tests for $sth->{ParamValues} attrib

confirming behavior of this attribute
before and after execution on prepared statements,
with and without bound values.

and confirming that no segfaults happen (gh perl5-dbi#447)

t/gh447-paramvalues.t

@@ -0,0 +1,134 @@
+use strict;
+use warnings;
+
+use Test::More;
+use DBI;
+use lib 't', '.';
+require 'lib.pl';
+
+my ($row, $sth, $dbh);
+my ($def, $rows, $errstr, $ret_ref);
+use vars qw($test_dsn $test_user $test_password);
+my $table = 'dbd_mysql_gh447';
+
+eval {$dbh = DBI->connect($test_dsn, $test_user, $test_password,
+    { RaiseError => 1, AutoCommit => 1});};
+
+if ($@) {
+    plan skip_all =>
+        "no database connection";
+}
+
+# in case exit early, ensure we clean up
+END {
+	if ($dbh) {
+		$dbh->do("DROP TABLE IF EXISTS $table");
+		$dbh->disconnect();
+	}
+}
+
+# ------ set up
+ok(defined $dbh, "Connected to database");
+$dbh->do("DROP TABLE IF EXISTS $table");
+$dbh->do("CREATE TABLE $table (id INT(4), name VARCHAR(64))");
+
+
+# test prepare/execute statement without a placeholder
+
+$sth = $dbh->prepare("SHOW TABLES LIKE '$table'");
+is_deeply($sth->{ParamValues}, {}, "ParamValues is empty hashref before SHOW");
+$sth->execute();
+
+is_deeply($sth->{ParamValues}, {}, "ParamValues is still empty after execution");
+
+$sth->finish;
+is_deeply($sth->{ParamValues}, {}, "ParamValues empty after finish");
+undef $sth;
+
+
+# test prepare/execute statement with a placeholder
+
+$sth = $dbh->prepare("INSERT INTO $table values (?, ?)");
+is_deeply($sth->{ParamValues}, {1 => undef, 2 => undef}, 
+	"ParamValues is correct hashref before INSERT");
+
+# insert rows with placeholder
+my %rowdata;
+my @chars = grep !/[0O1Iil]/, 0..9, 'A'..'Z', 'a'..'z';
+
+for (my $i = 1 ; $i < 4; $i++) {
+  my $word = join '', map { $chars[rand @chars] } 0 .. 16;
+  $rowdata{$i} = $word;  # save for later
+  $rows = $sth->execute($i, $word);
+  is($rows, 1, "Should have inserted one row");
+  my $attrib = $sth->{ParamValues};
+  is_deeply($attrib, {1 => $i, 2 => $word}, "row $i ParamValues hashref as expected");
+  # we're checking here that list context doesnt cause segfault
+  my %copy = %$attrib;
+  is_deeply(\%copy, {1 => $i, 2 => $word}, "...and copied hashref as well");
+}
+
+$sth->finish;
+is_deeply($sth->{ParamValues}, {}, "ParamValues empty after finish");
+undef $sth;
+
+
+# test prepare/execute with bind_param
+
+$sth = $dbh->prepare("SELECT * FROM $table WHERE id = ? OR name = ?");
+is_deeply($sth->{ParamValues}, {1 => undef, 2 => undef}, 
+	"ParamValues is hashref with keys before bind_param");
+$sth->bind_param(1, 1, DBI::SQL_INTEGER);
+$sth->bind_param(2, $rowdata{1});
+is_deeply($sth->{ParamValues}, {1 => 1, 2 => $rowdata{1}}, 
+	"ParamValues contains bound values after bind_param");
+
+my %copy = do { my $attrib = $sth->{ParamValues}; %$attrib };
+ok( %copy, 'copied ParamValues without segfault');
+
+$rows = $sth->execute;
+is($rows, 1, 'execute selected 1 row');
+is_deeply($sth->{ParamValues}, {1 => 1, 2 => $rowdata{1}}, 
+	"ParamValues still contains values after execute");
+%copy = do { my $attrib = $sth->{ParamValues}; %$attrib };
+ok( %copy, 'copied ParamValues without segfault');
+
+# try changing one parameter only
+$sth->bind_param(2, $rowdata{2});
+is_deeply($sth->{ParamValues}, {1 => 1, 2 => $rowdata{2}}, 
+	"ParamValues updated with another bind_param");
+$rows = $sth->execute;
+is($rows, 2, 'execute selected 2 rows because changed param value');
+
+# try execute with args (the bound values take precedent?)
+$rows = $sth->execute(3, $rowdata{3});
+is($rows, 2, 'execute used bound params, ignored exec args');
+is_deeply($sth->{ParamValues}, {1 => 1, 2 => $rowdata{2}}, 
+	"ParamValues reflect bound params -- execute args ignored");
+
+$sth->bind_param(1, undef, DBI::SQL_INTEGER);
+is_deeply($sth->{ParamValues}, {1 => undef, 2 => $rowdata{2}}, 
+	"ParamValues includes undef param after binding");
+%copy = do { my $attrib = $sth->{ParamValues}; %$attrib };
+ok( %copy, 'copied ParamValues without segfault');
+
+$rows = $sth->execute(1);
+is($rows, 1, 'execute used bound undef value, not exec arg');
+is_deeply($sth->{ParamValues}, {1 => undef, 2 => $rowdata{2}}, 
+	"ParamValues unchanged after execution");
+
+undef $sth;
+
+
+# clean up
+$dbh->do("DROP TABLE IF EXISTS $table");
+
+# Install a handler so that a warning about unfreed resources gets caught
+$SIG{__WARN__} = sub { die @_ };
+
+$dbh->disconnect();
+
+undef $dbh;
+
+done_testing();
+