From ad57337c4e60cca8fa4a89e6befbec79b7ff7714 Mon Sep 17 00:00:00 2001
From: Gunar Schorcht <gunar@schorcht.net>
Date: Thu, 14 Mar 2019 16:11:24 +0100
Subject: [PATCH] cpu/esp32: esp_wifi doesn't call memcpy if iol_len is 0

---
 cpu/esp32/esp-wifi/esp_wifi_netdev.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/cpu/esp32/esp-wifi/esp_wifi_netdev.c b/cpu/esp32/esp-wifi/esp_wifi_netdev.c
index afb8ee29b3..43f936d1f2 100644
--- a/cpu/esp32/esp-wifi/esp_wifi_netdev.c
+++ b/cpu/esp32/esp-wifi/esp_wifi_netdev.c
@@ -298,8 +298,10 @@ static int _esp_wifi_send(netdev_t *netdev, const iolist_t *iolist)
             mutex_unlock(&dev->dev_lock);
             return -EOVERFLOW;
         }
-        memcpy (dev->tx_buf + dev->tx_len, iol->iol_base, iol->iol_len);
-        dev->tx_len += iol->iol_len;
+        if (iol->iol_len) {
+            memcpy (dev->tx_buf + dev->tx_len, iol->iol_base, iol->iol_len);
+            dev->tx_len += iol->iol_len;
+        }
     }
 
     #if ENABLE_DEBUG