"uncleared child handles" warning not exercised by DBI's test suite

[jkeenan]

In #171 and
Perl/perl5#23306 we are working on a problem where we are getting unexpected terminal messages when running a small DBI program on FreeBSD using that platform's "vendor perl 5.40" (but not with perl executables we build ourselves).

Those messages are coded in DBI.xs:

1710:                warn("DBI %s handle 0x%lx cleared whilst still active",
1724:            warn("DBI %s handle 0x%lx has %d uncleared child handles",

Examining DBI's test suite, I see that the "1710" warning is exercised by the test suite, but the "1724" warning is not.

$ ack '(still active|uncleared child)' t
t/03handle.t
82:	local $SIG{__WARN__} = sub { ++$warn if $_[0] =~ /still active/i };
88:	cmp_ok($warn,'==', 1, '... we got warned about our first statement handle being still active');
110:	ok($sth1->{Active}, '... first statement handle is still active');

Would it be possible to write a unit test that exercises the uncleared child handles warning? That may give us some insight into the problem described at the beginning of this ticket.

Thank you very much.