From 589eb29eb322b12976b6bc64761372123838d60c Mon Sep 17 00:00:00 2001
From: "Earle F. Philhower, III" <earlephilhower@yahoo.com>
Date: Sat, 20 Jan 2018 20:14:37 -0800
Subject: [PATCH] Clear calloc block only if malloc succeeds

Calloc was calling memset(0) on NULL when its implicit malloc failed,
causing a crash in UMM.  Instead, only do the memset if the memory
allocation succeeds.

Fixes issue #4207
---
 cores/esp8266/umm_malloc/umm_malloc.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/cores/esp8266/umm_malloc/umm_malloc.c b/cores/esp8266/umm_malloc/umm_malloc.c
index 030042a1f..ac249b643 100644
--- a/cores/esp8266/umm_malloc/umm_malloc.c
+++ b/cores/esp8266/umm_malloc/umm_malloc.c
@@ -1685,7 +1685,9 @@ void *umm_calloc( size_t num, size_t item_size ) {
 
   size += POISON_SIZE(size);
   ret = _umm_malloc(size);
-  memset(ret, 0x00, size);
+  if (ret) {
+    memset(ret, 0x00, size);
+  }
 
   ret = GET_POISONED(ret, size);