| Subject: | Pointer being passed as (nil) in get_descriptor |
| Date: | Tue, 16 Mar 2010 06:36:17 +0800 |
| To: | "bug-device-usb [...] rt.cpan.org" <bug-device-usb [...] rt.cpan.org> |
| From: | "Cliffe, Stephen" <Stephen.Cliffe [...] andrew.com> |
I'm having a problem with Device::USB, specifically I'm getting the following warning:
Argument "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0..." isn't numeric in subroutine entry at /usr/lib/perl5/site_perl/5.8.8/i386-linux-thread-multi/Device/USB/Device.pm line 585, <DATA> line 1. This is then followed by a Segmentation fault.
This code from Device::USB that is causing this is:
sub get_descriptor
{
my $self = shift;
my $type = shift;
my $index = shift;
$self->_assert_open();
my $buf = "\0" x MAX_BUFFER_SIZE;
my $retlen = Device::USB::libusb_get_descriptor(
$self->{handle}, $type, $index, $buf, MAX_BUFFER_SIZE
);
return if $retlen < 0;
return substr( $buf, 0, $retlen );
}
The argument $buf ends up as (nil) in Device::USB::libusb_get_descriptor so there appears to be some problem with the argument passing.
I posted on Perl Monks (http://www.perlmonks.org/?node_id=828623) about this and the response was that it's a typemap problem (the buffer should be declared as a char * instead of void *) in libusb_get_descriptor. This fixed the problem for me.
Note that there are a number of other occurrences of this in other functions.
Steve.