1[](https://github.com/nlohmann/json/releases) 2 3[](https://ci.appveyor.com/project/nlohmann/json) 4[](https://github.com/nlohmann/json/actions?query=workflow%3AUbuntu) 5[](https://github.com/nlohmann/json/actions?query=workflow%3AmacOS) 6[](https://github.com/nlohmann/json/actions?query=workflow%3AWindows) 7[](https://coveralls.io/github/nlohmann/json?branch=develop) 8[](https://scan.coverity.com/projects/nlohmann-json) 9[](https://www.codacy.com/gh/nlohmann/json/dashboard?utm_source=github.com&utm_medium=referral&utm_content=nlohmann/json&utm_campaign=Badge_Grade) 10[](https://cirrus-ci.com/github/nlohmann/json) 11[](https://bugs.chromium.org/p/oss-fuzz/issues/list?sort=-opened&can=1&q=proj:json) 12[](https://wandbox.org/permlink/1mp10JbaANo6FUc7) 13[](https://json.nlohmann.me) 14[](https://raw.githubusercontent.com/nlohmann/json/master/LICENSE.MIT) 15[](https://github.com/nlohmann/json/releases) 16[](https://vcpkg.link/ports/nlohmann-json) 17[](https://repology.org/project/nlohmann-json/versions) 18[](https://github.com/nlohmann/json/releases) 19[](https://github.com/nlohmann/json/issues) 20[](https://isitmaintained.com/project/nlohmann/json "Average time to resolve an issue") 21[](https://bestpractices.coreinfrastructure.org/projects/289) 22[](https://github.com/sponsors/nlohmann) 23[](https://api.reuse.software/info/github.com/nlohmann/json) 24[](https://discord.gg/6mrGXKvX7y) 25 26- [Design goals](#design-goals) 27- [Sponsors](#sponsors) 28- [Support](#support) ([documentation](https://json.nlohmann.me), [FAQ](https://json.nlohmann.me/home/faq/), [discussions](https://github.com/nlohmann/json/discussions), [API](https://json.nlohmann.me/api/basic_json/), [bug issues](https://github.com/nlohmann/json/issues)) 29- [Examples](#examples) 30 - [Read JSON from a file](#read-json-from-a-file) 31 - [Creating `json` objects from JSON literals](#creating-json-objects-from-json-literals) 32 - [JSON as first-class data type](#json-as-first-class-data-type) 33 - [Serialization / Deserialization](#serialization--deserialization) 34 - [STL-like access](#stl-like-access) 35 - [Conversion from STL containers](#conversion-from-stl-containers) 36 - [JSON Pointer and JSON Patch](#json-pointer-and-json-patch) 37 - [JSON Merge Patch](#json-merge-patch) 38 - [Implicit conversions](#implicit-conversions) 39 - [Conversions to/from arbitrary types](#arbitrary-types-conversions) 40 - [Specializing enum conversion](#specializing-enum-conversion) 41 - [Binary formats (BSON, CBOR, MessagePack, UBJSON, and BJData)](#binary-formats-bson-cbor-messagepack-ubjson-and-bjdata) 42- [Supported compilers](#supported-compilers) 43- [Integration](#integration) 44 - [CMake](#cmake) 45 - [Package Managers](#package-managers) 46 - [Pkg-config](#pkg-config) 47- [License](#license) 48- [Contact](#contact) 49- [Thanks](#thanks) 50- [Used third-party tools](#used-third-party-tools) 51- [Projects using JSON for Modern C++](#projects-using-json-for-modern-c) 52- [Notes](#notes) 53- [Execute unit tests](#execute-unit-tests) 54 55## Design goals 56 57There are myriads of [JSON](https://json.org) libraries out there, and each may even have its reason to exist. Our class had these design goals: 58 59- **Intuitive syntax**. In languages such as Python, JSON feels like a first class data type. We used all the operator magic of modern C++ to achieve the same feeling in your code. Check out the [examples below](#examples) and you'll know what I mean. 60 61- **Trivial integration**. Our whole code consists of a single header file [`json.hpp`](https://github.com/nlohmann/json/blob/develop/single_include/nlohmann/json.hpp). That's it. No library, no subproject, no dependencies, no complex build system. The class is written in vanilla C++11. All in all, everything should require no adjustment of your compiler flags or project settings. 62 63- **Serious testing**. Our code is heavily [unit-tested](https://github.com/nlohmann/json/tree/develop/tests/src) and covers [100%](https://coveralls.io/r/nlohmann/json) of the code, including all exceptional behavior. Furthermore, we checked with [Valgrind](https://valgrind.org) and the [Clang Sanitizers](https://clang.llvm.org/docs/index.html) that there are no memory leaks. [Google OSS-Fuzz](https://github.com/google/oss-fuzz/tree/master/projects/json) additionally runs fuzz tests against all parsers 24/7, effectively executing billions of tests so far. To maintain high quality, the project is following the [Core Infrastructure Initiative (CII) best practices](https://bestpractices.coreinfrastructure.org/projects/289). 64 65Other aspects were not so important to us: 66 67- **Memory efficiency**. Each JSON object has an overhead of one pointer (the maximal size of a union) and one enumeration element (1 byte). The default generalization uses the following C++ data types: `std::string` for strings, `int64_t`, `uint64_t` or `double` for numbers, `std::map` for objects, `std::vector` for arrays, and `bool` for Booleans. However, you can template the generalized class `basic_json` to your needs. 68 69- **Speed**. There are certainly [faster JSON libraries](https://github.com/miloyip/nativejson-benchmark#parsing-time) out there. However, if your goal is to speed up your development by adding JSON support with a single header, then this library is the way to go. If you know how to use a `std::vector` or `std::map`, you are already set. 70 71See the [contribution guidelines](https://github.com/nlohmann/json/blob/master/.github/CONTRIBUTING.md#please-dont) for more information. 72 73 74## Sponsors 75 76You can sponsor this library at [GitHub Sponsors](https://github.com/sponsors/nlohmann). 77 78### :office: Corporate Sponsor 79 80[](https://github.com/codacy/About) 81 82### :label: Named Sponsors 83 84- [Michael Hartmann](https://github.com/reFX-Mike) 85- [Stefan Hagen](https://github.com/sthagen) 86- [Steve Sperandeo](https://github.com/homer6) 87- [Robert Jefe Lindstädt](https://github.com/eljefedelrodeodeljefe) 88- [Steve Wagner](https://github.com/ciroque) 89- [Lion Yang](https://github.com/LionNatsu) 90 91Thanks everyone! 92 93## Support 94 95:question: If you have a **question**, please check if it is already answered in the [**FAQ**](https://json.nlohmann.me/home/faq/) or the [**Q&A**](https://github.com/nlohmann/json/discussions/categories/q-a) section. If not, please [**ask a new question**](https://github.com/nlohmann/json/discussions/new) there. 96 97:books: If you want to **learn more** about how to use the library, check out the rest of the [**README**](#examples), have a look at [**code examples**](https://github.com/nlohmann/json/tree/develop/docs/examples), or browse through the [**help pages**](https://json.nlohmann.me). 98 99:construction: If you want to understand the **API** better, check out the [**API Reference**](https://json.nlohmann.me/api/basic_json/). 100 101:bug: If you found a **bug**, please check the [**FAQ**](https://json.nlohmann.me/home/faq/) if it is a known issue or the result of a design decision. Please also have a look at the [**issue list**](https://github.com/nlohmann/json/issues) before you [**create a new issue**](https://github.com/nlohmann/json/issues/new/choose). Please provide as much information as possible to help us understand and reproduce your issue. 102 103There is also a [**docset**](https://github.com/Kapeli/Dash-User-Contributions/tree/master/docsets/JSON_for_Modern_C%2B%2B) for the documentation browsers [Dash](https://kapeli.com/dash), [Velocity](https://velocity.silverlakesoftware.com), and [Zeal](https://zealdocs.org) that contains the full [documentation](https://json.nlohmann.me) as offline resource. 104 105## Examples 106 107Here are some examples to give you an idea how to use the class. 108 109Beside the examples below, you may want to: 110 111→ Check the [documentation](https://json.nlohmann.me/)\ 112→ Browse the [standalone example files](https://github.com/nlohmann/json/tree/develop/docs/examples) 113 114Every API function (documented in the [API Documentation](https://json.nlohmann.me/api/basic_json/)) has a corresponding standalone example file. For example, the [`emplace()`](https://json.nlohmann.me/api/basic_json/emplace/) function has a matching [emplace.cpp](https://github.com/nlohmann/json/blob/develop/docs/examples/emplace.cpp) example file. 115 116### Read JSON from a file 117 118The `json` class provides an API for manipulating a JSON value. To create a `json` object by reading a JSON file: 119 120```cpp 121#include <fstream> 122#include <nlohmann/json.hpp> 123using json = nlohmann::json; 124 125// ... 126 127std::ifstream f("example.json"); 128json data = json::parse(f); 129``` 130 131### Creating `json` objects from JSON literals 132 133Assume you want to create hard-code this literal JSON value in a file, as a `json` object: 134 135```json 136{ 137 "pi": 3.141, 138 "happy": true 139} 140``` 141 142There are various options: 143 144```cpp 145// Using (raw) string literals and json::parse 146json ex1 = json::parse(R"( 147 { 148 "pi": 3.141, 149 "happy": true 150 } 151)"); 152 153// Using user-defined (raw) string literals 154using namespace nlohmann::literals; 155json ex2 = R"( 156 { 157 "pi": 3.141, 158 "happy": true 159 } 160)"_json; 161 162// Using initializer lists 163json ex3 = { 164 {"happy", true}, 165 {"pi", 3.141}, 166}; 167``` 168 169### JSON as first-class data type 170 171Here are some examples to give you an idea how to use the class. 172 173Assume you want to create the JSON object 174 175```json 176{ 177 "pi": 3.141, 178 "happy": true, 179 "name": "Niels", 180 "nothing": null, 181 "answer": { 182 "everything": 42 183 }, 184 "list": [1, 0, 2], 185 "object": { 186 "currency": "USD", 187 "value": 42.99 188 } 189} 190``` 191 192With this library, you could write: 193 194```cpp 195// create an empty structure (null) 196json j; 197 198// add a number that is stored as double (note the implicit conversion of j to an object) 199j["pi"] = 3.141; 200 201// add a Boolean that is stored as bool 202j["happy"] = true; 203 204// add a string that is stored as std::string 205j["name"] = "Niels"; 206 207// add another null object by passing nullptr 208j["nothing"] = nullptr; 209 210// add an object inside the object 211j["answer"]["everything"] = 42; 212 213// add an array that is stored as std::vector (using an initializer list) 214j["list"] = { 1, 0, 2 }; 215 216// add another object (using an initializer list of pairs) 217j["object"] = { {"currency", "USD"}, {"value", 42.99} }; 218 219// instead, you could also write (which looks very similar to the JSON above) 220json j2 = { 221 {"pi", 3.141}, 222 {"happy", true}, 223 {"name", "Niels"}, 224 {"nothing", nullptr}, 225 {"answer", { 226 {"everything", 42} 227 }}, 228 {"list", {1, 0, 2}}, 229 {"object", { 230 {"currency", "USD"}, 231 {"value", 42.99} 232 }} 233}; 234``` 235 236Note that in all these cases, you never need to "tell" the compiler which JSON value type you want to use. If you want to be explicit or express some edge cases, the functions [`json::array()`](https://json.nlohmann.me/api/basic_json/array/) and [`json::object()`](https://json.nlohmann.me/api/basic_json/object/) will help: 237 238```cpp 239// a way to express the empty array [] 240json empty_array_explicit = json::array(); 241 242// ways to express the empty object {} 243json empty_object_implicit = json({}); 244json empty_object_explicit = json::object(); 245 246// a way to express an _array_ of key/value pairs [["currency", "USD"], ["value", 42.99]] 247json array_not_object = json::array({ {"currency", "USD"}, {"value", 42.99} }); 248``` 249 250### Serialization / Deserialization 251 252#### To/from strings 253 254You can create a JSON value (deserialization) by appending `_json` to a string literal: 255 256```cpp 257// create object from string literal 258json j = "{ \"happy\": true, \"pi\": 3.141 }"_json; 259 260// or even nicer with a raw string literal 261auto j2 = R"( 262 { 263 "happy": true, 264 "pi": 3.141 265 } 266)"_json; 267``` 268 269Note that without appending the `_json` suffix, the passed string literal is not parsed, but just used as JSON string 270value. That is, `json j = "{ \"happy\": true, \"pi\": 3.141 }"` would just store the string 271`"{ "happy": true, "pi": 3.141 }"` rather than parsing the actual object. 272 273The string literal should be brought into scope with `using namespace nlohmann::literals;` 274(see [`json::parse()`](https://json.nlohmann.me/api/operator_literal_json/)). 275 276The above example can also be expressed explicitly using [`json::parse()`](https://json.nlohmann.me/api/basic_json/parse/): 277 278```cpp 279// parse explicitly 280auto j3 = json::parse(R"({"happy": true, "pi": 3.141})"); 281``` 282 283You can also get a string representation of a JSON value (serialize): 284 285```cpp 286// explicit conversion to string 287std::string s = j.dump(); // {"happy":true,"pi":3.141} 288 289// serialization with pretty printing 290// pass in the amount of spaces to indent 291std::cout << j.dump(4) << std::endl; 292// { 293// "happy": true, 294// "pi": 3.141 295// } 296``` 297 298Note the difference between serialization and assignment: 299 300```cpp 301// store a string in a JSON value 302json j_string = "this is a string"; 303 304// retrieve the string value 305auto cpp_string = j_string.template get<std::string>(); 306// retrieve the string value (alternative when a variable already exists) 307std::string cpp_string2; 308j_string.get_to(cpp_string2); 309 310// retrieve the serialized value (explicit JSON serialization) 311std::string serialized_string = j_string.dump(); 312 313// output of original string 314std::cout << cpp_string << " == " << cpp_string2 << " == " << j_string.template get<std::string>() << '\n'; 315// output of serialized value 316std::cout << j_string << " == " << serialized_string << std::endl; 317``` 318 319[`.dump()`](https://json.nlohmann.me/api/basic_json/dump/) returns the originally stored string value. 320 321Note the library only supports UTF-8. When you store strings with different encodings in the library, calling [`dump()`](https://json.nlohmann.me/api/basic_json/dump/) may throw an exception unless `json::error_handler_t::replace` or `json::error_handler_t::ignore` are used as error handlers. 322 323#### To/from streams (e.g. files, string streams) 324 325You can also use streams to serialize and deserialize: 326 327```cpp 328// deserialize from standard input 329json j; 330std::cin >> j; 331 332// serialize to standard output 333std::cout << j; 334 335// the setw manipulator was overloaded to set the indentation for pretty printing 336std::cout << std::setw(4) << j << std::endl; 337``` 338 339These operators work for any subclasses of `std::istream` or `std::ostream`. Here is the same example with files: 340 341```cpp 342// read a JSON file 343std::ifstream i("file.json"); 344json j; 345i >> j; 346 347// write prettified JSON to another file 348std::ofstream o("pretty.json"); 349o << std::setw(4) << j << std::endl; 350``` 351 352Please note that setting the exception bit for `failbit` is inappropriate for this use case. It will result in program termination due to the `noexcept` specifier in use. 353 354#### Read from iterator range 355 356You can also parse JSON from an iterator range; that is, from any container accessible by iterators whose `value_type` is an integral type of 1, 2 or 4 bytes, which will be interpreted as UTF-8, UTF-16 and UTF-32 respectively. For instance, a `std::vector<std::uint8_t>`, or a `std::list<std::uint16_t>`: 357 358```cpp 359std::vector<std::uint8_t> v = {'t', 'r', 'u', 'e'}; 360json j = json::parse(v.begin(), v.end()); 361``` 362 363You may leave the iterators for the range [begin, end): 364 365```cpp 366std::vector<std::uint8_t> v = {'t', 'r', 'u', 'e'}; 367json j = json::parse(v); 368``` 369 370#### Custom data source 371 372Since the parse function accepts arbitrary iterator ranges, you can provide your own data sources by implementing the `LegacyInputIterator` concept. 373 374```cpp 375struct MyContainer { 376 void advance(); 377 const char& get_current(); 378}; 379 380struct MyIterator { 381 using difference_type = std::ptrdiff_t; 382 using value_type = char; 383 using pointer = const char*; 384 using reference = const char&; 385 using iterator_category = std::input_iterator_tag; 386 387 MyIterator& operator++() { 388 MyContainer.advance(); 389 return *this; 390 } 391 392 bool operator!=(const MyIterator& rhs) const { 393 return rhs.target != target; 394 } 395 396 reference operator*() const { 397 return target.get_current(); 398 } 399 400 MyContainer* target = nullptr; 401}; 402 403MyIterator begin(MyContainer& tgt) { 404 return MyIterator{&tgt}; 405} 406 407MyIterator end(const MyContainer&) { 408 return {}; 409} 410 411void foo() { 412 MyContainer c; 413 json j = json::parse(c); 414} 415``` 416 417#### SAX interface 418 419The library uses a SAX-like interface with the following functions: 420 421```cpp 422// called when null is parsed 423bool null(); 424 425// called when a boolean is parsed; value is passed 426bool boolean(bool val); 427 428// called when a signed or unsigned integer number is parsed; value is passed 429bool number_integer(number_integer_t val); 430bool number_unsigned(number_unsigned_t val); 431 432// called when a floating-point number is parsed; value and original string is passed 433bool number_float(number_float_t val, const string_t& s); 434 435// called when a string is parsed; value is passed and can be safely moved away 436bool string(string_t& val); 437// called when a binary value is parsed; value is passed and can be safely moved away 438bool binary(binary_t& val); 439 440// called when an object or array begins or ends, resp. The number of elements is passed (or -1 if not known) 441bool start_object(std::size_t elements); 442bool end_object(); 443bool start_array(std::size_t elements); 444bool end_array(); 445// called when an object key is parsed; value is passed and can be safely moved away 446bool key(string_t& val); 447 448// called when a parse error occurs; byte position, the last token, and an exception is passed 449bool parse_error(std::size_t position, const std::string& last_token, const detail::exception& ex); 450``` 451 452The return value of each function determines whether parsing should proceed. 453 454To implement your own SAX handler, proceed as follows: 455 4561. Implement the SAX interface in a class. You can use class `nlohmann::json_sax<json>` as base class, but you can also use any class where the functions described above are implemented and public. 4572. Create an object of your SAX interface class, e.g. `my_sax`. 4583. Call `bool json::sax_parse(input, &my_sax)`; where the first parameter can be any input like a string or an input stream and the second parameter is a pointer to your SAX interface. 459 460Note the `sax_parse` function only returns a `bool` indicating the result of the last executed SAX event. It does not return a `json` value - it is up to you to decide what to do with the SAX events. Furthermore, no exceptions are thrown in case of a parse error - it is up to you what to do with the exception object passed to your `parse_error` implementation. Internally, the SAX interface is used for the DOM parser (class `json_sax_dom_parser`) as well as the acceptor (`json_sax_acceptor`), see file [`json_sax.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/json_sax.hpp). 461 462### STL-like access 463 464We designed the JSON class to behave just like an STL container. In fact, it satisfies the [**ReversibleContainer**](https://en.cppreference.com/w/cpp/named_req/ReversibleContainer) requirement. 465 466```cpp 467// create an array using push_back 468json j; 469j.push_back("foo"); 470j.push_back(1); 471j.push_back(true); 472 473// also use emplace_back 474j.emplace_back(1.78); 475 476// iterate the array 477for (json::iterator it = j.begin(); it != j.end(); ++it) { 478 std::cout << *it << '\n'; 479} 480 481// range-based for 482for (auto& element : j) { 483 std::cout << element << '\n'; 484} 485 486// getter/setter 487const auto tmp = j[0].template get<std::string>(); 488j[1] = 42; 489bool foo = j.at(2); 490 491// comparison 492j == R"(["foo", 1, true, 1.78])"_json; // true 493 494// other stuff 495j.size(); // 4 entries 496j.empty(); // false 497j.type(); // json::value_t::array 498j.clear(); // the array is empty again 499 500// convenience type checkers 501j.is_null(); 502j.is_boolean(); 503j.is_number(); 504j.is_object(); 505j.is_array(); 506j.is_string(); 507 508// create an object 509json o; 510o["foo"] = 23; 511o["bar"] = false; 512o["baz"] = 3.141; 513 514// also use emplace 515o.emplace("weather", "sunny"); 516 517// special iterator member functions for objects 518for (json::iterator it = o.begin(); it != o.end(); ++it) { 519 std::cout << it.key() << " : " << it.value() << "\n"; 520} 521 522// the same code as range for 523for (auto& el : o.items()) { 524 std::cout << el.key() << " : " << el.value() << "\n"; 525} 526 527// even easier with structured bindings (C++17) 528for (auto& [key, value] : o.items()) { 529 std::cout << key << " : " << value << "\n"; 530} 531 532// find an entry 533if (o.contains("foo")) { 534 // there is an entry with key "foo" 535} 536 537// or via find and an iterator 538if (o.find("foo") != o.end()) { 539 // there is an entry with key "foo" 540} 541 542// or simpler using count() 543int foo_present = o.count("foo"); // 1 544int fob_present = o.count("fob"); // 0 545 546// delete an entry 547o.erase("foo"); 548``` 549 550 551### Conversion from STL containers 552 553Any sequence container (`std::array`, `std::vector`, `std::deque`, `std::forward_list`, `std::list`) whose values can be used to construct JSON values (e.g., integers, floating point numbers, Booleans, string types, or again STL containers described in this section) can be used to create a JSON array. The same holds for similar associative containers (`std::set`, `std::multiset`, `std::unordered_set`, `std::unordered_multiset`), but in these cases the order of the elements of the array depends on how the elements are ordered in the respective STL container. 554 555```cpp 556std::vector<int> c_vector {1, 2, 3, 4}; 557json j_vec(c_vector); 558// [1, 2, 3, 4] 559 560std::deque<double> c_deque {1.2, 2.3, 3.4, 5.6}; 561json j_deque(c_deque); 562// [1.2, 2.3, 3.4, 5.6] 563 564std::list<bool> c_list {true, true, false, true}; 565json j_list(c_list); 566// [true, true, false, true] 567 568std::forward_list<int64_t> c_flist {12345678909876, 23456789098765, 34567890987654, 45678909876543}; 569json j_flist(c_flist); 570// [12345678909876, 23456789098765, 34567890987654, 45678909876543] 571 572std::array<unsigned long, 4> c_array {{1, 2, 3, 4}}; 573json j_array(c_array); 574// [1, 2, 3, 4] 575 576std::set<std::string> c_set {"one", "two", "three", "four", "one"}; 577json j_set(c_set); // only one entry for "one" is used 578// ["four", "one", "three", "two"] 579 580std::unordered_set<std::string> c_uset {"one", "two", "three", "four", "one"}; 581json j_uset(c_uset); // only one entry for "one" is used 582// maybe ["two", "three", "four", "one"] 583 584std::multiset<std::string> c_mset {"one", "two", "one", "four"}; 585json j_mset(c_mset); // both entries for "one" are used 586// maybe ["one", "two", "one", "four"] 587 588std::unordered_multiset<std::string> c_umset {"one", "two", "one", "four"}; 589json j_umset(c_umset); // both entries for "one" are used 590// maybe ["one", "two", "one", "four"] 591``` 592 593Likewise, any associative key-value containers (`std::map`, `std::multimap`, `std::unordered_map`, `std::unordered_multimap`) whose keys can construct an `std::string` and whose values can be used to construct JSON values (see examples above) can be used to create a JSON object. Note that in case of multimaps only one key is used in the JSON object and the value depends on the internal order of the STL container. 594 595```cpp 596std::map<std::string, int> c_map { {"one", 1}, {"two", 2}, {"three", 3} }; 597json j_map(c_map); 598// {"one": 1, "three": 3, "two": 2 } 599 600std::unordered_map<const char*, double> c_umap { {"one", 1.2}, {"two", 2.3}, {"three", 3.4} }; 601json j_umap(c_umap); 602// {"one": 1.2, "two": 2.3, "three": 3.4} 603 604std::multimap<std::string, bool> c_mmap { {"one", true}, {"two", true}, {"three", false}, {"three", true} }; 605json j_mmap(c_mmap); // only one entry for key "three" is used 606// maybe {"one": true, "two": true, "three": true} 607 608std::unordered_multimap<std::string, bool> c_ummap { {"one", true}, {"two", true}, {"three", false}, {"three", true} }; 609json j_ummap(c_ummap); // only one entry for key "three" is used 610// maybe {"one": true, "two": true, "three": true} 611``` 612 613### JSON Pointer and JSON Patch 614 615The library supports **JSON Pointer** ([RFC 6901](https://tools.ietf.org/html/rfc6901)) as alternative means to address structured values. On top of this, **JSON Patch** ([RFC 6902](https://tools.ietf.org/html/rfc6902)) allows describing differences between two JSON values - effectively allowing patch and diff operations known from Unix. 616 617```cpp 618// a JSON value 619json j_original = R"({ 620 "baz": ["one", "two", "three"], 621 "foo": "bar" 622})"_json; 623 624// access members with a JSON pointer (RFC 6901) 625j_original["/baz/1"_json_pointer]; 626// "two" 627 628// a JSON patch (RFC 6902) 629json j_patch = R"([ 630 { "op": "replace", "path": "/baz", "value": "boo" }, 631 { "op": "add", "path": "/hello", "value": ["world"] }, 632 { "op": "remove", "path": "/foo"} 633])"_json; 634 635// apply the patch 636json j_result = j_original.patch(j_patch); 637// { 638// "baz": "boo", 639// "hello": ["world"] 640// } 641 642// calculate a JSON patch from two JSON values 643json::diff(j_result, j_original); 644// [ 645// { "op":" replace", "path": "/baz", "value": ["one", "two", "three"] }, 646// { "op": "remove","path": "/hello" }, 647// { "op": "add", "path": "/foo", "value": "bar" } 648// ] 649``` 650 651### JSON Merge Patch 652 653The library supports **JSON Merge Patch** ([RFC 7386](https://tools.ietf.org/html/rfc7386)) as a patch format. Instead of using JSON Pointer (see above) to specify values to be manipulated, it describes the changes using a syntax that closely mimics the document being modified. 654 655```cpp 656// a JSON value 657json j_document = R"({ 658 "a": "b", 659 "c": { 660 "d": "e", 661 "f": "g" 662 } 663})"_json; 664 665// a patch 666json j_patch = R"({ 667 "a":"z", 668 "c": { 669 "f": null 670 } 671})"_json; 672 673// apply the patch 674j_document.merge_patch(j_patch); 675// { 676// "a": "z", 677// "c": { 678// "d": "e" 679// } 680// } 681``` 682 683### Implicit conversions 684 685Supported types can be implicitly converted to JSON values. 686 687It is recommended to **NOT USE** implicit conversions **FROM** a JSON value. 688You can find more details about this recommendation [here](https://www.github.com/nlohmann/json/issues/958). 689You can switch off implicit conversions by defining `JSON_USE_IMPLICIT_CONVERSIONS` to `0` before including the `json.hpp` header. When using CMake, you can also achieve this by setting the option `JSON_ImplicitConversions` to `OFF`. 690 691```cpp 692// strings 693std::string s1 = "Hello, world!"; 694json js = s1; 695auto s2 = js.template get<std::string>(); 696// NOT RECOMMENDED 697std::string s3 = js; 698std::string s4; 699s4 = js; 700 701// Booleans 702bool b1 = true; 703json jb = b1; 704auto b2 = jb.template get<bool>(); 705// NOT RECOMMENDED 706bool b3 = jb; 707bool b4; 708b4 = jb; 709 710// numbers 711int i = 42; 712json jn = i; 713auto f = jn.template get<double>(); 714// NOT RECOMMENDED 715double f2 = jb; 716double f3; 717f3 = jb; 718 719// etc. 720``` 721 722Note that `char` types are not automatically converted to JSON strings, but to integer numbers. A conversion to a string must be specified explicitly: 723 724```cpp 725char ch = 'A'; // ASCII value 65 726json j_default = ch; // stores integer number 65 727json j_string = std::string(1, ch); // stores string "A" 728``` 729 730### Arbitrary types conversions 731 732Every type can be serialized in JSON, not just STL containers and scalar types. Usually, you would do something along those lines: 733 734```cpp 735namespace ns { 736 // a simple struct to model a person 737 struct person { 738 std::string name; 739 std::string address; 740 int age; 741 }; 742} 743 744ns::person p = {"Ned Flanders", "744 Evergreen Terrace", 60}; 745 746// convert to JSON: copy each value into the JSON object 747json j; 748j["name"] = p.name; 749j["address"] = p.address; 750j["age"] = p.age; 751 752// ... 753 754// convert from JSON: copy each value from the JSON object 755ns::person p { 756 j["name"].template get<std::string>(), 757 j["address"].template get<std::string>(), 758 j["age"].template get<int>() 759}; 760``` 761 762It works, but that's quite a lot of boilerplate... Fortunately, there's a better way: 763 764```cpp 765// create a person 766ns::person p {"Ned Flanders", "744 Evergreen Terrace", 60}; 767 768// conversion: person -> json 769json j = p; 770 771std::cout << j << std::endl; 772// {"address":"744 Evergreen Terrace","age":60,"name":"Ned Flanders"} 773 774// conversion: json -> person 775auto p2 = j.template get<ns::person>(); 776 777// that's it 778assert(p == p2); 779``` 780 781#### Basic usage 782 783To make this work with one of your types, you only need to provide two functions: 784 785```cpp 786using json = nlohmann::json; 787 788namespace ns { 789 void to_json(json& j, const person& p) { 790 j = json{{"name", p.name}, {"address", p.address}, {"age", p.age}}; 791 } 792 793 void from_json(const json& j, person& p) { 794 j.at("name").get_to(p.name); 795 j.at("address").get_to(p.address); 796 j.at("age").get_to(p.age); 797 } 798} // namespace ns 799``` 800 801That's all! When calling the `json` constructor with your type, your custom `to_json` method will be automatically called. 802Likewise, when calling `template get<your_type>()` or `get_to(your_type&)`, the `from_json` method will be called. 803 804Some important things: 805 806* Those methods **MUST** be in your type's namespace (which can be the global namespace), or the library will not be able to locate them (in this example, they are in namespace `ns`, where `person` is defined). 807* Those methods **MUST** be available (e.g., proper headers must be included) everywhere you use these conversions. Look at [issue 1108](https://github.com/nlohmann/json/issues/1108) for errors that may occur otherwise. 808* When using `template get<your_type>()`, `your_type` **MUST** be [DefaultConstructible](https://en.cppreference.com/w/cpp/named_req/DefaultConstructible). (There is a way to bypass this requirement described later.) 809* In function `from_json`, use function [`at()`](https://json.nlohmann.me/api/basic_json/at/) to access the object values rather than `operator[]`. In case a key does not exist, `at` throws an exception that you can handle, whereas `operator[]` exhibits undefined behavior. 810* You do not need to add serializers or deserializers for STL types like `std::vector`: the library already implements these. 811 812#### Simplify your life with macros 813 814If you just want to serialize/deserialize some structs, the `to_json`/`from_json` functions can be a lot of boilerplate. 815 816There are two macros to make your life easier as long as you (1) want to use a JSON object as serialization and (2) want to use the member variable names as object keys in that object: 817 818- `NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(name, member1, member2, ...)` is to be defined inside the namespace of the class/struct to create code for. 819- `NLOHMANN_DEFINE_TYPE_INTRUSIVE(name, member1, member2, ...)` is to be defined inside the class/struct to create code for. This macro can also access private members. 820 821In both macros, the first parameter is the name of the class/struct, and all remaining parameters name the members. 822 823##### Examples 824 825The `to_json`/`from_json` functions for the `person` struct above can be created with: 826 827```cpp 828namespace ns { 829 NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(person, name, address, age) 830} 831``` 832 833Here is an example with private members, where `NLOHMANN_DEFINE_TYPE_INTRUSIVE` is needed: 834 835```cpp 836namespace ns { 837 class address { 838 private: 839 std::string street; 840 int housenumber; 841 int postcode; 842 843 public: 844 NLOHMANN_DEFINE_TYPE_INTRUSIVE(address, street, housenumber, postcode) 845 }; 846} 847``` 848 849#### How do I convert third-party types? 850 851This requires a bit more advanced technique. But first, let's see how this conversion mechanism works: 852 853The library uses **JSON Serializers** to convert types to json. 854The default serializer for `nlohmann::json` is `nlohmann::adl_serializer` (ADL means [Argument-Dependent Lookup](https://en.cppreference.com/w/cpp/language/adl)). 855 856It is implemented like this (simplified): 857 858```cpp 859template <typename T> 860struct adl_serializer { 861 static void to_json(json& j, const T& value) { 862 // calls the "to_json" method in T's namespace 863 } 864 865 static void from_json(const json& j, T& value) { 866 // same thing, but with the "from_json" method 867 } 868}; 869``` 870 871This serializer works fine when you have control over the type's namespace. However, what about `boost::optional` or `std::filesystem::path` (C++17)? Hijacking the `boost` namespace is pretty bad, and it's illegal to add something other than template specializations to `std`... 872 873To solve this, you need to add a specialization of `adl_serializer` to the `nlohmann` namespace, here's an example: 874 875```cpp 876// partial specialization (full specialization works too) 877namespace nlohmann { 878 template <typename T> 879 struct adl_serializer<boost::optional<T>> { 880 static void to_json(json& j, const boost::optional<T>& opt) { 881 if (opt == boost::none) { 882 j = nullptr; 883 } else { 884 j = *opt; // this will call adl_serializer<T>::to_json which will 885 // find the free function to_json in T's namespace! 886 } 887 } 888 889 static void from_json(const json& j, boost::optional<T>& opt) { 890 if (j.is_null()) { 891 opt = boost::none; 892 } else { 893 opt = j.template get<T>(); // same as above, but with 894 // adl_serializer<T>::from_json 895 } 896 } 897 }; 898} 899``` 900 901#### How can I use `get()` for non-default constructible/non-copyable types? 902 903There is a way, if your type is [MoveConstructible](https://en.cppreference.com/w/cpp/named_req/MoveConstructible). You will need to specialize the `adl_serializer` as well, but with a special `from_json` overload: 904 905```cpp 906struct move_only_type { 907 move_only_type() = delete; 908 move_only_type(int ii): i(ii) {} 909 move_only_type(const move_only_type&) = delete; 910 move_only_type(move_only_type&&) = default; 911 912 int i; 913}; 914 915namespace nlohmann { 916 template <> 917 struct adl_serializer<move_only_type> { 918 // note: the return type is no longer 'void', and the method only takes 919 // one argument 920 static move_only_type from_json(const json& j) { 921 return {j.template get<int>()}; 922 } 923 924 // Here's the catch! You must provide a to_json method! Otherwise, you 925 // will not be able to convert move_only_type to json, since you fully 926 // specialized adl_serializer on that type 927 static void to_json(json& j, move_only_type t) { 928 j = t.i; 929 } 930 }; 931} 932``` 933 934#### Can I write my own serializer? (Advanced use) 935 936Yes. You might want to take a look at [`unit-udt.cpp`](https://github.com/nlohmann/json/blob/develop/tests/src/unit-udt.cpp) in the test suite, to see a few examples. 937 938If you write your own serializer, you'll need to do a few things: 939 940- use a different `basic_json` alias than `nlohmann::json` (the last template parameter of `basic_json` is the `JSONSerializer`) 941- use your `basic_json` alias (or a template parameter) in all your `to_json`/`from_json` methods 942- use `nlohmann::to_json` and `nlohmann::from_json` when you need ADL 943 944Here is an example, without simplifications, that only accepts types with a size <= 32, and uses ADL. 945 946```cpp 947// You should use void as a second template argument 948// if you don't need compile-time checks on T 949template<typename T, typename SFINAE = typename std::enable_if<sizeof(T) <= 32>::type> 950struct less_than_32_serializer { 951 template <typename BasicJsonType> 952 static void to_json(BasicJsonType& j, T value) { 953 // we want to use ADL, and call the correct to_json overload 954 using nlohmann::to_json; // this method is called by adl_serializer, 955 // this is where the magic happens 956 to_json(j, value); 957 } 958 959 template <typename BasicJsonType> 960 static void from_json(const BasicJsonType& j, T& value) { 961 // same thing here 962 using nlohmann::from_json; 963 from_json(j, value); 964 } 965}; 966``` 967 968Be **very** careful when reimplementing your serializer, you can stack overflow if you don't pay attention: 969 970```cpp 971template <typename T, void> 972struct bad_serializer 973{ 974 template <typename BasicJsonType> 975 static void to_json(BasicJsonType& j, const T& value) { 976 // this calls BasicJsonType::json_serializer<T>::to_json(j, value); 977 // if BasicJsonType::json_serializer == bad_serializer ... oops! 978 j = value; 979 } 980 981 template <typename BasicJsonType> 982 static void to_json(const BasicJsonType& j, T& value) { 983 // this calls BasicJsonType::json_serializer<T>::from_json(j, value); 984 // if BasicJsonType::json_serializer == bad_serializer ... oops! 985 value = j.template get<T>(); // oops! 986 } 987}; 988``` 989 990### Specializing enum conversion 991 992By default, enum values are serialized to JSON as integers. In some cases this could result in undesired behavior. If an enum is modified or re-ordered after data has been serialized to JSON, the later de-serialized JSON data may be undefined or a different enum value than was originally intended. 993 994It is possible to more precisely specify how a given enum is mapped to and from JSON as shown below: 995 996```cpp 997// example enum type declaration 998enum TaskState { 999 TS_STOPPED, 1000 TS_RUNNING, 1001 TS_COMPLETED, 1002 TS_INVALID=-1, 1003}; 1004 1005// map TaskState values to JSON as strings 1006NLOHMANN_JSON_SERIALIZE_ENUM( TaskState, { 1007 {TS_INVALID, nullptr}, 1008 {TS_STOPPED, "stopped"}, 1009 {TS_RUNNING, "running"}, 1010 {TS_COMPLETED, "completed"}, 1011}) 1012``` 1013 1014The `NLOHMANN_JSON_SERIALIZE_ENUM()` macro declares a set of `to_json()` / `from_json()` functions for type `TaskState` while avoiding repetition and boilerplate serialization code. 1015 1016**Usage:** 1017 1018```cpp 1019// enum to JSON as string 1020json j = TS_STOPPED; 1021assert(j == "stopped"); 1022 1023// json string to enum 1024json j3 = "running"; 1025assert(j3.template get<TaskState>() == TS_RUNNING); 1026 1027// undefined json value to enum (where the first map entry above is the default) 1028json jPi = 3.14; 1029assert(jPi.template get<TaskState>() == TS_INVALID ); 1030``` 1031 1032Just as in [Arbitrary Type Conversions](#arbitrary-types-conversions) above, 1033- `NLOHMANN_JSON_SERIALIZE_ENUM()` MUST be declared in your enum type's namespace (which can be the global namespace), or the library will not be able to locate it, and it will default to integer serialization. 1034- It MUST be available (e.g., proper headers must be included) everywhere you use the conversions. 1035 1036Other Important points: 1037- When using `template get<ENUM_TYPE>()`, undefined JSON values will default to the first pair specified in your map. Select this default pair carefully. 1038- If an enum or JSON value is specified more than once in your map, the first matching occurrence from the top of the map will be returned when converting to or from JSON. 1039 1040### Binary formats (BSON, CBOR, MessagePack, UBJSON, and BJData) 1041 1042Though JSON is a ubiquitous data format, it is not a very compact format suitable for data exchange, for instance over a network. Hence, the library supports [BSON](https://bsonspec.org) (Binary JSON), [CBOR](https://cbor.io) (Concise Binary Object Representation), [MessagePack](https://msgpack.org), [UBJSON](https://ubjson.org) (Universal Binary JSON Specification) and [BJData](https://neurojson.org/bjdata) (Binary JData) to efficiently encode JSON values to byte vectors and to decode such vectors. 1043 1044```cpp 1045// create a JSON value 1046json j = R"({"compact": true, "schema": 0})"_json; 1047 1048// serialize to BSON 1049std::vector<std::uint8_t> v_bson = json::to_bson(j); 1050 1051// 0x1B, 0x00, 0x00, 0x00, 0x08, 0x63, 0x6F, 0x6D, 0x70, 0x61, 0x63, 0x74, 0x00, 0x01, 0x10, 0x73, 0x63, 0x68, 0x65, 0x6D, 0x61, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 1052 1053// roundtrip 1054json j_from_bson = json::from_bson(v_bson); 1055 1056// serialize to CBOR 1057std::vector<std::uint8_t> v_cbor = json::to_cbor(j); 1058 1059// 0xA2, 0x67, 0x63, 0x6F, 0x6D, 0x70, 0x61, 0x63, 0x74, 0xF5, 0x66, 0x73, 0x63, 0x68, 0x65, 0x6D, 0x61, 0x00 1060 1061// roundtrip 1062json j_from_cbor = json::from_cbor(v_cbor); 1063 1064// serialize to MessagePack 1065std::vector<std::uint8_t> v_msgpack = json::to_msgpack(j); 1066 1067// 0x82, 0xA7, 0x63, 0x6F, 0x6D, 0x70, 0x61, 0x63, 0x74, 0xC3, 0xA6, 0x73, 0x63, 0x68, 0x65, 0x6D, 0x61, 0x00 1068 1069// roundtrip 1070json j_from_msgpack = json::from_msgpack(v_msgpack); 1071 1072// serialize to UBJSON 1073std::vector<std::uint8_t> v_ubjson = json::to_ubjson(j); 1074 1075// 0x7B, 0x69, 0x07, 0x63, 0x6F, 0x6D, 0x70, 0x61, 0x63, 0x74, 0x54, 0x69, 0x06, 0x73, 0x63, 0x68, 0x65, 0x6D, 0x61, 0x69, 0x00, 0x7D 1076 1077// roundtrip 1078json j_from_ubjson = json::from_ubjson(v_ubjson); 1079``` 1080 1081The library also supports binary types from BSON, CBOR (byte strings), and MessagePack (bin, ext, fixext). They are stored by default as `std::vector<std::uint8_t>` to be processed outside the library. 1082 1083```cpp 1084// CBOR byte string with payload 0xCAFE 1085std::vector<std::uint8_t> v = {0x42, 0xCA, 0xFE}; 1086 1087// read value 1088json j = json::from_cbor(v); 1089 1090// the JSON value has type binary 1091j.is_binary(); // true 1092 1093// get reference to stored binary value 1094auto& binary = j.get_binary(); 1095 1096// the binary value has no subtype (CBOR has no binary subtypes) 1097binary.has_subtype(); // false 1098 1099// access std::vector<std::uint8_t> member functions 1100binary.size(); // 2 1101binary[0]; // 0xCA 1102binary[1]; // 0xFE 1103 1104// set subtype to 0x10 1105binary.set_subtype(0x10); 1106 1107// serialize to MessagePack 1108auto cbor = json::to_msgpack(j); // 0xD5 (fixext2), 0x10, 0xCA, 0xFE 1109``` 1110 1111 1112## Supported compilers 1113 1114Though it's 2023 already, the support for C++11 is still a bit sparse. Currently, the following compilers are known to work: 1115 1116- GCC 4.8 - 12.0 (and possibly later) 1117- Clang 3.4 - 15.0 (and possibly later) 1118- Apple Clang 9.1 - 13.1 (and possibly later) 1119- Intel C++ Compiler 17.0.2 (and possibly later) 1120- Nvidia CUDA Compiler 11.0.221 (and possibly later) 1121- Microsoft Visual C++ 2015 / Build Tools 14.0.25123.0 (and possibly later) 1122- Microsoft Visual C++ 2017 / Build Tools 15.5.180.51428 (and possibly later) 1123- Microsoft Visual C++ 2019 / Build Tools 16.3.1+1def00d3d (and possibly later) 1124- Microsoft Visual C++ 2022 / Build Tools 19.30.30709.0 (and possibly later) 1125 1126I would be happy to learn about other compilers/versions. 1127 1128Please note: 1129 1130- GCC 4.8 has a bug [57824](https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57824)): multiline raw strings cannot be the arguments to macros. Don't use multiline raw strings directly in macros with this compiler. 1131- Android defaults to using very old compilers and C++ libraries. To fix this, add the following to your `Application.mk`. This will switch to the LLVM C++ library, the Clang compiler, and enable C++11 and other features disabled by default. 1132 1133 ``` 1134 APP_STL := c++_shared 1135 NDK_TOOLCHAIN_VERSION := clang3.6 1136 APP_CPPFLAGS += -frtti -fexceptions 1137 ``` 1138 1139 The code compiles successfully with [Android NDK](https://developer.android.com/ndk/index.html?hl=ml), Revision 9 - 11 (and possibly later) and [CrystaX's Android NDK](https://www.crystax.net/en/android/ndk) version 10. 1140 1141- For GCC running on MinGW or Android SDK, the error `'to_string' is not a member of 'std'` (or similarly, for `strtod` or `strtof`) may occur. Note this is not an issue with the code, but rather with the compiler itself. On Android, see above to build with a newer environment. For MinGW, please refer to [this site](https://tehsausage.com/mingw-to-string) and [this discussion](https://github.com/nlohmann/json/issues/136) for information on how to fix this bug. For Android NDK using `APP_STL := gnustl_static`, please refer to [this discussion](https://github.com/nlohmann/json/issues/219). 1142 1143- Unsupported versions of GCC and Clang are rejected by `#error` directives. This can be switched off by defining `JSON_SKIP_UNSUPPORTED_COMPILER_CHECK`. Note that you can expect no support in this case. 1144 1145The following compilers are currently used in continuous integration at [AppVeyor](https://ci.appveyor.com/project/nlohmann/json), [Cirrus CI](https://cirrus-ci.com/github/nlohmann/json), and [GitHub Actions](https://github.com/nlohmann/json/actions): 1146 1147| Compiler | Operating System | CI Provider | 1148|--------------------------------------------------------------------------------------------------------|--------------------|----------------| 1149| Apple Clang 11.0.3 (clang-1103.0.32.62); Xcode 11.7 | macOS 11.7.1 | GitHub Actions | 1150| Apple Clang 12.0.0 (clang-1200.0.32.29); Xcode 12.4 | macOS 11.7.1 | GitHub Actions | 1151| Apple Clang 12.0.5 (clang-1205.0.22.11); Xcode 12.5.1 | macOS 11.7.1 | GitHub Actions | 1152| Apple Clang 13.0.0 (clang-1300.0.29.3); Xcode 13.0 | macOS 11.7.1 | GitHub Actions | 1153| Apple Clang 13.0.0 (clang-1300.0.29.3); Xcode 13.1 | macOS 12.6.1 | GitHub Actions | 1154| Apple Clang 13.0.0 (clang-1300.0.29.30); Xcode 13.2.1 | macOS 12.6.1 | GitHub Actions | 1155| Apple Clang 13.1.6 (clang-1316.0.21.2.3); Xcode 13.3.1 | macOS 12.6.1 | GitHub Actions | 1156| Apple Clang 13.1.6 (clang-1316.0.21.2.5); Xcode 13.4.1 | macOS 12.6.1 | GitHub Actions | 1157| Apple Clang 14.0.0 (clang-1400.0.29.102); Xcode 14.0 | macOS 12.6.1 | GitHub Actions | 1158| Apple Clang 14.0.0 (clang-1400.0.29.102); Xcode 14.0.1 | macOS 12.6.1 | GitHub Actions | 1159| Apple Clang 14.0.0 (clang-1400.0.29.202); Xcode 14.1 | macOS 12.6.1 | GitHub Actions | 1160| Clang 3.5.2 | Ubuntu 20.04.3 LTS | GitHub Actions | 1161| Clang 3.6.2 | Ubuntu 20.04.3 LTS | GitHub Actions | 1162| Clang 3.7.1 | Ubuntu 20.04.3 LTS | GitHub Actions | 1163| Clang 3.8.1 | Ubuntu 20.04.3 LTS | GitHub Actions | 1164| Clang 3.9.1 | Ubuntu 20.04.3 LTS | GitHub Actions | 1165| Clang 4.0.1 | Ubuntu 20.04.3 LTS | GitHub Actions | 1166| Clang 5.0.2 | Ubuntu 20.04.3 LTS | GitHub Actions | 1167| Clang 6.0.1 | Ubuntu 20.04.3 LTS | GitHub Actions | 1168| Clang 7.0.1 | Ubuntu 20.04.3 LTS | GitHub Actions | 1169| Clang 8.0.0 | Ubuntu 20.04.3 LTS | GitHub Actions | 1170| Clang 9.0.0 | Ubuntu 20.04.3 LTS | GitHub Actions | 1171| Clang 10.0.0 | Ubuntu 20.04.3 LTS | GitHub Actions | 1172| Clang 10.0.0 with GNU-like command-line | Windows-10.0.17763 | GitHub Actions | 1173| Clang 11.0.0 with GNU-like command-line | Windows-10.0.17763 | GitHub Actions | 1174| Clang 11.0.0 with MSVC-like command-line | Windows-10.0.17763 | GitHub Actions | 1175| Clang 11.0.0 | Ubuntu 20.04.3 LTS | GitHub Actions | 1176| Clang 12.0.0 | Ubuntu 20.04.3 LTS | GitHub Actions | 1177| Clang 12.0.0 with GNU-like command-line | Windows-10.0.17763 | GitHub Actions | 1178| Clang 13.0.0 | Ubuntu 20.04.3 LTS | GitHub Actions | 1179| Clang 13.0.0 with GNU-like command-line | Windows-10.0.17763 | GitHub Actions | 1180| Clang 14.0.0 | Ubuntu 20.04.3 LTS | GitHub Actions | 1181| Clang 14.0.0 with GNU-like command-line | Windows-10.0.17763 | GitHub Actions | 1182| Clang 15.0.0 with GNU-like command-line | Windows-10.0.17763 | GitHub Actions | 1183| Clang 15.0.4 | Ubuntu 20.04.3 LTS | GitHub Actions | 1184| Clang 16.0.0 (16.0.0-++20221031071727+500876226c60-1~exp1~20221031071831.439) | Ubuntu 20.04.3 LTS | GitHub Actions | 1185| GCC 4.8.5 (Ubuntu 4.8.5-4ubuntu2) | Ubuntu 20.04.3 LTS | GitHub Actions | 1186| GCC 4.9.4 | Ubuntu 20.04.3 LTS | GitHub Actions | 1187| GCC 5.5.0 | Ubuntu 20.04.3 LTS | GitHub Actions | 1188| GCC 6.5.0 | Ubuntu 20.04.3 LTS | GitHub Actions | 1189| GCC 7.5.0 | Ubuntu 20.04.3 LTS | GitHub Actions | 1190| GCC 8.1.0 (i686-posix-dwarf-rev0, Built by MinGW-W64 project) | Windows-10.0.17763 | GitHub Actions | 1191| GCC 8.1.0 (x86_64-posix-seh-rev0, Built by MinGW-W64 project) | Windows-10.0.17763 | GitHub Actions | 1192| GCC 8.5.0 | Ubuntu 20.04.3 LTS | GitHub Actions | 1193| GCC 9.5.0 | Ubuntu 20.04.3 LTS | GitHub Actions | 1194| GCC 10.4.0 | Ubuntu 20.04.3 LTS | GitHub Actions | 1195| GCC 11.1.0 | Ubuntu (aarch64) | Cirrus CI | 1196| GCC 11.3.0 | Ubuntu 20.04.3 LTS | GitHub Actions | 1197| GCC 12.2.0 | Ubuntu 20.04.3 LTS | GitHub Actions | 1198| GCC 13.0.0 20220605 (experimental) | Ubuntu 20.04.3 LTS | GitHub Actions | 1199| Intel C++ Compiler 2021.5.0.20211109 | Ubuntu 20.04.3 LTS | GitHub Actions | 1200| NVCC 11.0.221 | Ubuntu 20.04.3 LTS | GitHub Actions | 1201| Visual Studio 14 2015 MSVC 19.0.24241.7 (Build Engine version 14.0.25420.1) | Windows-6.3.9600 | AppVeyor | 1202| Visual Studio 15 2017 MSVC 19.16.27035.0 (Build Engine version 15.9.21+g9802d43bc3 for .NET Framework) | Windows-10.0.14393 | AppVeyor | 1203| Visual Studio 16 2019 MSVC 19.28.29912.0 (Build Engine version 16.9.0+57a23d249 for .NET Framework) | Windows-10.0.17763 | GitHub Actions | 1204| Visual Studio 16 2019 MSVC 19.28.29912.0 (Build Engine version 16.9.0+57a23d249 for .NET Framework) | Windows-10.0.17763 | AppVeyor | 1205| Visual Studio 17 2022 MSVC 19.30.30709.0 (Build Engine version 17.0.31804.368 for .NET Framework) | Windows-10.0.20348 | GitHub Actions | 1206 1207 1208## Integration 1209 1210[`json.hpp`](https://github.com/nlohmann/json/blob/develop/single_include/nlohmann/json.hpp) is the single required file in `single_include/nlohmann` or [released here](https://github.com/nlohmann/json/releases). You need to add 1211 1212```cpp 1213#include <nlohmann/json.hpp> 1214 1215// for convenience 1216using json = nlohmann::json; 1217``` 1218 1219to the files you want to process JSON and set the necessary switches to enable C++11 (e.g., `-std=c++11` for GCC and Clang). 1220 1221You can further use file [`include/nlohmann/json_fwd.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/json_fwd.hpp) for forward-declarations. The installation of json_fwd.hpp (as part of cmake's install step), can be achieved by setting `-DJSON_MultipleHeaders=ON`. 1222 1223### CMake 1224 1225You can also use the `nlohmann_json::nlohmann_json` interface target in CMake. This target populates the appropriate usage requirements for `INTERFACE_INCLUDE_DIRECTORIES` to point to the appropriate include directories and `INTERFACE_COMPILE_FEATURES` for the necessary C++11 flags. 1226 1227#### External 1228 1229To use this library from a CMake project, you can locate it directly with `find_package()` and use the namespaced imported target from the generated package configuration: 1230 1231```cmake 1232# CMakeLists.txt 1233find_package(nlohmann_json 3.2.0 REQUIRED) 1234... 1235add_library(foo ...) 1236... 1237target_link_libraries(foo PRIVATE nlohmann_json::nlohmann_json) 1238``` 1239 1240The package configuration file, `nlohmann_jsonConfig.cmake`, can be used either from an install tree or directly out of the build tree. 1241 1242#### Embedded 1243 1244To embed the library directly into an existing CMake project, place the entire source tree in a subdirectory and call `add_subdirectory()` in your `CMakeLists.txt` file: 1245 1246```cmake 1247# Typically you don't care so much for a third party library's tests to be 1248# run from your own project's code. 1249set(JSON_BuildTests OFF CACHE INTERNAL "") 1250 1251# If you only include this third party in PRIVATE source files, you do not 1252# need to install it when your main project gets installed. 1253# set(JSON_Install OFF CACHE INTERNAL "") 1254 1255# Don't use include(nlohmann_json/CMakeLists.txt) since that carries with it 1256# unintended consequences that will break the build. It's generally 1257# discouraged (although not necessarily well documented as such) to use 1258# include(...) for pulling in other CMake projects anyways. 1259add_subdirectory(nlohmann_json) 1260... 1261add_library(foo ...) 1262... 1263target_link_libraries(foo PRIVATE nlohmann_json::nlohmann_json) 1264``` 1265 1266##### Embedded (FetchContent) 1267 1268Since CMake v3.11, 1269[FetchContent](https://cmake.org/cmake/help/v3.11/module/FetchContent.html) can 1270be used to automatically download a release as a dependency at configure time. 1271 1272Example: 1273```cmake 1274include(FetchContent) 1275 1276FetchContent_Declare(json URL https://github.com/nlohmann/json/releases/download/v3.11.3/json.tar.xz) 1277FetchContent_MakeAvailable(json) 1278 1279target_link_libraries(foo PRIVATE nlohmann_json::nlohmann_json) 1280``` 1281 1282**Note**: It is recommended to use the URL approach described above which is supported as of version 3.10.0. See 1283<https://json.nlohmann.me/integration/cmake/#fetchcontent> for more information. 1284 1285#### Supporting Both 1286 1287To allow your project to support either an externally supplied or an embedded JSON library, you can use a pattern akin to the following: 1288 1289``` cmake 1290# Top level CMakeLists.txt 1291project(FOO) 1292... 1293option(FOO_USE_EXTERNAL_JSON "Use an external JSON library" OFF) 1294... 1295add_subdirectory(thirdparty) 1296... 1297add_library(foo ...) 1298... 1299# Note that the namespaced target will always be available regardless of the 1300# import method 1301target_link_libraries(foo PRIVATE nlohmann_json::nlohmann_json) 1302``` 1303```cmake 1304# thirdparty/CMakeLists.txt 1305... 1306if(FOO_USE_EXTERNAL_JSON) 1307 find_package(nlohmann_json 3.2.0 REQUIRED) 1308else() 1309 set(JSON_BuildTests OFF CACHE INTERNAL "") 1310 add_subdirectory(nlohmann_json) 1311endif() 1312... 1313``` 1314 1315`thirdparty/nlohmann_json` is then a complete copy of this source tree. 1316 1317### Package Managers 1318 1319:beer: If you are using OS X and [Homebrew](https://brew.sh), just type `brew install nlohmann-json` and you're set. If you want the bleeding edge rather than the latest release, use `brew install nlohmann-json --HEAD`. See [nlohmann-json](https://formulae.brew.sh/formula/nlohmann-json) for more information. 1320 1321If you are using the [Meson Build System](https://mesonbuild.com), add this source tree as a [meson subproject](https://mesonbuild.com/Subprojects.html#using-a-subproject). You may also use the `include.zip` published in this project's [Releases](https://github.com/nlohmann/json/releases) to reduce the size of the vendored source tree. Alternatively, you can get a wrap file by downloading it from [Meson WrapDB](https://wrapdb.mesonbuild.com/nlohmann_json), or simply use `meson wrap install nlohmann_json`. Please see the meson project for any issues regarding the packaging. 1322 1323The provided `meson.build` can also be used as an alternative to CMake for installing `nlohmann_json` system-wide in which case a pkg-config file is installed. To use it, simply have your build system require the `nlohmann_json` pkg-config dependency. In Meson, it is preferred to use the [`dependency()`](https://mesonbuild.com/Reference-manual.html#dependency) object with a subproject fallback, rather than using the subproject directly. 1324 1325If you are using [Bazel](https://bazel.build/) you can simply reference this repository using `http_archive` or `git_repository` and depend on `@nlohmann_json//:json`. 1326 1327If you are using [Conan](https://www.conan.io/) to manage your dependencies, merely add [`nlohmann_json/x.y.z`](https://conan.io/center/nlohmann_json) to your `conanfile`'s requires, where `x.y.z` is the release version you want to use. Please file issues [here](https://github.com/conan-io/conan-center-index/issues) if you experience problems with the packages. 1328 1329If you are using [Spack](https://www.spack.io/) to manage your dependencies, you can use the [`nlohmann-json` package](https://spack.readthedocs.io/en/latest/package_list.html#nlohmann-json). Please see the [spack project](https://github.com/spack/spack) for any issues regarding the packaging. 1330 1331If you are using [hunter](https://github.com/cpp-pm/hunter) on your project for external dependencies, then you can use the [nlohmann_json package](https://hunter.readthedocs.io/en/latest/packages/pkg/nlohmann_json.html). Please see the hunter project for any issues regarding the packaging. 1332 1333If you are using [Buckaroo](https://buckaroo.pm), you can install this library's module with `buckaroo add github.com/buckaroo-pm/nlohmann-json`. Please file issues [here](https://github.com/buckaroo-pm/nlohmann-json). There is a demo repo [here](https://github.com/njlr/buckaroo-nholmann-json-example). 1334 1335If you are using [vcpkg](https://github.com/Microsoft/vcpkg/) on your project for external dependencies, then you can install the [nlohmann-json package](https://github.com/Microsoft/vcpkg/tree/master/ports/nlohmann-json) with `vcpkg install nlohmann-json` and follow the then displayed descriptions. Please see the vcpkg project for any issues regarding the packaging. 1336 1337If you are using [cget](https://cget.readthedocs.io/en/latest/), you can install the latest development version with `cget install nlohmann/json`. A specific version can be installed with `cget install nlohmann/json@v3.1.0`. Also, the multiple header version can be installed by adding the `-DJSON_MultipleHeaders=ON` flag (i.e., `cget install nlohmann/json -DJSON_MultipleHeaders=ON`). 1338 1339If you are using [CocoaPods](https://cocoapods.org), you can use the library by adding pod `"nlohmann_json", '~>3.1.2'` to your podfile (see [an example](https://bitbucket.org/benman/nlohmann_json-cocoapod/src/master/)). Please file issues [here](https://bitbucket.org/benman/nlohmann_json-cocoapod/issues?status=new&status=open). 1340 1341If you are using [Swift Package Manager](https://swift.org/package-manager/), you can use the library by adding a package dependency to this repository. And target dependency as `.product(name: "nlohmann-json", package: "json")`. 1342 1343If you are using [NuGet](https://www.nuget.org), you can use the package [nlohmann.json](https://www.nuget.org/packages/nlohmann.json/). Please check [this extensive description](https://github.com/nlohmann/json/issues/1132#issuecomment-452250255) on how to use the package. Please file issues [here](https://github.com/hnkb/nlohmann-json-nuget/issues). 1344 1345If you are using [conda](https://conda.io/), you can use the package [nlohmann_json](https://github.com/conda-forge/nlohmann_json-feedstock) from [conda-forge](https://conda-forge.org) executing `conda install -c conda-forge nlohmann_json`. Please file issues [here](https://github.com/conda-forge/nlohmann_json-feedstock/issues). 1346 1347If you are using [MSYS2](https://www.msys2.org/), you can use the [mingw-w64-nlohmann-json](https://packages.msys2.org/base/mingw-w64-nlohmann-json) package, just type `pacman -S mingw-w64-i686-nlohmann-json` or `pacman -S mingw-w64-x86_64-nlohmann-json` for installation. Please file issues [here](https://github.com/msys2/MINGW-packages/issues/new?title=%5Bnlohmann-json%5D) if you experience problems with the packages. 1348 1349If you are using [MacPorts](https://ports.macports.org), execute `sudo port install nlohmann-json` to install the [nlohmann-json](https://ports.macports.org/port/nlohmann-json/) package. 1350 1351If you are using [`build2`](https://build2.org), you can use the [`nlohmann-json`](https://cppget.org/nlohmann-json) package from the public repository https://cppget.org or directly from the [package's sources repository](https://github.com/build2-packaging/nlohmann-json). In your project's `manifest` file, just add `depends: nlohmann-json` (probably with some [version constraints](https://build2.org/build2-toolchain/doc/build2-toolchain-intro.xhtml#guide-add-remove-deps)). If you are not familiar with using dependencies in `build2`, [please read this introduction](https://build2.org/build2-toolchain/doc/build2-toolchain-intro.xhtml). 1352Please file issues [here](https://github.com/build2-packaging/nlohmann-json) if you experience problems with the packages. 1353 1354If you are using [`wsjcpp`](https://wsjcpp.org), you can use the command `wsjcpp install "https://github.com/nlohmann/json:develop"` to get the latest version. Note you can change the branch ":develop" to an existing tag or another branch. 1355 1356If you are using [`CPM.cmake`](https://github.com/TheLartians/CPM.cmake), you can check this [`example`](https://github.com/TheLartians/CPM.cmake/tree/master/examples/json). After [adding CPM script](https://github.com/TheLartians/CPM.cmake#adding-cpm) to your project, implement the following snippet to your CMake: 1357 1358```cmake 1359CPMAddPackage( 1360 NAME nlohmann_json 1361 GITHUB_REPOSITORY nlohmann/json 1362 VERSION 3.9.1) 1363``` 1364 1365### Pkg-config 1366 1367If you are using bare Makefiles, you can use `pkg-config` to generate the include flags that point to where the library is installed: 1368 1369```sh 1370pkg-config nlohmann_json --cflags 1371``` 1372 1373Users of the Meson build system will also be able to use a system-wide library, which will be found by `pkg-config`: 1374 1375```meson 1376json = dependency('nlohmann_json', required: true) 1377``` 1378 1379 1380## License 1381 1382<img align="right" src="https://opensource.org/trademarks/opensource/OSI-Approved-License-100x137.png"> 1383 1384The class is licensed under the [MIT License](https://opensource.org/licenses/MIT): 1385 1386Copyright © 2013-2022 [Niels Lohmann](https://nlohmann.me) 1387 1388Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: 1389 1390The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. 1391 1392THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. 1393 1394* * * 1395 1396The class contains the UTF-8 Decoder from Bjoern Hoehrmann which is licensed under the [MIT License](https://opensource.org/licenses/MIT) (see above). Copyright © 2008-2009 [Björn Hoehrmann](https://bjoern.hoehrmann.de/) <bjoern@hoehrmann.de> 1397 1398The class contains a slightly modified version of the Grisu2 algorithm from Florian Loitsch which is licensed under the [MIT License](https://opensource.org/licenses/MIT) (see above). Copyright © 2009 [Florian Loitsch](https://florian.loitsch.com/) 1399 1400The class contains a copy of [Hedley](https://nemequ.github.io/hedley/) from Evan Nemerson which is licensed as [CC0-1.0](https://creativecommons.org/publicdomain/zero/1.0/). 1401 1402The class contains parts of [Google Abseil](https://github.com/abseil/abseil-cpp) which is licensed under the [Apache 2.0 License](https://opensource.org/licenses/Apache-2.0). 1403 1404## Contact 1405 1406If you have questions regarding the library, I would like to invite you to [open an issue at GitHub](https://github.com/nlohmann/json/issues/new/choose). Please describe your request, problem, or question as detailed as possible, and also mention the version of the library you are using as well as the version of your compiler and operating system. Opening an issue at GitHub allows other users and contributors to this library to collaborate. For instance, I have little experience with MSVC, and most issues in this regard have been solved by a growing community. If you have a look at the [closed issues](https://github.com/nlohmann/json/issues?q=is%3Aissue+is%3Aclosed), you will see that we react quite timely in most cases. 1407 1408Only if your request would contain confidential information, please [send me an email](mailto:mail@nlohmann.me). For encrypted messages, please use [this key](https://keybase.io/nlohmann/pgp_keys.asc). 1409 1410## Security 1411 1412[Commits by Niels Lohmann](https://github.com/nlohmann/json/commits) and [releases](https://github.com/nlohmann/json/releases) are signed with this [PGP Key](https://keybase.io/nlohmann/pgp_keys.asc?fingerprint=797167ae41c0a6d9232e48457f3cea63ae251b69). 1413 1414## Thanks 1415 1416I deeply appreciate the help of the following people. 1417 1418<img src="https://raw.githubusercontent.com/nlohmann/json/develop/docs/avatars.png" align="right"> 1419 14201. [Teemperor](https://github.com/Teemperor) implemented CMake support and lcov integration, realized escape and Unicode handling in the string parser, and fixed the JSON serialization. 14212. [elliotgoodrich](https://github.com/elliotgoodrich) fixed an issue with double deletion in the iterator classes. 14223. [kirkshoop](https://github.com/kirkshoop) made the iterators of the class composable to other libraries. 14234. [wancw](https://github.com/wanwc) fixed a bug that hindered the class to compile with Clang. 14245. Tomas Åblad found a bug in the iterator implementation. 14256. [Joshua C. Randall](https://github.com/jrandall) fixed a bug in the floating-point serialization. 14267. [Aaron Burghardt](https://github.com/aburgh) implemented code to parse streams incrementally. Furthermore, he greatly improved the parser class by allowing the definition of a filter function to discard undesired elements while parsing. 14278. [Daniel Kopeček](https://github.com/dkopecek) fixed a bug in the compilation with GCC 5.0. 14289. [Florian Weber](https://github.com/Florianjw) fixed a bug in and improved the performance of the comparison operators. 142910. [Eric Cornelius](https://github.com/EricMCornelius) pointed out a bug in the handling with NaN and infinity values. He also improved the performance of the string escaping. 143011. [易思龙](https://github.com/likebeta) implemented a conversion from anonymous enums. 143112. [kepkin](https://github.com/kepkin) patiently pushed forward the support for Microsoft Visual studio. 143213. [gregmarr](https://github.com/gregmarr) simplified the implementation of reverse iterators and helped with numerous hints and improvements. In particular, he pushed forward the implementation of user-defined types. 143314. [Caio Luppi](https://github.com/caiovlp) fixed a bug in the Unicode handling. 143415. [dariomt](https://github.com/dariomt) fixed some typos in the examples. 143516. [Daniel Frey](https://github.com/d-frey) cleaned up some pointers and implemented exception-safe memory allocation. 143617. [Colin Hirsch](https://github.com/ColinH) took care of a small namespace issue. 143718. [Huu Nguyen](https://github.com/whoshuu) correct a variable name in the documentation. 143819. [Silverweed](https://github.com/silverweed) overloaded `parse()` to accept an rvalue reference. 143920. [dariomt](https://github.com/dariomt) fixed a subtlety in MSVC type support and implemented the `get_ref()` function to get a reference to stored values. 144021. [ZahlGraf](https://github.com/ZahlGraf) added a workaround that allows compilation using Android NDK. 144122. [whackashoe](https://github.com/whackashoe) replaced a function that was marked as unsafe by Visual Studio. 144223. [406345](https://github.com/406345) fixed two small warnings. 144324. [Glen Fernandes](https://github.com/glenfe) noted a potential portability problem in the `has_mapped_type` function. 144425. [Corbin Hughes](https://github.com/nibroc) fixed some typos in the contribution guidelines. 144526. [twelsby](https://github.com/twelsby) fixed the array subscript operator, an issue that failed the MSVC build, and floating-point parsing/dumping. He further added support for unsigned integer numbers and implemented better roundtrip support for parsed numbers. 144627. [Volker Diels-Grabsch](https://github.com/vog) fixed a link in the README file. 144728. [msm-](https://github.com/msm-) added support for American Fuzzy Lop. 144829. [Annihil](https://github.com/Annihil) fixed an example in the README file. 144930. [Themercee](https://github.com/Themercee) noted a wrong URL in the README file. 145031. [Lv Zheng](https://github.com/lv-zheng) fixed a namespace issue with `int64_t` and `uint64_t`. 145132. [abc100m](https://github.com/abc100m) analyzed the issues with GCC 4.8 and proposed a [partial solution](https://github.com/nlohmann/json/pull/212). 145233. [zewt](https://github.com/zewt) added useful notes to the README file about Android. 145334. [Róbert Márki](https://github.com/robertmrk) added a fix to use move iterators and improved the integration via CMake. 145435. [Chris Kitching](https://github.com/ChrisKitching) cleaned up the CMake files. 145536. [Tom Needham](https://github.com/06needhamt) fixed a subtle bug with MSVC 2015 which was also proposed by [Michael K.](https://github.com/Epidal). 145637. [Mário Feroldi](https://github.com/thelostt) fixed a small typo. 145738. [duncanwerner](https://github.com/duncanwerner) found a really embarrassing performance regression in the 2.0.0 release. 145839. [Damien](https://github.com/dtoma) fixed one of the last conversion warnings. 145940. [Thomas Braun](https://github.com/t-b) fixed a warning in a test case and adjusted MSVC calls in the CI. 146041. [Théo DELRIEU](https://github.com/theodelrieu) patiently and constructively oversaw the long way toward [iterator-range parsing](https://github.com/nlohmann/json/issues/290). He also implemented the magic behind the serialization/deserialization of user-defined types and split the single header file into smaller chunks. 146142. [Stefan](https://github.com/5tefan) fixed a minor issue in the documentation. 146243. [Vasil Dimov](https://github.com/vasild) fixed the documentation regarding conversions from `std::multiset`. 146344. [ChristophJud](https://github.com/ChristophJud) overworked the CMake files to ease project inclusion. 146445. [Vladimir Petrigo](https://github.com/vpetrigo) made a SFINAE hack more readable and added Visual Studio 17 to the build matrix. 146546. [Denis Andrejew](https://github.com/seeekr) fixed a grammar issue in the README file. 146647. [Pierre-Antoine Lacaze](https://github.com/palacaze) found a subtle bug in the `dump()` function. 146748. [TurpentineDistillery](https://github.com/TurpentineDistillery) pointed to [`std::locale::classic()`](https://en.cppreference.com/w/cpp/locale/locale/classic) to avoid too much locale joggling, found some nice performance improvements in the parser, improved the benchmarking code, and realized locale-independent number parsing and printing. 146849. [cgzones](https://github.com/cgzones) had an idea how to fix the Coverity scan. 146950. [Jared Grubb](https://github.com/jaredgrubb) silenced a nasty documentation warning. 147051. [Yixin Zhang](https://github.com/qwename) fixed an integer overflow check. 147152. [Bosswestfalen](https://github.com/Bosswestfalen) merged two iterator classes into a smaller one. 147253. [Daniel599](https://github.com/Daniel599) helped to get Travis execute the tests with Clang's sanitizers. 147354. [Jonathan Lee](https://github.com/vjon) fixed an example in the README file. 147455. [gnzlbg](https://github.com/gnzlbg) supported the implementation of user-defined types. 147556. [Alexej Harm](https://github.com/qis) helped to get the user-defined types working with Visual Studio. 147657. [Jared Grubb](https://github.com/jaredgrubb) supported the implementation of user-defined types. 147758. [EnricoBilla](https://github.com/EnricoBilla) noted a typo in an example. 147859. [Martin Hořeňovský](https://github.com/horenmar) found a way for a 2x speedup for the compilation time of the test suite. 147960. [ukhegg](https://github.com/ukhegg) found proposed an improvement for the examples section. 148061. [rswanson-ihi](https://github.com/rswanson-ihi) noted a typo in the README. 148162. [Mihai Stan](https://github.com/stanmihai4) fixed a bug in the comparison with `nullptr`s. 148263. [Tushar Maheshwari](https://github.com/tusharpm) added [cotire](https://github.com/sakra/cotire) support to speed up the compilation. 148364. [TedLyngmo](https://github.com/TedLyngmo) noted a typo in the README, removed unnecessary bit arithmetic, and fixed some `-Weffc++` warnings. 148465. [Krzysztof Woś](https://github.com/krzysztofwos) made exceptions more visible. 148566. [ftillier](https://github.com/ftillier) fixed a compiler warning. 148667. [tinloaf](https://github.com/tinloaf) made sure all pushed warnings are properly popped. 148768. [Fytch](https://github.com/Fytch) found a bug in the documentation. 148869. [Jay Sistar](https://github.com/Type1J) implemented a Meson build description. 148970. [Henry Lee](https://github.com/HenryRLee) fixed a warning in ICC and improved the iterator implementation. 149071. [Vincent Thiery](https://github.com/vthiery) maintains a package for the Conan package manager. 149172. [Steffen](https://github.com/koemeet) fixed a potential issue with MSVC and `std::min`. 149273. [Mike Tzou](https://github.com/Chocobo1) fixed some typos. 149374. [amrcode](https://github.com/amrcode) noted a misleading documentation about comparison of floats. 149475. [Oleg Endo](https://github.com/olegendo) reduced the memory consumption by replacing `<iostream>` with `<iosfwd>`. 149576. [dan-42](https://github.com/dan-42) cleaned up the CMake files to simplify including/reusing of the library. 149677. [Nikita Ofitserov](https://github.com/himikof) allowed for moving values from initializer lists. 149778. [Greg Hurrell](https://github.com/wincent) fixed a typo. 149879. [Dmitry Kukovinets](https://github.com/DmitryKuk) fixed a typo. 149980. [kbthomp1](https://github.com/kbthomp1) fixed an issue related to the Intel OSX compiler. 150081. [Markus Werle](https://github.com/daixtrose) fixed a typo. 150182. [WebProdPP](https://github.com/WebProdPP) fixed a subtle error in a precondition check. 150283. [Alex](https://github.com/leha-bot) noted an error in a code sample. 150384. [Tom de Geus](https://github.com/tdegeus) reported some warnings with ICC and helped to fix them. 150485. [Perry Kundert](https://github.com/pjkundert) simplified reading from input streams. 150586. [Sonu Lohani](https://github.com/sonulohani) fixed a small compilation error. 150687. [Jamie Seward](https://github.com/jseward) fixed all MSVC warnings. 150788. [Nate Vargas](https://github.com/eld00d) added a Doxygen tag file. 150889. [pvleuven](https://github.com/pvleuven) helped to fix a warning in ICC. 150990. [Pavel](https://github.com/crea7or) helped to fix some warnings in MSVC. 151091. [Jamie Seward](https://github.com/jseward) avoided unnecessary string copies in `find()` and `count()`. 151192. [Mitja](https://github.com/Itja) fixed some typos. 151293. [Jorrit Wronski](https://github.com/jowr) updated the Hunter package links. 151394. [Matthias Möller](https://github.com/TinyTinni) added a `.natvis` for the MSVC debug view. 151495. [bogemic](https://github.com/bogemic) fixed some C++17 deprecation warnings. 151596. [Eren Okka](https://github.com/erengy) fixed some MSVC warnings. 151697. [abolz](https://github.com/abolz) integrated the Grisu2 algorithm for proper floating-point formatting, allowing more roundtrip checks to succeed. 151798. [Vadim Evard](https://github.com/Pipeliner) fixed a Markdown issue in the README. 151899. [zerodefect](https://github.com/zerodefect) fixed a compiler warning. 1519100. [Kert](https://github.com/kaidokert) allowed to template the string type in the serialization and added the possibility to override the exceptional behavior. 1520101. [mark-99](https://github.com/mark-99) helped fixing an ICC error. 1521102. [Patrik Huber](https://github.com/patrikhuber) fixed links in the README file. 1522103. [johnfb](https://github.com/johnfb) found a bug in the implementation of CBOR's indefinite length strings. 1523104. [Paul Fultz II](https://github.com/pfultz2) added a note on the cget package manager. 1524105. [Wilson Lin](https://github.com/wla80) made the integration section of the README more concise. 1525106. [RalfBielig](https://github.com/ralfbielig) detected and fixed a memory leak in the parser callback. 1526107. [agrianius](https://github.com/agrianius) allowed to dump JSON to an alternative string type. 1527108. [Kevin Tonon](https://github.com/ktonon) overworked the C++11 compiler checks in CMake. 1528109. [Axel Huebl](https://github.com/ax3l) simplified a CMake check and added support for the [Spack package manager](https://spack.io). 1529110. [Carlos O'Ryan](https://github.com/coryan) fixed a typo. 1530111. [James Upjohn](https://github.com/jammehcow) fixed a version number in the compilers section. 1531112. [Chuck Atkins](https://github.com/chuckatkins) adjusted the CMake files to the CMake packaging guidelines and provided documentation for the CMake integration. 1532113. [Jan Schöppach](https://github.com/dns13) fixed a typo. 1533114. [martin-mfg](https://github.com/martin-mfg) fixed a typo. 1534115. [Matthias Möller](https://github.com/TinyTinni) removed the dependency from `std::stringstream`. 1535116. [agrianius](https://github.com/agrianius) added code to use alternative string implementations. 1536117. [Daniel599](https://github.com/Daniel599) allowed to use more algorithms with the `items()` function. 1537118. [Julius Rakow](https://github.com/jrakow) fixed the Meson include directory and fixed the links to [cppreference.com](cppreference.com). 1538119. [Sonu Lohani](https://github.com/sonulohani) fixed the compilation with MSVC 2015 in debug mode. 1539120. [grembo](https://github.com/grembo) fixed the test suite and re-enabled several test cases. 1540121. [Hyeon Kim](https://github.com/simnalamburt) introduced the macro `JSON_INTERNAL_CATCH` to control the exception handling inside the library. 1541122. [thyu](https://github.com/thyu) fixed a compiler warning. 1542123. [David Guthrie](https://github.com/LEgregius) fixed a subtle compilation error with Clang 3.4.2. 1543124. [Dennis Fischer](https://github.com/dennisfischer) allowed to call `find_package` without installing the library. 1544125. [Hyeon Kim](https://github.com/simnalamburt) fixed an issue with a double macro definition. 1545126. [Ben Berman](https://github.com/rivertam) made some error messages more understandable. 1546127. [zakalibit](https://github.com/zakalibit) fixed a compilation problem with the Intel C++ compiler. 1547128. [mandreyel](https://github.com/mandreyel) fixed a compilation problem. 1548129. [Kostiantyn Ponomarenko](https://github.com/koponomarenko) added version and license information to the Meson build file. 1549130. [Henry Schreiner](https://github.com/henryiii) added support for GCC 4.8. 1550131. [knilch](https://github.com/knilch0r) made sure the test suite does not stall when run in the wrong directory. 1551132. [Antonio Borondo](https://github.com/antonioborondo) fixed an MSVC 2017 warning. 1552133. [Dan Gendreau](https://github.com/dgendreau) implemented the `NLOHMANN_JSON_SERIALIZE_ENUM` macro to quickly define an enum/JSON mapping. 1553134. [efp](https://github.com/efp) added line and column information to parse errors. 1554135. [julian-becker](https://github.com/julian-becker) added BSON support. 1555136. [Pratik Chowdhury](https://github.com/pratikpc) added support for structured bindings. 1556137. [David Avedissian](https://github.com/davedissian) added support for Clang 5.0.1 (PS4 version). 1557138. [Jonathan Dumaresq](https://github.com/dumarjo) implemented an input adapter to read from `FILE*`. 1558139. [kjpus](https://github.com/kjpus) fixed a link in the documentation. 1559140. [Manvendra Singh](https://github.com/manu-chroma) fixed a typo in the documentation. 1560141. [ziggurat29](https://github.com/ziggurat29) fixed an MSVC warning. 1561142. [Sylvain Corlay](https://github.com/SylvainCorlay) added code to avoid an issue with MSVC. 1562143. [mefyl](https://github.com/mefyl) fixed a bug when JSON was parsed from an input stream. 1563144. [Millian Poquet](https://github.com/mpoquet) allowed to install the library via Meson. 1564145. [Michael Behrns-Miller](https://github.com/moodboom) found an issue with a missing namespace. 1565146. [Nasztanovics Ferenc](https://github.com/naszta) fixed a compilation issue with libc 2.12. 1566147. [Andreas Schwab](https://github.com/andreas-schwab) fixed the endian conversion. 1567148. [Mark-Dunning](https://github.com/Mark-Dunning) fixed a warning in MSVC. 1568149. [Gareth Sylvester-Bradley](https://github.com/garethsb-sony) added `operator/` for JSON Pointers. 1569150. [John-Mark](https://github.com/johnmarkwayve) noted a missing header. 1570151. [Vitaly Zaitsev](https://github.com/xvitaly) fixed compilation with GCC 9.0. 1571152. [Laurent Stacul](https://github.com/stac47) fixed compilation with GCC 9.0. 1572153. [Ivor Wanders](https://github.com/iwanders) helped to reduce the CMake requirement to version 3.1. 1573154. [njlr](https://github.com/njlr) updated the Buckaroo instructions. 1574155. [Lion](https://github.com/lieff) fixed a compilation issue with GCC 7 on CentOS. 1575156. [Isaac Nickaein](https://github.com/nickaein) improved the integer serialization performance and implemented the `contains()` function. 1576157. [past-due](https://github.com/past-due) suppressed an unfixable warning. 1577158. [Elvis Oric](https://github.com/elvisoric) improved Meson support. 1578159. [Matěj Plch](https://github.com/Afforix) fixed an example in the README. 1579160. [Mark Beckwith](https://github.com/wythe) fixed a typo. 1580161. [scinart](https://github.com/scinart) fixed bug in the serializer. 1581162. [Patrick Boettcher](https://github.com/pboettch) implemented `push_back()` and `pop_back()` for JSON Pointers. 1582163. [Bruno Oliveira](https://github.com/nicoddemus) added support for Conda. 1583164. [Michele Caini](https://github.com/skypjack) fixed links in the README. 1584165. [Hani](https://github.com/hnkb) documented how to install the library with NuGet. 1585166. [Mark Beckwith](https://github.com/wythe) fixed a typo. 1586167. [yann-morin-1998](https://github.com/yann-morin-1998) helped to reduce the CMake requirement to version 3.1. 1587168. [Konstantin Podsvirov](https://github.com/podsvirov) maintains a package for the MSYS2 software distro. 1588169. [remyabel](https://github.com/remyabel) added GNUInstallDirs to the CMake files. 1589170. [Taylor Howard](https://github.com/taylorhoward92) fixed a unit test. 1590171. [Gabe Ron](https://github.com/Macr0Nerd) implemented the `to_string` method. 1591172. [Watal M. Iwasaki](https://github.com/heavywatal) fixed a Clang warning. 1592173. [Viktor Kirilov](https://github.com/onqtam) switched the unit tests from [Catch](https://github.com/philsquared/Catch) to [doctest](https://github.com/onqtam/doctest) 1593174. [Juncheng E](https://github.com/ejcjason) fixed a typo. 1594175. [tete17](https://github.com/tete17) fixed a bug in the `contains` function. 1595176. [Xav83](https://github.com/Xav83) fixed some cppcheck warnings. 1596177. [0xflotus](https://github.com/0xflotus) fixed some typos. 1597178. [Christian Deneke](https://github.com/chris0x44) added a const version of `json_pointer::back`. 1598179. [Julien Hamaide](https://github.com/crazyjul) made the `items()` function work with custom string types. 1599180. [Evan Nemerson](https://github.com/nemequ) updated fixed a bug in Hedley and updated this library accordingly. 1600181. [Florian Pigorsch](https://github.com/flopp) fixed a lot of typos. 1601182. [Camille Bégué](https://github.com/cbegue) fixed an issue in the conversion from `std::pair` and `std::tuple` to `json`. 1602183. [Anthony VH](https://github.com/AnthonyVH) fixed a compile error in an enum deserialization. 1603184. [Yuriy Vountesmery](https://github.com/ua-code-dragon) noted a subtle bug in a preprocessor check. 1604185. [Chen](https://github.com/dota17) fixed numerous issues in the library. 1605186. [Antony Kellermann](https://github.com/aokellermann) added a CI step for GCC 10.1. 1606187. [Alex](https://github.com/gistrec) fixed an MSVC warning. 1607188. [Rainer](https://github.com/rvjr) proposed an improvement in the floating-point serialization in CBOR. 1608189. [Francois Chabot](https://github.com/FrancoisChabot) made performance improvements in the input adapters. 1609190. [Arthur Sonzogni](https://github.com/ArthurSonzogni) documented how the library can be included via `FetchContent`. 1610191. [Rimas Misevičius](https://github.com/rmisev) fixed an error message. 1611192. [Alexander Myasnikov](https://github.com/alexandermyasnikov) fixed some examples and a link in the README. 1612193. [Hubert Chathi](https://github.com/uhoreg) made CMake's version config file architecture-independent. 1613194. [OmnipotentEntity](https://github.com/OmnipotentEntity) implemented the binary values for CBOR, MessagePack, BSON, and UBJSON. 1614195. [ArtemSarmini](https://github.com/ArtemSarmini) fixed a compilation issue with GCC 10 and fixed a leak. 1615196. [Evgenii Sopov](https://github.com/sea-kg) integrated the library to the wsjcpp package manager. 1616197. [Sergey Linev](https://github.com/linev) fixed a compiler warning. 1617198. [Miguel Magalhães](https://github.com/magamig) fixed the year in the copyright. 1618199. [Gareth Sylvester-Bradley](https://github.com/garethsb-sony) fixed a compilation issue with MSVC. 1619200. [Alexander “weej” Jones](https://github.com/alex-weej) fixed an example in the README. 1620201. [Antoine Cœur](https://github.com/Coeur) fixed some typos in the documentation. 1621202. [jothepro](https://github.com/jothepro) updated links to the Hunter package. 1622203. [Dave Lee](https://github.com/kastiglione) fixed link in the README. 1623204. [Joël Lamotte](https://github.com/Klaim) added instruction for using Build2's package manager. 1624205. [Paul Jurczak](https://github.com/pauljurczak) fixed an example in the README. 1625206. [Sonu Lohani](https://github.com/sonulohani) fixed a warning. 1626207. [Carlos Gomes Martinho](https://github.com/gocarlos) updated the Conan package source. 1627208. [Konstantin Podsvirov](https://github.com/podsvirov) fixed the MSYS2 package documentation. 1628209. [Tridacnid](https://github.com/Tridacnid) improved the CMake tests. 1629210. [Michael](https://github.com/MBalszun) fixed MSVC warnings. 1630211. [Quentin Barbarat](https://github.com/quentin-dev) fixed an example in the documentation. 1631212. [XyFreak](https://github.com/XyFreak) fixed a compiler warning. 1632213. [TotalCaesar659](https://github.com/TotalCaesar659) fixed links in the README. 1633214. [Tanuj Garg](https://github.com/tanuj208) improved the fuzzer coverage for UBSAN input. 1634215. [AODQ](https://github.com/AODQ) fixed a compiler warning. 1635216. [jwittbrodt](https://github.com/jwittbrodt) made `NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE` inline. 1636217. [pfeatherstone](https://github.com/pfeatherstone) improved the upper bound of arguments of the `NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE`/`NLOHMANN_DEFINE_TYPE_INTRUSIVE` macros. 1637218. [Jan Procházka](https://github.com/jprochazk) fixed a bug in the CBOR parser for binary and string values. 1638219. [T0b1-iOS](https://github.com/T0b1-iOS) fixed a bug in the new hash implementation. 1639220. [Matthew Bauer](https://github.com/matthewbauer) adjusted the CBOR writer to create tags for binary subtypes. 1640221. [gatopeich](https://github.com/gatopeich) implemented an ordered map container for `nlohmann::ordered_json`. 1641222. [Érico Nogueira Rolim](https://github.com/ericonr) added support for pkg-config. 1642223. [KonanM](https://github.com/KonanM) proposed an implementation for the `NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE`/`NLOHMANN_DEFINE_TYPE_INTRUSIVE` macros. 1643224. [Guillaume Racicot](https://github.com/gracicot) implemented `string_view` support and allowed C++20 support. 1644225. [Alex Reinking](https://github.com/alexreinking) improved CMake support for `FetchContent`. 1645226. [Hannes Domani](https://github.com/ssbssa) provided a GDB pretty printer. 1646227. Lars Wirzenius reviewed the README file. 1647228. [Jun Jie](https://github.com/ongjunjie) fixed a compiler path in the CMake scripts. 1648229. [Ronak Buch](https://github.com/rbuch) fixed typos in the documentation. 1649230. [Alexander Karzhenkov](https://github.com/karzhenkov) fixed a move constructor and the Travis builds. 1650231. [Leonardo Lima](https://github.com/leozz37) added CPM.Cmake support. 1651232. [Joseph Blackman](https://github.com/jbzdarkid) fixed a warning. 1652233. [Yaroslav](https://github.com/YarikTH) updated doctest and implemented unit tests. 1653234. [Martin Stump](https://github.com/globberwops) fixed a bug in the CMake files. 1654235. [Jaakko Moisio](https://github.com/jasujm) fixed a bug in the input adapters. 1655236. [bl-ue](https://github.com/bl-ue) fixed some Markdown issues in the README file. 1656237. [William A. Wieselquist](https://github.com/wawiesel) fixed an example from the README. 1657238. [abbaswasim](https://github.com/abbaswasim) fixed an example from the README. 1658239. [Remy Jette](https://github.com/remyjette) fixed a warning. 1659240. [Fraser](https://github.com/frasermarlow) fixed the documentation. 1660241. [Ben Beasley](https://github.com/musicinmybrain) updated doctest. 1661242. [Doron Behar](https://github.com/doronbehar) fixed pkg-config.pc. 1662243. [raduteo](https://github.com/raduteo) fixed a warning. 1663244. [David Pfahler](https://github.com/theShmoo) added the possibility to compile the library without I/O support. 1664245. [Morten Fyhn Amundsen](https://github.com/mortenfyhn) fixed a typo. 1665246. [jpl-mac](https://github.com/jpl-mac) allowed to treat the library as a system header in CMake. 1666247. [Jason Dsouza](https://github.com/jasmcaus) fixed the indentation of the CMake file. 1667248. [offa](https://github.com/offa) added a link to Conan Center to the documentation. 1668249. [TotalCaesar659](https://github.com/TotalCaesar659) updated the links in the documentation to use HTTPS. 1669250. [Rafail Giavrimis](https://github.com/grafail) fixed the Google Benchmark default branch. 1670251. [Louis Dionne](https://github.com/ldionne) fixed a conversion operator. 1671252. [justanotheranonymoususer](https://github.com/justanotheranonymoususer) made the examples in the README more consistent. 1672253. [Finkman](https://github.com/Finkman) suppressed some `-Wfloat-equal` warnings. 1673254. [Ferry Huberts](https://github.com/fhuberts) fixed `-Wswitch-enum` warnings. 1674255. [Arseniy Terekhin](https://github.com/senyai) made the GDB pretty-printer robust against unset variable names. 1675256. [Amir Masoud Abdol](https://github.com/amirmasoudabdol) updated the Homebrew command as nlohmann/json is now in homebrew-core. 1676257. [Hallot](https://github.com/Hallot) fixed some `-Wextra-semi-stmt warnings`. 1677258. [Giovanni Cerretani](https://github.com/gcerretani) fixed `-Wunused` warnings on `JSON_DIAGNOSTICS`. 1678259. [Bogdan Popescu](https://github.com/Kapeli) hosts the [docset](https://github.com/Kapeli/Dash-User-Contributions/tree/master/docsets/JSON_for_Modern_C%2B%2B) for offline documentation viewers. 1679260. [Carl Smedstad](https://github.com/carlsmedstad) fixed an assertion error when using `JSON_DIAGNOSTICS`. 1680261. [miikka75](https://github.com/miikka75) provided an important fix to compile C++17 code with Clang 9. 1681262. [Maarten Becker](https://github.com/kernie) fixed a warning for shadowed variables. 1682263. [Cristi Vîjdea](https://github.com/axnsan12) fixed typos in the `operator[]` documentation. 1683264. [Alex Beregszaszi](https://github.com/axic) fixed spelling mistakes in comments. 1684265. [Dirk Stolle](https://github.com/striezel) fixed typos in documentation. 1685266. [Daniel Albuschat](https://github.com/daniel-kun) corrected the parameter name in the `parse` documentation. 1686267. [Prince Mendiratta](https://github.com/Prince-Mendiratta) fixed a link to the FAQ. 1687268. [Florian Albrechtskirchinger](https://github.com/falbrechtskirchinger) implemented `std::string_view` support for object keys and made dozens of other improvements. 1688269. [Qianqian Fang](https://github.com/fangq) implemented the Binary JData (BJData) format. 1689270. [pketelsen](https://github.com/pketelsen) added macros `NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT` and `NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT`. 1690271. [DarkZeros](https://github.com/DarkZeros) adjusted to code to not clash with Arduino defines. 1691272. [flagarde](https://github.com/flagarde) fixed the output of `meta()` for MSVC. 1692273. [Giovanni Cerretani](https://github.com/gcerretani) fixed a check for `std::filesystem`. 1693274. [Dimitris Apostolou](https://github.com/rex4539) fixed a typo. 1694275. [Ferry Huberts](https://github.com/fhuberts) fixed a typo. 1695276. [Michael Nosthoff](https://github.com/heinemml) fixed a typo. 1696277. [JungHoon Lee](https://github.com/jhnlee) fixed a typo. 1697278. [Faruk D.](https://github.com/fdiblen) fixed the CITATION.CFF file. 1698279. [Andrea Cocito](https://github.com/puffetto) added a clarification on macro usage to the documentation. 1699280. [Krzysiek Karbowiak](https://github.com/kkarbowiak) refactored the tests to use `CHECK_THROWS_WITH_AS`. 1700281. [Chaoqi Zhang](https://github.com/prncoprs) fixed a typo. 1701282. [ivanovmp](https://github.com/ivanovmp) fixed a whitespace error. 1702283. [KsaNL](https://github.com/KsaNL) fixed a build error when including `<windows.h>`. 1703284. [Andrea Pappacoda](https://github.com/Tachi107) moved `.pc` and `.cmake` files to `share` directory. 1704285. [Wolf Vollprecht](https://github.com/wolfv) added the `patch_inplace` function. 1705286. [Jake Zimmerman](https://github.com/jez) highlighted common usage patterns in the README file. 1706287. [NN](https://github.com/NN---) added the Visual Studio output directory to `.gitignore`. 1707288. [Romain Reignier](https://github.com/romainreignier) improved the performance the vector output adapter. 1708289. [Mike](https://github.com/Mike-Leo-Smith) fixed the `std::iterator_traits`. 1709290. [Richard Hozák](https://github.com/zxey) added macro `JSON_NO_ENUM` to disable default enum conversions. 1710291. [vakokako](https://github.com/vakokako) fixed tests when compiling with C++20. 1711292. [Alexander “weej” Jones](https://github.com/alexweej) fixed an example in the README. 1712293. [Eli Schwartz](https://github.com/eli-schwartz) added more files to the `include.zip` archive. 1713294. [Kevin Lu](https://github.com/kevinlul) fixed a compilation issue when typedefs with certain names were present. 1714295. [Trevor Hickey](https://github.com/luxe) improved the description of an example. 1715296. [Jef LeCompte](https://github.com/jef) updated the year in the README file. 1716297. [Alexandre Hamez](https://github.com/ahamez) fixed a warning. 1717298. [Maninderpal Badhan](https://github.com/mbadhan) fixed a typo. 1718299. [kevin--](https://github.com/kevin--) added a note to an example in the README file. 1719300. [I](https://github.com/wx257osn2) fixed a typo. 1720301. [Gregorio Litenstein](https://github.com/Lord-Kamina) fixed the Clang detection. 1721302. [Andreas Smas](https://github.com/andoma) added a Doozer badge. 1722303. [WanCW](https://github.com/wancw) fixed the string conversion with Clang. 1723304. [zhaohuaxishi](https://github.com/zhaohuaxishi) fixed a Doxygen error. 1724305. [emvivre](https://github.com/emvivre) removed an invalid parameter from CMake. 1725306. [Tobias Hermann](https://github.com/Dobiasd) fixed a link in the README file. 1726307. [Michael](https://github.com/traits) fixed a warning. 1727308. [Ryan Mulder](https://github.com/ryanjmulder) added `ensure_ascii` to the `dump` function. 1728309. [Muri Nicanor](https://github.com/murinicanor) fixed the `sed` discovery in the Makefile. 1729310. [David Avedissian](https://github.com/dgavedissian) implemented SFINAE-friendly `iterator_traits`. 1730311. [AQNOUCH Mohammed](https://github.com/aqnouch) fixed a typo in the README. 1731312. [Gareth Sylvester-Bradley](https://github.com/garethsb) added `operator/=` and `operator/` to construct JSON pointers. 1732313. [Michael Macnair](https://github.com/mykter) added support for afl-fuzz testing. 1733314. [Berkus Decker](https://github.com/berkus) fixed a typo in the README. 1734315. [Illia Polishchuk](https://github.com/effolkronium) improved the CMake testing. 1735316. [Ikko Ashimine](https://github.com/eltociear) fixed a typo. 1736317. [Raphael Grimm](https://github.com/barcode) added the possibility to define a custom base class. 1737318. [tocic](https://github.com/tocic) fixed typos in the documentation. 1738319. [Vertexwahn](https://github.com/Vertexwahn) added Bazel build support. 1739320. [Dirk Stolle](https://github.com/striezel) fixed typos in the documentation. 1740321. [DavidKorczynski](https://github.com/DavidKorczynski) added a CIFuzz CI GitHub action. 1741322. [Finkman](https://github.com/Finkman) fixed the debug pretty-printer. 1742323. [Florian Segginger](https://github.com/floriansegginger) bumped the years in the README. 1743324. [haadfida](https://github.com/haadfida) cleaned up the badges of used services. 1744325. [Arsen Arsenović](https://github.com/ArsenArsen) fixed a build error. 1745326. [theevilone45](https://github.com/theevilone45) fixed a typo in a CMake file. 1746327. [Sergei Trofimovich](https://github.com/trofi) fixed the custom allocator support. 1747328. [Joyce](https://github.com/joycebrum) fixed some security issues in the GitHub workflows. 1748329. [Nicolas Jakob](https://github.com/njakob) add vcpkg version badge. 1749330. [Tomerkm](https://github.com/Tomerkm) added tests. 1750331. [No.](https://github.com/tusooa) fixed the use of `get<>` calls. 1751332. [taro](https://github.com/tarolling) fixed a typo in the `CODEOWNERS` file. 1752333. [Ikko Eltociear Ashimine](https://github.com/eltociear) fixed a typo. 1753334. [Felix Yan](https://github.com/felixonmars) fixed a typo in the README. 1754335. [HO-COOH](https://github.com/HO-COOH) fixed a parentheses in the documentation. 1755336. [Ivor Wanders](https://github.com/iwanders) fixed the examples to catch exception by `const&`. 1756337. [miny1233](https://github.com/miny1233) fixed a parentheses in the documentation. 1757338. [tomalakgeretkal](https://github.com/tomalakgeretkal) fixed a compilation error. 1758339. [alferov](https://github.com/ALF-ONE) fixed a compilation error. 1759340. [Craig Scott](https://github.com/craigscott-crascit) fixed a deprecation warning in CMake. 1760341. [Vyacheslav Zhdanovskiy](https://github.com/ZeronSix) added macros for serialization-only types. 1761342. [Mathieu Westphal](https://github.com/mwestphal) fixed typos. 1762343. [scribam](https://github.com/scribam) fixed the MinGW workflow. 1763344. [Aleksei Sapitskii](https://github.com/aleksproger) added support for Apple's Swift Package Manager. 1764345. [Benjamin Buch](https://github.com/bebuch) fixed the installation path in CMake. 1765346. [Colby Haskell](https://github.com/colbychaskell) clarified the parse error message in case a file cannot be opened. 1766 1767Thanks a lot for helping out! Please [let me know](mailto:mail@nlohmann.me) if I forgot someone. 1768 1769 1770## Used third-party tools 1771 1772The library itself consists of a single header file licensed under the MIT license. However, it is built, tested, documented, and whatnot using a lot of third-party tools and services. Thanks a lot! 1773 1774- [**amalgamate.py - Amalgamate C source and header files**](https://github.com/edlund/amalgamate) to create a single header file 1775- [**American fuzzy lop**](https://lcamtuf.coredump.cx/afl/) for fuzz testing 1776- [**AppVeyor**](https://www.appveyor.com) for [continuous integration](https://ci.appveyor.com/project/nlohmann/json) on Windows 1777- [**Artistic Style**](http://astyle.sourceforge.net) for automatic source code indentation 1778- [**Clang**](https://clang.llvm.org) for compilation with code sanitizers 1779- [**CMake**](https://cmake.org) for build automation 1780- [**Codacy**](https://www.codacy.com) for further [code analysis](https://www.codacy.com/app/nlohmann/json) 1781- [**Coveralls**](https://coveralls.io) to measure [code coverage](https://coveralls.io/github/nlohmann/json) 1782- [**Coverity Scan**](https://scan.coverity.com) for [static analysis](https://scan.coverity.com/projects/nlohmann-json) 1783- [**cppcheck**](http://cppcheck.sourceforge.net) for static analysis 1784- [**doctest**](https://github.com/onqtam/doctest) for the unit tests 1785- [**git-update-ghpages**](https://github.com/rstacruz/git-update-ghpages) to upload the documentation to gh-pages 1786- [**GitHub Changelog Generator**](https://github.com/skywinder/github-changelog-generator) to generate the [ChangeLog](https://github.com/nlohmann/json/blob/develop/ChangeLog.md) 1787- [**Google Benchmark**](https://github.com/google/benchmark) to implement the benchmarks 1788- [**Hedley**](https://nemequ.github.io/hedley/) to avoid re-inventing several compiler-agnostic feature macros 1789- [**lcov**](http://ltp.sourceforge.net/coverage/lcov.php) to process coverage information and create an HTML view 1790- [**libFuzzer**](https://llvm.org/docs/LibFuzzer.html) to implement fuzz testing for OSS-Fuzz 1791- [**Material for MkDocs**](https://squidfunk.github.io/mkdocs-material/) for the style of the documentation site 1792- [**MkDocs**](https://www.mkdocs.org) for the documentation site 1793- [**OSS-Fuzz**](https://github.com/google/oss-fuzz) for continuous fuzz testing of the library ([project repository](https://github.com/google/oss-fuzz/tree/master/projects/json)) 1794- [**Probot**](https://probot.github.io) for automating maintainer tasks such as closing stale issues, requesting missing information, or detecting toxic comments. 1795- [**Valgrind**](https://valgrind.org) to check for correct memory management 1796 1797 1798## Projects using JSON for Modern C++ 1799 1800The library is currently used in Apple macOS Sierra-Monterey and iOS 10-15. I am not sure what they are using the library for, but I am happy that it runs on so many devices. 1801 1802 1803## Notes 1804 1805### Character encoding 1806 1807The library supports **Unicode input** as follows: 1808 1809- Only **UTF-8** encoded input is supported which is the default encoding for JSON according to [RFC 8259](https://tools.ietf.org/html/rfc8259.html#section-8.1). 1810- `std::u16string` and `std::u32string` can be parsed, assuming UTF-16 and UTF-32 encoding, respectively. These encodings are not supported when reading from files or other input containers. 1811- Other encodings such as Latin-1 or ISO 8859-1 are **not** supported and will yield parse or serialization errors. 1812- [Unicode noncharacters](https://www.unicode.org/faq/private_use.html#nonchar1) will not be replaced by the library. 1813- Invalid surrogates (e.g., incomplete pairs such as `\uDEAD`) will yield parse errors. 1814- The strings stored in the library are UTF-8 encoded. When using the default string type (`std::string`), note that its length/size functions return the number of stored bytes rather than the number of characters or glyphs. 1815- When you store strings with different encodings in the library, calling [`dump()`](https://json.nlohmann.me/api/basic_json/dump/) may throw an exception unless `json::error_handler_t::replace` or `json::error_handler_t::ignore` are used as error handlers. 1816- To store wide strings (e.g., `std::wstring`), you need to convert them to a UTF-8 encoded `std::string` before, see [an example](https://json.nlohmann.me/home/faq/#wide-string-handling). 1817 1818### Comments in JSON 1819 1820This library does not support comments by default. It does so for three reasons: 1821 18221. Comments are not part of the [JSON specification](https://tools.ietf.org/html/rfc8259). You may argue that `//` or `/* */` are allowed in JavaScript, but JSON is not JavaScript. 18232. This was not an oversight: Douglas Crockford [wrote on this](https://plus.google.com/118095276221607585885/posts/RK8qyGVaGSr) in May 2012: 1824 1825 > I removed comments from JSON because I saw people were using them to hold parsing directives, a practice which would have destroyed interoperability. I know that the lack of comments makes some people sad, but it shouldn't. 1826 1827 > Suppose you are using JSON to keep configuration files, which you would like to annotate. Go ahead and insert all the comments you like. Then pipe it through JSMin before handing it to your JSON parser. 1828 18293. It is dangerous for interoperability if some libraries would add comment support while others don't. Please check [The Harmful Consequences of the Robustness Principle](https://tools.ietf.org/html/draft-iab-protocol-maintenance-01) on this. 1830 1831However, you can pass set parameter `ignore_comments` to true in the `parse` function to ignore `//` or `/* */` comments. Comments will then be treated as whitespace. 1832 1833### Order of object keys 1834 1835By default, the library does not preserve the **insertion order of object elements**. This is standards-compliant, as the [JSON standard](https://tools.ietf.org/html/rfc8259.html) defines objects as "an unordered collection of zero or more name/value pairs". 1836 1837If you do want to preserve the insertion order, you can try the type [`nlohmann::ordered_json`](https://github.com/nlohmann/json/issues/2179). Alternatively, you can use a more sophisticated ordered map like [`tsl::ordered_map`](https://github.com/Tessil/ordered-map) ([integration](https://github.com/nlohmann/json/issues/546#issuecomment-304447518)) or [`nlohmann::fifo_map`](https://github.com/nlohmann/fifo_map) ([integration](https://github.com/nlohmann/json/issues/485#issuecomment-333652309)). 1838 1839### Memory Release 1840 1841We checked with Valgrind and the Address Sanitizer (ASAN) that there are no memory leaks. 1842 1843If you find that a parsing program with this library does not release memory, please consider the following case, and it may be unrelated to this library. 1844 1845**Your program is compiled with glibc.** There is a tunable threshold that glibc uses to decide whether to actually return memory to the system or whether to cache it for later reuse. If in your program you make lots of small allocations and those small allocations are not a contiguous block and are presumably below the threshold, then they will not get returned to the OS. 1846Here is a related issue [#1924](https://github.com/nlohmann/json/issues/1924). 1847 1848### Further notes 1849 1850- The code contains numerous debug **assertions** which can be switched off by defining the preprocessor macro `NDEBUG`, see the [documentation of `assert`](https://en.cppreference.com/w/cpp/error/assert). In particular, note [`operator[]`](https://json.nlohmann.me/api/basic_json/operator%5B%5D/) implements **unchecked access** for const objects: If the given key is not present, the behavior is undefined (think of a dereferenced null pointer) and yields an [assertion failure](https://github.com/nlohmann/json/issues/289) if assertions are switched on. If you are not sure whether an element in an object exists, use checked access with the [`at()` function](https://json.nlohmann.me/api/basic_json/at/). Furthermore, you can define `JSON_ASSERT(x)` to replace calls to `assert(x)`. 1851- As the exact number type is not defined in the [JSON specification](https://tools.ietf.org/html/rfc8259.html), this library tries to choose the best fitting C++ number type automatically. As a result, the type `double` may be used to store numbers which may yield [**floating-point exceptions**](https://github.com/nlohmann/json/issues/181) in certain rare situations if floating-point exceptions have been unmasked in the calling code. These exceptions are not caused by the library and need to be fixed in the calling code, such as by re-masking the exceptions prior to calling library functions. 1852- The code can be compiled without C++ **runtime type identification** features; that is, you can use the `-fno-rtti` compiler flag. 1853- **Exceptions** are used widely within the library. They can, however, be switched off with either using the compiler flag `-fno-exceptions` or by defining the symbol `JSON_NOEXCEPTION`. In this case, exceptions are replaced by `abort()` calls. You can further control this behavior by defining `JSON_THROW_USER` (overriding `throw`), `JSON_TRY_USER` (overriding `try`), and `JSON_CATCH_USER` (overriding `catch`). Note that `JSON_THROW_USER` should leave the current scope (e.g., by throwing or aborting), as continuing after it may yield undefined behavior. Note the explanatory [`what()`](https://en.cppreference.com/w/cpp/error/exception/what) string of exceptions is not available for MSVC if exceptions are disabled, see [#2824](https://github.com/nlohmann/json/discussions/2824). 1854 1855## Execute unit tests 1856 1857To compile and run the tests, you need to execute 1858 1859```sh 1860$ mkdir build 1861$ cd build 1862$ cmake .. -DJSON_BuildTests=On 1863$ cmake --build . 1864$ ctest --output-on-failure 1865``` 1866 1867Note that during the `ctest` stage, several JSON test files are downloaded from an [external repository](https://github.com/nlohmann/json_test_data). If policies forbid downloading artifacts during testing, you can download the files yourself and pass the directory with the test files via `-DJSON_TestDataDirectory=path` to CMake. Then, no Internet connectivity is required. See [issue #2189](https://github.com/nlohmann/json/issues/2189) for more information. 1868 1869If the test suite is not found, several test suites will fail like this: 1870 1871``` 1872=============================================================================== 1873json/tests/src/make_test_data_available.hpp:21: 1874TEST CASE: check test suite is downloaded 1875 1876json/tests/src/make_test_data_available.hpp:23: FATAL ERROR: REQUIRE( utils::check_testsuite_downloaded() ) is NOT correct! 1877 values: REQUIRE( false ) 1878 logged: Test data not found in 'json/cmake-build-debug/json_test_data'. 1879 Please execute target 'download_test_data' before running this test suite. 1880 See <https://github.com/nlohmann/json#execute-unit-tests> for more information. 1881 1882=============================================================================== 1883``` 1884 1885In case you have downloaded the library rather than checked out the code via Git, test `cmake_fetch_content_configure` will fail. Please execute `ctest -LE git_required` to skip these tests. See [issue #2189](https://github.com/nlohmann/json/issues/2189) for more information. 1886 1887Some tests change the installed files and hence make the whole process not reproducible. Please execute `ctest -LE not_reproducible` to skip these tests. See [issue #2324](https://github.com/nlohmann/json/issues/2324) for more information. 1888 1889Note you need to call `cmake -LE "not_reproducible|git_required"` to exclude both labels. See [issue #2596](https://github.com/nlohmann/json/issues/2596) for more information. 1890 1891As Intel compilers use unsafe floating point optimization by default, the unit tests may fail. Use flag [`/fp:precise`](https://software.intel.com/content/www/us/en/develop/documentation/cpp-compiler-developer-guide-and-reference/top/compiler-reference/compiler-options/compiler-option-details/floating-point-options/fp-model-fp.html) then. 1892
){kind=link}
){kind=link}
){kind=link}
){kind=link}
){kind=link}
){kind=link}
){kind=link}
){kind=link}
){kind=link}
){kind=link}
){kind=link}
){kind=link}
){kind=link}
){kind=link}
){kind=link}
