iflib: Cast the result of iflib_netmap_txq_init() to void.

[jhb]

Summary

This fixes a warning from GCC for kernels without netmap since the
return value is never used.

[erj]

sys/net/iflib.c

1288

I think @vmaffione would be the responsible one for these functions? But, why not just make this a void, too, since it only is called in one place and the return value is never checked there.

[jhb]

sys/net/iflib.c

1288

I think @vmaffione would be the responsible one for these functions? But, why not just make this a void, too, since it only is called in one place and the return value is never checked there.

I considered that, but wanted to defer. The other option is that if the driver wants to explicitly ignore the return value it could use '(void)' when calling the function which might also quiet the compiler complaint.

[vmaffione]

sys/net/iflib.c

1288

I would prefer to leave the return value as an int, even if the return value is not used right now by this particular driver. It's a matter of uniformity within netmap (RX counterpart, other drivers, Linux drivers, etc.).
If this change is meant to suppress a compiler warning, I think the best would be for iflib to explicitly cast the return value to void, as @jhb suggests.

[erj]

So, it sounds like it'd be preferred to use (void)0 instead of using an empty stub?

[jhb]

• Use a void cast instead.