If you open a pipe in a parent process via open(), then spawn a child, which then runs the close() on the open handle, close() fails with "No child processes": 

open PIPE, "| cat" or die $!;

my $pid = fork();

if( $pid == 0 ) {
    # child
    close PIPE or die $!;
    exit 0;
}

sleep 1;
my $reaped = waitpid(-1, 0 );
print "pid $reaped\n";

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Now you'll certainly say "Don't do that!" but the problem is that the open() happens in a module I maintain and the close() happens in its DESTROY method. If the user of the module decides that they want to spawn a child process, the error occurs! Who's to blame here? The module? The user? Perl? Should every module opening a pipe implement logic to check if the close fails for this obscure reason and suppress an error that's otherwise reported and will confuse the user?

In reply to close() on opened pipe fails in forked child by saintmike

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