From a27c8a9b003dbb7d611b66e9e1f2a017b3fa3193 Mon Sep 17 00:00:00 2001
From: ZhaoYandong00 <zhaoyandong00@hotmail.com>
Date: Thu, 4 Jun 2026 16:49:40 +0800
Subject: [PATCH] Improve string handling and null checks in cJSON.c

Refactor string handling in cJSON.c to improve null checks and prevent overlapping string issues.
---
 cJSON.c | 25 +++++++++++++------------
 1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/cJSON.c b/cJSON.c
index 88c2d95b..a2228be4 100644
--- a/cJSON.c
+++ b/cJSON.c
@@ -442,24 +442,25 @@ CJSON_PUBLIC(char*) cJSON_SetValuestring(cJSON *object, const char *valuestring)
     {
         return NULL;
     }
-    /* return NULL if the object is corrupted or valuestring is NULL */
-    if (object->valuestring == NULL || valuestring == NULL)
+    /* return NULL if valuestring is NULL */
+    if (valuestring == NULL)
     {
         return NULL;
     }
-
-    v1_len = strlen(valuestring);
-    v2_len = strlen(object->valuestring);
-
-    if (v1_len <= v2_len)
+    if(object->valuestring)
     {
-        /* strcpy does not handle overlapping string: [X1, X2] [Y1, Y2] => X2 < Y1 or Y2 < X1 */
-        if (!( valuestring + v1_len < object->valuestring || object->valuestring + v2_len < valuestring ))
+        v1_len = strlen(valuestring);
+        v2_len = strlen(object->valuestring);
+
+        if (v1_len <= v2_len)
         {
-            return NULL;
+            /* strcpy does not handle overlapping string: [X1, X2] [Y1, Y2] => X2 < Y1 or Y2 < X1 */
+            if ( valuestring + v1_len < object->valuestring || object->valuestring + v2_len < valuestring )
+            {
+                strcpy(object->valuestring, valuestring);
+                return object->valuestring;
+            }            
         }
-        strcpy(object->valuestring, valuestring);
-        return object->valuestring;
     }
     copy = (char*) cJSON_strdup((const unsigned char*)valuestring, &global_hooks);
     if (copy == NULL)