Win32::SerialPort constructor goes buffer-overflow when reference variable is given

Question

This works well:

my $PortObj;    
$PortObj = new Win32::SerialPort ("COM12") || die "Can't open COM\n";

However when I try to provide a variable instead of "COM12" from TK Entry, like this:

my $portNumVar = "12";
my $portNum = $mw->Entry(-justify=>'center',-width=>'5',-textvariable=>\$portNumVar)->pack();

Inside a subroutine (after a button click):

my $PortObj;
my $com = "COM".$portNumVar;
print $com;
$PortObj = new Win32::SerialPort ($com) || die "Can't open COM\n";

I get this error:

Win32::API::Call: parameter 1 had a buffer overflow at C:/Perlx86_5.16/site/lib/Win32API/CommPort.pm line 176.

How is it even possible? Shouldn't it be the same?

Thanks, Mark.

Interesting. How about you `use Carp::Always` and get a stack trace? — mob, Oct 01 '13 at 20:07

score 3 · Answer 1 · answered Sep 03 '15 at 14:17

3

Got the same problem with Wx and Win32::SerialPort. In my case this workaround worked: $PortObj = new Win32::SerialPort (eval(qq("$com"))) || die "Can't open COM\n";

answered Sep 03 '15 at 14:17

Valentin

31
2

@JAL The first few words of this post make it seem like not an answer, but the second sentence contains a proposed solution to the problem, so this seems like a valid answer to me. – Maximillian Laumeister Sep 03 '15 at 20:06
This worked for me, but can anyone explain why it worked? – Sekenre May 15 '17 at 16:27

score -1 · Answer 2 · answered Oct 02 '13 at 09:20

-1

You need to dereference a variable if it is a reference (passed as \$val) to get the right value and not its memory address (pointer).

my $com = "COM".$$portNumVar;

answered Oct 02 '13 at 09:20

user1126070

5,059
1
16
15

No. Using `$portNumVar` is OK here. The reference is just for the `-textvariable` option. – Slaven Rezic Oct 17 '13 at 08:39

Win32::SerialPort constructor goes buffer-overflow when reference variable is given

2 Answers2