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Postings from April 2004
$ perl -e 'print(system("true"), " $!\n")';
0
perl -MFileCache -e 'print(system("true"), " $!\n")';
-1 No child processes
$
FileCache does the following:
# Reap our children
${"$pkg\::SIG"}{'CLD'} = 'IGNORE' if $Config{sig_name} =~ /\bCLD\b/;
${"$pkg\::SIG"}{'CHLD'} = 'IGNORE' if $Config{sig_name} =~ /\bCHLD\b/;
${"$pkg\::SIG"}{'PIPE'} = 'IGNORE' if $Config{sig_name} =~ /\bPIPE\b/;
This is a VMS-safe version of the original change made by Jerrad in
Change 19770:
# Reap our children
@{"$pkg\::SIG"}{'CLD', 'CHLD', 'PIPE'} = ('IGNORE')x3;
As Rafael pointed out to me, that's wrong anyway as %SIG is in main::.
The other side-effect is that by ignoring SIGCHLD the waitid() done by
system() fails:
pipe() = 3 [4]
fork1() = 102184
lwp_sigmask(SIG_SETMASK, 0x00000000, 0x00000000) = 0xFFFFFFFFFFBFFEFF
[0x0000FFFF]
close(4) = 0
sigaction(SIGINT, 0xFFBFE870, 0xFFBFE9C0) = 0
sigaction(SIGQUIT, 0xFFBFE870, 0xFFBFE9A0) = 0
waitid(P_PID, 102184, 0xFFBFE7F0, WEXITED|WTRAPPED) Err#10 ECHILD
The FileCache docs contain the following:
----------
FileCache installs signal handlers for CHLD (a.k.a. CLD) and PIPE in the
calling package to handle deceased children from 2-arg C<cacheout> with
C<'|-'> or C<'-|'> I<expediently>. The children would otherwise be
reaped eventually, unless you terminated before repeatedly calling cacheout.
----------
That's as maybe, but breaking system() as a consequence doesn't seem
like a reasonable tradeoff. This bug has broken part of our HPC
ClusterTools package, so I'm interested in finding a resolution.
--
Alan Burlison
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