print warning for libfuzzer qemu driver
diff --git a/utils/aflpp_driver/aflpp_qemu_driver.c b/utils/aflpp_driver/aflpp_qemu_driver.c
index 79de5af..efa80bc 100644
--- a/utils/aflpp_driver/aflpp_qemu_driver.c
+++ b/utils/aflpp_driver/aflpp_qemu_driver.c
@@ -27,6 +27,9 @@
 
   } else {
 
+    fprintf(stderr
+            "Using shared-memory testcases. To read via stdin, set "
+            "AFL_QEMU_DRIVER_NO_HOOK=1.\n");
     uint8_t dummy_input[1024000] = {0};
     LLVMFuzzerTestOneInput(dummy_input, 1);