text: /*
   * Check if the kernel sets IORING_SQ_CQ_OVERFLOW so that peeking events
   * still enter the kernel to flush events, if the CQ side is overflown.
   */
  #include <stdio.h>
  #include <string.h>
  #include <assert.h>
  #include "liburing.h"
  
  static int test_cq_overflow(struct io_uring *ring)
  {
  	struct io_uring_cqe *cqe;
  	struct io_uring_sqe *sqe;
  	unsigned flags;
  	int issued = 0;
  	int ret = 0;
  
  	do {
  		sqe = io_uring_get_sqe(ring);
  		if (!sqe) {
  			fprintf(stderr, "get sqe failed\n");
  			goto err;
  		}
  		ret = io_uring_submit(ring);
  		if (ret <= 0) {
  			if (ret != -EBUSY)
  				fprintf(stderr, "sqe submit failed: %d\n", ret);
  			break;
  		}
  		issued++;
  	} while (ret > 0);
  
  	assert(ret == -EBUSY);
  
  	flags = IO_URING_READ_ONCE(*ring->sq.kflags);
  	if (!(flags & IORING_SQ_CQ_OVERFLOW)) {
  		fprintf(stdout, "OVERFLOW not set on -EBUSY, skipping\n");
  		goto done;
  	}
  
  	while (issued) {
  		ret = io_uring_peek_cqe(ring, &cqe);
  		if (ret) {
  			if (ret != -EAGAIN) {
  				fprintf(stderr, "peek completion failed: %s\n",
  					strerror(ret));
  				break;
  			}
  			continue;
  		}
  		io_uring_cqe_seen(ring, cqe);
  		issued--;
  	}
  
  done:
  	return 0;
  err:
  	return 1;
  }
  
  int main(int argc, char *argv[])
  {
  	int ret;
  	struct io_uring ring;
  	struct io_uring_params p = { };
  
  	if (argc > 1)
  		return 0;
  
  	ret = io_uring_queue_init_params(16, &ring, &p);
  	if (ret) {
  		fprintf(stderr, "ring setup failed: %d\n", ret);
  		return 1;
  	}
  
  	if (!(p.features & IORING_FEAT_NODROP)) {
  		fprintf(stdout, "No overflow protection, skipped\n");
  		return 0;
  	}
  
  	ret = test_cq_overflow(&ring);
  	if (ret) {
  		fprintf(stderr, "test_cq_overflow failed\n");
  		return 1;
  	}
  
  	return 0;
  }
  