.perl.org/rt2/Ticket/Display.html?id=24423 >



This is a bug report for perl from dbarmann@brick.net,
generated with the help of perlbug 1.34 running under perl v5.8.0.


-----------------------------------------------------------------
[Please enter your report here]

It seems that in some environments (but not all), ignoring SIGCHLD
corrputs the return value of system().

For a discussion on PerlMonks, see this thread:

   http://www.perlmonks.org/index.pl?node_id=304587

With assistance from those at PerlMonks, here are two programs that
illustrate the effect:


> ./prog1.pl
prog2.pl exited normally, returning 5
> ./prog1.pl ignore
prog2.pl was terminated with signal 127



--------- prog1.pl ----------
#!/usr/bin/perl
use POSIX;
if(@ARGV){ $SIG{'CHLD'} = 'IGNORE'; }
system('./prog2.pl');
$status=$?;

if(WIFEXITED($status)){
 print "prog2.pl exited normally, returning ",
       WEXITSTATUS($status), "\n";
}elsif(WIFSIGNALED($status)){
 print "prog2.pl was terminated with signal ",
       WTERMSIG($status), "\n";
}elsif(WIFSTOPPED($status)){
 print "prog2.pl is stopped for signal ",
       WSTOPSIG($status), "\n";
}else{
 print "can't understand what happened to prog2.pl; ",
       "status is ",$status,"\n";
}


--------- prog2.pl ----------
#!/usr/bin/perl
exit 5;




[Please do not change anything below this line]
-----------------------------------------------------------------
---
Flags:
    category=core
    severity=low
---
Site configuration information for perl v5.8.0:

Configured by bhcompile at Tue Feb 18 22:17:47 EST 2003.

Summary of my perl5 (revision 5.0 version 8 subversion 0) configuration:
  Platform:
    osname=linux, osvers=2.4.20-2.48smp, archname=i386-linux-thread-multi
    uname='linux stripples.devel.redhat.com 2.4.20-2.48smp #1 smp thu feb 13 11:44:55 est 2003 i686 i686 i386 gnulinux '
    config_args='-des -Doptimize=-O2 -march=i386 -mcpu=i686 -g -Dmyhostname=localhost -Dperladmin=root@localhost -Dcc=gcc -Dcf_by=Red Hat, Inc. -Dinstallprefix=/usr -Dprefix=/usr -Darchname=i386-linux -Dvendorprefix=/usr -Dsiteprefix=/usr -Dotherlibdirs=/usr/lib/perl5/5.8.0 -Duseshrplib -Dusethreads -Duseithreads -Duselargefiles -Dd_dosuid -Dd_semctl_semun -Di_db -Ui_ndbm -Di_gdbm -Di_shadow -Di_syslog -Dman3ext=3pm -Duseperlio -Dinstallusrbinperl -Ubincompat5005 -Uversiononly -Dpager=/usr/bin/less -isr'
    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=undef use64bitall=undef uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='gcc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -DTHREADS_HAVE_PIDS -DDEBUGGING -fno-strict-aliasing -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -I/usr/include/gdbm',
    optimize='-O2 -march=i386 -mcpu=i686 -g',
    cppflags='-D_REENTRANT -D_GNU_SOURCE -DTHREADS_HAVE_PIDS -DDEBUGGING -fno-strict-aliasing -I/usr/local/include -I/usr/include/gdbm'
    ccversion='', gccversion='3.2.2 20030213 (Red Hat Linux 8.0 3.2.2-1)', gccosandvers=''
    intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12
    ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8
    alignbytes=4, prototype=define
  Linker and Libraries:
    ld='gcc', ldflags =' -L/usr/local/lib'
    libpth=/usr/local/lib /lib /usr/lib
    libs=-lnsl -lgdbm -ldb -ldl -lm -lpthread -lc -lcrypt -lutil
    perllibs=-lnsl -ldl -lm -lpthread -lc -lcrypt -lutil
    libc=/lib/libc-2.3.1.so, so=so, useshrplib=true, libperl=libperl.so
    gnulibc_version='2.3.1'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-rdynamic -Wl,-rpath,/usr/lib/perl5/5.8.0/i386-linux-thread-multi/CORE'
    cccdlflags='-fPIC', lddlflags='-shared -L/usr/local/lib'

Locally applied patches:
    MAINT18379

---
@INC for perl v5.8.0:
    /usr/lib/perl5/5.8.0/i386-linux-thread-multi
    /usr/lib/perl5/5.8.0
    /usr/lib/perl5/site_perl/5.8.0/i386-linux-thread-multi
    /usr/lib/perl5/site_perl/5.8.0
    /usr/lib/perl5/site_perl
    /usr/lib/perl5/vendor_perl/5.8.0/i386-linux-thread-multi
    /usr/lib/perl5/vendor_perl/5.8.0
    /usr/lib/perl5/vendor_perl
    /usr/lib/perl5/5.8.0/i386-linux-thread-multi
    /usr/lib/perl5/5.8.0
    .

---
Environment for perl v5.8.0:
    HOME=/home/dbarmann
    LANG=en_US
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/home/dbarmann/bin:/bin:/opt/java/j2sdk1.4.1_01/bin:/usr/bin:/sbin:/usr/sbin:/usr/X11R6/bin:/usr/games:/usr/local/bin:/opt/bin
    PERLDOC_PAGER=less -R
    PERL_BADLANG (unset)
    SHELL=/bin/bash

• [perl #24423] ignoring SIGCHLD corrupts system() return value by perlbug-followup
• Re: [perl #24423] ignoring SIGCHLD corrupts system() return value by Steve Grazzini