Merijn Broeren wrote:
>Hello,
>
>This simple program exhibits the difference in behaviour between 0.32
>and 0.31 :
>
> use POE;
>
> my $rc = system("/bin/true");
>
> if ($rc == -1) {
> print "failed to execute: $!\n";
> } else {
> print "executed just fine\n";
> }
>
>Reading perldoc perlvar on $?:
>
> If you have installed a signal handler for "SIGCHLD", the value of $?
> will usually be wrong outside that handler.
>
>This happens because the import of POE.pm does an eval of use POE::Kernel.
>Its import in turn executes a POE::Kernel::->new, which then does
>amongst much other stuff a $self->_data_sig_initialize(); Which calls
>loop_ignore_signal. This has changed between 0.31 and 0.32 :
>
>@@ -53,6 +53,7 @@
>
> # Child process has stopped.
> if ($signal eq 'CHLD' or $signal eq 'CLD') {
>+ $SIG{$signal} = "DEFAULT";
> $self->_data_sig_begin_polling();
> return;
> }
>@@ -72,6 +73,13 @@
>
> if ($signal eq 'CHLD' or $signal eq 'CLD') {
> $self->_data_sig_cease_polling();
>+ $SIG{$signal} = "IGNORE";
>+ return;
>+ }
>+
>+ if ($signal eq 'PIPE') {
>+ $SIG{$signal} = "IGNORE";
>+ return;
> }
>
> $SIG{$signal} = "DEFAULT";
>
>So effectivelly all system calls in POE programs that want to check the
>result status of their calls cannot do so anymore directly. Or you have
>to install a SIGCHLD handler yourself. Much of our code has the above
>idiom, where we check immediately. Much unhappiness with 0.32 as it
>returns -1 now.
>
>Is this a desired change in behaviour?
>
>Cheers,
>
>
As a side note though, I just threw this bit of code together that
should make the concept of a system() call safe under POE.
DISCLAIMER: This code will attract the attention of ninjas and pirates.
Expect to be in the middle of something bad if you use it.
sub mysystem {
my $command = shift;
my $return;
{
local $SIG{CHLD} = "DEFAULT";
$return = system( $command );
}
ref( $SIG{CHLD} ) eq 'CODE' and $SIG{CHLD}->();
return $return;
}
mysystem( 'command' );
Adjust as necessary.
--Jonathan
