Re: [Libusb-win32-devel] LibUSB Win32 (And my inability to Program C) driving me crazy.....

[Spiro T. <an-...@sp...>]

Hello Shane,

* On Fri, Oct 30, 2009 at 05:24:12PM +0100 Shane O'Neill wrote:
 
> struct usb_dev_handle *Opendev(int vid, int pid)
> {
>     struct usb_bus *bus;
>     struct usb_device *dev;
>     char message[100];
> 
>     for (bus=usb_get_busses();bus;bus=bus->next)
>     {      
>         for (dev=bus->devices;dev;dev=dev->next)
>         {
>             if (dev->descriptor.idProduct == pid)
>             {
>                 if (dev->descriptor.idVendor == vid)
>                 {
>                     current = usb_open(dev);
>                     sprintf(message, "Pointer = %08x.", current);
>                     MessagePopup(message, message);
>                 }
>             }   
>         }
>     }
>     return current;
> }
> 
> current is of data type "usb_dev_handle *current".
[...]
> There are plenty of occasions where the value of "current" as displayed 
> by the message box is valid but the function still returns NULL.
> 
> Is there something obviously wrong with what I'm doing here

Do you use "current" in different occassions? Do you have some race
condition: That is, two different code paths in two threads that both
write to "current"?

I would expect the problem in parallelism. Can't you define your
"current" variable locally, inside of the Opendev() function? That would
solve this problem.

HTH,
Spiro.

-- 
Spiro R. Trikaliotis                              http://opencbm.sf.net/
http://www.trikaliotis.net/                     http://www.viceteam.org/