On Fri, 2006-02-17 at 19:01 +0530, Mukund JB. wrote:
> Dear All,
>
> I have seen a macro like this in the Linux kernel sources in
> include/linux/usb.h line no: 1090.
>
> #define usb_dotoggle(dev, ep, out) ((dev)->toggle[out] ^= (1 << (ep)))
>
> I did not understand how it works?
> I have written a small usermode program to test this.
>
> #define x 1
> #define y 2
> #define macro() (x = y)
> main()
> {
> int abc = macro();
> printf("abc = %d\n",abc);
> }
>
> This code results in a compile error.
> test.c:9: error: invalid lvalue in assignment.
See the pre-processor o/p of this program
and you'll get the answer! :)
(sorry about the disclaimer! :P)
>
> Why?
>
> Regards,
> Mukund Jampala
>
>
> --
> Kernelnewbies: Help each other learn about the Linux kernel.
> Archive: http://mail.nl.linux.org/kernelnewbies/
> FAQ: http://kernelnewbies.org/faq/
>
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