Don't store string literals by pointer anymore

Fixes #2189

CHANGELOG.md

@@ -1,6 +1,25 @@
 ArduinoJson: change log
 =======================
 
+HEAD
+----
+
+* Don't store string literals by pointer anymore (issue #2189)
+  Version 7.3 introduced a new way to detect string literals, but it fails in some edge cases.
+  I could not find a way to fix it, so I chose to remove the optimization rather than keep it broken.
+
+> ### BREAKING CHANGES
+>
+> Since version 7.3, you could pass a boolean to `JsonString`'s constructor to force the string to be stored by pointer.
+> This optimization has been removed, and you'll get a deprecation warning if you use it.
+> To fix the issue, you must remove the boolean argument from the constructor, or better yet, remove `JsonString` altogether.
+>
+> ```diff
+>   char name[] = "ArduinoJson";
+> - doc["name"] = JsonString(name, true);
+> + doc["name"] = name;
+> ```
+
 v7.4.2 (2025-06-20)
 ------
 

extras/tests/Deprecated/BasicJsonDocument.cpp

@@ -54,7 +54,7 @@ TEST_CASE("BasicJsonDocument") {
     doc["hello"] = "world";
     auto copy = doc;
     REQUIRE(copy.as<std::string>() == "{\"hello\":\"world\"}");
-    REQUIRE(allocatorLog == "AA");
+    REQUIRE(allocatorLog == "AAAAAA");
   }
 
   SECTION("capacity") {

extras/tests/JsonArray/add.cpp

@@ -56,6 +56,7 @@ TEST_CASE("JsonArray::add(T)") {
     REQUIRE(array[0].is<int>() == false);
     REQUIRE(spy.log() == AllocatorLog{
                              Allocate(sizeofPool()),
+                             Allocate(sizeofString("hello")),
                          });
   }
 

extras/tests/JsonDeserializer/destination_types.cpp

@@ -104,6 +104,8 @@ TEST_CASE("deserializeJson(MemberProxy)") {
 
     REQUIRE(err == DeserializationError::Ok);
     REQUIRE(doc.as<std::string>() == "{\"hello\":\"world\",\"value\":[42]}");
-    REQUIRE(spy.log() == AllocatorLog{});
+    REQUIRE(spy.log() == AllocatorLog{
+                             Allocate(sizeofString("value")),
+                         });
   }
 }

extras/tests/JsonDocument/ElementProxy.cpp

@@ -31,6 +31,7 @@ TEST_CASE("ElementProxy::add()") {
     REQUIRE(doc.as<std::string>() == "[[\"world\"]]");
     REQUIRE(spy.log() == AllocatorLog{
                              Allocate(sizeofPool()),
+                             Allocate(sizeofString("world")),
                          });
   }
 

extras/tests/JsonDocument/MemberProxy.cpp

@@ -25,6 +25,7 @@ TEST_CASE("MemberProxy::add()") {
     REQUIRE(doc.as<std::string>() == "{\"hello\":[42]}");
     REQUIRE(spy.log() == AllocatorLog{
                              Allocate(sizeofPool()),
+                             Allocate(sizeofString("hello")),
                          });
   }
 
@@ -34,6 +35,8 @@ TEST_CASE("MemberProxy::add()") {
     REQUIRE(doc.as<std::string>() == "{\"hello\":[\"world\"]}");
     REQUIRE(spy.log() == AllocatorLog{
                              Allocate(sizeofPool()),
+                             Allocate(sizeofString("hello")),
+                             Allocate(sizeofString("world")),
                          });
   }
 
@@ -44,6 +47,7 @@ TEST_CASE("MemberProxy::add()") {
     REQUIRE(doc.as<std::string>() == "{\"hello\":[\"world\"]}");
     REQUIRE(spy.log() == AllocatorLog{
                              Allocate(sizeofPool()),
+                             Allocate(sizeofString("hello")),
                              Allocate(sizeofString("world")),
                          });
   }
@@ -55,6 +59,7 @@ TEST_CASE("MemberProxy::add()") {
     REQUIRE(doc.as<std::string>() == "{\"hello\":[\"world\"]}");
     REQUIRE(spy.log() == AllocatorLog{
                              Allocate(sizeofPool()),
+                             Allocate(sizeofString("hello")),
                              Allocate(sizeofString("world")),
 
                          });
@@ -71,6 +76,7 @@ TEST_CASE("MemberProxy::add()") {
     REQUIRE(doc.as<std::string>() == "{\"hello\":[\"world\"]}");
     REQUIRE(spy.log() == AllocatorLog{
                              Allocate(sizeofPool()),
+                             Allocate(sizeofString("hello")),
                              Allocate(sizeofString("world")),
                          });
   }

extras/tests/JsonDocument/add.cpp

@@ -32,6 +32,7 @@ TEST_CASE("JsonDocument::add(T)") {
     REQUIRE(doc.as<std::string>() == "[\"hello\"]");
     REQUIRE(spy.log() == AllocatorLog{
                              Allocate(sizeofPool()),
+                             Allocate(sizeofString("hello")),
                          });
   }
 

extras/tests/JsonDocument/constructor.cpp

@@ -64,6 +64,8 @@ TEST_CASE("JsonDocument constructor") {
     REQUIRE(doc2.as<std::string>() == "{\"hello\":\"world\"}");
     REQUIRE(spyingAllocator.log() == AllocatorLog{
                                          Allocate(sizeofPool()),
+                                         Allocate(sizeofString("hello")),
+                                         Allocate(sizeofString("world")),
                                      });
   }
 
@@ -87,6 +89,7 @@ TEST_CASE("JsonDocument constructor") {
     REQUIRE(doc2.as<std::string>() == "[\"hello\"]");
     REQUIRE(spyingAllocator.log() == AllocatorLog{
                                          Allocate(sizeofPool()),
+                                         Allocate(sizeofString("hello")),
                                      });
   }
 

extras/tests/JsonDocument/set.cpp

@@ -37,7 +37,9 @@ TEST_CASE("JsonDocument::set()") {
     doc.set("example");
 
     REQUIRE(doc.as<const char*>() == "example"_s);
-    REQUIRE(spy.log() == AllocatorLog{});
+    REQUIRE(spy.log() == AllocatorLog{
+                             Allocate(sizeofString("example")),
+                         });
   }
 
   SECTION("const char*") {

extras/tests/JsonDocument/shrinkToFit.cpp

@@ -69,17 +69,8 @@ TEST_CASE("JsonDocument::shrinkToFit()") {
     REQUIRE(spyingAllocator.log() == AllocatorLog{});
   }
 
-  SECTION("linked string") {
-    doc.set("hello");
-
-    doc.shrinkToFit();
-
-    REQUIRE(doc.as<std::string>() == "hello");
-    REQUIRE(spyingAllocator.log() == AllocatorLog{});
-  }
-
-  SECTION("owned string") {
-    doc.set("abcdefg"_s);
+  SECTION("string") {
+    doc.set("abcdefg");
     REQUIRE(doc.as<std::string>() == "abcdefg");
 
     doc.shrinkToFit();
@@ -101,20 +92,7 @@ TEST_CASE("JsonDocument::shrinkToFit()") {
                                      });
   }
 
-  SECTION("linked key") {
-    doc["key"] = 42;
-
-    doc.shrinkToFit();
-
-    REQUIRE(doc.as<std::string>() == "{\"key\":42}");
-    REQUIRE(spyingAllocator.log() ==
-            AllocatorLog{
-                Allocate(sizeofPool()),
-                Reallocate(sizeofPool(), sizeofObject(1)),
-            });
-  }
-
-  SECTION("owned key") {
+  SECTION("object key") {
     doc["abcdefg"_s] = 42;
 
     doc.shrinkToFit();
@@ -128,20 +106,7 @@ TEST_CASE("JsonDocument::shrinkToFit()") {
             });
   }
 
-  SECTION("linked string in array") {
-    doc.add("hello");
-
-    doc.shrinkToFit();
-
-    REQUIRE(doc.as<std::string>() == "[\"hello\"]");
-    REQUIRE(spyingAllocator.log() ==
-            AllocatorLog{
-                Allocate(sizeofPool()),
-                Reallocate(sizeofPool(), sizeofArray(1)),
-            });
-  }
-
-  SECTION("owned string in array") {
+  SECTION("string in array") {
     doc.add("abcdefg"_s);
 
     doc.shrinkToFit();
@@ -155,20 +120,7 @@ TEST_CASE("JsonDocument::shrinkToFit()") {
             });
   }
 
-  SECTION("linked string in object") {
-    doc["key"] = "hello";
-
-    doc.shrinkToFit();
-
-    REQUIRE(doc.as<std::string>() == "{\"key\":\"hello\"}");
-    REQUIRE(spyingAllocator.log() ==
-            AllocatorLog{
-                Allocate(sizeofPool()),
-                Reallocate(sizeofPool(), sizeofObject(1)),
-            });
-  }
-
-  SECTION("owned string in object") {
+  SECTION("string in object") {
     doc["key"] = "abcdefg"_s;
 
     doc.shrinkToFit();

extras/tests/JsonDocument/subscript.cpp

@@ -114,6 +114,7 @@ TEST_CASE("JsonDocument::operator[] key storage") {
     REQUIRE(doc.as<std::string>() == "{\"hello\":0}");
     REQUIRE(spy.log() == AllocatorLog{
                              Allocate(sizeofPool()),
+                             Allocate(sizeofString("hello")),
                          });
   }
 

extras/tests/JsonObject/set.cpp

@@ -16,44 +16,18 @@ TEST_CASE("JsonObject::set()") {
   JsonObject obj1 = doc1.to<JsonObject>();
   JsonObject obj2 = doc2.to<JsonObject>();
 
-  SECTION("doesn't copy static string in key or value") {
+  SECTION("copy key and string value") {
     obj1["hello"] = "world";
     spy.clearLog();
 
     bool success = obj2.set(obj1);
 
-    REQUIRE(success == true);
-    REQUIRE(obj2["hello"] == "world"_s);
-    REQUIRE(spy.log() == AllocatorLog{
-                             Allocate(sizeofPool()),
-                         });
-  }
-
-  SECTION("copy local string value") {
-    obj1["hello"] = "world"_s;
-    spy.clearLog();
-
-    bool success = obj2.set(obj1);
-
-    REQUIRE(success == true);
-    REQUIRE(obj2["hello"] == "world"_s);
-    REQUIRE(spy.log() == AllocatorLog{
-                             Allocate(sizeofPool()),
-                             Allocate(sizeofString("world")),
-                         });
-  }
-
-  SECTION("copy local key") {
-    obj1["hello"_s] = "world";
-    spy.clearLog();
-
-    bool success = obj2.set(obj1);
-
     REQUIRE(success == true);
     REQUIRE(obj2["hello"] == "world"_s);
     REQUIRE(spy.log() == AllocatorLog{
                              Allocate(sizeofPool()),
                              Allocate(sizeofString("hello")),
+                             Allocate(sizeofString("world")),
                          });
   }
 
@@ -110,7 +84,7 @@ TEST_CASE("JsonObject::set()") {
   }
 
   SECTION("copy fails in the middle of an array") {
-    TimebombAllocator timebomb(1);
+    TimebombAllocator timebomb(2);
     JsonDocument doc3(&timebomb);
     JsonObject obj3 = doc3.to<JsonObject>();
 

extras/tests/JsonObject/subscript.cpp

@@ -101,30 +101,8 @@ TEST_CASE("JsonObject::operator[]") {
     obj[key] = 42;
     REQUIRE(42 == obj[key]);
   }
-
-  SECTION("should not duplicate const char*") {
+  SECTION("should duplicate key and value strings") {
     obj["hello"] = "world";
-    REQUIRE(spy.log() == AllocatorLog{Allocate(sizeofPool())});
-  }
-
-  SECTION("should duplicate char* value") {
-    obj["hello"] = const_cast<char*>("world");
-    REQUIRE(spy.log() == AllocatorLog{
-                             Allocate(sizeofPool()),
-                             Allocate(sizeofString("world")),
-                         });
-  }
-
-  SECTION("should duplicate char* key") {
-    obj[const_cast<char*>("hello")] = "world";
-    REQUIRE(spy.log() == AllocatorLog{
-                             Allocate(sizeofPool()),
-                             Allocate(sizeofString("hello")),
-                         });
-  }
-
-  SECTION("should duplicate char* key&value") {
-    obj[const_cast<char*>("hello")] = const_cast<char*>("world");
     REQUIRE(spy.log() == AllocatorLog{
                              Allocate(sizeofPool()),
                              Allocate(sizeofString("hello")),
@@ -132,46 +110,6 @@ TEST_CASE("JsonObject::operator[]") {
                          });
   }
 
-  SECTION("should duplicate std::string value") {
-    obj["hello"] = "world"_s;
-    REQUIRE(spy.log() == AllocatorLog{
-                             Allocate(sizeofPool()),
-                             Allocate(sizeofString("world")),
-                         });
-  }
-
-  SECTION("should duplicate std::string key") {
-    obj["hello"_s] = "world";
-    REQUIRE(spy.log() == AllocatorLog{
-                             Allocate(sizeofPool()),
-                             Allocate(sizeofString("hello")),
-                         });
-  }
-
-  SECTION("should duplicate std::string key&value") {
-    obj["hello"_s] = "world"_s;
-    REQUIRE(spy.log() == AllocatorLog{
-                             Allocate(sizeofPool()),
-                             Allocate(sizeofString("hello")),
-                             Allocate(sizeofString("world")),
-                         });
-  }
-
-  SECTION("should duplicate a non-static JsonString key") {
-    obj[JsonString("hello", false)] = "world";
-    REQUIRE(spy.log() == AllocatorLog{
-                             Allocate(sizeofPool()),
-                             Allocate(sizeofString("hello")),
-                         });
-  }
-
-  SECTION("should not duplicate a static JsonString key") {
-    obj[JsonString("hello", true)] = "world";
-    REQUIRE(spy.log() == AllocatorLog{
-                             Allocate(sizeofPool()),
-                         });
-  }
-
   SECTION("should ignore null key") {
     // object must have a value to make a call to strcmp()
     obj["dummy"] = 42;

extras/tests/JsonVariant/as.cpp

@@ -185,7 +185,6 @@ TEST_CASE("JsonVariant::as()") {
     REQUIRE(variant.as<long>() == 42L);
     REQUIRE(variant.as<double>() == 42);
     REQUIRE(variant.as<JsonString>() == "42");
-    REQUIRE(variant.as<JsonString>().isStatic() == true);
   }
 
   SECTION("set(\"hello\")") {
@@ -208,7 +207,6 @@ TEST_CASE("JsonVariant::as()") {
     REQUIRE(variant.as<const char*>() == "4.2"_s);
     REQUIRE(variant.as<std::string>() == "4.2"_s);
     REQUIRE(variant.as<JsonString>() == "4.2");
-    REQUIRE(variant.as<JsonString>().isStatic() == false);
   }
 
   SECTION("set(std::string(\"123.45\"))") {
@@ -220,7 +218,6 @@ TEST_CASE("JsonVariant::as()") {
     REQUIRE(variant.as<const char*>() == "123.45"_s);
     REQUIRE(variant.as<std::string>() == "123.45"_s);
     REQUIRE(variant.as<JsonString>() == "123.45");
-    REQUIRE(variant.as<JsonString>().isStatic() == false);
   }
 
   SECTION("set(\"true\")") {

extras/tests/JsonVariant/copy.cpp

@@ -38,13 +38,15 @@ TEST_CASE("JsonVariant::set(JsonVariant)") {
     REQUIRE(var1.as<std::string>() == "{\"value\":[42]}");
   }
 
-  SECTION("stores const char* by reference") {
+  SECTION("stores string literals by copy") {
     var1.set("hello!!");
     spyingAllocator.clearLog();
 
     var2.set(var1);
 
-    REQUIRE(spyingAllocator.log() == AllocatorLog{});
+    REQUIRE(spyingAllocator.log() == AllocatorLog{
+                                         Allocate(sizeofString("hello!!")),
+                                     });
   }
 
   SECTION("stores char* by copy") {

extras/tests/JsonVariant/set.cpp

@@ -9,6 +9,7 @@
 #include "Literals.hpp"
 
 using ArduinoJson::detail::sizeofObject;
+using ArduinoJson::detail::sizeofString;
 
 enum ErrorCode { ERROR_01 = 1, ERROR_10 = 10 };
 
@@ -21,9 +22,10 @@ TEST_CASE("JsonVariant::set() when there is enough memory") {
     bool result = variant.set("hello\0world");
 
     REQUIRE(result == true);
-    CHECK(variant ==
-          "hello"_s);  // linked string cannot contain '\0' at the moment
-    CHECK(spy.log() == AllocatorLog{});
+    REQUIRE(variant == "hello\0world"_s);  // stores by copy
+    REQUIRE(spy.log() == AllocatorLog{
+                             Allocate(sizeofString(11)),
+                         });
   }
 
   SECTION("const char*") {
@@ -140,19 +142,7 @@ TEST_CASE("JsonVariant::set() when there is enough memory") {
                          });
   }
 
-  SECTION("static JsonString") {
-    char str[16];
-
-    strcpy(str, "hello");
-    bool result = variant.set(JsonString(str, true));
-    strcpy(str, "world");
-
-    REQUIRE(result == true);
-    REQUIRE(variant == "world");  // stores by pointer
-    REQUIRE(spy.log() == AllocatorLog{});
-  }
-
-  SECTION("non-static JsonString") {
+  SECTION("JsonString") {
     char str[16];
 
     strcpy(str, "hello");

extras/tests/Misc/JsonString.cpp

@@ -13,7 +13,6 @@ TEST_CASE("JsonString") {
 
     CHECK(s.isNull() == true);
     CHECK(s.c_str() == 0);
-    CHECK(s.isStatic() == true);
     CHECK(s == JsonString());
     CHECK(s != "");
   }
@@ -96,7 +95,6 @@ TEST_CASE("JsonString") {
     JsonString s("hello world", 5);
 
     CHECK(s.size() == 5);
-    CHECK(s.isStatic() == false);
     CHECK(s == "hello");
     CHECK(s != "hello world");
   }

extras/tests/Misc/StringAdapters.cpp

@@ -22,7 +22,6 @@ TEST_CASE("adaptString()") {
 
     CHECK(s.isNull() == false);
     CHECK(s.size() == 11);
-    CHECK(s.isStatic() == true);
   }
 
   SECTION("null const char*") {
@@ -38,7 +37,6 @@ TEST_CASE("adaptString()") {
 
     CHECK(s.isNull() == false);
     CHECK(s.size() == 5);
-    CHECK(s.isStatic() == false);
     CHECK(s.data() == p);
   }
 
@@ -46,7 +44,6 @@ TEST_CASE("adaptString()") {
     auto s = adaptString(static_cast<const char*>(0), 10);
 
     CHECK(s.isNull() == true);
-    CHECK(s.isStatic() == false);
   }
 
   SECTION("non-null const char* + size") {
@@ -54,7 +51,6 @@ TEST_CASE("adaptString()") {
 
     CHECK(s.isNull() == false);
     CHECK(s.size() == 5);
-    CHECK(s.isStatic() == false);
   }
 
   SECTION("null Flash string") {
@@ -62,7 +58,6 @@ TEST_CASE("adaptString()") {
 
     CHECK(s.isNull() == true);
     CHECK(s.size() == 0);
-    CHECK(s.isStatic() == false);
   }
 
   SECTION("non-null Flash string") {
@@ -70,7 +65,6 @@ TEST_CASE("adaptString()") {
 
     CHECK(s.isNull() == false);
     CHECK(s.size() == 5);
-    CHECK(s.isStatic() == false);
   }
 
   SECTION("std::string") {
@@ -79,7 +73,6 @@ TEST_CASE("adaptString()") {
 
     CHECK(s.isNull() == false);
     CHECK(s.size() == 5);
-    CHECK(s.isStatic() == false);
   }
 
   SECTION("Arduino String") {
@@ -88,7 +81,6 @@ TEST_CASE("adaptString()") {
 
     CHECK(s.isNull() == false);
     CHECK(s.size() == 5);
-    CHECK(s.isStatic() == false);
   }
 
   SECTION("custom_string") {
@@ -97,25 +89,14 @@ TEST_CASE("adaptString()") {
 
     CHECK(s.isNull() == false);
     CHECK(s.size() == 5);
-    CHECK(s.isStatic() == false);
   }
 
-  SECTION("JsonString linked") {
-    JsonString orig("hello", true);
+  SECTION("JsonString") {
+    JsonString orig("hello");
     auto s = adaptString(orig);
 
     CHECK(s.isNull() == false);
     CHECK(s.size() == 5);
-    CHECK(s.isStatic() == true);
-  }
-
-  SECTION("JsonString copied") {
-    JsonString orig("hello", false);
-    auto s = adaptString(orig);
-
-    CHECK(s.isNull() == false);
-    CHECK(s.size() == 5);
-    CHECK(s.isStatic() == false);
   }
 }
 

extras/tests/MixedConfiguration/string_length_size_4.cpp

@@ -89,58 +89,71 @@ TEST_CASE("ARDUINOJSON_STRING_LENGTH_SIZE == 4") {
 
       REQUIRE(err != DeserializationError::Ok);
     }
-  }
 
-  SECTION("bin 32 deserialization") {
-    auto str = std::string(65536, '?');
-    auto input = "\xc6\x00\x01\x00\x00"_s + str;
+    SECTION("bin 32") {
+      auto str = std::string(65536, '?');
+      auto input = "\xc6\x00\x01\x00\x00"_s + str;
 
-    auto err = deserializeMsgPack(doc, input);
+      auto err = deserializeMsgPack(doc, input);
 
-    REQUIRE(err == DeserializationError::Ok);
-    REQUIRE(doc.is<MsgPackBinary>());
-    auto binary = doc.as<MsgPackBinary>();
-    REQUIRE(binary.size() == 65536);
-    REQUIRE(binary.data() != nullptr);
-    REQUIRE(std::string(reinterpret_cast<const char*>(binary.data()),
-                        binary.size()) == str);
-  }
+      REQUIRE(err == DeserializationError::Ok);
+      REQUIRE(doc.is<MsgPackBinary>());
+      auto binary = doc.as<MsgPackBinary>();
+      REQUIRE(binary.size() == 65536);
+      REQUIRE(binary.data() != nullptr);
+      REQUIRE(std::string(reinterpret_cast<const char*>(binary.data()),
+                          binary.size()) == str);
+    }
 
-  SECTION("bin 32 serialization") {
-    auto str = std::string(65536, '?');
-    doc.set(MsgPackBinary(str.data(), str.size()));
+    SECTION("ext 32 deserialization") {
+      auto str = std::string(65536, '?');
+      auto input = "\xc9\x00\x01\x00\x00\x2a"_s + str;
 
-    std::string output;
-    auto result = serializeMsgPack(doc, output);
+      auto err = deserializeMsgPack(doc, input);
 
-    REQUIRE(result == 5 + str.size());
-    REQUIRE(output == "\xc6\x00\x01\x00\x00"_s + str);
+      REQUIRE(err == DeserializationError::Ok);
+      REQUIRE(doc.is<MsgPackExtension>());
+      auto value = doc.as<MsgPackExtension>();
+      REQUIRE(value.type() == 42);
+      REQUIRE(value.size() == 65536);
+      REQUIRE(value.data() != nullptr);
+      REQUIRE(std::string(reinterpret_cast<const char*>(value.data()),
+                          value.size()) == str);
+    }
   }
 
-  SECTION("ext 32 deserialization") {
-    auto str = std::string(65536, '?');
-    auto input = "\xc9\x00\x01\x00\x00\x2a"_s + str;
+  SECTION("serializeMsgPack()") {
+    SECTION("bin 32 serialization") {
+      auto str = std::string(65536, '?');
+      doc.set(MsgPackBinary(str.data(), str.size()));
 
-    auto err = deserializeMsgPack(doc, input);
+      std::string output;
+      auto result = serializeMsgPack(doc, output);
 
-    REQUIRE(err == DeserializationError::Ok);
-    REQUIRE(doc.is<MsgPackExtension>());
-    auto value = doc.as<MsgPackExtension>();
-    REQUIRE(value.type() == 42);
-    REQUIRE(value.size() == 65536);
-    REQUIRE(value.data() != nullptr);
-    REQUIRE(std::string(reinterpret_cast<const char*>(value.data()),
-                        value.size()) == str);
-  }
+      REQUIRE(result == 5 + str.size());
+      REQUIRE(output == "\xc6\x00\x01\x00\x00"_s + str);
+    }
+
+    SECTION("ext 32 serialization") {
+      auto str = std::string(65536, '?');
+      doc.set(MsgPackExtension(42, str.data(), str.size()));
 
-  SECTION("ext 32 serialization") {
-    auto str = std::string(65536, '?');
-    doc.set(MsgPackExtension(42, str.data(), str.size()));
+      std::string output;
+      auto result = serializeMsgPack(doc, output);
 
-    std::string output;
-    auto result = serializeMsgPack(doc, output);
+      REQUIRE(result == 6 + str.size());
+      REQUIRE(output == "\xc9\x00\x01\x00\x00\x2a"_s + str);
+    }
+
+    SECTION("str 32 serialization") {
+      auto str = std::string(65536, '?');
+      doc.set(str);
 
-    REQUIRE(result == 6 + str.size());
-    REQUIRE(output == "\xc9\x00\x01\x00\x00\x2a"_s + str);
+      std::string output;
+      auto result = serializeMsgPack(doc, output);
+
+      REQUIRE(result == 5 + str.size());
+      REQUIRE(output == "\xDB\x00\x01\x00\x00"_s + str);
+    }
   }
 }

extras/tests/MsgPackDeserializer/destination_types.cpp

@@ -104,6 +104,8 @@ TEST_CASE("deserializeMsgPack(MemberProxy)") {
 
     REQUIRE(err == DeserializationError::Ok);
     REQUIRE(doc.as<std::string>() == "{\"hello\":\"world\",\"value\":[42]}");
-    REQUIRE(spy.log() == AllocatorLog{});
+    REQUIRE(spy.log() == AllocatorLog{
+                             Allocate(sizeofString("value")),
+                         });
   }
 }

extras/tests/MsgPackSerializer/serializeVariant.cpp

@@ -137,11 +137,12 @@ TEST_CASE("serialize MsgPack value") {
     checkVariant(longest.c_str(), "\xDA\xFF\xFF"_s + longest);
   }
 
+#if ARDUINOJSON_STRING_LENGTH_SIZE > 2
   SECTION("str 32") {
     std::string shortest(65536, '?');
-    checkVariant(JsonString(shortest.c_str(), true),  // force store by pointer
-                 "\xDB\x00\x01\x00\x00"_s + shortest);
+    checkVariant(shortest.c_str(), "\xDB\x00\x01\x00\x00"_s + shortest);
   }
+#endif
 
   SECTION("serialized(const char*)") {
     checkVariant(serialized("\xDA\xFF\xFF"), "\xDA\xFF\xFF");

extras/tests/ResourceManager/StringBuffer.cpp

@@ -30,7 +30,7 @@ TEST_CASE("StringBuffer") {
     memcpy(ptr, "a\0b", 3);
     sb.save(&variant);
 
-    REQUIRE(variant.type() == VariantType::OwnedString);
+    REQUIRE(variant.type() == VariantType::LongString);
 
     auto str = variant.asString();
     REQUIRE(str.size() == 3);
@@ -44,7 +44,7 @@ TEST_CASE("StringBuffer") {
     strcpy(ptr, "alfa");
     sb.save(&variant);
 
-    REQUIRE(variant.type() == VariantType::OwnedString);
+    REQUIRE(variant.type() == VariantType::LongString);
     REQUIRE(variant.asString() == "alfa");
   }
 }

src/ArduinoJson/Memory/StringBuffer.hpp

@@ -43,7 +43,7 @@ class StringBuffer {
     if (isTinyString(s, size_))
       data->setTinyString(adaptString(s, size_));
     else
-      data->setOwnedString(commitStringNode());
+      data->setLongString(commitStringNode());
   }
 
   void saveRaw(VariantData* data) {

src/ArduinoJson/Memory/StringBuilder.hpp

@@ -45,7 +45,7 @@ class StringBuilder {
     } else {
       node->references++;
     }
-    variant->setOwnedString(node);
+    variant->setLongString(node);
   }
 
   void append(const char* s) {

src/ArduinoJson/Strings/Adapters/FlashString.hpp

@@ -63,10 +63,6 @@ class FlashString {
     ::memcpy_P(p, s.str_, n);
   }
 
-  bool isStatic() const {
-    return false;
-  }
-
  private:
   const char* str_;
   size_t size_;

src/ArduinoJson/Strings/Adapters/RamString.hpp

@@ -20,14 +20,8 @@ struct IsChar
 class RamString {
  public:
   static const size_t typeSortKey = 2;
-#if ARDUINOJSON_SIZEOF_POINTER <= 2
-  static constexpr size_t sizeMask = size_t(-1) >> 1;
-#else
-  static constexpr size_t sizeMask = size_t(-1);
-#endif
-
-  RamString(const char* str, size_t sz, bool isStatic = false)
-      : str_(str), size_(sz & sizeMask), static_(isStatic) {
+
+  RamString(const char* str, size_t sz) : str_(str), size_(sz) {
     ARDUINOJSON_ASSERT(size_ == sz);
   }
 
@@ -49,21 +43,9 @@ class RamString {
     return str_;
   }
 
-  bool isStatic() const {
-    return static_;
-  }
-
  protected:
   const char* str_;
-
-#if ARDUINOJSON_SIZEOF_POINTER <= 2
-  // Use a bitfield only on 8-bit microcontrollers
-  size_t size_ : sizeof(size_t) * 8 - 1;
-  bool static_ : 1;
-#else
   size_t size_;
-  bool static_;
-#endif
 };
 
 template <typename TChar>
@@ -91,7 +73,7 @@ struct StringAdapter<const char (&)[N]> {
   using AdaptedString = RamString;
 
   static AdaptedString adapt(const char (&p)[N]) {
-    return RamString(p, N - 1, true);
+    return RamString(p, N - 1);
   }
 };
 

src/ArduinoJson/Strings/JsonString.hpp

@@ -19,17 +19,25 @@ class JsonString {
   friend struct detail::StringAdapter<JsonString>;
 
  public:
-  JsonString() : str_(nullptr, 0, true) {}
+  JsonString() : str_(nullptr, 0) {}
 
-  JsonString(const char* data, bool isStatic = false)
-      : str_(data, data ? ::strlen(data) : 0, isStatic) {}
+  JsonString(const char* data) : str_(data, data ? ::strlen(data) : 0) {}
+
+  ARDUINOJSON_DEPRECATED(
+      "ArduinoJson doesn't differentiate between static and dynamic strings "
+      "anymore. Remove the second argument to fix this warning.")
+  JsonString(const char* data, bool) : JsonString(data) {}
 
   template <typename TSize,
             detail::enable_if_t<detail::is_integral<TSize>::value &&
                                     !detail::is_same<TSize, bool>::value,
                                 int> = 0>
-  JsonString(const char* data, TSize sz, bool isStatic = false)
-      : str_(data, size_t(sz), isStatic) {}
+  JsonString(const char* data, TSize sz) : str_(data, size_t(sz)) {}
+
+  ARDUINOJSON_DEPRECATED(
+      "ArduinoJson doesn't differentiate between static and dynamic strings "
+      "anymore. Remove the third argument to fix this warning.")
+  JsonString(const char* data, size_t sz, bool) : JsonString(data, sz) {}
 
   // Returns a pointer to the characters.
   const char* c_str() const {
@@ -41,10 +49,10 @@ class JsonString {
     return str_.isNull();
   }
 
-  // Returns true if the string is stored by address.
-  // Returns false if the string is stored by copy.
+  // Deprecated: always returns false.
+  ARDUINOJSON_DEPRECATED("The isStatic() was removed in v7.5")
   bool isStatic() const {
-    return str_.isStatic();
+    return false;
   }
 
   // Returns length of the string.

src/ArduinoJson/Variant/VariantContent.hpp

@@ -23,15 +23,14 @@ enum class VariantTypeBits : uint8_t {
 };
 
 enum class VariantType : uint8_t {
-  Null = 0,             // 0000 0000
-  TinyString = 0x02,    // 0000 0010
-  RawString = 0x03,     // 0000 0011
-  LinkedString = 0x04,  // 0000 0100
-  OwnedString = 0x05,   // 0000 0101
-  Boolean = 0x06,       // 0000 0110
-  Uint32 = 0x0A,        // 0000 1010
-  Int32 = 0x0C,         // 0000 1100
-  Float = 0x0E,         // 0000 1110
+  Null = 0,           // 0000 0000
+  TinyString = 0x02,  // 0000 0010
+  RawString = 0x03,   // 0000 0011
+  LongString = 0x05,  // 0000 0101
+  Boolean = 0x06,     // 0000 0110
+  Uint32 = 0x0A,      // 0000 1010
+  Int32 = 0x0C,       // 0000 1100
+  Float = 0x0E,       // 0000 1110
 #if ARDUINOJSON_USE_LONG_LONG
   Uint64 = 0x1A,  // 0001 1010
   Int64 = 0x1C,   // 0001 1100
@@ -62,8 +61,7 @@ union VariantContent {
   ArrayData asArray;
   ObjectData asObject;
   CollectionData asCollection;
-  const char* asLinkedString;
-  struct StringNode* asOwnedString;
+  struct StringNode* asStringNode;
   char asTinyString[tinyStringMaxLength + 1];
 };
 

src/ArduinoJson/Variant/VariantData.hpp

@@ -76,16 +76,13 @@ class VariantData {
       case VariantType::TinyString:
         return visit.visit(JsonString(content_.asTinyString));
 
-      case VariantType::LinkedString:
-        return visit.visit(JsonString(content_.asLinkedString, true));
-
-      case VariantType::OwnedString:
-        return visit.visit(JsonString(content_.asOwnedString->data,
-                                      content_.asOwnedString->length));
+      case VariantType::LongString:
+        return visit.visit(JsonString(content_.asStringNode->data,
+                                      content_.asStringNode->length));
 
       case VariantType::RawString:
-        return visit.visit(RawString(content_.asOwnedString->data,
-                                     content_.asOwnedString->length));
+        return visit.visit(RawString(content_.asStringNode->data,
+                                     content_.asStringNode->length));
 
       case VariantType::Int32:
         return visit.visit(static_cast<JsonInteger>(content_.asInt32));
@@ -215,11 +212,8 @@ class VariantData {
       case VariantType::TinyString:
         str = content_.asTinyString;
         break;
-      case VariantType::LinkedString:
-        str = content_.asLinkedString;
-        break;
-      case VariantType::OwnedString:
-        str = content_.asOwnedString->data;
+      case VariantType::LongString:
+        str = content_.asStringNode->data;
         break;
       case VariantType::Float:
         return static_cast<T>(content_.asFloat);
@@ -260,11 +254,8 @@ class VariantData {
       case VariantType::TinyString:
         str = content_.asTinyString;
         break;
-      case VariantType::LinkedString:
-        str = content_.asLinkedString;
-        break;
-      case VariantType::OwnedString:
-        str = content_.asOwnedString->data;
+      case VariantType::LongString:
+        str = content_.asStringNode->data;
         break;
       case VariantType::Float:
         return convertNumber<T>(content_.asFloat);
@@ -291,8 +282,8 @@ class VariantData {
   JsonString asRawString() const {
     switch (type_) {
       case VariantType::RawString:
-        return JsonString(content_.asOwnedString->data,
-                          content_.asOwnedString->length);
+        return JsonString(content_.asStringNode->data,
+                          content_.asStringNode->length);
       default:
         return JsonString();
     }
@@ -302,11 +293,9 @@ class VariantData {
     switch (type_) {
       case VariantType::TinyString:
         return JsonString(content_.asTinyString);
-      case VariantType::LinkedString:
-        return JsonString(content_.asLinkedString, true);
-      case VariantType::OwnedString:
-        return JsonString(content_.asOwnedString->data,
-                          content_.asOwnedString->length);
+      case VariantType::LongString:
+        return JsonString(content_.asStringNode->data,
+                          content_.asStringNode->length);
       default:
         return JsonString();
     }
@@ -415,9 +404,7 @@ class VariantData {
   }
 
   bool isString() const {
-    return type_ == VariantType::LinkedString ||
-           type_ == VariantType::OwnedString ||
-           type_ == VariantType::TinyString;
+    return type_ == VariantType::LongString || type_ == VariantType::TinyString;
   }
 
   size_t nesting(const ResourceManager* resources) const {
@@ -492,7 +479,7 @@ class VariantData {
     ARDUINOJSON_ASSERT(type_ == VariantType::Null);  // must call clear() first
     ARDUINOJSON_ASSERT(s);
     type_ = VariantType::RawString;
-    content_.asOwnedString = s;
+    content_.asStringNode = s;
   }
 
   template <typename T>
@@ -519,13 +506,6 @@ class VariantData {
     var->setString(value, resources);
   }
 
-  void setLinkedString(const char* s) {
-    ARDUINOJSON_ASSERT(type_ == VariantType::Null);  // must call clear() first
-    ARDUINOJSON_ASSERT(s);
-    type_ = VariantType::LinkedString;
-    content_.asLinkedString = s;
-  }
-
   template <typename TAdaptedString>
   void setTinyString(const TAdaptedString& s) {
     ARDUINOJSON_ASSERT(type_ == VariantType::Null);  // must call clear() first
@@ -543,11 +523,11 @@ class VariantData {
     content_.asTinyString[n] = 0;
   }
 
-  void setOwnedString(StringNode* s) {
+  void setLongString(StringNode* s) {
     ARDUINOJSON_ASSERT(type_ == VariantType::Null);  // must call clear() first
     ARDUINOJSON_ASSERT(s);
-    type_ = VariantType::OwnedString;
-    content_.asOwnedString = s;
+    type_ = VariantType::LongString;
+    content_.asStringNode = s;
   }
 
   size_t size(const ResourceManager* resources) const {

src/ArduinoJson/Variant/VariantImpl.hpp

@@ -26,11 +26,6 @@ inline bool VariantData::setString(TAdaptedString value,
   if (value.isNull())
     return false;
 
-  if (value.isStatic()) {
-    setLinkedString(value.data());
-    return true;
-  }
-
   if (isTinyString(value, value.size())) {
     setTinyString(value);
     return true;
@@ -38,7 +33,7 @@ inline bool VariantData::setString(TAdaptedString value,
 
   auto dup = resources->saveString(value);
   if (dup) {
-    setOwnedString(dup);
+    setLongString(dup);
     return true;
   }
 
@@ -47,7 +42,7 @@ inline bool VariantData::setString(TAdaptedString value,
 
 inline void VariantData::clear(ResourceManager* resources) {
   if (type_ & VariantTypeBits::OwnedStringBit)
-    resources->dereferenceString(content_.asOwnedString->data);
+    resources->dereferenceString(content_.asStringNode->data);
 
 #if ARDUINOJSON_USE_EXTENSIONS
   if (type_ & VariantTypeBits::ExtensionBit)