Add __maybe_unused attribute

And then apply it in src/register.c:io_uring_register_buf_ring() as we
don't currently use the flags argument.

Link: #622
Signed-off-by: Jens Axboe <[email protected]>

Author: axboe

src/lib.h

@@ -33,6 +33,8 @@
 	})
 #endif
 
+#define __maybe_unused		__attribute__((__unused__))
+
 void *__uring_malloc(size_t len);
 void __uring_free(void *p);
 

src/register.c

@@ -332,7 +332,8 @@ int io_uring_unregister_ring_fd(struct io_uring *ring)
 }
 
 int io_uring_register_buf_ring(struct io_uring *ring,
-			       struct io_uring_buf_reg *reg, unsigned int flags)
+			       struct io_uring_buf_reg *reg,
+			       unsigned int __maybe_unused flags)
 {
 	return ____sys_io_uring_register(ring->ring_fd,
 					 IORING_REGISTER_PBUF_RING, reg, 1);