Fixed null values that could be pass to strcmp() (closes #745)

src/ArduinoJson/JsonObject.hpp

@@ -286,15 +286,21 @@ class JsonObject : public Internals::JsonPrintable<JsonObject>,
 
   template <typename TStringRef, typename TValueRef>
   bool set_impl(TStringRef key, TValueRef value) {
+    // ignore null key
+    if (Internals::StringTraits<TStringRef>::is_null(key)) return false;
+
+    // search a matching key
     iterator it = findKey<TStringRef>(key);
     if (it == end()) {
+      // add the key
       it = Internals::List<JsonPair>::add();
       if (it == end()) return false;
-
       bool key_ok =
           Internals::ValueSaver<TStringRef>::save(_buffer, it->key, key);
       if (!key_ok) return false;
     }
+
+    // save the value
     return Internals::ValueSaver<TValueRef>::save(_buffer, it->value, value);
   }
 
@@ -318,5 +324,5 @@ struct JsonVariantDefault<JsonObject> {
     return JsonObject::invalid();
   }
 };
-}
-}
+}  // namespace Internals
+}  // namespace ArduinoJson

src/ArduinoJson/JsonVariantComparisons.hpp

@@ -129,10 +129,11 @@ class JsonVariantComparisons {
     if (is<JsonObject>() && right.template is<JsonObject>())
       return as<JsonObject>() == right.template as<JsonObject>();
     if (is<char *>() && right.template is<char *>())
-      return strcmp(as<char *>(), right.template as<char *>()) == 0;
+      return StringTraits<const char *>::equals(as<char *>(),
+                                                right.template as<char *>());
 
     return false;
   }
 };
-}
-}
+}  // namespace Internals
+}  // namespace ArduinoJson

src/ArduinoJson/StringTraits/CharPointer.hpp

@@ -30,7 +30,9 @@ struct CharPointerTraits {
   };
 
   static bool equals(const TChar* str, const char* expected) {
-    return strcmp(reinterpret_cast<const char*>(str), expected) == 0;
+    const char* actual = reinterpret_cast<const char*>(str);
+    if (!actual || !expected) return actual == expected;
+    return strcmp(actual, expected) == 0;
   }
 
   static bool is_null(const TChar* str) {
@@ -58,5 +60,5 @@ struct CharPointerTraits {
 template <typename TChar>
 struct StringTraits<TChar*, typename EnableIf<IsChar<TChar>::value>::type>
     : CharPointerTraits<TChar> {};
-}
-}
+}  // namespace Internals
+}  // namespace ArduinoJson

src/ArduinoJson/StringTraits/FlashString.hpp

@@ -31,7 +31,9 @@ struct StringTraits<const __FlashStringHelper*, void> {
   };
 
   static bool equals(const __FlashStringHelper* str, const char* expected) {
-    return strcmp_P(expected, (const char*)str) == 0;
+    const char* actual = reinterpret_cast<const char*>(str);
+    if (!actual || !expected) return actual == expected;
+    return strcmp_P(expected, actual) == 0;
   }
 
   static bool is_null(const __FlashStringHelper* str) {
@@ -53,7 +55,7 @@ struct StringTraits<const __FlashStringHelper*, void> {
   static const bool has_equals = true;
   static const bool should_duplicate = true;
 };
-}
-}
+}  // namespace Internals
+}  // namespace ArduinoJson
 
 #endif

src/ArduinoJson/StringTraits/StdString.hpp

@@ -40,7 +40,10 @@ struct StdStringTraits {
   };
 
   static bool equals(const TString& str, const char* expected) {
-    return 0 == strcmp(str.c_str(), expected);
+    // Arduino's String::c_str() can return NULL
+    const char* actual = str.c_str();
+    if (!actual || !expected) return actual == expected;
+    return 0 == strcmp(actual, expected);
   }
 
   static void append(TString& str, char c) {
@@ -68,7 +71,7 @@ struct StringTraits<StringSumHelper, void> : StdStringTraits<StringSumHelper> {
 template <>
 struct StringTraits<std::string, void> : StdStringTraits<std::string> {};
 #endif
-}
-}
+}  // namespace Internals
+}  // namespace ArduinoJson
 
 #endif