Merge branch 'release/3.3.0'

Fix warning C4127: conditional expression is constant

.github/CONTRIBUTING.md

@@ -54,7 +54,7 @@ To make changes, you need to edit the following files:
 
 ## Please don't
 
-- The C++11 support varies between different **compilers** and versions. Please note the [list of supported compilers](https://github.com/nlohmann/json/blob/master/README.md#supported-compilers). Some compilers like GCC 4.8 (and earlier), Clang 3.3 (and earlier), or Microsoft Visual Studio 13.0 and earlier are known not to work due to missing or incomplete C++11 support. Please refrain from proposing changes that work around these compiler's limitations with `#ifdef`s or other means.
+- The C++11 support varies between different **compilers** and versions. Please note the [list of supported compilers](https://github.com/nlohmann/json/blob/master/README.md#supported-compilers). Some compilers like GCC 4.7 (and earlier), Clang 3.3 (and earlier), or Microsoft Visual Studio 13.0 and earlier are known not to work due to missing or incomplete C++11 support. Please refrain from proposing changes that work around these compiler's limitations with `#ifdef`s or other means.
 - Specifically, I am aware of compilation problems with **Microsoft Visual Studio** (there even is an [issue label](https://github.com/nlohmann/json/issues?utf8=✓&q=label%3A%22visual+studio%22+) for these kind of bugs). I understand that even in 2016, complete C++11 support isn't there yet. But please also understand that I do not want to drop features or uglify the code just to make Microsoft's sub-standard compiler happy. The past has shown that there are ways to express the functionality such that the code compiles with the most recent MSVC - unfortunately, this is not the main objective of the project.
 - Please refrain from proposing changes that would **break [JSON](http://json.org) conformance**. If you propose a conformant extension of JSON to be supported by the library, please motivate this extension.
   - We shall not extend the library to **support comments**. There is quite some [controversy](https://www.reddit.com/r/programming/comments/4v6chu/why_json_doesnt_support_comments_douglas_crockford/) around this topic, and there were quite some [issues](https://github.com/nlohmann/json/issues/376) on this. We believe that JSON is fine without comments.

.github/ISSUE_TEMPLATE/Bug_report.md

@@ -1,22 +1,19 @@
-**Bug Report**
-
-- What is the issue you have?
-
-- Please describe the steps to reproduce the issue. Can you provide a small but working code example?
-
-- What is the expected behavior?
-
-- And what is the actual behavior instead?
-
-- Which compiler and operating system are you using? Is it a [supported compiler](https://github.com/nlohmann/json#supported-compilers)?
-
-- Did you use a released version of the library or the version from the `develop` branch?
-
-- If you experience a compilation error: can you [compile and run the unit tests](https://github.com/nlohmann/json#execute-unit-tests)?
-
-
-**Feature Request**
-
-- Describe the feature in as much detail as possible.
-
-- Include sample usage where appropriate.
+---
+name: Bug report
+about: Create a report to help us improve
+
+---
+
+- What is the issue you have?
+
+- Please describe the steps to reproduce the issue. Can you provide a small but working code example?
+
+- What is the expected behavior?
+
+- And what is the actual behavior instead?
+
+- Which compiler and operating system are you using? Is it a [supported compiler](https://github.com/nlohmann/json#supported-compilers)?
+
+- Did you use a released version of the library or the version from the `develop` branch?
+
+- If you experience a compilation error: can you [compile and run the unit tests](https://github.com/nlohmann/json#execute-unit-tests)?

.github/ISSUE_TEMPLATE/Feature_request.md

@@ -0,0 +1,9 @@
+---
+name: Feature request
+about: Suggest an idea for this project
+
+---
+
+- Describe the feature in as much detail as possible.
+
+- Include sample usage where appropriate.

.github/PULL_REQUEST_TEMPLATE.md

@@ -13,7 +13,7 @@ Read the [Contribution Guidelines](https://github.com/nlohmann/json/blob/develop
 
 ## Please don't
 
-- The C++11 support varies between different **compilers** and versions. Please note the [list of supported compilers](https://github.com/nlohmann/json/blob/master/README.md#supported-compilers). Some compilers like GCC 4.8 (and earlier), Clang 3.3 (and earlier), or Microsoft Visual Studio 13.0 and earlier are known not to work due to missing or incomplete C++11 support. Please refrain from proposing changes that work around these compiler's limitations with `#ifdef`s or other means.
+- The C++11 support varies between different **compilers** and versions. Please note the [list of supported compilers](https://github.com/nlohmann/json/blob/master/README.md#supported-compilers). Some compilers like GCC 4.7 (and earlier), Clang 3.3 (and earlier), or Microsoft Visual Studio 13.0 and earlier are known not to work due to missing or incomplete C++11 support. Please refrain from proposing changes that work around these compiler's limitations with `#ifdef`s or other means.
 - Specifically, I am aware of compilation problems with **Microsoft Visual Studio** (there even is an [issue label](https://github.com/nlohmann/json/issues?utf8=✓&q=label%3A%22visual+studio%22+) for these kind of bugs). I understand that even in 2016, complete C++11 support isn't there yet. But please also understand that I do not want to drop features or uglify the code just to make Microsoft's sub-standard compiler happy. The past has shown that there are ways to express the functionality such that the code compiles with the most recent MSVC - unfortunately, this is not the main objective of the project.
 - Please refrain from proposing changes that would **break [JSON](http://json.org) conformance**. If you propose a conformant extension of JSON to be supported by the library, please motivate this extension.
 - Please do not open pull requests that address **multiple issues**.

.travis.yml

@@ -155,11 +155,28 @@ matrix:
   - os: osx
     osx_image: xcode9.2
 
+  - os: osx
+    osx_image: xcode9.3
+
+  - os: osx
+    osx_image: xcode9.4
+
+  - os: osx
+    osx_image: xcode10
+
   # Linux / GCC
 
   - os: linux
     compiler: gcc
-    env: COMPILER=g++-4.9
+    env: compiler=g++-4.8
+    addons:
+      apt:
+        sources: ['ubuntu-toolchain-r-test']
+        packages: ['g++-4.8', 'ninja-build']
+
+  - os: linux
+    compiler: gcc
+    env: compiler=g++-4.9
     addons:
       apt:
         sources: ['ubuntu-toolchain-r-test']
@@ -189,15 +206,23 @@ matrix:
         sources: ['ubuntu-toolchain-r-test']
         packages: ['g++-7', 'ninja-build']
 
+  - os: linux
+    compiler: gcc
+    env: COMPILER=g++-8
+    addons:
+      apt:
+        sources: ['ubuntu-toolchain-r-test']
+        packages: ['g++-8', 'ninja-build']
+
   - os: linux
     compiler: gcc
     env:
-      - COMPILER=g++-7
+      - COMPILER=g++-8
       - CXXFLAGS=-std=c++17
     addons:
       apt:
         sources: ['ubuntu-toolchain-r-test']
-        packages: ['g++-7', 'ninja-build']
+        packages: ['g++-8', 'ninja-build']
 
   # Linux / Clang
 
@@ -257,15 +282,23 @@ matrix:
         sources: ['ubuntu-toolchain-r-test', 'llvm-toolchain-trusty-5.0']
         packages: ['g++-6', 'clang-5.0', 'ninja-build']
 
+  - os: linux
+    compiler: clang
+    env: COMPILER=clang++-6.0
+    addons:
+      apt:
+        sources: ['ubuntu-toolchain-r-test', 'llvm-toolchain-trusty-6.0']
+        packages: ['g++-6', 'clang-6.0', 'ninja-build']
+
   - os: linux
     compiler: clang
     env:
-      - COMPILER=clang++-5.0
+      - COMPILER=clang++-6.0
       - CXXFLAGS=-std=c++1z
     addons:
       apt:
-        sources: ['ubuntu-toolchain-r-test', 'llvm-toolchain-trusty-5.0']
-        packages: ['g++-6', 'clang-5.0', 'ninja-build']
+        sources: ['ubuntu-toolchain-r-test', 'llvm-toolchain-trusty-6.0']
+        packages: ['g++-6', 'clang-6.0', 'ninja-build']
 
 ################
 # build script #
@@ -277,6 +310,7 @@ script:
      if [[ (-x $(which brew)) ]]; then
        brew update
        brew install cmake ninja
+       brew upgrade cmake
        cmake --version
      fi
 

CMakeLists.txt

@@ -1,10 +1,10 @@
-cmake_minimum_required(VERSION 3.0.0)
+cmake_minimum_required(VERSION 3.8)
 
 ##
 ## PROJECT
 ## name and version
 ##
-project(nlohmann_json VERSION 3.1.2 LANGUAGES CXX)
+project(nlohmann_json VERSION 3.3.0 LANGUAGES CXX)
 
 ##
 ## INCLUDE
@@ -22,13 +22,15 @@ option(JSON_MultipleHeaders "Use non-amalgamated version of the library." OFF)
 ## CONFIGURATION
 ##
 set(NLOHMANN_JSON_TARGET_NAME               ${PROJECT_NAME})
-set(NLOHMANN_JSON_CONFIG_INSTALL_DIR        "lib/cmake/${PROJECT_NAME}")
+set(NLOHMANN_JSON_CONFIG_INSTALL_DIR        "lib/cmake/${PROJECT_NAME}"
+  CACHE INTERNAL "")
 set(NLOHMANN_JSON_INCLUDE_INSTALL_DIR       "include")
 set(NLOHMANN_JSON_TARGETS_EXPORT_NAME       "${PROJECT_NAME}Targets")
 set(NLOHMANN_JSON_CMAKE_CONFIG_TEMPLATE     "cmake/config.cmake.in")
-set(NLOHMANN_JSON_CMAKE_CONFIG_DIR          "${CMAKE_CURRENT_BINARY_DIR}/cmake_config")
+set(NLOHMANN_JSON_CMAKE_CONFIG_DIR          "${CMAKE_CURRENT_BINARY_DIR}")
 set(NLOHMANN_JSON_CMAKE_VERSION_CONFIG_FILE "${NLOHMANN_JSON_CMAKE_CONFIG_DIR}/${PROJECT_NAME}ConfigVersion.cmake")
 set(NLOHMANN_JSON_CMAKE_PROJECT_CONFIG_FILE "${NLOHMANN_JSON_CMAKE_CONFIG_DIR}/${PROJECT_NAME}Config.cmake")
+set(NLOHMANN_JSON_CMAKE_PROJECT_TARGETS_FILE "${NLOHMANN_JSON_CMAKE_CONFIG_DIR}/${PROJECT_NAME}Targets.cmake")
 
 if (JSON_MultipleHeaders)
     set(NLOHMANN_JSON_INCLUDE_BUILD_DIR "${PROJECT_SOURCE_DIR}/include/")
@@ -43,6 +45,8 @@ endif()
 ## create target and add include path
 ##
 add_library(${NLOHMANN_JSON_TARGET_NAME} INTERFACE)
+add_library(${PROJECT_NAME}::${NLOHMANN_JSON_TARGET_NAME} ALIAS ${NLOHMANN_JSON_TARGET_NAME})
+target_compile_features(${NLOHMANN_JSON_TARGET_NAME} INTERFACE cxx_std_11)
 
 target_include_directories(
     ${NLOHMANN_JSON_TARGET_NAME}
@@ -51,8 +55,8 @@ target_include_directories(
     $<INSTALL_INTERFACE:include>
 )
 
-## add debug view defintion file for msvc (natvis) [cmake <= 3.2.2 does not support export of source files]
-if (MSVC AND CMAKE_VERSION VERSION_GREATER "3.2.2")
+## add debug view definition file for msvc (natvis)
+if (MSVC)
     set(NLOHMANN_ADD_NATVIS TRUE)
     set(NLOHMANN_NATVIS_FILE "nlohmann_json.natvis")
     target_sources(
@@ -62,7 +66,7 @@ if (MSVC AND CMAKE_VERSION VERSION_GREATER "3.2.2")
             $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/${NLOHMANN_NATVIS_FILE}>  
     )
 endif()
-           
+
 ##
 ## TESTS
 ## create and configure the unit test target
@@ -82,10 +86,10 @@ include(CMakePackageConfigHelpers)
 write_basic_package_version_file(
     ${NLOHMANN_JSON_CMAKE_VERSION_CONFIG_FILE} COMPATIBILITY SameMajorVersion
 )
-configure_package_config_file(
+configure_file(
     ${NLOHMANN_JSON_CMAKE_CONFIG_TEMPLATE}
     ${NLOHMANN_JSON_CMAKE_PROJECT_CONFIG_FILE}
-    INSTALL_DESTINATION ${NLOHMANN_JSON_CONFIG_INSTALL_DIR}
+    @ONLY
 )
 
 install(
@@ -102,6 +106,11 @@ if (NLOHMANN_ADD_NATVIS)
         DESTINATION .
 )
 endif()
+export(
+    TARGETS ${NLOHMANN_JSON_TARGET_NAME}
+    NAMESPACE ${PROJECT_NAME}::
+    FILE ${NLOHMANN_JSON_CMAKE_PROJECT_TARGETS_FILE}
+)
 install(
     TARGETS ${NLOHMANN_JSON_TARGET_NAME}
     EXPORT ${NLOHMANN_JSON_TARGETS_EXPORT_NAME}
@@ -109,5 +118,6 @@ install(
 )
 install(
     EXPORT ${NLOHMANN_JSON_TARGETS_EXPORT_NAME}
+    NAMESPACE ${PROJECT_NAME}::
     DESTINATION ${NLOHMANN_JSON_CONFIG_INSTALL_DIR}
 )

ChangeLog.md

@@ -1,6 +1,254 @@
 # Change Log
 All notable changes to this project will be documented in this file. This project adheres to [Semantic Versioning](http://semver.org/).
 
+## [v3.3.0](https://github.com/nlohmann/json/releases/tag/v3.3.0) (2018-10-05)
+[Full Changelog](https://github.com/nlohmann/json/compare/v3.2.0...v3.3.0)
+
+- When key is not found print the key name into error too [\#1273](https://github.com/nlohmann/json/issues/1273)
+- Visual Studio 2017 15.8.5 "conditional expression is constant" warning on Line 1851 in json.hpp [\#1268](https://github.com/nlohmann/json/issues/1268)
+- how can we get this working on WSL? [\#1264](https://github.com/nlohmann/json/issues/1264)
+- Help needed [\#1259](https://github.com/nlohmann/json/issues/1259)
+- A way to get to a JSON values "key" [\#1258](https://github.com/nlohmann/json/issues/1258)
+- Two blackslashes on json output file [\#1253](https://github.com/nlohmann/json/issues/1253)
+- Including nlohmann the badwrong way. [\#1250](https://github.com/nlohmann/json/issues/1250)
+- how to build with clang? [\#1247](https://github.com/nlohmann/json/issues/1247)
+- Cmake target\_link\_libraries unable to find nlohmann\_json since version 3.2.0 [\#1243](https://github.com/nlohmann/json/issues/1243)
+- \[Question\] Access to end\(\) iterator reference [\#1242](https://github.com/nlohmann/json/issues/1242)
+- Parsing different json format [\#1241](https://github.com/nlohmann/json/issues/1241)
+- Parsing Multiple JSON Files [\#1240](https://github.com/nlohmann/json/issues/1240)
+- Doesn't compile under C++17 [\#1239](https://github.com/nlohmann/json/issues/1239)
+- Conversion operator for nlohmann::json is not SFINAE friendly [\#1237](https://github.com/nlohmann/json/issues/1237)
+- Custom deserialization of number\_float\_t [\#1236](https://github.com/nlohmann/json/issues/1236)
+- Move tests to a separate repo [\#1235](https://github.com/nlohmann/json/issues/1235)
+- deprecated-declarations warnings when compiling tests with GCC 8.2.1. [\#1233](https://github.com/nlohmann/json/issues/1233)
+- Incomplete type with json\_fwd.hpp [\#1232](https://github.com/nlohmann/json/issues/1232)
+- Parse Error [\#1229](https://github.com/nlohmann/json/issues/1229)
+- json::get function with argument [\#1227](https://github.com/nlohmann/json/issues/1227)
+- questions regarding from\_json [\#1226](https://github.com/nlohmann/json/issues/1226)
+- Lambda in unevaluated context [\#1225](https://github.com/nlohmann/json/issues/1225)
+- NLohmann doesn't compile when enabling strict warning policies [\#1224](https://github.com/nlohmann/json/issues/1224)
+- Creating array of objects [\#1223](https://github.com/nlohmann/json/issues/1223)
+- Somewhat unhelpful error message "cannot use operator\[\] with object" [\#1220](https://github.com/nlohmann/json/issues/1220)
+- single\_include json.hpp [\#1218](https://github.com/nlohmann/json/issues/1218)
+- Maps with enum class keys which are convertible to JSON strings should be converted to JSON dictionaries [\#1217](https://github.com/nlohmann/json/issues/1217)
+- Adding JSON Array to the Array  [\#1216](https://github.com/nlohmann/json/issues/1216)
+- Best way to output a vector of a given type to json [\#1215](https://github.com/nlohmann/json/issues/1215)
+- compiler warning: double definition of macro JSON\_INTERNAL\_CATCH  [\#1213](https://github.com/nlohmann/json/issues/1213)
+- Compilation error when using MOCK\_METHOD1 from GMock and nlohmann::json [\#1212](https://github.com/nlohmann/json/issues/1212)
+- Issues parsing a previously encoded binary \(non-UTF8\) string. [\#1211](https://github.com/nlohmann/json/issues/1211)
+- Yet another ordering question: char \* and parse\(\) [\#1209](https://github.com/nlohmann/json/issues/1209)
+- Error using gcc 8.1.0 on Ubuntu 14.04 [\#1207](https://github.com/nlohmann/json/issues/1207)
+- "type must be string, but is " std::string\(j.type\_name\(\)  [\#1206](https://github.com/nlohmann/json/issues/1206)
+- Returning empty json object from a function of type const json& ? [\#1205](https://github.com/nlohmann/json/issues/1205)
+- VS2017 compiler suggests using constexpr if [\#1204](https://github.com/nlohmann/json/issues/1204)
+- Template instatiation error on compiling [\#1203](https://github.com/nlohmann/json/issues/1203)
+- Soften the landing when dumping non-UTF8 strings \(type\_error.316 exception\) [\#1198](https://github.com/nlohmann/json/issues/1198)
+- BUG - json dump field with unicode -\> array of ints \(instead of string\) [\#1197](https://github.com/nlohmann/json/issues/1197)
+- Compile error using Code::Blocks // mingw-w64 GCC 8.1.0 - "Incomplete Type" [\#1193](https://github.com/nlohmann/json/issues/1193)
+- SEGFAULT on arm target  [\#1190](https://github.com/nlohmann/json/issues/1190)
+- Compiler crash with old Clang [\#1179](https://github.com/nlohmann/json/issues/1179)
+- Custom Precision on floating point numbers [\#1170](https://github.com/nlohmann/json/issues/1170)
+- Can we have a json\_view class like std::string\_view? [\#1158](https://github.com/nlohmann/json/issues/1158)
+- improve error handling [\#1152](https://github.com/nlohmann/json/issues/1152)
+- We should remove static\_asserts [\#960](https://github.com/nlohmann/json/issues/960)
+
+- Fix warning C4127: conditional expression is constant [\#1272](https://github.com/nlohmann/json/pull/1272) ([antonioborondo](https://github.com/antonioborondo))
+- Turn off additional deprecation warnings for GCC. [\#1271](https://github.com/nlohmann/json/pull/1271) ([chuckatkins](https://github.com/chuckatkins))
+- docs: Add additional CMake documentation [\#1270](https://github.com/nlohmann/json/pull/1270) ([chuckatkins](https://github.com/chuckatkins))
+- unit-testsuites.cpp: fix hangup if file not found [\#1262](https://github.com/nlohmann/json/pull/1262) ([knilch0r](https://github.com/knilch0r))
+- Fix broken cmake imported target alias [\#1260](https://github.com/nlohmann/json/pull/1260) ([chuckatkins](https://github.com/chuckatkins))
+- GCC 48 [\#1257](https://github.com/nlohmann/json/pull/1257) ([henryiii](https://github.com/henryiii))
+- Add version and license to meson.build [\#1252](https://github.com/nlohmann/json/pull/1252) ([koponomarenko](https://github.com/koponomarenko))
+- \#1179 Reordered the code. It seems to stop clang 3.4.2 in RHEL 7 from crash… [\#1249](https://github.com/nlohmann/json/pull/1249) ([LEgregius](https://github.com/LEgregius))
+- Use a version check to provide backwards comatible CMake imported target names [\#1245](https://github.com/nlohmann/json/pull/1245) ([chuckatkins](https://github.com/chuckatkins))
+- Fix issue \#1237 [\#1238](https://github.com/nlohmann/json/pull/1238) ([theodelrieu](https://github.com/theodelrieu))
+- Add a get overload taking a parameter. [\#1231](https://github.com/nlohmann/json/pull/1231) ([theodelrieu](https://github.com/theodelrieu))
+- Move lambda out of unevaluated context [\#1230](https://github.com/nlohmann/json/pull/1230) ([mandreyel](https://github.com/mandreyel))
+- Remove static asserts [\#1228](https://github.com/nlohmann/json/pull/1228) ([theodelrieu](https://github.com/theodelrieu))
+- Better error 305 [\#1221](https://github.com/nlohmann/json/pull/1221) ([rivertam](https://github.com/rivertam))
+- Fix \#1213 [\#1214](https://github.com/nlohmann/json/pull/1214) ([simnalamburt](https://github.com/simnalamburt))
+- Export package to allow builds without installing [\#1202](https://github.com/nlohmann/json/pull/1202) ([dennisfischer](https://github.com/dennisfischer))
+
+## [v3.2.0](https://github.com/nlohmann/json/releases/tag/v3.2.0) (2018-08-20)
+[Full Changelog](https://github.com/nlohmann/json/compare/v3.1.2...v3.2.0)
+
+- Am I doing this wrong? Getting an empty string [\#1199](https://github.com/nlohmann/json/issues/1199)
+- Incompatible Pointer Type [\#1196](https://github.com/nlohmann/json/issues/1196)
+- json.exception.type\_error.316 [\#1195](https://github.com/nlohmann/json/issues/1195)
+- Strange warnings in Code::Blocks 17.12, GNU GCC [\#1192](https://github.com/nlohmann/json/issues/1192)
+- \[Question\] Current place in code to change floating point resolution [\#1191](https://github.com/nlohmann/json/issues/1191)
+- Add key name when throwing type error [\#1189](https://github.com/nlohmann/json/issues/1189)
+- Not able to include in visual studio code? [\#1188](https://github.com/nlohmann/json/issues/1188)
+- Get an Index or row number of an element [\#1186](https://github.com/nlohmann/json/issues/1186)
+- reduce repos size [\#1185](https://github.com/nlohmann/json/issues/1185)
+- Difference between `merge\_patch` and `update` [\#1183](https://github.com/nlohmann/json/issues/1183)
+- Is there a way to get an element from a JSON without throwing an exception on failure? [\#1182](https://github.com/nlohmann/json/issues/1182)
+- to\_string? [\#1181](https://github.com/nlohmann/json/issues/1181)
+- How to cache a json object's pointer into a map? [\#1180](https://github.com/nlohmann/json/issues/1180)
+- Can this library work within a Qt project for Android using Qt Creator? [\#1178](https://github.com/nlohmann/json/issues/1178)
+- How to get all keys of one object? [\#1177](https://github.com/nlohmann/json/issues/1177)
+- How can I only parse the first level and get the value as string? [\#1175](https://github.com/nlohmann/json/issues/1175)
+- I have a query regarding nlohmann::basic\_json::basic\_json [\#1174](https://github.com/nlohmann/json/issues/1174)
+- unordered\_map with vectors won't convert to json? [\#1173](https://github.com/nlohmann/json/issues/1173)
+- return json objects from functions [\#1172](https://github.com/nlohmann/json/issues/1172)
+- Problem when exporting to CBOR [\#1171](https://github.com/nlohmann/json/issues/1171)
+- Roundtripping null to nullptr does not work [\#1169](https://github.com/nlohmann/json/issues/1169)
+- MSVC fails to compile std::swap specialization for nlohmann::json [\#1168](https://github.com/nlohmann/json/issues/1168)
+- Unexpected behaviour of is\_null - Part II [\#1167](https://github.com/nlohmann/json/issues/1167)
+- Floating point imprecision [\#1166](https://github.com/nlohmann/json/issues/1166)
+- Combine json objects into one? [\#1165](https://github.com/nlohmann/json/issues/1165)
+- Is there any way to know if the object has changed? [\#1164](https://github.com/nlohmann/json/issues/1164)
+- Value throws on null string [\#1163](https://github.com/nlohmann/json/issues/1163)
+- Weird template issue in large project [\#1162](https://github.com/nlohmann/json/issues/1162)
+- \_json returns a different result vs ::parse [\#1161](https://github.com/nlohmann/json/issues/1161)
+- Showing difference between two json objects [\#1160](https://github.com/nlohmann/json/issues/1160)
+- no instance of overloaded function "std::swap" matches the specified type	 [\#1159](https://github.com/nlohmann/json/issues/1159)
+- resize\(...\)? [\#1157](https://github.com/nlohmann/json/issues/1157)
+- Issue with struct nested in class' to\_json [\#1155](https://github.com/nlohmann/json/issues/1155)
+- Deserialize std::map with std::nan [\#1154](https://github.com/nlohmann/json/issues/1154)
+- Parse throwing errors [\#1149](https://github.com/nlohmann/json/issues/1149)
+- cocoapod integration [\#1148](https://github.com/nlohmann/json/issues/1148)
+- wstring parsing [\#1147](https://github.com/nlohmann/json/issues/1147)
+- Is it possible to dump a two-dimensional array to "\[\[null\],\[1,2,3\]\]"? [\#1146](https://github.com/nlohmann/json/issues/1146)
+- Want to write a class member variable and a struct variable \( this structure is inside the class\) to the json file [\#1145](https://github.com/nlohmann/json/issues/1145)
+- Does json support converting an instance of a struct into json string? [\#1143](https://github.com/nlohmann/json/issues/1143)
+- \#Most efficient way to search for child parameters \(recursive find?\) [\#1141](https://github.com/nlohmann/json/issues/1141)
+-  could not find to\_json\(\) method in T's namespace [\#1140](https://github.com/nlohmann/json/issues/1140)
+- chars get treated as JSON numbers not JSON strings [\#1139](https://github.com/nlohmann/json/issues/1139)
+- How do I count number of objects in array? [\#1137](https://github.com/nlohmann/json/issues/1137)
+- Serializing a vector of classes? [\#1136](https://github.com/nlohmann/json/issues/1136)
+- Compile error. Unable convert form nullptr to nullptr&& [\#1135](https://github.com/nlohmann/json/issues/1135)
+- std::unordered\_map in struct, serialization [\#1133](https://github.com/nlohmann/json/issues/1133)
+- dump\(\) can't handle umlauts [\#1131](https://github.com/nlohmann/json/issues/1131)
+- Add a way to get a key reference from the iterator [\#1127](https://github.com/nlohmann/json/issues/1127)
+- can't not parse "\\“ string [\#1123](https://github.com/nlohmann/json/issues/1123)
+-  if  json file  contain Internationalization   chars   ,  get  exception [\#1122](https://github.com/nlohmann/json/issues/1122)
+- How to use a json::iterator dereferenced value in code? [\#1120](https://github.com/nlohmann/json/issues/1120)
+- clang compiler: error : unknown type name 'not' [\#1119](https://github.com/nlohmann/json/issues/1119)
+- Disable implicit conversions from json to std::initializer\_list\<T\> for any T [\#1118](https://github.com/nlohmann/json/issues/1118)
+- Implicit conversions to complex types can lead to surprising and confusing errors [\#1116](https://github.com/nlohmann/json/issues/1116)
+- How can I write from\_json for a complex datatype that is not default constructible? [\#1115](https://github.com/nlohmann/json/issues/1115)
+- Compile error in VS2015 when compiling unit-conversions.cpp [\#1114](https://github.com/nlohmann/json/issues/1114)
+- ADL Serializer for std::any / boost::any [\#1113](https://github.com/nlohmann/json/issues/1113)
+- Unexpected behaviour of is\_null [\#1112](https://github.com/nlohmann/json/issues/1112)
+- How to resolve  " undefined reference to `std::\_\_throw\_bad\_cast\(\)'" [\#1111](https://github.com/nlohmann/json/issues/1111)
+- cannot compile on ubuntu 18.04 and 16.04 [\#1110](https://github.com/nlohmann/json/issues/1110)
+- JSON representation for floating point values has too many digits [\#1109](https://github.com/nlohmann/json/issues/1109)
+- Not working for classes containing "\_declspec\(dllimport\)" in their declaration [\#1108](https://github.com/nlohmann/json/issues/1108)
+- Get keys from json object [\#1107](https://github.com/nlohmann/json/issues/1107)
+- dump\(\) without alphabetical order [\#1106](https://github.com/nlohmann/json/issues/1106)
+- Cannot deserialize types using std::ratio [\#1105](https://github.com/nlohmann/json/issues/1105)
+-  i want to learn json [\#1104](https://github.com/nlohmann/json/issues/1104)
+- Type checking during compile [\#1103](https://github.com/nlohmann/json/issues/1103)
+- Iterate through sub items [\#1102](https://github.com/nlohmann/json/issues/1102)
+- cppcheck failing for version 3.1.2 [\#1101](https://github.com/nlohmann/json/issues/1101)
+- Deserializing std::map [\#1100](https://github.com/nlohmann/json/issues/1100)
+- accessing key by reference [\#1098](https://github.com/nlohmann/json/issues/1098)
+- clang 3.8.0 croaks while trying to compile with debug symbols [\#1097](https://github.com/nlohmann/json/issues/1097)
+- Serialize a list of class objects with json [\#1096](https://github.com/nlohmann/json/issues/1096)
+- Null bytes in files are treated like EOF [\#1095](https://github.com/nlohmann/json/issues/1095)
+- Small question [\#1094](https://github.com/nlohmann/json/issues/1094)
+- Upgrading to 3.x: to\_/from\_json with enum class [\#1093](https://github.com/nlohmann/json/issues/1093)
+- Q: few questions about json construction [\#1092](https://github.com/nlohmann/json/issues/1092)
+- general crayCC compilation failure [\#1091](https://github.com/nlohmann/json/issues/1091)
+- Merge Patch clears original data [\#1090](https://github.com/nlohmann/json/issues/1090)
+- \[Question\] how to use nlohmann/json in c++? [\#1088](https://github.com/nlohmann/json/issues/1088)
+- C++17 decomposition declaration support [\#1087](https://github.com/nlohmann/json/issues/1087)
+- \[Question\] Access multi-level json objects [\#1086](https://github.com/nlohmann/json/issues/1086)
+- Serializing vector [\#1085](https://github.com/nlohmann/json/issues/1085)
+- update nested value in multi hierarchy json object [\#1084](https://github.com/nlohmann/json/issues/1084)
+- Overriding default values? [\#1083](https://github.com/nlohmann/json/issues/1083)
+- detail namespace collision with Cereal? [\#1082](https://github.com/nlohmann/json/issues/1082)
+- Error using json.dump\(\); [\#1081](https://github.com/nlohmann/json/issues/1081)
+- Consuming TCP Stream [\#1080](https://github.com/nlohmann/json/issues/1080)
+- Compilation error with strong typed enums in map in combination with namespaces [\#1079](https://github.com/nlohmann/json/issues/1079)
+- cassert error [\#1076](https://github.com/nlohmann/json/issues/1076)
+- Valid json data not being parsed [\#1075](https://github.com/nlohmann/json/issues/1075)
+- Feature request :: Better testing for key existance without try/catch [\#1074](https://github.com/nlohmann/json/issues/1074)
+- Hi, I have input like a.b.c and want to convert it to \"a\"{\"b\": \"c\"} form. Any suggestions how do I do this? Thanks. [\#1073](https://github.com/nlohmann/json/issues/1073)
+- ADL deserializer not picked up for non default-constructible type [\#1072](https://github.com/nlohmann/json/issues/1072)
+- Deserializing std::array doesn't compiler \(no insert\(\)\) [\#1071](https://github.com/nlohmann/json/issues/1071)
+- Serializing OpenCV Mat problem [\#1070](https://github.com/nlohmann/json/issues/1070)
+- Compilation error with ICPC compiler [\#1068](https://github.com/nlohmann/json/issues/1068)
+- Minimal branch? [\#1066](https://github.com/nlohmann/json/issues/1066)
+- Not existing value, crash [\#1065](https://github.com/nlohmann/json/issues/1065)
+- cyryllic symbols [\#1064](https://github.com/nlohmann/json/issues/1064)
+- newbie usage question [\#1063](https://github.com/nlohmann/json/issues/1063)
+- Trying j\["strTest"\] = "%A" produces "strTest": "-0X1.CCCCCCCCCCCCCP+205" [\#1062](https://github.com/nlohmann/json/issues/1062)
+- convert json value to std::string??? [\#1061](https://github.com/nlohmann/json/issues/1061)
+- Commented out test cases, should they be removed? [\#1060](https://github.com/nlohmann/json/issues/1060)
+- different behaviour between clang and gcc with braced initialization [\#1059](https://github.com/nlohmann/json/issues/1059)
+- json array:  initialize with prescribed size and `resize` method. [\#1057](https://github.com/nlohmann/json/issues/1057)
+- Is it possible to use exceptions istead of assertions? [\#1056](https://github.com/nlohmann/json/issues/1056)
+- when using assign operator in with json object a static assertion fails.. [\#1055](https://github.com/nlohmann/json/issues/1055)
+- Iterate over leafs of a JSON data structure: enrich the JSON pointer API [\#1054](https://github.com/nlohmann/json/issues/1054)
+- \[Feature request\] Access by path [\#1053](https://github.com/nlohmann/json/issues/1053)
+- document that implicit js -\> primitive conversion does not work for std::string::value\_type and why [\#1052](https://github.com/nlohmann/json/issues/1052)
+- error: ‘BasicJsonType’ in namespace ‘::’ does not name a type [\#1051](https://github.com/nlohmann/json/issues/1051)
+- Destructor is called when filling object through assignement [\#1050](https://github.com/nlohmann/json/issues/1050)
+- Is this thing thread safe for reads? [\#1049](https://github.com/nlohmann/json/issues/1049)
+- clang-tidy: Call to virtual function during construction  [\#1046](https://github.com/nlohmann/json/issues/1046)
+- Using STL algorithms with JSON containers with expected results? [\#1045](https://github.com/nlohmann/json/issues/1045)
+- Usage with gtest/gmock not working as expected [\#1044](https://github.com/nlohmann/json/issues/1044)
+- Consequences of from\_json / to\_json being in namespace of data struct. [\#1042](https://github.com/nlohmann/json/issues/1042)
+- const\_reference operator\[\]\(const typename object\_t::key\_type& key\) const throw instead of assert [\#1039](https://github.com/nlohmann/json/issues/1039)
+- Trying to retrieve data from nested objects [\#1038](https://github.com/nlohmann/json/issues/1038)
+- Direct download link for json\_fwd.hpp? [\#1037](https://github.com/nlohmann/json/issues/1037)
+- I know the library supports UTF-8, but failed to dump the value [\#1036](https://github.com/nlohmann/json/issues/1036)
+- Putting a Vec3-like vector into a json object [\#1035](https://github.com/nlohmann/json/issues/1035)
+- Ternary operator crash [\#1034](https://github.com/nlohmann/json/issues/1034)
+- Issued with Clion Inspection Resolution since 2018.1 [\#1033](https://github.com/nlohmann/json/issues/1033)
+- Some testcases fail and one never finishes [\#1032](https://github.com/nlohmann/json/issues/1032)
+- Can this class work with wchar\_t / std::wstring? [\#1031](https://github.com/nlohmann/json/issues/1031)
+- Makefile: Valgrind flags have no effect [\#1030](https://github.com/nlohmann/json/issues/1030)
+- 「==」 Should be 「\>」 [\#1029](https://github.com/nlohmann/json/issues/1029)
+- HOCON reader? [\#1027](https://github.com/nlohmann/json/issues/1027)
+- add json string in previous string?? [\#1025](https://github.com/nlohmann/json/issues/1025)
+- RFC: fluent parsing interface [\#1023](https://github.com/nlohmann/json/issues/1023)
+- Does it support chinese character? [\#1022](https://github.com/nlohmann/json/issues/1022)
+- to/from\_msgpack only works with standard typization [\#1021](https://github.com/nlohmann/json/issues/1021)
+- Build failure using latest clang and GCC compilers [\#1020](https://github.com/nlohmann/json/issues/1020)
+- can two json objects be concatenated? [\#1019](https://github.com/nlohmann/json/issues/1019)
+- Erase by integer index [\#1018](https://github.com/nlohmann/json/issues/1018)
+- Function find overload taking a json\_pointer [\#1017](https://github.com/nlohmann/json/issues/1017)
+- I think should implement an parser function [\#1016](https://github.com/nlohmann/json/issues/1016)
+- Readme gif [\#1015](https://github.com/nlohmann/json/issues/1015)
+- Python bindings [\#1014](https://github.com/nlohmann/json/issues/1014)
+- how to add two json string in single object?? [\#1012](https://github.com/nlohmann/json/issues/1012)
+- how to serialize class Object \(convert data in object into json\)?? [\#1011](https://github.com/nlohmann/json/issues/1011)
+- Enable forward declaration of json by making json a class instead of a using declaration [\#997](https://github.com/nlohmann/json/issues/997)
+- compilation error while using intel c++ compiler 2018 [\#994](https://github.com/nlohmann/json/issues/994)
+- How to create a json variable? [\#990](https://github.com/nlohmann/json/issues/990)
+- istream \>\> json  --- 1st character skipped in stream [\#976](https://github.com/nlohmann/json/issues/976)
+- Add a SAX parser [\#971](https://github.com/nlohmann/json/issues/971)
+- Add Key name to Exception [\#932](https://github.com/nlohmann/json/issues/932)
+- How to solve large json file? [\#927](https://github.com/nlohmann/json/issues/927)
+- json\_pointer public push\_back, pop\_back [\#837](https://github.com/nlohmann/json/issues/837)
+- Using input\_adapter in a slightly unexpected way [\#834](https://github.com/nlohmann/json/issues/834)
+- Stack-overflow \(OSS-Fuzz 4234\) [\#832](https://github.com/nlohmann/json/issues/832)
+
+- Fix -Wno-sometimes-uninitialized by initializing "result" in parse\_sax [\#1200](https://github.com/nlohmann/json/pull/1200) ([thyu](https://github.com/thyu))
+- \[RFC\] Introduce a new macro function: JSON\_INTERNAL\_CATCH [\#1187](https://github.com/nlohmann/json/pull/1187) ([simnalamburt](https://github.com/simnalamburt))
+- Fix unit tests that were silently skipped or crashed \(depending on the compiler\) [\#1176](https://github.com/nlohmann/json/pull/1176) ([grembo](https://github.com/grembo))
+- Refactor/no virtual sax [\#1153](https://github.com/nlohmann/json/pull/1153) ([theodelrieu](https://github.com/theodelrieu))
+- Fixed compiler error in VS 2015 for debug mode [\#1151](https://github.com/nlohmann/json/pull/1151) ([sonulohani](https://github.com/sonulohani))
+- Fix links to cppreference named requirements \(formerly concepts\) [\#1144](https://github.com/nlohmann/json/pull/1144) ([jrakow](https://github.com/jrakow))
+- meson: fix include directory [\#1142](https://github.com/nlohmann/json/pull/1142) ([jrakow](https://github.com/jrakow))
+- Feature/unordered map conversion [\#1138](https://github.com/nlohmann/json/pull/1138) ([theodelrieu](https://github.com/theodelrieu))
+- fixed compile error for \#1045 [\#1134](https://github.com/nlohmann/json/pull/1134) ([Daniel599](https://github.com/Daniel599))
+-  test \(non\)equality for alt\_string implementation  [\#1130](https://github.com/nlohmann/json/pull/1130) ([agrianius](https://github.com/agrianius))
+- remove stringstream dependency [\#1117](https://github.com/nlohmann/json/pull/1117) ([TinyTinni](https://github.com/TinyTinni))
+- Provide a from\_json overload for std::map [\#1089](https://github.com/nlohmann/json/pull/1089) ([theodelrieu](https://github.com/theodelrieu))
+- fix typo in README [\#1078](https://github.com/nlohmann/json/pull/1078) ([martin-mfg](https://github.com/martin-mfg))
+- Fix typo [\#1058](https://github.com/nlohmann/json/pull/1058) ([dns13](https://github.com/dns13))
+- Misc cmake packaging enhancements [\#1048](https://github.com/nlohmann/json/pull/1048) ([chuckatkins](https://github.com/chuckatkins))
+- Fixed incorrect LLVM version number in README [\#1047](https://github.com/nlohmann/json/pull/1047) ([jammehcow](https://github.com/jammehcow))
+- Fix trivial typo in comment. [\#1043](https://github.com/nlohmann/json/pull/1043) ([coryan](https://github.com/coryan))
+- Package Manager: Spack [\#1041](https://github.com/nlohmann/json/pull/1041) ([ax3l](https://github.com/ax3l))
+- CMake: 3.8+ is Sufficient [\#1040](https://github.com/nlohmann/json/pull/1040) ([ax3l](https://github.com/ax3l))
+- Added support for string\_view in C++17 [\#1028](https://github.com/nlohmann/json/pull/1028) ([gracicot](https://github.com/gracicot))
+- Added public target\_compile\_features for auto and constexpr [\#1026](https://github.com/nlohmann/json/pull/1026) ([ktonon](https://github.com/ktonon))
+
 ## [v3.1.2](https://github.com/nlohmann/json/releases/tag/v3.1.2) (2018-03-14)
 [Full Changelog](https://github.com/nlohmann/json/compare/v3.1.1...v3.1.2)
 
@@ -16,7 +264,6 @@ All notable changes to this project will be documented in this file. This projec
 - get\<T\> for types that are not default constructible [\#996](https://github.com/nlohmann/json/issues/996)
 - Prevent Null values to appear in .dump\(\) [\#995](https://github.com/nlohmann/json/issues/995)
 - number parsing [\#993](https://github.com/nlohmann/json/issues/993)
-- How to create a json variable? [\#990](https://github.com/nlohmann/json/issues/990)
 - C2664 \(C++/CLR\) cannot convert 'nullptr' to 'nullptr &&' [\#987](https://github.com/nlohmann/json/issues/987)
 - Uniform initialization from another json object differs between gcc and clang. [\#985](https://github.com/nlohmann/json/issues/985)
 - Problem with adding the lib as a submodule [\#983](https://github.com/nlohmann/json/issues/983)
@@ -785,7 +1032,6 @@ All notable changes to this project will be documented in this file. This projec
 - json::diff generates incorrect patch when removing multiple array elements. [\#269](https://github.com/nlohmann/json/issues/269)
 - Docs - What does Json\[key\] return? [\#267](https://github.com/nlohmann/json/issues/267)
 - Compiler Errors With JSON.hpp [\#265](https://github.com/nlohmann/json/issues/265)
-- Throw exception instead of crashing my app [\#264](https://github.com/nlohmann/json/issues/264)
 - Ambiguous push\_back and operator+= overloads [\#263](https://github.com/nlohmann/json/issues/263)
 - Preseving order of items in json [\#262](https://github.com/nlohmann/json/issues/262)
 - '\' char problem in strings [\#261](https://github.com/nlohmann/json/issues/261)

Makefile

@@ -9,6 +9,7 @@ SRCS = include/nlohmann/json.hpp \
        include/nlohmann/detail/exceptions.hpp \
        include/nlohmann/detail/input/binary_reader.hpp \
        include/nlohmann/detail/input/input_adapters.hpp \
+       include/nlohmann/detail/input/json_sax.hpp \
        include/nlohmann/detail/input/lexer.hpp \
        include/nlohmann/detail/input/parser.hpp \
        include/nlohmann/detail/iterators/internal_iterator.hpp \
@@ -20,7 +21,10 @@ SRCS = include/nlohmann/json.hpp \
        include/nlohmann/detail/json_ref.hpp \
        include/nlohmann/detail/macro_scope.hpp \
        include/nlohmann/detail/macro_unscope.hpp \
-       include/nlohmann/detail/meta.hpp \
+       include/nlohmann/detail/meta/cpp_future.hpp \
+       include/nlohmann/detail/meta/detected.hpp \
+       include/nlohmann/detail/meta/type_traits.hpp \
+       include/nlohmann/detail/meta/void_t.hpp \
        include/nlohmann/detail/output/binary_writer.hpp \
        include/nlohmann/detail/output/output_adapters.hpp \
        include/nlohmann/detail/output/serializer.hpp \
@@ -82,9 +86,9 @@ clean:
 
 coverage:
 	mkdir build_coverage
-	cd build_coverage ; CXX=g++-5 cmake .. -GNinja -DJSON_Coverage=ON -DJSON_MultipleHeaders=ON
+	cd build_coverage ; CXX=g++-7 cmake .. -GNinja -DJSON_Coverage=ON -DJSON_MultipleHeaders=ON
 	cd build_coverage ; ninja
-	cd build_coverage ; ctest -j10
+	cd build_coverage ; ctest -E '.*_default' -j10
 	cd build_coverage ; ninja lcov_html
 	open build_coverage/test/html/index.html
 
@@ -187,7 +191,10 @@ pedantic_gcc:
 		-Wunused-macros \
 		-Wunused-parameter \
 		-Wuseless-cast \
-		-Wvariadic-macros"
+		-Wvariadic-macros \
+		-Wctor-dtor-privacy \
+		-Winit-self \
+		-Wstrict-null-sentinel"
 
 ##########################################################################
 # benchmarks

README.md

@@ -5,6 +5,7 @@
 [![Coverage Status](https://img.shields.io/coveralls/nlohmann/json.svg)](https://coveralls.io/r/nlohmann/json)
 [![Coverity Scan Build Status](https://scan.coverity.com/projects/5550/badge.svg)](https://scan.coverity.com/projects/nlohmann-json)
 [![Codacy Badge](https://api.codacy.com/project/badge/Grade/f3732b3327e34358a0e9d1fe9f661f08)](https://www.codacy.com/app/nlohmann/json?utm_source=github.com&utm_medium=referral&utm_content=nlohmann/json&utm_campaign=Badge_Grade)
+[![Language grade: C/C++](https://img.shields.io/lgtm/grade/cpp/g/nlohmann/json.svg?logo=lgtm&logoWidth=18)](https://lgtm.com/projects/g/nlohmann/json/context:cpp)
 [![Try online](https://img.shields.io/badge/try-online-blue.svg)](https://wandbox.org/permlink/TarF5pPn9NtHQjhf)
 [![Documentation](https://img.shields.io/badge/docs-doxygen-blue.svg)](http://nlohmann.github.io/json)
 [![GitHub license](https://img.shields.io/badge/license-MIT-blue.svg)](https://raw.githubusercontent.com/nlohmann/json/master/LICENSE.MIT)
@@ -15,6 +16,8 @@
 
 - [Design goals](#design-goals)
 - [Integration](#integration)
+  - [CMake](#cmake)
+  - [Package Managers](#package-managers)
 - [Examples](#examples)
   - [JSON as first-class data type](#json-as-first-class-data-type)
   - [Serialization / Deserialization](#serialization--deserialization)
@@ -68,6 +71,71 @@ to the files you want to process JSON and set the necessary switches to enable C
 
 You 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`.
 
+### CMake
+
+You 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.
+
+#### External
+
+To 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:
+```cmake
+# CMakeLists.txt
+find_package(nlohmann_json 3.2.0 REQUIRED)
+...
+add_library(foo ...)
+...
+target_link_libraries(foo PRIVATE nlohmann_json::nlohmann_json)
+```
+The package configuration file, `nlohmann_jsonConfig.cmake`, can be used either from an install tree or directly out of the build tree.
+
+#### Embedded
+
+To 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:
+```cmake
+# Typically you don't care so much for a third party library's tests to be
+# run from your own project's code.
+set(JSON_BuildTests OFF CACHE INTERNAL "")
+
+# Don't use include(nlohmann_json/CMakeLists.txt) since that carries with it
+# inintended consequences that will break the build.  It's generally
+# discouraged (although not necessarily well documented as such) to use
+# include(...) for pulling in other CMake projects anyways.
+add_subdirectory(nlohmann_json)
+...
+add_library(foo ...)
+...
+target_link_libraries(foo PRIVATE nlohmann_json::nlohmann_json)
+```
+
+#### Supporting Both
+To allow your project to support either an externally supplied or an embedded JSON library, you can use a pattern akin to the following:
+``` cmake
+# Top level CMakeLists.txt
+project(FOO)
+...
+option(FOO_USE_EXTERNAL_JSON "Use an external JSON library" OFF)
+...
+add_subdirectory(thirdparty)
+...
+add_library(foo ...)
+...
+# Note that the namespaced target will always be available regardless of the
+# import method
+target_link_libraries(foo PRIVATE nlohmann_json::nlohmann_json)
+```
+```cmake
+# thirdparty/CMakeLists.txt
+...
+if(FOO_USE_EXTERNAL_JSON)
+  find_package(nlohmann_json 3.2.0 REQUIRED)
+else()
+  set(JSON_BuildTests OFF CACHE INTERNAL "")
+  add_subdirectory(nlohmann_json)
+endif()
+...
+```
+`thirdparty/nlohmann_json` is then a complete copy of this source tree.
+
 ### Package Managers
 
 :beer: If you are using OS X and [Homebrew](http://brew.sh), just type `brew tap nlohmann/json` and `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`.
@@ -76,6 +144,8 @@ If you are using the [Meson Build System](http://mesonbuild.com), then you can w
 
 If you are using [Conan](https://www.conan.io/) to manage your dependencies, merely add `jsonformoderncpp/x.y.z@vthiery/stable` to your `conanfile.py`'s requires, where `x.y.z` is the release version you want to use. Please file issues [here](https://github.com/vthiery/conan-jsonformoderncpp/issues) if you experience problems with the packages.
 
+If you are using [Spack](https://www.spack.io/) to manage your dependencies, you can use the `nlohmann_json` package. Please see the [spack project](https://github.com/spack/spack) for any issues regarding the packaging.
+
 If you are using [hunter](https://github.com/ruslo/hunter/) on your project for external dependencies, then you can use the [nlohmann_json package](https://docs.hunter.sh/en/latest/packages/pkg/nlohmann_json.html). Please see the hunter project for any issues regarding the packaging.
 
 If you are using [Buckaroo](https://buckaroo.pm), you can install this library's module with `buckaroo install nlohmann/json`. Please file issues [here](https://github.com/LoopPerfect/buckaroo-recipes/issues/new?title=nlohmann/nlohmann/json).
@@ -84,6 +154,8 @@ If you are using [vcpkg](https://github.com/Microsoft/vcpkg/) on your project fo
 
 If you are using [cget](http://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`).
 
+If 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).
+
 ## Examples
 
 Beside the examples below, you may want to check the [documentation](https://nlohmann.github.io/json/) where each function contains a separate code example (e.g., check out [`emplace()`](https://nlohmann.github.io/json/classnlohmann_1_1basic__json_a5338e282d1d02bed389d852dd670d98d.html#a5338e282d1d02bed389d852dd670d98d)). All [example files](https://github.com/nlohmann/json/tree/develop/doc/examples) can be compiled and executed on their own (e.g., file [emplace.cpp](https://github.com/nlohmann/json/blob/develop/doc/examples/emplace.cpp)).
@@ -169,7 +241,6 @@ json empty_object_explicit = json::object();
 json array_not_object = json::array({ {"currency", "USD"}, {"value", 42.99} });
 ```
 
-
 ### Serialization / Deserialization
 
 #### To/from strings
@@ -223,18 +294,22 @@ json j_string = "this is a string";
 std::string cpp_string = j_string;
 // retrieve the string value (explicit JSON to std::string conversion)
 auto cpp_string2 = j_string.get<std::string>();
+// retrieve the string value (alternative explicit JSON to std::string conversion)
+std::string cpp_string3;
+j_string.get_to(cpp_string3);
 
 // retrieve the serialized value (explicit JSON serialization)
 std::string serialized_string = j_string.dump();
 
 // output of original string
-std::cout << cpp_string << " == " << cpp_string2 << " == " << j_string.get<std::string>() << '\n';
+std::cout << cpp_string << " == " << cpp_string2 << " == " << cpp_string3 << " == " << j_string.get<std::string>() << '\n';
 // output of serialized value
 std::cout << j_string << " == " << serialized_string << std::endl;
 ```
 
 [`.dump()`](https://nlohmann.github.io/json/classnlohmann_1_1basic__json_a5adea76fedba9898d404fef8598aa663.html#a5adea76fedba9898d404fef8598aa663) always returns the serialized value, and [`.get<std::string>()`](https://nlohmann.github.io/json/classnlohmann_1_1basic__json_a16f9445f7629f634221a42b967cdcd43.html#a16f9445f7629f634221a42b967cdcd43) returns the originally stored string value.
 
+Note the library only supports UTF-8. When you store strings with different encodings in the library, calling [`dump()`](https://nlohmann.github.io/json/classnlohmann_1_1basic__json_a5adea76fedba9898d404fef8598aa663.html#a5adea76fedba9898d404fef8598aa663) may throw an exception.
 
 #### To/from streams (e.g. files, string streams)
 
@@ -283,10 +358,53 @@ std::vector<std::uint8_t> v = {'t', 'r', 'u', 'e'};
 json j = json::parse(v);
 ```
 
+#### SAX interface
+
+The library uses a SAX-like interface with the following functions:
+
+```cpp
+// called when null is parsed
+bool null();
+
+// called when a boolean is parsed; value is passed
+bool boolean(bool val);
+
+// called when a signed or unsigned integer number is parsed; value is passed
+bool number_integer(number_integer_t val);
+bool number_unsigned(number_unsigned_t val);
+
+// called when a floating-point number is parsed; value and original string is passed
+bool number_float(number_float_t val, const string_t& s);
+
+// called when a string is parsed; value is passed and can be safely moved away
+bool string(string_t& val);
+
+// called when an object or array begins or ends, resp. The number of elements is passed (or -1 if not known)
+bool start_object(std::size_t elements);
+bool end_object();
+bool start_array(std::size_t elements);
+bool end_array();
+// called when an object key is parsed; value is passed and can be safely moved away
+bool key(string_t& val);
+
+// called when a parse error occurs; byte position, the last token, and an exception is passed
+bool parse_error(std::size_t position, const std::string& last_token, const detail::exception& ex);
+```
+
+The return value of each function determines whether parsing should proceed.
+
+To implement your own SAX handler, proceed as follows:
+
+1. 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.
+2. Create an object of your SAX interface class, e.g. `my_sax`.
+3. 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.
+
+Note 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).
+
 
 ### STL-like access
 
-We designed the JSON class to behave just like an STL container. In fact, it satisfies the [**ReversibleContainer**](http://en.cppreference.com/w/cpp/concept/ReversibleContainer) requirement.
+We 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.
 
 ```cpp
 // create an array using push_back
@@ -523,6 +641,14 @@ int vi = jn.get<int>();
 // etc.
 ```
 
+Note that `char` types are not automatically converted to JSON strings, but to integer numbers. A conversion to a string must be specified explicitly:
+
+```cpp
+char ch = 'A';                       // ASCII value 65
+json j_default = ch;                 // stores integer number 65
+json j_string = std::string(1, ch);  // stores string "A"
+```
+
 ### Arbitrary types conversions
 
 Every type can be serialized in JSON, not just STL containers and scalar types. Usually, you would do something along those lines:
@@ -587,24 +713,24 @@ namespace ns {
     }
 
     void from_json(const json& j, person& p) {
-        p.name = j.at("name").get<std::string>();
-        p.address = j.at("address").get<std::string>();
-        p.age = j.at("age").get<int>();
+        j.at("name").get_to(p.name);
+        j.at("address").get_to(p.address);
+        j.at("age").get_to(p.age);
     }
 } // namespace ns
 ```
 
 That's all! When calling the `json` constructor with your type, your custom `to_json` method will be automatically called.
-Likewise, when calling `get<your_type>()`, the `from_json` method will be called.
+Likewise, when calling `get<your_type>()` or `get_to(your_type&)`, the `from_json` method will be called.
 
 Some important things:
 
 * 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).
-* When using `get<your_type>()`, `your_type` **MUST** be [DefaultConstructible](http://en.cppreference.com/w/cpp/concept/DefaultConstructible). (There is a way to bypass this requirement described later.)
+* Those methods **MUST** be available (e.g., properly headers must be included) everywhere you use the implicit conversions. Look at [issue 1108](https://github.com/nlohmann/json/issues/1108) for errors that may occur otherwise.
+* When using `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.)
 * In function `from_json`, use function [`at()`](https://nlohmann.github.io/json/classnlohmann_1_1basic__json_a93403e803947b86f4da2d1fb3345cf2c.html#a93403e803947b86f4da2d1fb3345cf2c) 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.
-* In case your type contains several `operator=` definitions, code like `your_variable = your_json;` [may not compile](https://github.com/nlohmann/json/issues/667). You need to write `your_variable = your_json.get<decltype your_variable>();` instead.
+* In case your type contains several `operator=` definitions, code like `your_variable = your_json;` [may not compile](https://github.com/nlohmann/json/issues/667). You need to write `your_variable = your_json.get<decltype(your_variable)>();` or `your_json.get_to(your_variable);` instead.
 * You do not need to add serializers or deserializers for STL types like `std::vector`: the library already implements these.
-* Be careful with the definition order of the `from_json`/`to_json` functions: If a type `B` has a member of type `A`, you **MUST** define `to_json(A)` before `to_json(B)`. Look at [issue 561](https://github.com/nlohmann/json/issues/561) for more details.
 
 
 #### How do I convert third-party types?
@@ -612,7 +738,7 @@ Some important things:
 This requires a bit more advanced technique. But first, let's see how this conversion mechanism works:
 
 The library uses **JSON Serializers** to convert types to json.
-The default serializer for `nlohmann::json` is `nlohmann::adl_serializer` (ADL means [Argument-Dependent Lookup](http://en.cppreference.com/w/cpp/language/adl)).
+The default serializer for `nlohmann::json` is `nlohmann::adl_serializer` (ADL means [Argument-Dependent Lookup](https://en.cppreference.com/w/cpp/language/adl)).
 
 It is implemented like this (simplified):
 
@@ -661,7 +787,7 @@ namespace nlohmann {
 
 #### How can I use `get()` for non-default constructible/non-copyable types?
 
-There is a way, if your type is [MoveConstructible](http://en.cppreference.com/w/cpp/concept/MoveConstructible). You will need to specialize the `adl_serializer` as well, but with a special `from_json` overload:
+There 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:
 
 ```cpp
 struct move_only_type {
@@ -786,8 +912,8 @@ json j_from_ubjson = json::from_ubjson(v_ubjson);
 
 Though it's 2018 already, the support for C++11 is still a bit sparse. Currently, the following compilers are known to work:
 
-- GCC 4.9 - 7.2 (and possibly later)
-- Clang 3.4 - 5.0 (and possibly later)
+- GCC 4.8 - 8.2 (and possibly later)
+- Clang 3.4 - 6.1 (and possibly later)
 - Intel C++ Compiler 17.0.2 (and possibly later)
 - Microsoft Visual C++ 2015 / Build Tools 14.0.25123.0 (and possibly later)
 - Microsoft Visual C++ 2017 / Build Tools 15.5.180.51428 (and possibly later)
@@ -796,7 +922,7 @@ I would be happy to learn about other compilers/versions.
 
 Please note:
 
-- GCC 4.8 does not work because of two bugs ([55817](https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55817) and [57824](https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57824)) in the C++11 support. Note there is a [pull request](https://github.com/nlohmann/json/pull/212) to fix some of the issues.
+- 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.
 - 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.
 
     ```
@@ -809,32 +935,40 @@ Please note:
 
 - For GCC running on MinGW or Android SDK, the error `'to_string' is not a member of 'std'` (or similarly, for `strtod`) 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](http://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).
 
+- 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.
+
 The following compilers are currently used in continuous integration at [Travis](https://travis-ci.org/nlohmann/json) and [AppVeyor](https://ci.appveyor.com/project/nlohmann/json):
 
 | Compiler        | Operating System             | Version String |
 |-----------------|------------------------------|----------------|
-| GCC 4.9.4       | Ubuntu 14.04.5 LTS           | g++-4.9 (Ubuntu 4.9.4-2ubuntu1~14.04.1) 4.9.4 |
-| GCC 5.4.1       | Ubuntu 14.04.5 LTS           | g++-5 (Ubuntu 5.4.1-2ubuntu1~14.04) 5.4.1 20160904 |
-| GCC 6.3.0       | Ubuntu 14.04.5 LTS           | g++-6 (Ubuntu/Linaro 6.3.0-18ubuntu2~14.04) 6.3.0 20170519 |
-| GCC 7.1.0       | Ubuntu 14.04.5 LTS           | g++-7 (Ubuntu 7.1.0-5ubuntu2~14.04) 7.1.0
-| Clang 3.5.0     | Ubuntu 14.04.5 LTS           | clang version 3.5.0-4ubuntu2~trusty2 (tags/RELEASE_350/final) |
-| Clang 3.6.2     | Ubuntu 14.04.5 LTS           | clang version 3.6.2-svn240577-1~exp1 (branches/release_36) |
-| Clang 3.7.1     | Ubuntu 14.04.5 LTS           | clang version 3.7.1-svn253571-1~exp1 (branches/release_37) |
-| Clang 3.8.0     | Ubuntu 14.04.5 LTS           | clang version 3.8.0-2ubuntu3~trusty5 (tags/RELEASE_380/final) |
-| Clang 3.9.1     | Ubuntu 14.04.5 LTS           | clang version 3.9.1-4ubuntu3~14.04.2 (tags/RELEASE_391/rc2) |
-| Clang 4.0.1     | Ubuntu 14.04.5 LTS           | clang version 4.0.1-svn305264-1~exp1 (branches/release_40) |
-| Clang 5.0.0     | Ubuntu 14.04.5 LTS           | clang version 5.0.0-svn310902-1~exp1 (branches/release_50) |
-| Clang Xcode 6.4 | Darwin Kernel Version 14.3.0 (OSX 10.10.3) | Apple LLVM version 6.1.0 (clang-602.0.53) (based on LLVM 3.6.0svn) |
-| Clang Xcode 7.3 | Darwin Kernel Version 15.0.0 (OSX 10.10.5) | Apple LLVM version 7.3.0 (clang-703.0.29) |
-| Clang Xcode 8.0 | Darwin Kernel Version 15.6.0 | Apple LLVM version 8.0.0 (clang-800.0.38) |
-| Clang Xcode 8.1 | Darwin Kernel Version 16.1.0 (macOS 10.12.1) | Apple LLVM version 8.0.0 (clang-800.0.42.1) |
-| Clang Xcode 8.2 | Darwin Kernel Version 16.1.0 (macOS 10.12.1) | Apple LLVM version 8.0.0 (clang-800.0.42.1) |
-| Clang Xcode 8.3 | Darwin Kernel Version 16.5.0 (macOS 10.12.4) | Apple LLVM version 8.1.0 (clang-802.0.38) |
-| Clang Xcode 9.0 | Darwin Kernel Version 16.7.0 (macOS 10.12.6) | Apple LLVM version 9.0.0 (clang-900.0.37) |
-| Clang Xcode 9.1 | Darwin Kernel Version 16.7.0 (macOS 10.12.6) | Apple LLVM version 9.0.0 (clang-900.0.38) |
-| Clang Xcode 9.2 | Darwin Kernel Version 16.7.0 (macOS 10.12.6) | Apple LLVM version 8.1.0 (clang-900.0.39.2) |
+| GCC 4.8.5       | Ubuntu 14.04.5 LTS           | g++-4.8 (Ubuntu 4.8.5-2ubuntu1~14.04.2) 4.8.5 |
+| GCC 4.9.4       | Ubuntu 14.04.1 LTS           | g++-4.9 (Ubuntu 4.9.4-2ubuntu1~14.04.1) 4.9.4 |
+| GCC 5.5.0       | Ubuntu 14.04.1 LTS           | g++-5 (Ubuntu 5.5.0-12ubuntu1~14.04) 5.5.0 20171010 |
+| GCC 6.4.0       | Ubuntu 14.04.1 LTS           | g++-6 (Ubuntu 6.4.0-17ubuntu1~14.04) 6.4.0 20180424 |
+| GCC 7.3.0       | Ubuntu 14.04.1 LTS           | g++-7 (Ubuntu 7.3.0-21ubuntu1~14.04) 7.3.0 |
+| GCC 7.3.0       | Windows Server 2012 R2 (x64) | g++ (x86_64-posix-seh-rev0, Built by MinGW-W64 project) 7.3.0 |
+| GCC 8.1.0       | Ubuntu 14.04.1 LTS           | g++-8 (Ubuntu 8.1.0-5ubuntu1~14.04) 8.1.0 |
+| Clang 3.5.0     | Ubuntu 14.04.1 LTS           | clang version 3.5.0-4ubuntu2~trusty2 (tags/RELEASE_350/final) (based on LLVM 3.5.0) |
+| Clang 3.6.2     | Ubuntu 14.04.1 LTS           | clang version 3.6.2-svn240577-1~exp1 (branches/release_36) (based on LLVM 3.6.2) |
+| Clang 3.7.1     | Ubuntu 14.04.1 LTS           | clang version 3.7.1-svn253571-1~exp1 (branches/release_37) (based on LLVM 3.7.1) |
+| Clang 3.8.0     | Ubuntu 14.04.1 LTS           | clang version 3.8.0-2ubuntu3~trusty5 (tags/RELEASE_380/final) |
+| Clang 3.9.1     | Ubuntu 14.04.1 LTS           | clang version 3.9.1-4ubuntu3~14.04.3 (tags/RELEASE_391/rc2) |
+| Clang 4.0.1     | Ubuntu 14.04.1 LTS           | clang version 4.0.1-svn305264-1~exp1 (branches/release_40) |
+| Clang 5.0.2     | Ubuntu 14.04.1 LTS           | clang version 5.0.2-svn328729-1~exp1~20180509123505.100 (branches/release_50) |
+| Clang 6.0.1     | Ubuntu 14.04.1 LTS           | clang version 6.0.1-svn334776-1~exp1~20180726133705.85 (branches/release_60) |
+| Clang Xcode 6.4 | OSX 10.10.5 | Apple LLVM version 6.1.0 (clang-602.0.53) (based on LLVM 3.6.0svn) |
+| Clang Xcode 7.3 | OSX 10.11.6 | Apple LLVM version 7.3.0 (clang-703.0.31) |
+| Clang Xcode 8.0 | OSX 10.11.6 | Apple LLVM version 8.0.0 (clang-800.0.38) |
+| Clang Xcode 8.1 | OSX 10.12.6 | Apple LLVM version 8.0.0 (clang-800.0.42.1) |
+| Clang Xcode 8.2 | OSX 10.12.6 | Apple LLVM version 8.0.0 (clang-800.0.42.1) |
+| Clang Xcode 8.3 | OSX 10.11.6 | Apple LLVM version 8.1.0 (clang-802.0.38) |
+| Clang Xcode 9.0 | OSX 10.12.6 | Apple LLVM version 9.0.0 (clang-900.0.37) |
+| Clang Xcode 9.1 | OSX 10.12.6 | Apple LLVM version 9.0.0 (clang-900.0.38) |
+| Clang Xcode 9.2 | OSX 10.13.3 | Apple LLVM version 9.1.0 (clang-902.0.39.1) |
+| Clang Xcode 9.3 | OSX 10.13.3 | Apple LLVM version 9.1.0 (clang-902.0.39.2) |
+| Clang Xcode 10.0 | OSX 10.13.3 | Apple LLVM version 10.0.0 (clang-1000.11.45.2) |
 | Visual Studio 14 2015 | Windows Server 2012 R2 (x64) | Microsoft (R) Build Engine version 14.0.25420.1, MSVC 19.0.24215.1 |
-| Visual Studio 2017 | Windows Server 2016 | Microsoft (R) Build Engine version 15.5.180.51428, MSVC 19.12.25830.2 |
+| Visual Studio 2017 | Windows Server 2016 | Microsoft (R) Build Engine version 15.7.180.61344, MSVC 19.14.26433.0 |
 
 ## License
 
@@ -862,6 +996,9 @@ If you have questions regarding the library, I would like to invite you to [open
 
 Only 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).
 
+## Security
+
+[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).
 
 ## Thanks
 
@@ -916,7 +1053,7 @@ I deeply appreciate the help of the following people.
 - [Vladimir Petrigo](https://github.com/vpetrigo) made a SFINAE hack more readable and added Visual Studio 17 to the build matrix.
 - [Denis Andrejew](https://github.com/seeekr) fixed a grammar issue in the README file.
 - [Pierre-Antoine Lacaze](https://github.com/palacaze) found a subtle bug in the `dump()` function.
-- [TurpentineDistillery](https://github.com/TurpentineDistillery) pointed to [`std::locale::classic()`](http://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.
+- [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.
 - [cgzones](https://github.com/cgzones) had an idea how to fix the Coverity scan.
 - [Jared Grubb](https://github.com/jaredgrubb) silenced a nasty documentation warning.
 - [Yixin Zhang](https://github.com/qwename) fixed an integer overflow check.
@@ -975,14 +1112,39 @@ I deeply appreciate the help of the following people.
 - [Paul Fultz II](https://github.com/pfultz2) added a note on the cget package manager.
 - [Wilson Lin](https://github.com/wla80) made the integration section of the README more concise.
 - [RalfBielig](https://github.com/ralfbielig) detected and fixed a memory leak in the parser callback.
-- [agrianius](https://github.com/agrianius) allowed to dump JSON to an alternative string type
+- [agrianius](https://github.com/agrianius) allowed to dump JSON to an alternative string type.
+- [Kevin Tonon](https://github.com/ktonon) overworked the C++11 compiler checks in CMake.
+- [Axel Huebl](https://github.com/ax3l) simplified a CMake check and added support for the [Spack package manager](https://spack.io).
+- [Carlos O'Ryan](https://github.com/coryan) fixed a typo.
+- [James Upjohn](https://github.com/jammehcow) fixed a version number in the compilers section.
+- [Chuck Atkins](https://github.com/chuckatkins) adjusted the CMake files to the CMake packaging guidelines and provided documentation for the CMake integration.
+- [Jan Schöppach](https://github.com/dns13) fixed a typo.
+- [martin-mfg](https://github.com/martin-mfg) fixed a typo.
+- [Matthias Möller](https://github.com/TinyTinni) removed the dependency from `std::stringstream`.
+- [agrianius](https://github.com/agrianius) added code to use alternative string implementations.
+- [Daniel599](https://github.com/Daniel599) allowed to use more algorithms with the `items()` function.
+- [Julius Rakow](https://github.com/jrakow) fixed the Meson include directory and fixed the links to [cppreference.com](cppreference.com).
+- [Sonu Lohani](https://github.com/sonulohani) fixed the compilation with MSVC 2015 in debug mode.
+- [grembo](https://github.com/grembo) fixed the test suite and re-enabled several test cases.
+- [Hyeon Kim](https://github.com/simnalamburt) introduced the macro `JSON_INTERNAL_CATCH` to control the exception handling inside the library.
+- [thyu](https://github.com/thyu) fixed a compiler warning.
+- [David Guthrie](https://github.com/LEgregius) fixed a subtle compilation error with Clang 3.4.2.
+- [Dennis Fischer](https://github.com/dennisfischer) allowed to call `find_package` without installing the library.
+- [Hyeon Kim](https://github.com/simnalamburt) fixed an issue with a double macro definition.
+- [Ben Berman](https://github.com/rivertam) made some error messages more understandable.
+- [zakalibit](https://github.com/zakalibit) fixed a compilation problem with the Intel C++ compiler.
+- [mandreyel](https://github.com/mandreyel) fixed a compilation problem.
+- [Kostiantyn Ponomarenko](https://github.com/koponomarenko) added version and license information to the Meson build file.
+- [Henry Schreiner](https://github.com/henryiii) added support for GCC 4.8.
+- [knilch](https://github.com/knilch0r) made sure the test suite does not stall when run in the wrong directory.
+- [Antonio Borondo](https://github.com/antonioborondo) fixed an MSVC 2017 warning.
 
 Thanks a lot for helping out! Please [let me know](mailto:mail@nlohmann.me) if I forgot someone.
 
 
 ## Used third-party tools
 
-The library itself contains 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!
+The 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!
 
 - [**amalgamate.py - Amalgamate C source and header files**](https://github.com/edlund/amalgamate) to create a single header file
 - [**American fuzzy lop**](http://lcamtuf.coredump.cx/afl/) for fuzz testing
@@ -1015,7 +1177,7 @@ The library is currently used in Apple macOS Sierra and iOS 10. I am not sure wh
 
 ## Notes
 
-- The code contains numerous debug **assertions** which can be switched off by defining the preprocessor macro `NDEBUG`, see the [documentation of `assert`](http://en.cppreference.com/w/cpp/error/assert). In particular, note [`operator[]`](https://nlohmann.github.io/json/classnlohmann_1_1basic__json_a2e26bd0b0168abb61f67ad5bcd5b9fa1.html#a2e26bd0b0168abb61f67ad5bcd5b9fa1) 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://nlohmann.github.io/json/classnlohmann_1_1basic__json_a674de1ee73e6bf4843fc5dc1351fb726.html#a674de1ee73e6bf4843fc5dc1351fb726).
+- 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://nlohmann.github.io/json/classnlohmann_1_1basic__json_a2e26bd0b0168abb61f67ad5bcd5b9fa1.html#a2e26bd0b0168abb61f67ad5bcd5b9fa1) 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://nlohmann.github.io/json/classnlohmann_1_1basic__json_a674de1ee73e6bf4843fc5dc1351fb726.html#a674de1ee73e6bf4843fc5dc1351fb726).
 - As the exact type of a number is not defined in the [JSON specification](http://rfc7159.net/rfc7159), 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.
 - The library supports **Unicode input** as follows:
   - Only **UTF-8** encoded input is supported which is the default encoding for JSON according to [RFC 7159](http://rfc7159.net/rfc7159#rfc.section.8.1).

appveyor.yml

@@ -1,26 +1,58 @@
 version: '{build}'
 
-os: 
-  - Visual Studio 2015
-  - Visual Studio 2017
-
 environment:
   matrix:
-  - additional_flags: ""
-  - additional_flags: "/permissive- /std:c++latest /utf-8"
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
+      COMPILER: mingw
+      platform: x86
+      FLAGS: ""
+      GENERATOR: Ninja
 
-matrix:
-  exclude:
-    - additional_flags: "/permissive- /std:c++latest /utf-8"
-      os: Visual Studio 2015
-  
-init: []
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
+      platform: x86
+      FLAGS: ""
+      GENERATOR: Visual Studio 14 2015
 
-install: []
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+      platform: x86
+      FLAGS: ""
+      GENERATOR: Visual Studio 15 2017
+
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+      platform: x86
+      FLAGS: "/permissive- /std:c++latest /utf-8"
+      GENERATOR: Visual Studio 15 2017
+
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
+      platform: x64
+      FLAGS: ""
+      GENERATOR: Visual Studio 14 2015
+
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+      platform: x64
+      FLAGS: ""
+      GENERATOR: Visual Studio 15 2017
+
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+      platform: x64
+      FLAGS: "/permissive- /std:c++latest /utf-8"
+      GENERATOR: Visual Studio 15 2017
+
+init:
+  - cmake --version
+  - msbuild /version
+
+install:
+  - if "%COMPILER%"=="mingw" appveyor DownloadFile https://github.com/ninja-build/ninja/releases/download/v1.6.0/ninja-win.zip -FileName ninja.zip
+  - if "%COMPILER%"=="mingw" 7z x ninja.zip -oC:\projects\deps\ninja > nul
+  - if "%COMPILER%"=="mingw" set PATH=C:\projects\deps\ninja;%PATH%
+  - if "%COMPILER%"=="mingw" set PATH=C:\mingw-w64\x86_64-7.3.0-posix-seh-rt_v5-rev0\mingw64\bin;%PATH%
+  - if "%COMPILER%"=="mingw" g++ --version
+
+before_build:
+  - cmake . -G "%GENERATOR%" -DCMAKE_CXX_FLAGS="%FLAGS%" -DCMAKE_IGNORE_PATH="C:/Program Files/Git/usr/bin"
 
 build_script:
-  - IF "%APPVEYOR_BUILD_WORKER_IMAGE%" == "Visual Studio 2015" ( SET GEN="Visual Studio 14 2015") ELSE (SET GEN="Visual Studio 15 2017")
-  - cmake . -G%GEN% -DCMAKE_CXX_FLAGS="%additional_flags%"
   - cmake --build . --config Release
 
 test_script:

benchmarks/CMakeLists.txt

@@ -1,9 +1,9 @@
-cmake_minimum_required(VERSION 3.0)
+cmake_minimum_required(VERSION 3.8)
 project(JSON_Benchmarks LANGUAGES CXX)
 
 # set compiler flags
 if((CMAKE_CXX_COMPILER_ID MATCHES GNU) OR (CMAKE_CXX_COMPILER_ID MATCHES Clang))
-   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -flto -DNDEBUG -O3")
+   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -flto -DNDEBUG -O3")
 endif()
 
 # configure Google Benchmarks
@@ -23,4 +23,5 @@ file(COPY ${CMAKE_SOURCE_DIR}/../test/data/regression/floats.json
 
 # benchmark binary
 add_executable(json_benchmarks src/benchmarks.cpp)
+target_compile_features(json_benchmarks PRIVATE cxx_std_11)
 target_link_libraries(json_benchmarks benchmark ${CMAKE_THREAD_LIBS_INIT})

cmake/config.cmake.in

@@ -1,3 +1,15 @@
-@PACKAGE_INIT@
-include("${CMAKE_CURRENT_LIST_DIR}/@NLOHMANN_JSON_TARGETS_EXPORT_NAME@.cmake")
-check_required_components("@PROJECT_NAME@")
+include(FindPackageHandleStandardArgs)
+set(${CMAKE_FIND_PACKAGE_NAME}_CONFIG ${CMAKE_CURRENT_LIST_FILE})
+find_package_handle_standard_args(@PROJECT_NAME@ CONFIG_MODE)
+
+if(NOT TARGET @PROJECT_NAME@::@NLOHMANN_JSON_TARGET_NAME@)
+    include("${CMAKE_CURRENT_LIST_DIR}/@NLOHMANN_JSON_TARGETS_EXPORT_NAME@.cmake")
+    if((NOT TARGET @NLOHMANN_JSON_TARGET_NAME@) AND
+       (NOT @PROJECT_NAME@_FIND_VERSION OR
+        @PROJECT_NAME@_FIND_VERSION VERSION_LESS 3.2.0))
+        add_library(@NLOHMANN_JSON_TARGET_NAME@ INTERFACE IMPORTED)
+        set_target_properties(@NLOHMANN_JSON_TARGET_NAME@ PROPERTIES
+            INTERFACE_LINK_LIBRARIES @PROJECT_NAME@::@NLOHMANN_JSON_TARGET_NAME@
+        )
+    endif()
+endif()

doc/Doxyfile

@@ -5,7 +5,7 @@
 #---------------------------------------------------------------------------
 DOXYFILE_ENCODING      = UTF-8
 PROJECT_NAME           = "JSON for Modern C++"
-PROJECT_NUMBER         = 3.1.2
+PROJECT_NUMBER         = 3.3.0
 PROJECT_BRIEF          =
 PROJECT_LOGO           =
 OUTPUT_DIRECTORY       = .

doc/examples/README.cpp

@@ -1,4 +1,5 @@
 #include <iostream>
+#include <iomanip>
 #include <nlohmann/json.hpp>
 
 using json = nlohmann::json;

doc/examples/README.link

@@ -1 +1 @@
-<a target="_blank" href="https://wandbox.org/permlink/TarF5pPn9NtHQjhf"><b>online</b></a>
+<a target="_blank" href="https://wandbox.org/permlink/RWX63GizBsDZ5EnQ"><b>online</b></a>

doc/examples/diff.cpp

@@ -1,4 +1,5 @@
 #include <iostream>
+#include <iomanip>
 #include <nlohmann/json.hpp>
 
 using json = nlohmann::json;

doc/examples/diff.link

@@ -1 +1 @@
-<a target="_blank" href="https://wandbox.org/permlink/tfI8DuCuZs3VB9VF"><b>online</b></a>
+<a target="_blank" href="https://wandbox.org/permlink/3OPLSVPyweUyEHaX"><b>online</b></a>

doc/examples/flatten.cpp

@@ -1,4 +1,5 @@
 #include <iostream>
+#include <iomanip>
 #include <nlohmann/json.hpp>
 
 using json = nlohmann::json;

doc/examples/flatten.link

@@ -1 +1 @@
-<a target="_blank" href="https://wandbox.org/permlink/E1HQedkl1zo48WW5"><b>online</b></a>
+<a target="_blank" href="https://wandbox.org/permlink/4bn447WQbTERfBaL"><b>online</b></a>

doc/examples/from_cbor.cpp

@@ -1,4 +1,5 @@
 #include <iostream>
+#include <iomanip>
 #include <nlohmann/json.hpp>
 
 using json = nlohmann::json;

doc/examples/from_cbor.link

@@ -1 +1 @@
-<a target="_blank" href="https://wandbox.org/permlink/mya8dUDcDDVoUlBZ"><b>online</b></a>
+<a target="_blank" href="https://wandbox.org/permlink/AHKW5EMQN4YQ68TY"><b>online</b></a>

doc/examples/from_msgpack.cpp

@@ -1,4 +1,5 @@
 #include <iostream>
+#include <iomanip>
 #include <nlohmann/json.hpp>
 
 using json = nlohmann::json;

doc/examples/from_msgpack.link

@@ -1 +1 @@
-<a target="_blank" href="https://wandbox.org/permlink/sMmEKxW5MGOgLC7z"><b>online</b></a>
+<a target="_blank" href="https://wandbox.org/permlink/J0KoQF8sOpdMg4kN"><b>online</b></a>

doc/examples/from_ubjson.cpp

@@ -1,4 +1,5 @@
 #include <iostream>
+#include <iomanip>
 #include <nlohmann/json.hpp>
 
 using json = nlohmann::json;

doc/examples/from_ubjson.link

@@ -1 +1 @@
-<a target="_blank" href="https://wandbox.org/permlink/qq29jfETq7nZRrh5"><b>online</b></a>
+<a target="_blank" href="https://wandbox.org/permlink/uuQK0DAjhbSd96K6"><b>online</b></a>

doc/examples/get_to.cpp

@@ -0,0 +1,60 @@
+#include <iostream>
+#include <unordered_map>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    // create a JSON value with different types
+    json json_types =
+    {
+        {"boolean", true},
+        {
+            "number", {
+                {"integer", 42},
+                {"floating-point", 17.23}
+            }
+        },
+        {"string", "Hello, world!"},
+        {"array", {1, 2, 3, 4, 5}},
+        {"null", nullptr}
+    };
+
+    bool v1;
+    int v2;
+    short v3;
+    float v4;
+    int v5;
+    std::string v6;
+    std::vector<short> v7;
+    std::unordered_map<std::string, json> v8;
+
+
+    // use explicit conversions
+    json_types["boolean"].get_to(v1);
+    json_types["number"]["integer"].get_to(v2);
+    json_types["number"]["integer"].get_to(v3);
+    json_types["number"]["floating-point"].get_to(v4);
+    json_types["number"]["floating-point"].get_to(v5);
+    json_types["string"].get_to(v6);
+    json_types["array"].get_to(v7);
+    json_types.get_to(v8);
+
+    // print the conversion results
+    std::cout << v1 << '\n';
+    std::cout << v2 << ' ' << v3 << '\n';
+    std::cout << v4 << ' ' << v5 << '\n';
+    std::cout << v6 << '\n';
+
+    for (auto i : v7)
+    {
+        std::cout << i << ' ';
+    }
+    std::cout << "\n\n";
+
+    for (auto i : v8)
+    {
+        std::cout << i.first << ": " << i.second << '\n';
+    }
+}

doc/examples/get_to.link

@@ -0,0 +1 @@
+<a target="_blank" href="https://wandbox.org/permlink/QxtxaO6JZAMJPutC"><b>online</b></a>

doc/examples/get_to.output

@@ -0,0 +1,11 @@
+1
+42 42
+17.23 17
+Hello, world!
+1 2 3 4 5 
+
+string: "Hello, world!"
+number: {"floating-point":17.23,"integer":42}
+null: null
+boolean: true
+array: [1,2,3,4,5]

doc/examples/meta.cpp

@@ -1,4 +1,5 @@
 #include <iostream>
+#include <iomanip>
 #include <nlohmann/json.hpp>
 
 using json = nlohmann::json;

doc/examples/meta.link

@@ -1 +1 @@
-<a target="_blank" href="https://wandbox.org/permlink/0zdmfNQCe4TMw0iI"><b>online</b></a>
+<a target="_blank" href="https://wandbox.org/permlink/eFzRNyod3g4aVkvl"><b>online</b></a>

doc/examples/meta.output

@@ -2,7 +2,7 @@
     "compiler": {
         "c++": "201103",
         "family": "clang",
-        "version": "9.0.0 (clang-900.0.39.2)"
+        "version": "10.0.0 (clang-1000.10.43.1)"
     },
     "copyright": "(C) 2013-2017 Niels Lohmann",
     "name": "JSON for Modern C++",
@@ -10,8 +10,8 @@
     "url": "https://github.com/nlohmann/json",
     "version": {
         "major": 3,
-        "minor": 1,
-        "patch": 2,
-        "string": "3.1.2"
+        "minor": 3,
+        "patch": 0,
+        "string": "3.3.0"
     }
 }

doc/examples/operator__greater.cpp

@@ -17,8 +17,8 @@ int main()
 
     // output values and comparisons
     std::cout << std::boolalpha;
-    std::cout << array_1 << " == " << array_2 << " " << (array_1 > array_2) << '\n';
-    std::cout << object_1 << " == " << object_2 << " " << (object_1 > object_2) << '\n';
-    std::cout << number_1 << " == " << number_2 << " " << (number_1 > number_2) << '\n';
-    std::cout << string_1 << " == " << string_2 << " " << (string_1 > string_2) << '\n';
+    std::cout << array_1 << " > " << array_2 << " " << (array_1 > array_2) << '\n';
+    std::cout << object_1 << " > " << object_2 << " " << (object_1 > object_2) << '\n';
+    std::cout << number_1 << " > " << number_2 << " " << (number_1 > number_2) << '\n';
+    std::cout << string_1 << " > " << string_2 << " " << (string_1 > string_2) << '\n';
 }

doc/examples/operator__greater.link

@@ -1 +1 @@
-<a target="_blank" href="https://wandbox.org/permlink/yiz7oCHVpFHSALB1"><b>online</b></a>
+<a target="_blank" href="https://wandbox.org/permlink/ntF7DMzC85gbQKHu"><b>online</b></a>

doc/examples/operator__greater.output

@@ -1,4 +1,4 @@
-[1,2,3] == [1,2,4] false
-{"A":"a","B":"b"} == {"A":"a","B":"b"} false
-17 == 17.0000000000001 false
-"foo" == "bar" true
+[1,2,3] > [1,2,4] false
+{"A":"a","B":"b"} > {"A":"a","B":"b"} false
+17 > 17.0000000000001 false
+"foo" > "bar" true

doc/examples/operator_deserialize.cpp

@@ -1,4 +1,6 @@
 #include <iostream>
+#include <iomanip>
+#include <sstream>
 #include <nlohmann/json.hpp>
 
 using json = nlohmann::json;

doc/examples/operator_deserialize.link

@@ -1 +1 @@
-<a target="_blank" href="https://wandbox.org/permlink/YrUqrUFMD7JHwSQR"><b>online</b></a>
+<a target="_blank" href="https://wandbox.org/permlink/IvgowYGaX0SgOFIG"><b>online</b></a>

doc/examples/operator_serialize.cpp

@@ -1,4 +1,5 @@
 #include <iostream>
+#include <iomanip>
 #include <nlohmann/json.hpp>
 
 using json = nlohmann::json;

doc/examples/operator_serialize.link

@@ -1 +1 @@
-<a target="_blank" href="https://wandbox.org/permlink/wXcm4ObnoaXw7CRt"><b>online</b></a>
+<a target="_blank" href="https://wandbox.org/permlink/ckGZIBookDffV00n"><b>online</b></a>

doc/examples/operatorarray__key_type.cpp

@@ -1,4 +1,5 @@
 #include <iostream>
+#include <iomanip>
 #include <nlohmann/json.hpp>
 
 using json = nlohmann::json;

doc/examples/operatorarray__key_type.link

@@ -1 +1 @@
-<a target="_blank" href="https://wandbox.org/permlink/vxt8d8qvYorXS2yq"><b>online</b></a>
+<a target="_blank" href="https://wandbox.org/permlink/oKnfnFrLHG8H1OAl"><b>online</b></a>

doc/examples/parse__array__parser_callback_t.cpp

@@ -1,4 +1,5 @@
 #include <iostream>
+#include <iomanip>
 #include <nlohmann/json.hpp>
 
 using json = nlohmann::json;

doc/examples/parse__array__parser_callback_t.link

@@ -1 +1 @@
-<a target="_blank" href="https://wandbox.org/permlink/TSNxHmegVwLW2pXf"><b>online</b></a>
+<a target="_blank" href="https://wandbox.org/permlink/i3BBhl7Ub5y9b0yp"><b>online</b></a>

doc/examples/parse__contiguouscontainer__parser_callback_t.cpp

@@ -1,4 +1,5 @@
 #include <iostream>
+#include <iomanip>
 #include <nlohmann/json.hpp>
 
 using json = nlohmann::json;

doc/examples/parse__contiguouscontainer__parser_callback_t.link

@@ -1 +1 @@
-<a target="_blank" href="https://wandbox.org/permlink/l3zNo3YKC2X8yAw9"><b>online</b></a>
+<a target="_blank" href="https://wandbox.org/permlink/sGdJMOaJnFNJBtH7"><b>online</b></a>

doc/examples/parse__istream__parser_callback_t.cpp

@@ -1,4 +1,6 @@
 #include <iostream>
+#include <iomanip>
+#include <sstream>
 #include <nlohmann/json.hpp>
 
 using json = nlohmann::json;

doc/examples/parse__istream__parser_callback_t.link

@@ -1 +1 @@
-<a target="_blank" href="https://wandbox.org/permlink/Mf7A6JtvqT1Na7Pk"><b>online</b></a>
+<a target="_blank" href="https://wandbox.org/permlink/UZgRBIeqdZhm6M8F"><b>online</b></a>

doc/examples/parse__iteratortype__parser_callback_t.cpp

@@ -1,4 +1,5 @@
 #include <iostream>
+#include <iomanip>
 #include <nlohmann/json.hpp>
 
 using json = nlohmann::json;

doc/examples/parse__iteratortype__parser_callback_t.link

@@ -1 +1 @@
-<a target="_blank" href="https://wandbox.org/permlink/oa6BVkBXjG8DNkzX"><b>online</b></a>
+<a target="_blank" href="https://wandbox.org/permlink/VThe0hdMSUdNSOLK"><b>online</b></a>

doc/examples/parse__string__parser_callback_t.cpp

@@ -1,4 +1,5 @@
 #include <iostream>
+#include <iomanip>
 #include <nlohmann/json.hpp>
 
 using json = nlohmann::json;

doc/examples/parse__string__parser_callback_t.link

@@ -1 +1 @@
-<a target="_blank" href="https://wandbox.org/permlink/QXdl4yzts3qPeZ0U"><b>online</b></a>
+<a target="_blank" href="https://wandbox.org/permlink/QZgjsR0PiAw2Lqpk"><b>online</b></a>

doc/examples/patch.cpp

@@ -1,4 +1,5 @@
 #include <iostream>
+#include <iomanip>
 #include <nlohmann/json.hpp>
 
 using json = nlohmann::json;

doc/examples/patch.link

@@ -1 +1 @@
-<a target="_blank" href="https://wandbox.org/permlink/8ObNa6ejw4BXQ5qG"><b>online</b></a>
+<a target="_blank" href="https://wandbox.org/permlink/hFd1W46W2Hb81sHN"><b>online</b></a>

doc/examples/sax_parse.cpp

@@ -0,0 +1,124 @@
+#include <iostream>
+#include <iomanip>
+#include <sstream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+// a simple event consumer that collects string representations of the passed
+// values; not inheriting from json::json_sax_t is not required, but can
+// help not to forget a required function
+class sax_event_consumer : public json::json_sax_t
+{
+  public:
+    std::vector<std::string> events;
+
+    bool null() override
+    {
+        events.push_back("value: null");
+        return true;
+    }
+
+    bool boolean(bool val) override
+    {
+        events.push_back("value: " + std::string(val ? "true" : "false"));
+        return true;
+    }
+
+    bool number_integer(number_integer_t val) override
+    {
+        events.push_back("value: " + std::to_string(val));
+        return true;
+    }
+
+    bool number_unsigned(number_unsigned_t val) override
+    {
+        events.push_back("value: " + std::to_string(val));
+        return true;
+    }
+
+    bool number_float(number_float_t val, const string_t& s) override
+    {
+        events.push_back("value: " + s);
+        return true;
+    }
+
+    bool string(string_t& val) override
+    {
+        events.push_back("value: " + val);
+        return true;
+    }
+
+    bool start_object(std::size_t elements) override
+    {
+        events.push_back("start: object");
+        return true;
+    }
+
+    bool end_object() override
+    {
+        events.push_back("end: object");
+        return true;
+    }
+
+    bool start_array(std::size_t elements) override
+    {
+        events.push_back("start: array");
+        return true;
+    }
+
+    bool end_array() override
+    {
+        events.push_back("end: array");
+        return true;
+    }
+
+    bool key(string_t& val) override
+    {
+        events.push_back("key: " + val);
+        return true;
+    }
+
+    bool parse_error(std::size_t position, const std::string& last_token, const json::exception& ex) override
+    {
+        events.push_back("error: " + std::string(ex.what()));
+        return false;
+    }
+};
+
+int main()
+{
+    // a JSON text
+    auto text = R"(
+    {
+        "Image": {
+            "Width":  800,
+            "Height": 600,
+            "Title":  "View from 15th Floor",
+            "Thumbnail": {
+                "Url":    "http://www.example.com/image/481989943",
+                "Height": 125,
+                "Width":  100
+            },
+            "Animated" : false,
+            "IDs": [116, 943, 234, 38793],
+            "Distance": 12.723374634
+        }
+    }
+    )";
+
+    // create a SAX event consumer object
+    sax_event_consumer sec;
+
+    // parse and serialize JSON
+    bool result = json::sax_parse(text, &sec);
+
+    // output the recorded events
+    for (auto& event : sec.events)
+    {
+        std::cout << "(" << event << ") ";
+    }
+
+    // output the result of sax_parse
+    std::cout << "\nresult: " << std::boolalpha << result << std::endl;
+}

doc/examples/sax_parse.link

@@ -0,0 +1 @@
+<a target="_blank" href="https://wandbox.org/permlink/fGkQLWbQn7enKkIG"><b>online</b></a>

doc/examples/sax_parse.output

@@ -0,0 +1,2 @@
+(start: object) (key: Image) (start: object) (key: Width) (value: 800) (key: Height) (value: 600) (key: Title) (value: View from 15th Floor) (key: Thumbnail) (start: object) (key: Url) (value: http://www.example.com/image/481989943) (key: Height) (value: 125) (key: Width) (value: 100) (end: object) (key: Animated) (value: false) (key: IDs) (start: array) (value: 116) (value: 943) (value: 234) (value: 38793) (end: array) (key: Distance) (value: 12.723374634) (end: object) (end: object) 
+result: true

doc/examples/to_cbor.cpp

@@ -1,4 +1,5 @@
 #include <iostream>
+#include <iomanip>
 #include <nlohmann/json.hpp>
 
 using json = nlohmann::json;

doc/examples/to_cbor.link

@@ -1 +1 @@
-<a target="_blank" href="https://wandbox.org/permlink/4bQSclXeqjVFYVL3"><b>online</b></a>
+<a target="_blank" href="https://wandbox.org/permlink/LRM37xarSuPJmv92"><b>online</b></a>

doc/examples/to_msgpack.cpp

@@ -1,4 +1,5 @@
 #include <iostream>
+#include <iomanip>
 #include <nlohmann/json.hpp>
 
 using json = nlohmann::json;

doc/examples/to_msgpack.link

@@ -1 +1 @@
-<a target="_blank" href="https://wandbox.org/permlink/WvT2Q0r9vlJYyMM8"><b>online</b></a>
+<a target="_blank" href="https://wandbox.org/permlink/CaRFhkrefL4miesE"><b>online</b></a>

doc/examples/to_ubjson.cpp

@@ -1,4 +1,5 @@
 #include <iostream>
+#include <iomanip>
 #include <nlohmann/json.hpp>
 
 using json = nlohmann::json;

doc/examples/to_ubjson.link

@@ -1 +1 @@
-<a target="_blank" href="https://wandbox.org/permlink/j3HE6cOkCmKbxxAt"><b>online</b></a>
+<a target="_blank" href="https://wandbox.org/permlink/2luqHy9iADx4UNm7"><b>online</b></a>

doc/examples/unflatten.cpp

@@ -1,4 +1,5 @@
 #include <iostream>
+#include <iomanip>
 #include <nlohmann/json.hpp>
 
 using json = nlohmann::json;

doc/examples/unflatten.link

@@ -1 +1 @@
-<a target="_blank" href="https://wandbox.org/permlink/U45AGi5nsDtoDf3u"><b>online</b></a>
+<a target="_blank" href="https://wandbox.org/permlink/knK4jnD2hIVxQoyk"><b>online</b></a>

doc/examples/update.cpp

@@ -1,4 +1,5 @@
 #include <iostream>
+#include <iomanip>
 #include <nlohmann/json.hpp>
 
 using json = nlohmann::json;

doc/examples/update.link

@@ -1 +1 @@
-<a target="_blank" href="https://wandbox.org/permlink/TGvdYyJtstacZxWq"><b>online</b></a>
+<a target="_blank" href="https://wandbox.org/permlink/kjcoWACW7FMqKRBG"><b>online</b></a>

doc/examples/update__range.cpp

@@ -1,4 +1,5 @@
 #include <iostream>
+#include <iomanip>
 #include <nlohmann/json.hpp>
 
 using json = nlohmann::json;

doc/examples/update__range.link

@@ -1 +1 @@
-<a target="_blank" href="https://wandbox.org/permlink/BMlas6312rkE4cxz"><b>online</b></a>
+<a target="_blank" href="https://wandbox.org/permlink/0LBIsEa18IrerWwy"><b>online</b></a>

doc/index.md

@@ -39,9 +39,11 @@ These pages contain the API documentation of JSON for Modern C++, a C++11 header
     - @link nlohmann::basic_json::dump dump @endlink serialize to string
     - @link nlohmann::basic_json::operator<<(std::ostream&, const basic_json &) operator<< @endlink serialize to stream
   - deserialization / parsing
-    - @link nlohmann::basic_json::parse parse @endlink parse from string
+    - @link nlohmann::basic_json::parse parse @endlink parse from input (string, file, etc.) and return JSON value
+    - @link nlohmann::basic_json::sax_parse sax_parse @endlink parse from input (string, file, etc.) and generate SAX events
     - @link nlohmann::basic_json::operator>>(std::istream&, basic_json&) operator>> @endlink parse from stream
     - @link nlohmann::basic_json::accept accept @endlink check for syntax errors without parsing
+    - @link nlohmann::json_sax SAX interface @endlink define a user-defined SAX event consumer
   - [binary formats](binary_formats.md):
     - CBOR: @link nlohmann::basic_json::from_cbor from_cbor @endlink / @link nlohmann::basic_json::to_cbor to_cbor @endlink
     - MessagePack: @link nlohmann::basic_json::from_msgpack from_msgpack @endlink / @link nlohmann::basic_json::to_msgpack to_msgpack @endlink
@@ -304,4 +306,4 @@ Note that this table only lists those exceptions thrown due to the type. For ins
 @author [Niels Lohmann](http://nlohmann.me)
 @see https://github.com/nlohmann/json to download the source code
 
-@version 3.1.2
+@version 3.3.0

include/nlohmann/adl_serializer.hpp

@@ -20,8 +20,10 @@ struct adl_serializer
     @param[in,out] val  value to write to
     */
     template<typename BasicJsonType, typename ValueType>
-    static void from_json(BasicJsonType&& j, ValueType& val) noexcept(
-        noexcept(::nlohmann::from_json(std::forward<BasicJsonType>(j), val)))
+    static auto from_json(BasicJsonType&& j, ValueType& val) noexcept(
+        noexcept(::nlohmann::from_json(std::forward<BasicJsonType>(j), val))) -> decltype(
+            ::nlohmann::from_json(std::forward<BasicJsonType>(j), val), void()
+        )
     {
         ::nlohmann::from_json(std::forward<BasicJsonType>(j), val);
     }
@@ -35,9 +37,11 @@ struct adl_serializer
     @param[in,out] j  JSON value to write to
     @param[in] val     value to read from
     */
-    template<typename BasicJsonType, typename ValueType>
-    static void to_json(BasicJsonType& j, ValueType&& val) noexcept(
+    template <typename BasicJsonType, typename ValueType>
+    static auto to_json(BasicJsonType& j, ValueType&& val) noexcept(
         noexcept(::nlohmann::to_json(j, std::forward<ValueType>(val))))
+    -> decltype(::nlohmann::to_json(j, std::forward<ValueType>(val)),
+                void())
     {
         ::nlohmann::to_json(j, std::forward<ValueType>(val));
     }

include/nlohmann/detail/conversions/from_json.hpp

@@ -5,21 +5,34 @@
 #include <ciso646> // and, not
 #include <forward_list> // forward_list
 #include <iterator> // inserter, front_inserter, end
+#include <map> // map
 #include <string> // string
 #include <tuple> // tuple, make_tuple
 #include <type_traits> // is_arithmetic, is_same, is_enum, underlying_type, is_convertible
+#include <unordered_map> // unordered_map
 #include <utility> // pair, declval
 #include <valarray> // valarray
 
 #include <nlohmann/detail/exceptions.hpp>
 #include <nlohmann/detail/macro_scope.hpp>
-#include <nlohmann/detail/meta.hpp>
+#include <nlohmann/detail/meta/cpp_future.hpp>
+#include <nlohmann/detail/meta/type_traits.hpp>
 #include <nlohmann/detail/value_t.hpp>
 
 namespace nlohmann
 {
 namespace detail
 {
+template<typename BasicJsonType>
+void from_json(const BasicJsonType& j, typename std::nullptr_t& n)
+{
+    if (JSON_UNLIKELY(not j.is_null()))
+    {
+        JSON_THROW(type_error::create(302, "type must be null, but is " + std::string(j.type_name())));
+    }
+    n = nullptr;
+}
+
 // overloads for basic_json template parameters
 template<typename BasicJsonType, typename ArithmeticType,
          enable_if_t<std::is_arithmetic<ArithmeticType>::value and
@@ -70,6 +83,23 @@ void from_json(const BasicJsonType& j, typename BasicJsonType::string_t& s)
     s = *j.template get_ptr<const typename BasicJsonType::string_t*>();
 }
 
+template <
+    typename BasicJsonType, typename CompatibleStringType,
+    enable_if_t <
+        is_compatible_string_type<BasicJsonType, CompatibleStringType>::value and
+        not std::is_same<typename BasicJsonType::string_t,
+                         CompatibleStringType>::value,
+        int > = 0 >
+void from_json(const BasicJsonType& j, CompatibleStringType& s)
+{
+    if (JSON_UNLIKELY(not j.is_string()))
+    {
+        JSON_THROW(type_error::create(302, "type must be string, but is " + std::string(j.type_name())));
+    }
+
+    s = *j.template get_ptr<const typename BasicJsonType::string_t*>();
+}
+
 template<typename BasicJsonType>
 void from_json(const BasicJsonType& j, typename BasicJsonType::number_float_t& val)
 {
@@ -97,16 +127,6 @@ void from_json(const BasicJsonType& j, EnumType& e)
     e = static_cast<EnumType>(val);
 }
 
-template<typename BasicJsonType>
-void from_json(const BasicJsonType& j, typename BasicJsonType::array_t& arr)
-{
-    if (JSON_UNLIKELY(not j.is_array()))
-    {
-        JSON_THROW(type_error::create(302, "type must be array, but is " + std::string(j.type_name())));
-    }
-    arr = *j.template get_ptr<const typename BasicJsonType::array_t*>();
-}
-
 // forward_list doesn't have an insert method
 template<typename BasicJsonType, typename T, typename Allocator,
          enable_if_t<std::is_convertible<BasicJsonType, T>::value, int> = 0>
@@ -136,24 +156,28 @@ void from_json(const BasicJsonType& j, std::valarray<T>& l)
     std::copy(j.m_value.array->begin(), j.m_value.array->end(), std::begin(l));
 }
 
-template<typename BasicJsonType, typename CompatibleArrayType>
-void from_json_array_impl(const BasicJsonType& j, CompatibleArrayType& arr, priority_tag<0> /*unused*/)
+template<typename BasicJsonType>
+void from_json_array_impl(const BasicJsonType& j, typename BasicJsonType::array_t& arr, priority_tag<3> /*unused*/)
 {
-    using std::end;
+    arr = *j.template get_ptr<const typename BasicJsonType::array_t*>();
+}
 
-    std::transform(j.begin(), j.end(),
-                   std::inserter(arr, end(arr)), [](const BasicJsonType & i)
+template <typename BasicJsonType, typename T, std::size_t N>
+auto from_json_array_impl(const BasicJsonType& j, std::array<T, N>& arr,
+                          priority_tag<2> /*unused*/)
+-> decltype(j.template get<T>(), void())
+{
+    for (std::size_t i = 0; i < N; ++i)
     {
-        // get<BasicJsonType>() returns *this, this won't call a from_json
-        // method when value_type is BasicJsonType
-        return i.template get<typename CompatibleArrayType::value_type>();
-    });
+        arr[i] = j.at(i).template get<T>();
+    }
 }
 
 template<typename BasicJsonType, typename CompatibleArrayType>
 auto from_json_array_impl(const BasicJsonType& j, CompatibleArrayType& arr, priority_tag<1> /*unused*/)
 -> decltype(
     arr.reserve(std::declval<typename CompatibleArrayType::size_type>()),
+    j.template get<typename CompatibleArrayType::value_type>(),
     void())
 {
     using std::end;
@@ -168,25 +192,34 @@ auto from_json_array_impl(const BasicJsonType& j, CompatibleArrayType& arr, prio
     });
 }
 
-template<typename BasicJsonType, typename T, std::size_t N>
-void from_json_array_impl(const BasicJsonType& j, std::array<T, N>& arr, priority_tag<2> /*unused*/)
+template <typename BasicJsonType, typename CompatibleArrayType>
+void from_json_array_impl(const BasicJsonType& j, CompatibleArrayType& arr,
+                          priority_tag<0> /*unused*/)
 {
-    for (std::size_t i = 0; i < N; ++i)
+    using std::end;
+
+    std::transform(
+        j.begin(), j.end(), std::inserter(arr, end(arr)),
+        [](const BasicJsonType & i)
     {
-        arr[i] = j.at(i).template get<T>();
-    }
+        // get<BasicJsonType>() returns *this, this won't call a from_json
+        // method when value_type is BasicJsonType
+        return i.template get<typename CompatibleArrayType::value_type>();
+    });
 }
 
-template <
-    typename BasicJsonType, typename CompatibleArrayType,
-    enable_if_t <
-        is_compatible_array_type<BasicJsonType, CompatibleArrayType>::value and
-        not std::is_same<typename BasicJsonType::array_t,
-                         CompatibleArrayType>::value and
-        std::is_constructible <
-            BasicJsonType, typename CompatibleArrayType::value_type >::value,
-        int > = 0 >
-void from_json(const BasicJsonType& j, CompatibleArrayType& arr)
+template <typename BasicJsonType, typename CompatibleArrayType,
+          enable_if_t <
+              is_compatible_array_type<BasicJsonType, CompatibleArrayType>::value and
+              not is_compatible_object_type<BasicJsonType, CompatibleArrayType>::value and
+              not is_compatible_string_type<BasicJsonType, CompatibleArrayType>::value and
+              not is_basic_json<CompatibleArrayType>::value,
+              int > = 0 >
+
+auto from_json(const BasicJsonType& j, CompatibleArrayType& arr)
+-> decltype(from_json_array_impl(j, arr, priority_tag<3> {}),
+j.template get<typename CompatibleArrayType::value_type>(),
+void())
 {
     if (JSON_UNLIKELY(not j.is_array()))
     {
@@ -194,7 +227,7 @@ void from_json(const BasicJsonType& j, CompatibleArrayType& arr)
                                       std::string(j.type_name())));
     }
 
-    from_json_array_impl(j, arr, priority_tag<2> {});
+    from_json_array_impl(j, arr, priority_tag<3> {});
 }
 
 template<typename BasicJsonType, typename CompatibleObjectType,
@@ -277,37 +310,53 @@ void from_json(const BasicJsonType& j, std::tuple<Args...>& t)
     from_json_tuple_impl(j, t, index_sequence_for<Args...> {});
 }
 
+template <typename BasicJsonType, typename Key, typename Value, typename Compare, typename Allocator,
+          typename = enable_if_t<not std::is_constructible<
+                                     typename BasicJsonType::string_t, Key>::value>>
+void from_json(const BasicJsonType& j, std::map<Key, Value, Compare, Allocator>& m)
+{
+    if (JSON_UNLIKELY(not j.is_array()))
+    {
+        JSON_THROW(type_error::create(302, "type must be array, but is " + std::string(j.type_name())));
+    }
+    for (const auto& p : j)
+    {
+        if (JSON_UNLIKELY(not p.is_array()))
+        {
+            JSON_THROW(type_error::create(302, "type must be array, but is " + std::string(p.type_name())));
+        }
+        m.emplace(p.at(0).template get<Key>(), p.at(1).template get<Value>());
+    }
+}
+
+template <typename BasicJsonType, typename Key, typename Value, typename Hash, typename KeyEqual, typename Allocator,
+          typename = enable_if_t<not std::is_constructible<
+                                     typename BasicJsonType::string_t, Key>::value>>
+void from_json(const BasicJsonType& j, std::unordered_map<Key, Value, Hash, KeyEqual, Allocator>& m)
+{
+    if (JSON_UNLIKELY(not j.is_array()))
+    {
+        JSON_THROW(type_error::create(302, "type must be array, but is " + std::string(j.type_name())));
+    }
+    for (const auto& p : j)
+    {
+        if (JSON_UNLIKELY(not p.is_array()))
+        {
+            JSON_THROW(type_error::create(302, "type must be array, but is " + std::string(p.type_name())));
+        }
+        m.emplace(p.at(0).template get<Key>(), p.at(1).template get<Value>());
+    }
+}
+
 struct from_json_fn
 {
-  private:
     template<typename BasicJsonType, typename T>
-    auto call(const BasicJsonType& j, T& val, priority_tag<1> /*unused*/) const
+    auto operator()(const BasicJsonType& j, T& val) const
     noexcept(noexcept(from_json(j, val)))
     -> decltype(from_json(j, val), void())
     {
         return from_json(j, val);
     }
-
-    template<typename BasicJsonType, typename T>
-    void call(const BasicJsonType& /*unused*/, T& /*unused*/, priority_tag<0> /*unused*/) const noexcept
-    {
-        static_assert(sizeof(BasicJsonType) == 0,
-                      "could not find from_json() method in T's namespace");
-#ifdef _MSC_VER
-        // MSVC does not show a stacktrace for the above assert
-        using decayed = uncvref_t<T>;
-        static_assert(sizeof(typename decayed::force_msvc_stacktrace) == 0,
-                      "forcing MSVC stacktrace to show which T we're talking about.");
-#endif
-    }
-
-  public:
-    template<typename BasicJsonType, typename T>
-    void operator()(const BasicJsonType& j, T& val) const
-    noexcept(noexcept(std::declval<from_json_fn>().call(j, val, priority_tag<1> {})))
-    {
-        return call(j, val, priority_tag<1> {});
-    }
 };
 }
 

include/nlohmann/detail/conversions/to_chars.hpp

@@ -887,7 +887,7 @@ void grisu2(char* buf, int& len, int& decimal_exponent, FloatType value)
     // numbers, all float's can be recovered using strtod (and strtof). However, the resulting
     // decimal representations are not exactly "short".
     //
-    // The documentation for 'std::to_chars' (http://en.cppreference.com/w/cpp/utility/to_chars)
+    // The documentation for 'std::to_chars' (https://en.cppreference.com/w/cpp/utility/to_chars)
     // says "value is converted to a string as if by std::sprintf in the default ("C") locale"
     // and since sprintf promotes float's to double's, I think this is exactly what 'std::to_chars'
     // does.

include/nlohmann/detail/conversions/to_json.hpp

@@ -8,8 +8,10 @@
 #include <valarray> // valarray
 #include <vector> // vector
 
-#include <nlohmann/detail/meta.hpp>
+#include <nlohmann/detail/meta/cpp_future.hpp>
+#include <nlohmann/detail/meta/type_traits.hpp>
 #include <nlohmann/detail/value_t.hpp>
+#include <nlohmann/detail/iterators/iteration_proxy.hpp>
 
 namespace nlohmann
 {
@@ -51,6 +53,16 @@ struct external_constructor<value_t::string>
         j.m_value = std::move(s);
         j.assert_invariant();
     }
+
+    template<typename BasicJsonType, typename CompatibleStringType,
+             enable_if_t<not std::is_same<CompatibleStringType, typename BasicJsonType::string_t>::value,
+                         int> = 0>
+    static void construct(BasicJsonType& j, const CompatibleStringType& str)
+    {
+        j.m_type = value_t::string;
+        j.m_value.string = j.template create<typename BasicJsonType::string_t>(str);
+        j.assert_invariant();
+    }
 };
 
 template<>
@@ -236,10 +248,14 @@ void to_json(BasicJsonType& j, const std::vector<bool>& e)
     external_constructor<value_t::array>::construct(j, e);
 }
 
-template<typename BasicJsonType, typename CompatibleArrayType,
-         enable_if_t<is_compatible_array_type<BasicJsonType, CompatibleArrayType>::value or
-                     std::is_same<typename BasicJsonType::array_t, CompatibleArrayType>::value,
-                     int> = 0>
+template <typename BasicJsonType, typename CompatibleArrayType,
+          enable_if_t<is_compatible_array_type<BasicJsonType,
+                      CompatibleArrayType>::value and
+                      not is_compatible_object_type<
+                          BasicJsonType, CompatibleArrayType>::value and
+                      not is_compatible_string_type<BasicJsonType, CompatibleArrayType>::value and
+                      not is_basic_json<CompatibleArrayType>::value,
+                      int> = 0>
 void to_json(BasicJsonType& j, const CompatibleArrayType& arr)
 {
     external_constructor<value_t::array>::construct(j, arr);
@@ -247,7 +263,7 @@ void to_json(BasicJsonType& j, const CompatibleArrayType& arr)
 
 template<typename BasicJsonType, typename T,
          enable_if_t<std::is_convertible<T, BasicJsonType>::value, int> = 0>
-void to_json(BasicJsonType& j, std::valarray<T> arr)
+void to_json(BasicJsonType& j, const std::valarray<T>& arr)
 {
     external_constructor<value_t::array>::construct(j, std::move(arr));
 }
@@ -259,7 +275,7 @@ void to_json(BasicJsonType& j, typename BasicJsonType::array_t&& arr)
 }
 
 template<typename BasicJsonType, typename CompatibleObjectType,
-         enable_if_t<is_compatible_object_type<BasicJsonType, CompatibleObjectType>::value, int> = 0>
+         enable_if_t<is_compatible_object_type<BasicJsonType, CompatibleObjectType>::value and not is_basic_json<CompatibleObjectType>::value, int> = 0>
 void to_json(BasicJsonType& j, const CompatibleObjectType& obj)
 {
     external_constructor<value_t::object>::construct(j, obj);
@@ -271,9 +287,12 @@ void to_json(BasicJsonType& j, typename BasicJsonType::object_t&& obj)
     external_constructor<value_t::object>::construct(j, std::move(obj));
 }
 
-template<typename BasicJsonType, typename T, std::size_t N,
-         enable_if_t<not std::is_constructible<typename BasicJsonType::string_t, T (&)[N]>::value, int> = 0>
-void to_json(BasicJsonType& j, T (&arr)[N])
+template <
+    typename BasicJsonType, typename T, std::size_t N,
+    enable_if_t<not std::is_constructible<typename BasicJsonType::string_t,
+                const T (&)[N]>::value,
+                int> = 0 >
+void to_json(BasicJsonType& j, const T (&arr)[N])
 {
     external_constructor<value_t::array>::construct(j, arr);
 }
@@ -284,6 +303,14 @@ void to_json(BasicJsonType& j, const std::pair<Args...>& p)
     j = {p.first, p.second};
 }
 
+// for https://github.com/nlohmann/json/pull/1134
+template<typename BasicJsonType, typename T,
+         enable_if_t<std::is_same<T, typename iteration_proxy<typename BasicJsonType::iterator>::iteration_proxy_internal>::value, int> = 0>
+void to_json(BasicJsonType& j, T b) noexcept
+{
+    j = {{b.key(), b.value()}};
+}
+
 template<typename BasicJsonType, typename Tuple, std::size_t... Idx>
 void to_json_tuple_impl(BasicJsonType& j, const Tuple& t, index_sequence<Idx...>)
 {
@@ -298,35 +325,12 @@ void to_json(BasicJsonType& j, const std::tuple<Args...>& t)
 
 struct to_json_fn
 {
-  private:
     template<typename BasicJsonType, typename T>
-    auto call(BasicJsonType& j, T&& val, priority_tag<1> /*unused*/) const noexcept(noexcept(to_json(j, std::forward<T>(val))))
+    auto operator()(BasicJsonType& j, T&& val) const noexcept(noexcept(to_json(j, std::forward<T>(val))))
     -> decltype(to_json(j, std::forward<T>(val)), void())
     {
         return to_json(j, std::forward<T>(val));
     }
-
-    template<typename BasicJsonType, typename T>
-    void call(BasicJsonType& /*unused*/, T&& /*unused*/, priority_tag<0> /*unused*/) const noexcept
-    {
-        static_assert(sizeof(BasicJsonType) == 0,
-                      "could not find to_json() method in T's namespace");
-
-#ifdef _MSC_VER
-        // MSVC does not show a stacktrace for the above assert
-        using decayed = uncvref_t<T>;
-        static_assert(sizeof(typename decayed::force_msvc_stacktrace) == 0,
-                      "forcing MSVC stacktrace to show which T we're talking about.");
-#endif
-    }
-
-  public:
-    template<typename BasicJsonType, typename T>
-    void operator()(BasicJsonType& j, T&& val) const
-    noexcept(noexcept(std::declval<to_json_fn>().call(j, std::forward<T>(val), priority_tag<1> {})))
-    {
-        return call(j, std::forward<T>(val), priority_tag<1> {});
-    }
 };
 }
 

include/nlohmann/detail/input/input_adapters.hpp

@@ -1,11 +1,8 @@
 #pragma once
 
-#include <algorithm> // min
-#include <array> // array
 #include <cassert> // assert
 #include <cstddef> // size_t
 #include <cstring> // strlen
-#include <ios> // streamsize, streamoff, streampos
 #include <istream> // istream
 #include <iterator> // begin, end, iterator_traits, random_access_iterator_tag, distance, next
 #include <memory> // shared_ptr, make_shared, addressof
@@ -20,6 +17,9 @@ namespace nlohmann
 {
 namespace detail
 {
+/// the supported input formats
+enum class input_format_t { json, cbor, msgpack, ubjson };
+
 ////////////////////
 // input adapters //
 ////////////////////
@@ -28,19 +28,17 @@ namespace detail
 @brief abstract input adapter interface
 
 Produces a stream of std::char_traits<char>::int_type characters from a
-std::istream, a buffer, or some other input type.  Accepts the return of exactly
-one non-EOF character for future input.  The int_type characters returned
-consist of all valid char values as positive values (typically unsigned char),
-plus an EOF value outside that range, specified by the value of the function
-std::char_traits<char>::eof().  This value is typically -1, but could be any
-arbitrary value which is not a valid char value.
+std::istream, a buffer, or some other input type. Accepts the return of
+exactly one non-EOF character for future input. The int_type characters
+returned consist of all valid char values as positive values (typically
+unsigned char), plus an EOF value outside that range, specified by the value
+of the function std::char_traits<char>::eof(). This value is typically -1, but
+could be any arbitrary value which is not a valid char value.
 */
 struct input_adapter_protocol
 {
     /// get a character [0,255] or std::char_traits<char>::eof().
     virtual std::char_traits<char>::int_type get_character() = 0;
-    /// restore the last non-eof() character to input
-    virtual void unget_character() = 0;
     virtual ~input_adapter_protocol() = default;
 };
 
@@ -68,34 +66,7 @@ class input_stream_adapter : public input_adapter_protocol
 
     explicit input_stream_adapter(std::istream& i)
         : is(i), sb(*i.rdbuf())
-    {
-        // skip byte order mark
-        std::char_traits<char>::int_type c;
-        if ((c = get_character()) == 0xEF)
-        {
-            if ((c = get_character()) == 0xBB)
-            {
-                if ((c = get_character()) == 0xBF)
-                {
-                    return; // Ignore BOM
-                }
-                else if (c != std::char_traits<char>::eof())
-                {
-                    is.unget();
-                }
-                is.putback('\xBB');
-            }
-            else if (c != std::char_traits<char>::eof())
-            {
-                is.unget();
-            }
-            is.putback('\xEF');
-        }
-        else if (c != std::char_traits<char>::eof())
-        {
-            is.unget(); // no byte order mark; process as usual
-        }
-    }
+    {}
 
     // delete because of pointer members
     input_stream_adapter(const input_stream_adapter&) = delete;
@@ -109,11 +80,6 @@ class input_stream_adapter : public input_adapter_protocol
         return sb.sbumpc();
     }
 
-    void unget_character() override
-    {
-        sb.sungetc();  // is.unget() avoided for performance
-    }
-
   private:
     /// the associated input stream
     std::istream& is;
@@ -125,14 +91,8 @@ class input_buffer_adapter : public input_adapter_protocol
 {
   public:
     input_buffer_adapter(const char* b, const std::size_t l)
-        : cursor(b), limit(b + l), start(b)
-    {
-        // skip byte order mark
-        if (l >= 3 and b[0] == '\xEF' and b[1] == '\xBB' and b[2] == '\xBF')
-        {
-            cursor += 3;
-        }
-    }
+        : cursor(b), limit(b + l)
+    {}
 
     // delete because of pointer members
     input_buffer_adapter(const input_buffer_adapter&) = delete;
@@ -148,21 +108,172 @@ class input_buffer_adapter : public input_adapter_protocol
         return std::char_traits<char>::eof();
     }
 
-    void unget_character() noexcept override
-    {
-        if (JSON_LIKELY(cursor > start))
-        {
-            --cursor;
-        }
-    }
-
   private:
     /// pointer to the current character
     const char* cursor;
     /// pointer past the last character
-    const char* limit;
-    /// pointer to the first character
-    const char* start;
+    const char* const limit;
+};
+
+template<typename WideStringType, size_t T>
+struct wide_string_input_helper
+{
+    // UTF-32
+    static void fill_buffer(const WideStringType& str, size_t& current_wchar, std::array<std::char_traits<char>::int_type, 4>& utf8_bytes, size_t& utf8_bytes_index, size_t& utf8_bytes_filled)
+    {
+        utf8_bytes_index = 0;
+
+        if (current_wchar == str.size())
+        {
+            utf8_bytes[0] = std::char_traits<char>::eof();
+            utf8_bytes_filled = 1;
+        }
+        else
+        {
+            // get the current character
+            const int wc = static_cast<int>(str[current_wchar++]);
+
+            // UTF-32 to UTF-8 encoding
+            if (wc < 0x80)
+            {
+                utf8_bytes[0] = wc;
+                utf8_bytes_filled = 1;
+            }
+            else if (wc <= 0x7FF)
+            {
+                utf8_bytes[0] = 0xC0 | ((wc >> 6) & 0x1F);
+                utf8_bytes[1] = 0x80 | (wc & 0x3F);
+                utf8_bytes_filled = 2;
+            }
+            else if (wc <= 0xFFFF)
+            {
+                utf8_bytes[0] = 0xE0 | ((wc >> 12) & 0x0F);
+                utf8_bytes[1] = 0x80 | ((wc >> 6) & 0x3F);
+                utf8_bytes[2] = 0x80 | (wc & 0x3F);
+                utf8_bytes_filled = 3;
+            }
+            else if (wc <= 0x10FFFF)
+            {
+                utf8_bytes[0] = 0xF0 | ((wc >> 18) & 0x07);
+                utf8_bytes[1] = 0x80 | ((wc >> 12) & 0x3F);
+                utf8_bytes[2] = 0x80 | ((wc >> 6) & 0x3F);
+                utf8_bytes[3] = 0x80 | (wc & 0x3F);
+                utf8_bytes_filled = 4;
+            }
+            else
+            {
+                // unknown character
+                utf8_bytes[0] = wc;
+                utf8_bytes_filled = 1;
+            }
+        }
+    }
+};
+
+template<typename WideStringType>
+struct wide_string_input_helper<WideStringType, 2>
+{
+    // UTF-16
+    static void fill_buffer(const WideStringType& str, size_t& current_wchar, std::array<std::char_traits<char>::int_type, 4>& utf8_bytes, size_t& utf8_bytes_index, size_t& utf8_bytes_filled)
+    {
+        utf8_bytes_index = 0;
+
+        if (current_wchar == str.size())
+        {
+            utf8_bytes[0] = std::char_traits<char>::eof();
+            utf8_bytes_filled = 1;
+        }
+        else
+        {
+            // get the current character
+            const int wc = static_cast<int>(str[current_wchar++]);
+
+            // UTF-16 to UTF-8 encoding
+            if (wc < 0x80)
+            {
+                utf8_bytes[0] = wc;
+                utf8_bytes_filled = 1;
+            }
+            else if (wc <= 0x7FF)
+            {
+                utf8_bytes[0] = 0xC0 | ((wc >> 6));
+                utf8_bytes[1] = 0x80 | (wc & 0x3F);
+                utf8_bytes_filled = 2;
+            }
+            else if (0xD800 > wc or wc >= 0xE000)
+            {
+                utf8_bytes[0] = 0xE0 | ((wc >> 12));
+                utf8_bytes[1] = 0x80 | ((wc >> 6) & 0x3F);
+                utf8_bytes[2] = 0x80 | (wc & 0x3F);
+                utf8_bytes_filled = 3;
+            }
+            else
+            {
+                if (current_wchar < str.size())
+                {
+                    const int wc2 = static_cast<int>(str[current_wchar++]);
+                    const int charcode = 0x10000 + (((wc & 0x3FF) << 10) | (wc2 & 0x3FF));
+                    utf8_bytes[0] = 0xf0 | (charcode >> 18);
+                    utf8_bytes[1] = 0x80 | ((charcode >> 12) & 0x3F);
+                    utf8_bytes[2] = 0x80 | ((charcode >> 6) & 0x3F);
+                    utf8_bytes[3] = 0x80 | (charcode & 0x3F);
+                    utf8_bytes_filled = 4;
+                }
+                else
+                {
+                    // unknown character
+                    ++current_wchar;
+                    utf8_bytes[0] = wc;
+                    utf8_bytes_filled = 1;
+                }
+            }
+        }
+    }
+};
+
+template<typename WideStringType>
+class wide_string_input_adapter : public input_adapter_protocol
+{
+  public:
+    explicit wide_string_input_adapter(const WideStringType& w) : str(w) {}
+
+    std::char_traits<char>::int_type get_character() noexcept override
+    {
+        // check if buffer needs to be filled
+        if (utf8_bytes_index == utf8_bytes_filled)
+        {
+            fill_buffer<sizeof(typename WideStringType::value_type)>();
+
+            assert(utf8_bytes_filled > 0);
+            assert(utf8_bytes_index == 0);
+        }
+
+        // use buffer
+        assert(utf8_bytes_filled > 0);
+        assert(utf8_bytes_index < utf8_bytes_filled);
+        return utf8_bytes[utf8_bytes_index++];
+    }
+
+  private:
+    template<size_t T>
+    void fill_buffer()
+    {
+        wide_string_input_helper<WideStringType, T>::fill_buffer(str, current_wchar, utf8_bytes, utf8_bytes_index, utf8_bytes_filled);
+    }
+
+    /// the wstring to process
+    const WideStringType& str;
+
+    /// index of the current wchar in str
+    std::size_t current_wchar = 0;
+
+    /// a buffer for UTF-8 bytes
+    std::array<std::char_traits<char>::int_type, 4> utf8_bytes = {{0, 0, 0, 0}};
+
+    /// index to the utf8_codes array for the next valid byte
+    std::size_t utf8_bytes_index = 0;
+    /// number of valid bytes in the utf8_codes array
+    std::size_t utf8_bytes_filled = 0;
 };
 
 class input_adapter
@@ -178,6 +289,15 @@ class input_adapter
     input_adapter(std::istream&& i)
         : ia(std::make_shared<input_stream_adapter>(i)) {}
 
+    input_adapter(const std::wstring& ws)
+        : ia(std::make_shared<wide_string_input_adapter<std::wstring>>(ws)) {}
+
+    input_adapter(const std::u16string& ws)
+        : ia(std::make_shared<wide_string_input_adapter<std::u16string>>(ws)) {}
+
+    input_adapter(const std::u32string& ws)
+        : ia(std::make_shared<wide_string_input_adapter<std::u32string>>(ws)) {}
+
     /// input adapter for buffer
     template<typename CharT,
              typename std::enable_if<
@@ -208,15 +328,18 @@ class input_adapter
                  int>::type = 0>
     input_adapter(IteratorType first, IteratorType last)
     {
+#ifndef NDEBUG
         // assertion to check that the iterator range is indeed contiguous,
         // see http://stackoverflow.com/a/35008842/266378 for more discussion
-        assert(std::accumulate(
-                   first, last, std::pair<bool, int>(true, 0),
-                   [&first](std::pair<bool, int> res, decltype(*first) val)
+        const auto is_contiguous = std::accumulate(
+                                       first, last, std::pair<bool, int>(true, 0),
+                                       [&first](std::pair<bool, int> res, decltype(*first) val)
         {
             res.first &= (val == *(std::next(std::addressof(*first), res.second++)));
             return res;
-        }).first);
+        }).first;
+        assert(is_contiguous);
+#endif
 
         // assertion to check that each element is 1 byte long
         static_assert(

include/nlohmann/detail/input/json_sax.hpp

@@ -0,0 +1,702 @@
+#pragma once
+
+#include <cstddef>
+#include <string>
+#include <vector>
+
+#include <nlohmann/detail/input/parser.hpp>
+#include <nlohmann/detail/exceptions.hpp>
+
+namespace nlohmann
+{
+
+/*!
+@brief SAX interface
+
+This class describes the SAX interface used by @ref nlohmann::json::sax_parse.
+Each function is called in different situations while the input is parsed. The
+boolean return value informs the parser whether to continue processing the
+input.
+*/
+template<typename BasicJsonType>
+struct json_sax
+{
+    /// type for (signed) integers
+    using number_integer_t = typename BasicJsonType::number_integer_t;
+    /// type for unsigned integers
+    using number_unsigned_t = typename BasicJsonType::number_unsigned_t;
+    /// type for floating-point numbers
+    using number_float_t = typename BasicJsonType::number_float_t;
+    /// type for strings
+    using string_t = typename BasicJsonType::string_t;
+
+    /*!
+    @brief a null value was read
+    @return whether parsing should proceed
+    */
+    virtual bool null() = 0;
+
+    /*!
+    @brief a boolean value was read
+    @param[in] val  boolean value
+    @return whether parsing should proceed
+    */
+    virtual bool boolean(bool val) = 0;
+
+    /*!
+    @brief an integer number was read
+    @param[in] val  integer value
+    @return whether parsing should proceed
+    */
+    virtual bool number_integer(number_integer_t val) = 0;
+
+    /*!
+    @brief an unsigned integer number was read
+    @param[in] val  unsigned integer value
+    @return whether parsing should proceed
+    */
+    virtual bool number_unsigned(number_unsigned_t val) = 0;
+
+    /*!
+    @brief an floating-point number was read
+    @param[in] val  floating-point value
+    @param[in] s    raw token value
+    @return whether parsing should proceed
+    */
+    virtual bool number_float(number_float_t val, const string_t& s) = 0;
+
+    /*!
+    @brief a string was read
+    @param[in] val  string value
+    @return whether parsing should proceed
+    @note It is safe to move the passed string.
+    */
+    virtual bool string(string_t& val) = 0;
+
+    /*!
+    @brief the beginning of an object was read
+    @param[in] elements  number of object elements or -1 if unknown
+    @return whether parsing should proceed
+    @note binary formats may report the number of elements
+    */
+    virtual bool start_object(std::size_t elements) = 0;
+
+    /*!
+    @brief an object key was read
+    @param[in] val  object key
+    @return whether parsing should proceed
+    @note It is safe to move the passed string.
+    */
+    virtual bool key(string_t& val) = 0;
+
+    /*!
+    @brief the end of an object was read
+    @return whether parsing should proceed
+    */
+    virtual bool end_object() = 0;
+
+    /*!
+    @brief the beginning of an array was read
+    @param[in] elements  number of array elements or -1 if unknown
+    @return whether parsing should proceed
+    @note binary formats may report the number of elements
+    */
+    virtual bool start_array(std::size_t elements) = 0;
+
+    /*!
+    @brief the end of an array was read
+    @return whether parsing should proceed
+    */
+    virtual bool end_array() = 0;
+
+    /*!
+    @brief a parse error occurred
+    @param[in] position    the position in the input where the error occurs
+    @param[in] last_token  the last read token
+    @param[in] error_msg   a detailed error message
+    @return whether parsing should proceed (must return false)
+    */
+    virtual bool parse_error(std::size_t position,
+                             const std::string& last_token,
+                             const detail::exception& ex) = 0;
+
+    virtual ~json_sax() = default;
+};
+
+
+namespace detail
+{
+/*!
+@brief SAX implementation to create a JSON value from SAX events
+
+This class implements the @ref json_sax interface and processes the SAX events
+to create a JSON value which makes it basically a DOM parser. The structure or
+hierarchy of the JSON value is managed by the stack `ref_stack` which contains
+a pointer to the respective array or object for each recursion depth.
+
+After successful parsing, the value that is passed by reference to the
+constructor contains the parsed value.
+
+@tparam BasicJsonType  the JSON type
+*/
+template<typename BasicJsonType>
+class json_sax_dom_parser
+{
+  public:
+    using number_integer_t = typename BasicJsonType::number_integer_t;
+    using number_unsigned_t = typename BasicJsonType::number_unsigned_t;
+    using number_float_t = typename BasicJsonType::number_float_t;
+    using string_t = typename BasicJsonType::string_t;
+
+    /*!
+    @param[in, out] r  reference to a JSON value that is manipulated while
+                       parsing
+    @param[in] allow_exceptions_  whether parse errors yield exceptions
+    */
+    explicit json_sax_dom_parser(BasicJsonType& r, const bool allow_exceptions_ = true)
+        : root(r), allow_exceptions(allow_exceptions_)
+    {}
+
+    bool null()
+    {
+        handle_value(nullptr);
+        return true;
+    }
+
+    bool boolean(bool val)
+    {
+        handle_value(val);
+        return true;
+    }
+
+    bool number_integer(number_integer_t val)
+    {
+        handle_value(val);
+        return true;
+    }
+
+    bool number_unsigned(number_unsigned_t val)
+    {
+        handle_value(val);
+        return true;
+    }
+
+    bool number_float(number_float_t val, const string_t&)
+    {
+        handle_value(val);
+        return true;
+    }
+
+    bool string(string_t& val)
+    {
+        handle_value(val);
+        return true;
+    }
+
+    bool start_object(std::size_t len)
+    {
+        ref_stack.push_back(handle_value(BasicJsonType::value_t::object));
+
+        if (JSON_UNLIKELY(len != std::size_t(-1) and len > ref_stack.back()->max_size()))
+        {
+            JSON_THROW(out_of_range::create(408,
+                                            "excessive object size: " + std::to_string(len)));
+        }
+
+        return true;
+    }
+
+    bool key(string_t& val)
+    {
+        // add null at given key and store the reference for later
+        object_element = &(ref_stack.back()->m_value.object->operator[](val));
+        return true;
+    }
+
+    bool end_object()
+    {
+        ref_stack.pop_back();
+        return true;
+    }
+
+    bool start_array(std::size_t len)
+    {
+        ref_stack.push_back(handle_value(BasicJsonType::value_t::array));
+
+        if (JSON_UNLIKELY(len != std::size_t(-1) and len > ref_stack.back()->max_size()))
+        {
+            JSON_THROW(out_of_range::create(408,
+                                            "excessive array size: " + std::to_string(len)));
+        }
+
+        return true;
+    }
+
+    bool end_array()
+    {
+        ref_stack.pop_back();
+        return true;
+    }
+
+    bool parse_error(std::size_t, const std::string&,
+                     const detail::exception& ex)
+    {
+        errored = true;
+        if (allow_exceptions)
+        {
+            // determine the proper exception type from the id
+            switch ((ex.id / 100) % 100)
+            {
+                case 1:
+                    JSON_THROW(*reinterpret_cast<const detail::parse_error*>(&ex));
+                case 4:
+                    JSON_THROW(*reinterpret_cast<const detail::out_of_range*>(&ex));
+                // LCOV_EXCL_START
+                case 2:
+                    JSON_THROW(*reinterpret_cast<const detail::invalid_iterator*>(&ex));
+                case 3:
+                    JSON_THROW(*reinterpret_cast<const detail::type_error*>(&ex));
+                case 5:
+                    JSON_THROW(*reinterpret_cast<const detail::other_error*>(&ex));
+                default:
+                    assert(false);
+                    // LCOV_EXCL_STOP
+            }
+        }
+        return false;
+    }
+
+    constexpr bool is_errored() const
+    {
+        return errored;
+    }
+
+  private:
+    /*!
+    @invariant If the ref stack is empty, then the passed value will be the new
+               root.
+    @invariant If the ref stack contains a value, then it is an array or an
+               object to which we can add elements
+    */
+    template<typename Value>
+    BasicJsonType* handle_value(Value&& v)
+    {
+        if (ref_stack.empty())
+        {
+            root = BasicJsonType(std::forward<Value>(v));
+            return &root;
+        }
+        else
+        {
+            assert(ref_stack.back()->is_array() or ref_stack.back()->is_object());
+            if (ref_stack.back()->is_array())
+            {
+                ref_stack.back()->m_value.array->emplace_back(std::forward<Value>(v));
+                return &(ref_stack.back()->m_value.array->back());
+            }
+            else
+            {
+                assert(object_element);
+                *object_element = BasicJsonType(std::forward<Value>(v));
+                return object_element;
+            }
+        }
+    }
+
+    /// the parsed JSON value
+    BasicJsonType& root;
+    /// stack to model hierarchy of values
+    std::vector<BasicJsonType*> ref_stack;
+    /// helper to hold the reference for the next object element
+    BasicJsonType* object_element = nullptr;
+    /// whether a syntax error occurred
+    bool errored = false;
+    /// whether to throw exceptions in case of errors
+    const bool allow_exceptions = true;
+};
+
+template<typename BasicJsonType>
+class json_sax_dom_callback_parser
+{
+  public:
+    using number_integer_t = typename BasicJsonType::number_integer_t;
+    using number_unsigned_t = typename BasicJsonType::number_unsigned_t;
+    using number_float_t = typename BasicJsonType::number_float_t;
+    using string_t = typename BasicJsonType::string_t;
+    using parser_callback_t = typename BasicJsonType::parser_callback_t;
+    using parse_event_t = typename BasicJsonType::parse_event_t;
+
+    json_sax_dom_callback_parser(BasicJsonType& r,
+                                 const parser_callback_t cb,
+                                 const bool allow_exceptions_ = true)
+        : root(r), callback(cb), allow_exceptions(allow_exceptions_)
+    {
+        keep_stack.push_back(true);
+    }
+
+    bool null()
+    {
+        handle_value(nullptr);
+        return true;
+    }
+
+    bool boolean(bool val)
+    {
+        handle_value(val);
+        return true;
+    }
+
+    bool number_integer(number_integer_t val)
+    {
+        handle_value(val);
+        return true;
+    }
+
+    bool number_unsigned(number_unsigned_t val)
+    {
+        handle_value(val);
+        return true;
+    }
+
+    bool number_float(number_float_t val, const string_t&)
+    {
+        handle_value(val);
+        return true;
+    }
+
+    bool string(string_t& val)
+    {
+        handle_value(val);
+        return true;
+    }
+
+    bool start_object(std::size_t len)
+    {
+        // check callback for object start
+        const bool keep = callback(static_cast<int>(ref_stack.size()), parse_event_t::object_start, discarded);
+        keep_stack.push_back(keep);
+
+        auto val = handle_value(BasicJsonType::value_t::object, true);
+        ref_stack.push_back(val.second);
+
+        // check object limit
+        if (ref_stack.back())
+        {
+            if (JSON_UNLIKELY(len != std::size_t(-1) and len > ref_stack.back()->max_size()))
+            {
+                JSON_THROW(out_of_range::create(408,
+                                                "excessive object size: " + std::to_string(len)));
+            }
+        }
+
+        return true;
+    }
+
+    bool key(string_t& val)
+    {
+        BasicJsonType k = BasicJsonType(val);
+
+        // check callback for key
+        const bool keep = callback(static_cast<int>(ref_stack.size()), parse_event_t::key, k);
+        key_keep_stack.push_back(keep);
+
+        // add discarded value at given key and store the reference for later
+        if (keep and ref_stack.back())
+        {
+            object_element = &(ref_stack.back()->m_value.object->operator[](val) = discarded);
+        }
+
+        return true;
+    }
+
+    bool end_object()
+    {
+        if (ref_stack.back())
+        {
+            if (not callback(static_cast<int>(ref_stack.size()) - 1, parse_event_t::object_end, *ref_stack.back()))
+            {
+                // discard object
+                *ref_stack.back() = discarded;
+            }
+        }
+
+        assert(not ref_stack.empty());
+        assert(not keep_stack.empty());
+        ref_stack.pop_back();
+        keep_stack.pop_back();
+
+        if (not ref_stack.empty() and ref_stack.back())
+        {
+            // remove discarded value
+            if (ref_stack.back()->is_object())
+            {
+                for (auto it = ref_stack.back()->begin(); it != ref_stack.back()->end(); ++it)
+                {
+                    if (it->is_discarded())
+                    {
+                        ref_stack.back()->erase(it);
+                        break;
+                    }
+                }
+            }
+        }
+
+        return true;
+    }
+
+    bool start_array(std::size_t len)
+    {
+        const bool keep = callback(static_cast<int>(ref_stack.size()), parse_event_t::array_start, discarded);
+        keep_stack.push_back(keep);
+
+        auto val = handle_value(BasicJsonType::value_t::array, true);
+        ref_stack.push_back(val.second);
+
+        // check array limit
+        if (ref_stack.back())
+        {
+            if (JSON_UNLIKELY(len != std::size_t(-1) and len > ref_stack.back()->max_size()))
+            {
+                JSON_THROW(out_of_range::create(408,
+                                                "excessive array size: " + std::to_string(len)));
+            }
+        }
+
+        return true;
+    }
+
+    bool end_array()
+    {
+        bool keep = true;
+
+        if (ref_stack.back())
+        {
+            keep = callback(static_cast<int>(ref_stack.size()) - 1, parse_event_t::array_end, *ref_stack.back());
+            if (not keep)
+            {
+                // discard array
+                *ref_stack.back() = discarded;
+            }
+        }
+
+        assert(not ref_stack.empty());
+        assert(not keep_stack.empty());
+        ref_stack.pop_back();
+        keep_stack.pop_back();
+
+        // remove discarded value
+        if (not keep and not ref_stack.empty())
+        {
+            if (ref_stack.back()->is_array())
+            {
+                ref_stack.back()->m_value.array->pop_back();
+            }
+        }
+
+        return true;
+    }
+
+    bool parse_error(std::size_t, const std::string&,
+                     const detail::exception& ex)
+    {
+        errored = true;
+        if (allow_exceptions)
+        {
+            // determine the proper exception type from the id
+            switch ((ex.id / 100) % 100)
+            {
+                case 1:
+                    JSON_THROW(*reinterpret_cast<const detail::parse_error*>(&ex));
+                case 4:
+                    JSON_THROW(*reinterpret_cast<const detail::out_of_range*>(&ex));
+                // LCOV_EXCL_START
+                case 2:
+                    JSON_THROW(*reinterpret_cast<const detail::invalid_iterator*>(&ex));
+                case 3:
+                    JSON_THROW(*reinterpret_cast<const detail::type_error*>(&ex));
+                case 5:
+                    JSON_THROW(*reinterpret_cast<const detail::other_error*>(&ex));
+                default:
+                    assert(false);
+                    // LCOV_EXCL_STOP
+            }
+        }
+        return false;
+    }
+
+    constexpr bool is_errored() const
+    {
+        return errored;
+    }
+
+  private:
+    /*!
+    @param[in] v  value to add to the JSON value we build during parsing
+    @param[in] skip_callback  whether we should skip calling the callback
+               function; this is required after start_array() and
+               start_object() SAX events, because otherwise we would call the
+               callback function with an empty array or object, respectively.
+
+    @invariant If the ref stack is empty, then the passed value will be the new
+               root.
+    @invariant If the ref stack contains a value, then it is an array or an
+               object to which we can add elements
+
+    @return pair of boolean (whether value should be kept) and pointer (to the
+            passed value in the ref_stack hierarchy; nullptr if not kept)
+    */
+    template<typename Value>
+    std::pair<bool, BasicJsonType*> handle_value(Value&& v, const bool skip_callback = false)
+    {
+        assert(not keep_stack.empty());
+
+        // do not handle this value if we know it would be added to a discarded
+        // container
+        if (not keep_stack.back())
+        {
+            return {false, nullptr};
+        }
+
+        // create value
+        auto value = BasicJsonType(std::forward<Value>(v));
+
+        // check callback
+        const bool keep = skip_callback or callback(static_cast<int>(ref_stack.size()), parse_event_t::value, value);
+
+        // do not handle this value if we just learnt it shall be discarded
+        if (not keep)
+        {
+            return {false, nullptr};
+        }
+
+        if (ref_stack.empty())
+        {
+            root = std::move(value);
+            return {true, &root};
+        }
+        else
+        {
+            // skip this value if we already decided to skip the parent
+            // (https://github.com/nlohmann/json/issues/971#issuecomment-413678360)
+            if (not ref_stack.back())
+            {
+                return {false, nullptr};
+            }
+
+            assert(ref_stack.back()->is_array() or ref_stack.back()->is_object());
+            if (ref_stack.back()->is_array())
+            {
+                ref_stack.back()->m_value.array->push_back(std::move(value));
+                return {true, &(ref_stack.back()->m_value.array->back())};
+            }
+            else
+            {
+                // check if we should store an element for the current key
+                assert(not key_keep_stack.empty());
+                const bool store_element = key_keep_stack.back();
+                key_keep_stack.pop_back();
+
+                if (not store_element)
+                {
+                    return {false, nullptr};
+                }
+
+                assert(object_element);
+                *object_element = std::move(value);
+                return {true, object_element};
+            }
+        }
+    }
+
+    /// the parsed JSON value
+    BasicJsonType& root;
+    /// stack to model hierarchy of values
+    std::vector<BasicJsonType*> ref_stack;
+    /// stack to manage which values to keep
+    std::vector<bool> keep_stack;
+    /// stack to manage which object keys to keep
+    std::vector<bool> key_keep_stack;
+    /// helper to hold the reference for the next object element
+    BasicJsonType* object_element = nullptr;
+    /// whether a syntax error occurred
+    bool errored = false;
+    /// callback function
+    const parser_callback_t callback = nullptr;
+    /// whether to throw exceptions in case of errors
+    const bool allow_exceptions = true;
+    /// a discarded value for the callback
+    BasicJsonType discarded = BasicJsonType::value_t::discarded;
+};
+
+template<typename BasicJsonType>
+class json_sax_acceptor
+{
+  public:
+    using number_integer_t = typename BasicJsonType::number_integer_t;
+    using number_unsigned_t = typename BasicJsonType::number_unsigned_t;
+    using number_float_t = typename BasicJsonType::number_float_t;
+    using string_t = typename BasicJsonType::string_t;
+
+    bool null()
+    {
+        return true;
+    }
+
+    bool boolean(bool)
+    {
+        return true;
+    }
+
+    bool number_integer(number_integer_t)
+    {
+        return true;
+    }
+
+    bool number_unsigned(number_unsigned_t)
+    {
+        return true;
+    }
+
+    bool number_float(number_float_t, const string_t&)
+    {
+        return true;
+    }
+
+    bool string(string_t&)
+    {
+        return true;
+    }
+
+    bool start_object(std::size_t = std::size_t(-1))
+    {
+        return true;
+    }
+
+    bool key(string_t&)
+    {
+        return true;
+    }
+
+    bool end_object()
+    {
+        return true;
+    }
+
+    bool start_array(std::size_t = std::size_t(-1))
+    {
+        return true;
+    }
+
+    bool end_array()
+    {
+        return true;
+    }
+
+    bool parse_error(std::size_t, const std::string&, const detail::exception&)
+    {
+        return false;
+    }
+};
+}
+
+}

include/nlohmann/detail/input/lexer.hpp

@@ -3,10 +3,8 @@
 #include <clocale> // localeconv
 #include <cstddef> // size_t
 #include <cstdlib> // strtof, strtod, strtold, strtoll, strtoull
+#include <cstdio> // snprintf
 #include <initializer_list> // initializer_list
-#include <ios> // hex, uppercase
-#include <iomanip> // setw, setfill
-#include <sstream> // stringstream
 #include <string> // char_traits, string
 #include <vector> // vector
 
@@ -94,12 +92,14 @@ class lexer
                 return "end of input";
             case token_type::literal_or_value:
                 return "'[', '{', or a literal";
+            // LCOV_EXCL_START
             default: // catch non-enum values
-                return "unknown token"; // LCOV_EXCL_LINE
+                return "unknown token";
+                // LCOV_EXCL_STOP
         }
     }
 
-    explicit lexer(detail::input_adapter_t adapter)
+    explicit lexer(detail::input_adapter_t&& adapter)
         : ia(std::move(adapter)), decimal_point_char(get_decimal_point()) {}
 
     // delete because of pointer members
@@ -747,11 +747,13 @@ class lexer
                 goto scan_number_any1;
             }
 
+            // LCOV_EXCL_START
             default:
             {
                 // all other characters are rejected outside scan_number()
-                assert(false); // LCOV_EXCL_LINE
+                assert(false);
             }
+                // LCOV_EXCL_STOP
         }
 
 scan_number_minus:
@@ -1081,7 +1083,16 @@ scan_number_done:
     std::char_traits<char>::int_type get()
     {
         ++chars_read;
-        current = ia->get_character();
+        if (next_unget)
+        {
+            // just reset the next_unget variable and work with current
+            next_unget = false;
+        }
+        else
+        {
+            current = ia->get_character();
+        }
+
         if (JSON_LIKELY(current != std::char_traits<char>::eof()))
         {
             token_string.push_back(std::char_traits<char>::to_char_type(current));
@@ -1089,13 +1100,20 @@ scan_number_done:
         return current;
     }
 
-    /// unget current character (return it again on next get)
+    /*!
+    @brief unget current character (read it again on next get)
+
+    We implement unget by setting variable next_unget to true. The input is not
+    changed - we just simulate ungetting by modifying chars_read and
+    token_string. The next call to get() will behave as if the unget character
+    is read again.
+    */
     void unget()
     {
+        next_unget = true;
         --chars_read;
         if (JSON_LIKELY(current != std::char_traits<char>::eof()))
         {
-            ia->unget_character();
             assert(token_string.size() != 0);
             token_string.pop_back();
         }
@@ -1131,9 +1149,9 @@ scan_number_done:
     }
 
     /// return current string value (implicitly resets the token; useful only once)
-    string_t&& move_string()
+    string_t& get_string()
     {
-        return std::move(token_buffer);
+        return token_buffer;
     }
 
     /////////////////////
@@ -1158,10 +1176,9 @@ scan_number_done:
             if ('\x00' <= c and c <= '\x1F')
             {
                 // escape control characters
-                std::stringstream ss;
-                ss << "<U+" << std::setw(4) << std::uppercase << std::setfill('0')
-                   << std::hex << static_cast<int>(c) << ">";
-                result += ss.str();
+                char cs[9];
+                snprintf(cs, 9, "<U+%.4X>", static_cast<unsigned char>(c));
+                result += cs;
             }
             else
             {
@@ -1183,8 +1200,43 @@ scan_number_done:
     // actual scanner
     /////////////////////
 
+    /*!
+    @brief skip the UTF-8 byte order mark
+    @return true iff there is no BOM or the correct BOM has been skipped
+    */
+    bool skip_bom()
+    {
+        if (get() == 0xEF)
+        {
+            if (get() == 0xBB and get() == 0xBF)
+            {
+                // we completely parsed the BOM
+                return true;
+            }
+            else
+            {
+                // after reading 0xEF, an unexpected character followed
+                return false;
+            }
+        }
+        else
+        {
+            // the first character is not the beginning of the BOM; unget it to
+            // process is later
+            unget();
+            return true;
+        }
+    }
+
     token_type scan()
     {
+        // initially, skip the BOM
+        if (chars_read == 0 and not skip_bom())
+        {
+            error_message = "invalid BOM; must be 0xEF 0xBB 0xBF if given";
+            return token_type::parse_error;
+        }
+
         // read next character and ignore whitespace
         do
         {
@@ -1254,6 +1306,9 @@ scan_number_done:
     /// the current character
     std::char_traits<char>::int_type current = std::char_traits<char>::eof();
 
+    /// whether the next get() call should just return current
+    bool next_unget = false;
+
     /// the number of characters read
     std::size_t chars_read = 0;
 

include/nlohmann/detail/input/parser.hpp

@@ -9,7 +9,9 @@
 
 #include <nlohmann/detail/exceptions.hpp>
 #include <nlohmann/detail/macro_scope.hpp>
+#include <nlohmann/detail/meta/is_sax.hpp>
 #include <nlohmann/detail/input/input_adapters.hpp>
+#include <nlohmann/detail/input/json_sax.hpp>
 #include <nlohmann/detail/input/lexer.hpp>
 #include <nlohmann/detail/value_t.hpp>
 
@@ -57,11 +59,14 @@ class parser
         std::function<bool(int depth, parse_event_t event, BasicJsonType& parsed)>;
 
     /// a parser reading from an input adapter
-    explicit parser(detail::input_adapter_t adapter,
+    explicit parser(detail::input_adapter_t&& adapter,
                     const parser_callback_t cb = nullptr,
                     const bool allow_exceptions_ = true)
-        : callback(cb), m_lexer(adapter), allow_exceptions(allow_exceptions_)
-    {}
+        : callback(cb), m_lexer(std::move(adapter)), allow_exceptions(allow_exceptions_)
+    {
+        // read first token
+        get_token();
+    }
 
     /*!
     @brief public parser interface
@@ -75,31 +80,54 @@ class parser
     */
     void parse(const bool strict, BasicJsonType& result)
     {
-        // read first token
-        get_token();
-
-        parse_internal(true, result);
-        result.assert_invariant();
-
-        // in strict mode, input must be completely read
-        if (strict)
+        if (callback)
         {
-            get_token();
-            expect(token_type::end_of_input);
+            json_sax_dom_callback_parser<BasicJsonType> sdp(result, callback, allow_exceptions);
+            sax_parse_internal(&sdp);
+            result.assert_invariant();
+
+            // in strict mode, input must be completely read
+            if (strict and (get_token() != token_type::end_of_input))
+            {
+                sdp.parse_error(m_lexer.get_position(),
+                                m_lexer.get_token_string(),
+                                parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_of_input)));
+            }
+
+            // in case of an error, return discarded value
+            if (sdp.is_errored())
+            {
+                result = value_t::discarded;
+                return;
+            }
+
+            // set top-level value to null if it was discarded by the callback
+            // function
+            if (result.is_discarded())
+            {
+                result = nullptr;
+            }
         }
-
-        // in case of an error, return discarded value
-        if (errored)
+        else
         {
-            result = value_t::discarded;
-            return;
-        }
+            json_sax_dom_parser<BasicJsonType> sdp(result, allow_exceptions);
+            sax_parse_internal(&sdp);
+            result.assert_invariant();
 
-        // set top-level value to null if it was discarded by the callback
-        // function
-        if (result.is_discarded())
-        {
-            result = nullptr;
+            // in strict mode, input must be completely read
+            if (strict and (get_token() != token_type::end_of_input))
+            {
+                sdp.parse_error(m_lexer.get_position(),
+                                m_lexer.get_token_string(),
+                                parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_of_input)));
+            }
+
+            // in case of an error, return discarded value
+            if (sdp.is_errored())
+            {
+                result = value_t::discarded;
+                return;
+            }
         }
     }
 
@@ -111,414 +139,311 @@ class parser
     */
     bool accept(const bool strict = true)
     {
-        // read first token
-        get_token();
+        json_sax_acceptor<BasicJsonType> sax_acceptor;
+        return sax_parse(&sax_acceptor, strict);
+    }
 
-        if (not accept_internal())
+    template <typename SAX>
+    bool sax_parse(SAX* sax, const bool strict = true)
+    {
+        (void)detail::is_sax_static_asserts<SAX, BasicJsonType> {};
+        const bool result = sax_parse_internal(sax);
+
+        // strict mode: next byte must be EOF
+        if (result and strict and (get_token() != token_type::end_of_input))
         {
-            return false;
+            return sax->parse_error(m_lexer.get_position(),
+                                    m_lexer.get_token_string(),
+                                    parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_of_input)));
         }
 
-        // strict => last token must be EOF
-        return not strict or (get_token() == token_type::end_of_input);
+        return result;
     }
 
   private:
-    /*!
-    @brief the actual parser
-    @throw parse_error.101 in case of an unexpected token
-    @throw parse_error.102 if to_unicode fails or surrogate error
-    @throw parse_error.103 if to_unicode fails
-    */
-    void parse_internal(bool keep, BasicJsonType& result)
+    template <typename SAX>
+    bool sax_parse_internal(SAX* sax)
     {
-        // never parse after a parse error was detected
-        assert(not errored);
+        // stack to remember the hieararchy of structured values we are parsing
+        // true = array; false = object
+        std::vector<bool> states;
+        // value to avoid a goto (see comment where set to true)
+        bool skip_to_state_evaluation = false;
 
-        // start with a discarded value
-        if (not result.is_discarded())
+        while (true)
         {
-            result.m_value.destroy(result.m_type);
-            result.m_type = value_t::discarded;
-        }
-
-        switch (last_token)
-        {
-            case token_type::begin_object:
+            if (not skip_to_state_evaluation)
             {
-                if (keep)
+                // invariant: get_token() was called before each iteration
+                switch (last_token)
                 {
-                    if (callback)
+                    case token_type::begin_object:
                     {
-                        keep = callback(depth++, parse_event_t::object_start, result);
-                    }
-
-                    if (not callback or keep)
-                    {
-                        // explicitly set result to object to cope with {}
-                        result.m_type = value_t::object;
-                        result.m_value = value_t::object;
-                    }
-                }
-
-                // read next token
-                get_token();
-
-                // closing } -> we are done
-                if (last_token == token_type::end_object)
-                {
-                    if (keep and callback and not callback(--depth, parse_event_t::object_end, result))
-                    {
-                        result.m_value.destroy(result.m_type);
-                        result.m_type = value_t::discarded;
-                    }
-                    break;
-                }
-
-                // parse values
-                string_t key;
-                BasicJsonType value;
-                while (true)
-                {
-                    // store key
-                    if (not expect(token_type::value_string))
-                    {
-                        return;
-                    }
-                    key = m_lexer.move_string();
-
-                    bool keep_tag = false;
-                    if (keep)
-                    {
-                        if (callback)
+                        if (JSON_UNLIKELY(not sax->start_object(std::size_t(-1))))
                         {
-                            BasicJsonType k(key);
-                            keep_tag = callback(depth, parse_event_t::key, k);
+                            return false;
+                        }
+
+                        // closing } -> we are done
+                        if (get_token() == token_type::end_object)
+                        {
+                            if (JSON_UNLIKELY(not sax->end_object()))
+                            {
+                                return false;
+                            }
+                            break;
+                        }
+
+                        // parse key
+                        if (JSON_UNLIKELY(last_token != token_type::value_string))
+                        {
+                            return sax->parse_error(m_lexer.get_position(),
+                                                    m_lexer.get_token_string(),
+                                                    parse_error::create(101, m_lexer.get_position(), exception_message(token_type::value_string)));
                         }
                         else
                         {
-                            keep_tag = true;
+                            if (JSON_UNLIKELY(not sax->key(m_lexer.get_string())))
+                            {
+                                return false;
+                            }
+                        }
+
+                        // parse separator (:)
+                        if (JSON_UNLIKELY(get_token() != token_type::name_separator))
+                        {
+                            return sax->parse_error(m_lexer.get_position(),
+                                                    m_lexer.get_token_string(),
+                                                    parse_error::create(101, m_lexer.get_position(), exception_message(token_type::name_separator)));
+                        }
+
+                        // remember we are now inside an object
+                        states.push_back(false);
+
+                        // parse values
+                        get_token();
+                        continue;
+                    }
+
+                    case token_type::begin_array:
+                    {
+                        if (JSON_UNLIKELY(not sax->start_array(std::size_t(-1))))
+                        {
+                            return false;
+                        }
+
+                        // closing ] -> we are done
+                        if (get_token() == token_type::end_array)
+                        {
+                            if (JSON_UNLIKELY(not sax->end_array()))
+                            {
+                                return false;
+                            }
+                            break;
+                        }
+
+                        // remember we are now inside an array
+                        states.push_back(true);
+
+                        // parse values (no need to call get_token)
+                        continue;
+                    }
+
+                    case token_type::value_float:
+                    {
+                        const auto res = m_lexer.get_number_float();
+
+                        if (JSON_UNLIKELY(not std::isfinite(res)))
+                        {
+                            return sax->parse_error(m_lexer.get_position(),
+                                                    m_lexer.get_token_string(),
+                                                    out_of_range::create(406, "number overflow parsing '" + m_lexer.get_token_string() + "'"));
+                        }
+                        else
+                        {
+                            if (JSON_UNLIKELY(not sax->number_float(res, m_lexer.get_string())))
+                            {
+                                return false;
+                            }
+                            break;
                         }
                     }
 
-                    // parse separator (:)
-                    get_token();
-                    if (not expect(token_type::name_separator))
+                    case token_type::literal_false:
                     {
-                        return;
+                        if (JSON_UNLIKELY(not sax->boolean(false)))
+                        {
+                            return false;
+                        }
+                        break;
                     }
 
-                    // parse and add value
-                    get_token();
-                    value.m_value.destroy(value.m_type);
-                    value.m_type = value_t::discarded;
-                    parse_internal(keep, value);
-
-                    if (JSON_UNLIKELY(errored))
+                    case token_type::literal_null:
                     {
-                        return;
+                        if (JSON_UNLIKELY(not sax->null()))
+                        {
+                            return false;
+                        }
+                        break;
                     }
 
-                    if (keep and keep_tag and not value.is_discarded())
+                    case token_type::literal_true:
                     {
-                        result.m_value.object->emplace(std::move(key), std::move(value));
+                        if (JSON_UNLIKELY(not sax->boolean(true)))
+                        {
+                            return false;
+                        }
+                        break;
                     }
 
-                    // comma -> next value
-                    get_token();
-                    if (last_token == token_type::value_separator)
+                    case token_type::value_integer:
                     {
-                        get_token();
-                        continue;
+                        if (JSON_UNLIKELY(not sax->number_integer(m_lexer.get_number_integer())))
+                        {
+                            return false;
+                        }
+                        break;
                     }
 
-                    // closing }
-                    if (not expect(token_type::end_object))
+                    case token_type::value_string:
                     {
-                        return;
-                    }
-                    break;
-                }
-
-                if (keep and callback and not callback(--depth, parse_event_t::object_end, result))
-                {
-                    result.m_value.destroy(result.m_type);
-                    result.m_type = value_t::discarded;
-                }
-                break;
-            }
-
-            case token_type::begin_array:
-            {
-                if (keep)
-                {
-                    if (callback)
-                    {
-                        keep = callback(depth++, parse_event_t::array_start, result);
+                        if (JSON_UNLIKELY(not sax->string(m_lexer.get_string())))
+                        {
+                            return false;
+                        }
+                        break;
                     }
 
-                    if (not callback or keep)
+                    case token_type::value_unsigned:
                     {
-                        // explicitly set result to array to cope with []
-                        result.m_type = value_t::array;
-                        result.m_value = value_t::array;
+                        if (JSON_UNLIKELY(not sax->number_unsigned(m_lexer.get_number_unsigned())))
+                        {
+                            return false;
+                        }
+                        break;
+                    }
+
+                    case token_type::parse_error:
+                    {
+                        // using "uninitialized" to avoid "expected" message
+                        return sax->parse_error(m_lexer.get_position(),
+                                                m_lexer.get_token_string(),
+                                                parse_error::create(101, m_lexer.get_position(), exception_message(token_type::uninitialized)));
+                    }
+
+                    default: // the last token was unexpected
+                    {
+                        return sax->parse_error(m_lexer.get_position(),
+                                                m_lexer.get_token_string(),
+                                                parse_error::create(101, m_lexer.get_position(), exception_message(token_type::literal_or_value)));
                     }
                 }
-
-                // read next token
-                get_token();
-
-                // closing ] -> we are done
-                if (last_token == token_type::end_array)
-                {
-                    if (callback and not callback(--depth, parse_event_t::array_end, result))
-                    {
-                        result.m_value.destroy(result.m_type);
-                        result.m_type = value_t::discarded;
-                    }
-                    break;
-                }
-
-                // parse values
-                BasicJsonType value;
-                while (true)
-                {
-                    // parse value
-                    value.m_value.destroy(value.m_type);
-                    value.m_type = value_t::discarded;
-                    parse_internal(keep, value);
-
-                    if (JSON_UNLIKELY(errored))
-                    {
-                        return;
-                    }
-
-                    if (keep and not value.is_discarded())
-                    {
-                        result.m_value.array->push_back(std::move(value));
-                    }
-
-                    // comma -> next value
-                    get_token();
-                    if (last_token == token_type::value_separator)
-                    {
-                        get_token();
-                        continue;
-                    }
-
-                    // closing ]
-                    if (not expect(token_type::end_array))
-                    {
-                        return;
-                    }
-                    break;
-                }
-
-                if (keep and callback and not callback(--depth, parse_event_t::array_end, result))
-                {
-                    result.m_value.destroy(result.m_type);
-                    result.m_type = value_t::discarded;
-                }
-                break;
             }
-
-            case token_type::literal_null:
+            else
             {
-                result.m_type = value_t::null;
-                break;
+                skip_to_state_evaluation = false;
             }
 
-            case token_type::value_string:
+            // we reached this line after we successfully parsed a value
+            if (states.empty())
             {
-                result.m_type = value_t::string;
-                result.m_value = m_lexer.move_string();
-                break;
-            }
-
-            case token_type::literal_true:
-            {
-                result.m_type = value_t::boolean;
-                result.m_value = true;
-                break;
-            }
-
-            case token_type::literal_false:
-            {
-                result.m_type = value_t::boolean;
-                result.m_value = false;
-                break;
-            }
-
-            case token_type::value_unsigned:
-            {
-                result.m_type = value_t::number_unsigned;
-                result.m_value = m_lexer.get_number_unsigned();
-                break;
-            }
-
-            case token_type::value_integer:
-            {
-                result.m_type = value_t::number_integer;
-                result.m_value = m_lexer.get_number_integer();
-                break;
-            }
-
-            case token_type::value_float:
-            {
-                result.m_type = value_t::number_float;
-                result.m_value = m_lexer.get_number_float();
-
-                // throw in case of infinity or NAN
-                if (JSON_UNLIKELY(not std::isfinite(result.m_value.number_float)))
-                {
-                    if (allow_exceptions)
-                    {
-                        JSON_THROW(out_of_range::create(406, "number overflow parsing '" +
-                                                        m_lexer.get_token_string() + "'"));
-                    }
-                    expect(token_type::uninitialized);
-                }
-                break;
-            }
-
-            case token_type::parse_error:
-            {
-                // using "uninitialized" to avoid "expected" message
-                if (not expect(token_type::uninitialized))
-                {
-                    return;
-                }
-                break; // LCOV_EXCL_LINE
-            }
-
-            default:
-            {
-                // the last token was unexpected; we expected a value
-                if (not expect(token_type::literal_or_value))
-                {
-                    return;
-                }
-                break; // LCOV_EXCL_LINE
-            }
-        }
-
-        if (keep and callback and not callback(depth, parse_event_t::value, result))
-        {
-            result.m_value.destroy(result.m_type);
-            result.m_type = value_t::discarded;
-        }
-    }
-
-    /*!
-    @brief the actual acceptor
-
-    @invariant 1. The last token is not yet processed. Therefore, the caller
-                  of this function must make sure a token has been read.
-               2. When this function returns, the last token is processed.
-                  That is, the last read character was already considered.
-
-    This invariant makes sure that no token needs to be "unput".
-    */
-    bool accept_internal()
-    {
-        switch (last_token)
-        {
-            case token_type::begin_object:
-            {
-                // read next token
-                get_token();
-
-                // closing } -> we are done
-                if (last_token == token_type::end_object)
-                {
-                    return true;
-                }
-
-                // parse values
-                while (true)
-                {
-                    // parse key
-                    if (last_token != token_type::value_string)
-                    {
-                        return false;
-                    }
-
-                    // parse separator (:)
-                    get_token();
-                    if (last_token != token_type::name_separator)
-                    {
-                        return false;
-                    }
-
-                    // parse value
-                    get_token();
-                    if (not accept_internal())
-                    {
-                        return false;
-                    }
-
-                    // comma -> next value
-                    get_token();
-                    if (last_token == token_type::value_separator)
-                    {
-                        get_token();
-                        continue;
-                    }
-
-                    // closing }
-                    return (last_token == token_type::end_object);
-                }
-            }
-
-            case token_type::begin_array:
-            {
-                // read next token
-                get_token();
-
-                // closing ] -> we are done
-                if (last_token == token_type::end_array)
-                {
-                    return true;
-                }
-
-                // parse values
-                while (true)
-                {
-                    // parse value
-                    if (not accept_internal())
-                    {
-                        return false;
-                    }
-
-                    // comma -> next value
-                    get_token();
-                    if (last_token == token_type::value_separator)
-                    {
-                        get_token();
-                        continue;
-                    }
-
-                    // closing ]
-                    return (last_token == token_type::end_array);
-                }
-            }
-
-            case token_type::value_float:
-            {
-                // reject infinity or NAN
-                return std::isfinite(m_lexer.get_number_float());
-            }
-
-            case token_type::literal_false:
-            case token_type::literal_null:
-            case token_type::literal_true:
-            case token_type::value_integer:
-            case token_type::value_string:
-            case token_type::value_unsigned:
+                // empty stack: we reached the end of the hieararchy: done
                 return true;
+            }
+            else
+            {
+                if (states.back())  // array
+                {
+                    // comma -> next value
+                    if (get_token() == token_type::value_separator)
+                    {
+                        // parse a new value
+                        get_token();
+                        continue;
+                    }
 
-            default: // the last token was unexpected
-                return false;
+                    // closing ]
+                    if (JSON_LIKELY(last_token == token_type::end_array))
+                    {
+                        if (JSON_UNLIKELY(not sax->end_array()))
+                        {
+                            return false;
+                        }
+
+                        // We are done with this array. Before we can parse a
+                        // new value, we need to evaluate the new state first.
+                        // By setting skip_to_state_evaluation to false, we
+                        // are effectively jumping to the beginning of this if.
+                        assert(not states.empty());
+                        states.pop_back();
+                        skip_to_state_evaluation = true;
+                        continue;
+                    }
+                    else
+                    {
+                        return sax->parse_error(m_lexer.get_position(),
+                                                m_lexer.get_token_string(),
+                                                parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_array)));
+                    }
+                }
+                else  // object
+                {
+                    // comma -> next value
+                    if (get_token() == token_type::value_separator)
+                    {
+                        // parse key
+                        if (JSON_UNLIKELY(get_token() != token_type::value_string))
+                        {
+                            return sax->parse_error(m_lexer.get_position(),
+                                                    m_lexer.get_token_string(),
+                                                    parse_error::create(101, m_lexer.get_position(), exception_message(token_type::value_string)));
+                        }
+                        else
+                        {
+                            if (JSON_UNLIKELY(not sax->key(m_lexer.get_string())))
+                            {
+                                return false;
+                            }
+                        }
+
+                        // parse separator (:)
+                        if (JSON_UNLIKELY(get_token() != token_type::name_separator))
+                        {
+                            return sax->parse_error(m_lexer.get_position(),
+                                                    m_lexer.get_token_string(),
+                                                    parse_error::create(101, m_lexer.get_position(), exception_message(token_type::name_separator)));
+                        }
+
+                        // parse values
+                        get_token();
+                        continue;
+                    }
+
+                    // closing }
+                    if (JSON_LIKELY(last_token == token_type::end_object))
+                    {
+                        if (JSON_UNLIKELY(not sax->end_object()))
+                        {
+                            return false;
+                        }
+
+                        // We are done with this object. Before we can parse a
+                        // new value, we need to evaluate the new state first.
+                        // By setting skip_to_state_evaluation to false, we
+                        // are effectively jumping to the beginning of this if.
+                        assert(not states.empty());
+                        states.pop_back();
+                        skip_to_state_evaluation = true;
+                        continue;
+                    }
+                    else
+                    {
+                        return sax->parse_error(m_lexer.get_position(),
+                                                m_lexer.get_token_string(),
+                                                parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_object)));
+                    }
+                }
+            }
         }
     }
 
@@ -528,29 +453,7 @@ class parser
         return (last_token = m_lexer.scan());
     }
 
-    /*!
-    @throw parse_error.101 if expected token did not occur
-    */
-    bool expect(token_type t)
-    {
-        if (JSON_UNLIKELY(t != last_token))
-        {
-            errored = true;
-            expected = t;
-            if (allow_exceptions)
-            {
-                throw_exception();
-            }
-            else
-            {
-                return false;
-            }
-        }
-
-        return true;
-    }
-
-    [[noreturn]] void throw_exception() const
+    std::string exception_message(const token_type expected)
     {
         std::string error_msg = "syntax error - ";
         if (last_token == token_type::parse_error)
@@ -568,22 +471,16 @@ class parser
             error_msg += "; expected " + std::string(lexer_t::token_type_name(expected));
         }
 
-        JSON_THROW(parse_error::create(101, m_lexer.get_position(), error_msg));
+        return error_msg;
     }
 
   private:
-    /// current level of recursion
-    int depth = 0;
     /// callback function
     const parser_callback_t callback = nullptr;
     /// the type of the last read token
     token_type last_token = token_type::uninitialized;
     /// the lexer
     lexer_t m_lexer;
-    /// whether a syntax error occurred
-    bool errored = false;
-    /// possible reason for the syntax error
-    token_type expected = token_type::uninitialized;
     /// whether to throw exceptions in case of errors
     const bool allow_exceptions = true;
 };

include/nlohmann/detail/iterators/iter_impl.hpp

@@ -8,7 +8,7 @@
 #include <nlohmann/detail/iterators/internal_iterator.hpp>
 #include <nlohmann/detail/iterators/primitive_iterator.hpp>
 #include <nlohmann/detail/macro_scope.hpp>
-#include <nlohmann/detail/meta.hpp>
+#include <nlohmann/detail/meta/cpp_future.hpp>
 #include <nlohmann/detail/value_t.hpp>
 
 namespace nlohmann
@@ -31,7 +31,7 @@ This class implements a both iterators (iterator and const_iterator) for the
 
 @requirement The class satisfies the following concept requirements:
 -
-[BidirectionalIterator](http://en.cppreference.com/w/cpp/concept/BidirectionalIterator):
+[BidirectionalIterator](https://en.cppreference.com/w/cpp/named_req/BidirectionalIterator):
   The iterator that can be moved can be moved in both directions (i.e.
   incremented and decremented).
 
@@ -583,7 +583,7 @@ class iter_impl
     @brief  return the key of an object iterator
     @pre The iterator is initialized; i.e. `m_object != nullptr`.
     */
-    typename object_t::key_type key() const
+    const typename object_t::key_type& key() const
     {
         assert(m_object != nullptr);
 

include/nlohmann/detail/iterators/iteration_proxy.hpp

@@ -2,6 +2,7 @@
 
 #include <cstddef> // size_t
 #include <string> // string, to_string
+#include <iterator> // input_iterator_tag
 
 #include <nlohmann/detail/value_t.hpp>
 
@@ -16,15 +17,31 @@ template<typename IteratorType> class iteration_proxy
     /// helper class for iteration
     class iteration_proxy_internal
     {
+      public:
+        using difference_type = std::ptrdiff_t;
+        using value_type = iteration_proxy_internal;
+        using pointer = iteration_proxy_internal*;
+        using reference = iteration_proxy_internal&;
+        using iterator_category = std::input_iterator_tag;
+
       private:
         /// the iterator
         IteratorType anchor;
         /// an index for arrays (used to create key names)
         std::size_t array_index = 0;
+        /// last stringified array index
+        mutable std::size_t array_index_last = 0;
+        /// a string representation of the array index
+        mutable std::string array_index_str = "0";
+        /// an empty string (to return a reference for primitive values)
+        const std::string empty_str = "";
 
       public:
         explicit iteration_proxy_internal(IteratorType it) noexcept : anchor(it) {}
 
+        iteration_proxy_internal(const iteration_proxy_internal&) = default;
+        iteration_proxy_internal& operator=(const iteration_proxy_internal&) = default;
+
         /// dereference operator (needed for range-based for)
         iteration_proxy_internal& operator*()
         {
@@ -40,6 +57,12 @@ template<typename IteratorType> class iteration_proxy
             return *this;
         }
 
+        /// equality operator (needed for InputIterator)
+        bool operator==(const iteration_proxy_internal& o) const noexcept
+        {
+            return anchor == o.anchor;
+        }
+
         /// inequality operator (needed for range-based for)
         bool operator!=(const iteration_proxy_internal& o) const noexcept
         {
@@ -47,7 +70,7 @@ template<typename IteratorType> class iteration_proxy
         }
 
         /// return key of the iterator
-        std::string key() const
+        const std::string& key() const
         {
             assert(anchor.m_object != nullptr);
 
@@ -55,7 +78,14 @@ template<typename IteratorType> class iteration_proxy
             {
                 // use integer array index as key
                 case value_t::array:
-                    return std::to_string(array_index);
+                {
+                    if (array_index != array_index_last)
+                    {
+                        array_index_str = std::to_string(array_index);
+                        array_index_last = array_index;
+                    }
+                    return array_index_str;
+                }
 
                 // use key from the object
                 case value_t::object:
@@ -63,7 +93,7 @@ template<typename IteratorType> class iteration_proxy
 
                 // use an empty key for all primitive types
                 default:
-                    return "";
+                    return empty_str;
             }
         }
 

include/nlohmann/detail/iterators/json_reverse_iterator.hpp

@@ -21,10 +21,10 @@ create @ref const_reverse_iterator).
 
 @requirement The class satisfies the following concept requirements:
 -
-[BidirectionalIterator](http://en.cppreference.com/w/cpp/concept/BidirectionalIterator):
+[BidirectionalIterator](https://en.cppreference.com/w/cpp/named_req/BidirectionalIterator):
   The iterator that can be moved can be moved in both directions (i.e.
   incremented and decremented).
-- [OutputIterator](http://en.cppreference.com/w/cpp/concept/OutputIterator):
+- [OutputIterator](https://en.cppreference.com/w/cpp/named_req/OutputIterator):
   It is possible to write to the pointed-to element (only if @a Base is
   @ref iterator).
 
@@ -41,11 +41,11 @@ class json_reverse_iterator : public std::reverse_iterator<Base>
     using reference = typename Base::reference;
 
     /// create reverse iterator from iterator
-    json_reverse_iterator(const typename base_iterator::iterator_type& it) noexcept
+    explicit json_reverse_iterator(const typename base_iterator::iterator_type& it) noexcept
         : base_iterator(it) {}
 
     /// create reverse iterator from base class
-    json_reverse_iterator(const base_iterator& it) noexcept : base_iterator(it) {}
+    explicit json_reverse_iterator(const base_iterator& it) noexcept : base_iterator(it) {}
 
     /// post-increment (it++)
     json_reverse_iterator const operator++(int)

include/nlohmann/detail/iterators/primitive_iterator.hpp

@@ -87,7 +87,7 @@ class primitive_iterator_t
     primitive_iterator_t const operator++(int) noexcept
     {
         auto result = *this;
-        m_it++;
+        ++m_it;
         return result;
     }
 
@@ -100,7 +100,7 @@ class primitive_iterator_t
     primitive_iterator_t const operator--(int) noexcept
     {
         auto result = *this;
-        m_it--;
+        --m_it;
         return result;
     }
 

include/nlohmann/detail/macro_scope.hpp

@@ -4,13 +4,15 @@
 // You MUST include macro_unscope.hpp at the end of json.hpp to undef all of them
 
 // exclude unsupported compilers
-#if defined(__clang__)
-    #if (__clang_major__ * 10000 + __clang_minor__ * 100 + __clang_patchlevel__) < 30400
-        #error "unsupported Clang version - see https://github.com/nlohmann/json#supported-compilers"
-    #endif
-#elif defined(__GNUC__) && !(defined(__ICC) || defined(__INTEL_COMPILER))
-    #if (__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__) < 40900
-        #error "unsupported GCC version - see https://github.com/nlohmann/json#supported-compilers"
+#if !defined(JSON_SKIP_UNSUPPORTED_COMPILER_CHECK)
+    #if defined(__clang__)
+        #if (__clang_major__ * 10000 + __clang_minor__ * 100 + __clang_patchlevel__) < 30400
+            #error "unsupported Clang version - see https://github.com/nlohmann/json#supported-compilers"
+        #endif
+    #elif defined(__GNUC__) && !(defined(__ICC) || defined(__INTEL_COMPILER))
+        #if (__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__) < 40800
+            #error "unsupported GCC version - see https://github.com/nlohmann/json#supported-compilers"
+        #endif
     #endif
 #endif
 
@@ -40,10 +42,12 @@
     #define JSON_THROW(exception) throw exception
     #define JSON_TRY try
     #define JSON_CATCH(exception) catch(exception)
+    #define JSON_INTERNAL_CATCH(exception) catch(exception)
 #else
     #define JSON_THROW(exception) std::abort()
     #define JSON_TRY if(true)
     #define JSON_CATCH(exception) if(false)
+    #define JSON_INTERNAL_CATCH(exception) if(false)
 #endif
 
 // override exception macros
@@ -58,6 +62,12 @@
 #if defined(JSON_CATCH_USER)
     #undef JSON_CATCH
     #define JSON_CATCH JSON_CATCH_USER
+    #undef JSON_INTERNAL_CATCH
+    #define JSON_INTERNAL_CATCH JSON_CATCH_USER
+#endif
+#if defined(JSON_INTERNAL_CATCH_USER)
+    #undef JSON_INTERNAL_CATCH
+    #define JSON_INTERNAL_CATCH JSON_INTERNAL_CATCH_USER
 #endif
 
 // manual branch prediction
@@ -92,24 +102,3 @@
     basic_json<ObjectType, ArrayType, StringType, BooleanType,             \
     NumberIntegerType, NumberUnsignedType, NumberFloatType,                \
     AllocatorType, JSONSerializer>
-
-/*!
-@brief Helper to determine whether there's a key_type for T.
-
-This helper is used to tell associative containers apart from other containers
-such as sequence containers. For instance, `std::map` passes the test as it
-contains a `mapped_type`, whereas `std::vector` fails the test.
-
-@sa http://stackoverflow.com/a/7728728/266378
-@since version 1.0.0, overworked in version 2.0.6
-*/
-#define NLOHMANN_JSON_HAS_HELPER(type)                                        \
-    template<typename T> struct has_##type {                                  \
-    private:                                                                  \
-        template<typename U, typename = typename U::type>                     \
-        static int detect(U &&);                                              \
-        static void detect(...);                                              \
-    public:                                                                   \
-        static constexpr bool value =                                         \
-                std::is_integral<decltype(detect(std::declval<T>()))>::value; \
-    }

include/nlohmann/detail/macro_unscope.hpp

@@ -9,6 +9,7 @@
 #endif
 
 // clean up
+#undef JSON_INTERNAL_CATCH
 #undef JSON_CATCH
 #undef JSON_THROW
 #undef JSON_TRY
@@ -19,4 +20,3 @@
 #undef JSON_HAS_CPP_17
 #undef NLOHMANN_BASIC_JSON_TPL_DECLARATION
 #undef NLOHMANN_BASIC_JSON_TPL
-#undef NLOHMANN_JSON_HAS_HELPER

include/nlohmann/detail/meta.hpp

@@ -1,258 +0,0 @@
-#pragma once
-
-#include <ciso646> // not
-#include <cstddef> // size_t
-#include <limits> // numeric_limits
-#include <type_traits> // conditional, enable_if, false_type, integral_constant, is_constructible, is_integral, is_same, remove_cv, remove_reference, true_type
-#include <utility> // declval
-
-#include <nlohmann/json_fwd.hpp>
-#include <nlohmann/detail/macro_scope.hpp>
-
-namespace nlohmann
-{
-/*!
-@brief detail namespace with internal helper functions
-
-This namespace collects functions that should not be exposed,
-implementations of some @ref basic_json methods, and meta-programming helpers.
-
-@since version 2.1.0
-*/
-namespace detail
-{
-/////////////
-// helpers //
-/////////////
-
-template<typename> struct is_basic_json : std::false_type {};
-
-NLOHMANN_BASIC_JSON_TPL_DECLARATION
-struct is_basic_json<NLOHMANN_BASIC_JSON_TPL> : std::true_type {};
-
-// alias templates to reduce boilerplate
-template<bool B, typename T = void>
-using enable_if_t = typename std::enable_if<B, T>::type;
-
-template<typename T>
-using uncvref_t = typename std::remove_cv<typename std::remove_reference<T>::type>::type;
-
-// implementation of C++14 index_sequence and affiliates
-// source: https://stackoverflow.com/a/32223343
-template<std::size_t... Ints>
-struct index_sequence
-{
-    using type = index_sequence;
-    using value_type = std::size_t;
-    static constexpr std::size_t size() noexcept
-    {
-        return sizeof...(Ints);
-    }
-};
-
-template<class Sequence1, class Sequence2>
-struct merge_and_renumber;
-
-template<std::size_t... I1, std::size_t... I2>
-struct merge_and_renumber<index_sequence<I1...>, index_sequence<I2...>>
-        : index_sequence < I1..., (sizeof...(I1) + I2)... > {};
-
-template<std::size_t N>
-struct make_index_sequence
-    : merge_and_renumber < typename make_index_sequence < N / 2 >::type,
-      typename make_index_sequence < N - N / 2 >::type > {};
-
-template<> struct make_index_sequence<0> : index_sequence<> {};
-template<> struct make_index_sequence<1> : index_sequence<0> {};
-
-template<typename... Ts>
-using index_sequence_for = make_index_sequence<sizeof...(Ts)>;
-
-/*
-Implementation of two C++17 constructs: conjunction, negation. This is needed
-to avoid evaluating all the traits in a condition
-
-For example: not std::is_same<void, T>::value and has_value_type<T>::value
-will not compile when T = void (on MSVC at least). Whereas
-conjunction<negation<std::is_same<void, T>>, has_value_type<T>>::value will
-stop evaluating if negation<...>::value == false
-
-Please note that those constructs must be used with caution, since symbols can
-become very long quickly (which can slow down compilation and cause MSVC
-internal compiler errors). Only use it when you have to (see example ahead).
-*/
-template<class...> struct conjunction : std::true_type {};
-template<class B1> struct conjunction<B1> : B1 {};
-template<class B1, class... Bn>
-struct conjunction<B1, Bn...> : std::conditional<bool(B1::value), conjunction<Bn...>, B1>::type {};
-
-template<class B> struct negation : std::integral_constant<bool, not B::value> {};
-
-// dispatch utility (taken from ranges-v3)
-template<unsigned N> struct priority_tag : priority_tag < N - 1 > {};
-template<> struct priority_tag<0> {};
-
-////////////////////////
-// has_/is_ functions //
-////////////////////////
-
-// source: https://stackoverflow.com/a/37193089/4116453
-
-template <typename T, typename = void>
-struct is_complete_type : std::false_type {};
-
-template <typename T>
-struct is_complete_type<T, decltype(void(sizeof(T)))> : std::true_type {};
-
-NLOHMANN_JSON_HAS_HELPER(mapped_type);
-NLOHMANN_JSON_HAS_HELPER(key_type);
-NLOHMANN_JSON_HAS_HELPER(value_type);
-NLOHMANN_JSON_HAS_HELPER(iterator);
-
-template<bool B, class RealType, class CompatibleObjectType>
-struct is_compatible_object_type_impl : std::false_type {};
-
-template<class RealType, class CompatibleObjectType>
-struct is_compatible_object_type_impl<true, RealType, CompatibleObjectType>
-{
-    static constexpr auto value =
-        std::is_constructible<typename RealType::key_type, typename CompatibleObjectType::key_type>::value and
-        std::is_constructible<typename RealType::mapped_type, typename CompatibleObjectType::mapped_type>::value;
-};
-
-template<class BasicJsonType, class CompatibleObjectType>
-struct is_compatible_object_type
-{
-    static auto constexpr value = is_compatible_object_type_impl <
-                                  conjunction<negation<std::is_same<void, CompatibleObjectType>>,
-                                  has_mapped_type<CompatibleObjectType>,
-                                  has_key_type<CompatibleObjectType>>::value,
-                                  typename BasicJsonType::object_t, CompatibleObjectType >::value;
-};
-
-template<typename BasicJsonType, typename T>
-struct is_basic_json_nested_type
-{
-    static auto constexpr value = std::is_same<T, typename BasicJsonType::iterator>::value or
-                                  std::is_same<T, typename BasicJsonType::const_iterator>::value or
-                                  std::is_same<T, typename BasicJsonType::reverse_iterator>::value or
-                                  std::is_same<T, typename BasicJsonType::const_reverse_iterator>::value;
-};
-
-template<class BasicJsonType, class CompatibleArrayType>
-struct is_compatible_array_type
-{
-    static auto constexpr value =
-        conjunction<negation<std::is_same<void, CompatibleArrayType>>,
-        negation<is_compatible_object_type<
-        BasicJsonType, CompatibleArrayType>>,
-        negation<std::is_constructible<typename BasicJsonType::string_t,
-        CompatibleArrayType>>,
-        negation<is_basic_json_nested_type<BasicJsonType, CompatibleArrayType>>,
-        has_value_type<CompatibleArrayType>,
-        has_iterator<CompatibleArrayType>>::value;
-};
-
-template<bool, typename, typename>
-struct is_compatible_integer_type_impl : std::false_type {};
-
-template<typename RealIntegerType, typename CompatibleNumberIntegerType>
-struct is_compatible_integer_type_impl<true, RealIntegerType, CompatibleNumberIntegerType>
-{
-    // is there an assert somewhere on overflows?
-    using RealLimits = std::numeric_limits<RealIntegerType>;
-    using CompatibleLimits = std::numeric_limits<CompatibleNumberIntegerType>;
-
-    static constexpr auto value =
-        std::is_constructible<RealIntegerType, CompatibleNumberIntegerType>::value and
-        CompatibleLimits::is_integer and
-        RealLimits::is_signed == CompatibleLimits::is_signed;
-};
-
-template<typename RealIntegerType, typename CompatibleNumberIntegerType>
-struct is_compatible_integer_type
-{
-    static constexpr auto value =
-        is_compatible_integer_type_impl <
-        std::is_integral<CompatibleNumberIntegerType>::value and
-        not std::is_same<bool, CompatibleNumberIntegerType>::value,
-        RealIntegerType, CompatibleNumberIntegerType > ::value;
-};
-
-// trait checking if JSONSerializer<T>::from_json(json const&, udt&) exists
-template<typename BasicJsonType, typename T>
-struct has_from_json
-{
-  private:
-    // also check the return type of from_json
-    template<typename U, typename = enable_if_t<std::is_same<void, decltype(uncvref_t<U>::from_json(
-                 std::declval<BasicJsonType>(), std::declval<T&>()))>::value>>
-    static int detect(U&&);
-    static void detect(...);
-
-  public:
-    static constexpr bool value = std::is_integral<decltype(
-                                      detect(std::declval<typename BasicJsonType::template json_serializer<T, void>>()))>::value;
-};
-
-// This trait checks if JSONSerializer<T>::from_json(json const&) exists
-// this overload is used for non-default-constructible user-defined-types
-template<typename BasicJsonType, typename T>
-struct has_non_default_from_json
-{
-  private:
-    template <
-        typename U,
-        typename = enable_if_t<std::is_same<
-                                   T, decltype(uncvref_t<U>::from_json(std::declval<BasicJsonType>()))>::value >>
-    static int detect(U&&);
-    static void detect(...);
-
-  public:
-    static constexpr bool value = std::is_integral<decltype(detect(
-                                      std::declval<typename BasicJsonType::template json_serializer<T, void>>()))>::value;
-};
-
-// This trait checks if BasicJsonType::json_serializer<T>::to_json exists
-template<typename BasicJsonType, typename T>
-struct has_to_json
-{
-  private:
-    template<typename U, typename = decltype(uncvref_t<U>::to_json(
-                 std::declval<BasicJsonType&>(), std::declval<T>()))>
-    static int detect(U&&);
-    static void detect(...);
-
-  public:
-    static constexpr bool value = std::is_integral<decltype(detect(
-                                      std::declval<typename BasicJsonType::template json_serializer<T, void>>()))>::value;
-};
-
-template <typename BasicJsonType, typename CompatibleCompleteType>
-struct is_compatible_complete_type
-{
-    static constexpr bool value =
-        not std::is_base_of<std::istream, CompatibleCompleteType>::value and
-        not is_basic_json<CompatibleCompleteType>::value and
-        not is_basic_json_nested_type<BasicJsonType, CompatibleCompleteType>::value and
-        has_to_json<BasicJsonType, CompatibleCompleteType>::value;
-};
-
-template <typename BasicJsonType, typename CompatibleType>
-struct is_compatible_type
-    : conjunction<is_complete_type<CompatibleType>,
-      is_compatible_complete_type<BasicJsonType, CompatibleType>>
-{
-};
-
-// taken from ranges-v3
-template<typename T>
-struct static_const
-{
-    static constexpr T value{};
-};
-
-template<typename T>
-constexpr T static_const<T>::value;
-}
-}

include/nlohmann/detail/meta/cpp_future.hpp

@@ -0,0 +1,63 @@
+#pragma once
+
+#include <ciso646> // not
+#include <cstddef> // size_t
+#include <type_traits> // conditional, enable_if, false_type, integral_constant, is_constructible, is_integral, is_same, remove_cv, remove_reference, true_type
+
+namespace nlohmann
+{
+namespace detail
+{
+// alias templates to reduce boilerplate
+template<bool B, typename T = void>
+using enable_if_t = typename std::enable_if<B, T>::type;
+
+template<typename T>
+using uncvref_t = typename std::remove_cv<typename std::remove_reference<T>::type>::type;
+
+// implementation of C++14 index_sequence and affiliates
+// source: https://stackoverflow.com/a/32223343
+template<std::size_t... Ints>
+struct index_sequence
+{
+    using type = index_sequence;
+    using value_type = std::size_t;
+    static constexpr std::size_t size() noexcept
+    {
+        return sizeof...(Ints);
+    }
+};
+
+template<class Sequence1, class Sequence2>
+struct merge_and_renumber;
+
+template<std::size_t... I1, std::size_t... I2>
+struct merge_and_renumber<index_sequence<I1...>, index_sequence<I2...>>
+        : index_sequence < I1..., (sizeof...(I1) + I2)... > {};
+
+template<std::size_t N>
+struct make_index_sequence
+    : merge_and_renumber < typename make_index_sequence < N / 2 >::type,
+      typename make_index_sequence < N - N / 2 >::type > {};
+
+template<> struct make_index_sequence<0> : index_sequence<> {};
+template<> struct make_index_sequence<1> : index_sequence<0> {};
+
+template<typename... Ts>
+using index_sequence_for = make_index_sequence<sizeof...(Ts)>;
+
+// dispatch utility (taken from ranges-v3)
+template<unsigned N> struct priority_tag : priority_tag < N - 1 > {};
+template<> struct priority_tag<0> {};
+
+// taken from ranges-v3
+template<typename T>
+struct static_const
+{
+    static constexpr T value{};
+};
+
+template<typename T>
+constexpr T static_const<T>::value;
+}
+}

include/nlohmann/detail/meta/detected.hpp

@@ -0,0 +1,56 @@
+#pragma once
+
+#include <type_traits>
+
+#include <nlohmann/detail/meta/void_t.hpp>
+
+// http://en.cppreference.com/w/cpp/experimental/is_detected
+namespace nlohmann
+{
+namespace detail
+{
+struct nonesuch
+{
+    nonesuch() = delete;
+    ~nonesuch() = delete;
+    nonesuch(nonesuch const&) = delete;
+    void operator=(nonesuch const&) = delete;
+};
+
+template <class Default,
+          class AlwaysVoid,
+          template <class...> class Op,
+          class... Args>
+struct detector
+{
+    using value_t = std::false_type;
+    using type = Default;
+};
+
+template <class Default, template <class...> class Op, class... Args>
+struct detector<Default, void_t<Op<Args...>>, Op, Args...>
+{
+    using value_t = std::true_type;
+    using type = Op<Args...>;
+};
+
+template <template <class...> class Op, class... Args>
+using is_detected = typename detector<nonesuch, void, Op, Args...>::value_t;
+
+template <template <class...> class Op, class... Args>
+using detected_t = typename detector<nonesuch, void, Op, Args...>::type;
+
+template <class Default, template <class...> class Op, class... Args>
+using detected_or = detector<Default, void, Op, Args...>;
+
+template <class Default, template <class...> class Op, class... Args>
+using detected_or_t = typename detected_or<Default, Op, Args...>::type;
+
+template <class Expected, template <class...> class Op, class... Args>
+using is_detected_exact = std::is_same<Expected, detected_t<Op, Args...>>;
+
+template <class To, template <class...> class Op, class... Args>
+using is_detected_convertible =
+    std::is_convertible<detected_t<Op, Args...>, To>;
+}
+}

include/nlohmann/detail/meta/is_sax.hpp

@@ -0,0 +1,141 @@
+#pragma once
+
+#include <cstdint> // size_t
+#include <utility> // declval
+
+#include <nlohmann/detail/meta/detected.hpp>
+#include <nlohmann/detail/meta/type_traits.hpp>
+
+namespace nlohmann
+{
+namespace detail
+{
+template <typename T>
+using null_function_t = decltype(std::declval<T&>().null());
+
+template <typename T>
+using boolean_function_t =
+    decltype(std::declval<T&>().boolean(std::declval<bool>()));
+
+template <typename T, typename Integer>
+using number_integer_function_t =
+    decltype(std::declval<T&>().number_integer(std::declval<Integer>()));
+
+template <typename T, typename Unsigned>
+using number_unsigned_function_t =
+    decltype(std::declval<T &>().number_unsigned(std::declval<Unsigned>()));
+
+template <typename T, typename Float, typename String>
+using number_float_function_t = decltype(std::declval<T &>().number_float(
+    std::declval<Float>(), std::declval<const String &>()));
+
+template <typename T, typename String>
+using string_function_t =
+    decltype(std::declval<T &>().string(std::declval<String &>()));
+
+template <typename T>
+using start_object_function_t =
+    decltype(std::declval<T &>().start_object(std::declval<std::size_t>()));
+
+template <typename T, typename String>
+using key_function_t =
+    decltype(std::declval<T &>().key(std::declval<String &>()));
+
+template <typename T>
+using end_object_function_t = decltype(std::declval<T &>().end_object());
+
+template <typename T>
+using start_array_function_t =
+    decltype(std::declval<T &>().start_array(std::declval<std::size_t>()));
+
+template <typename T>
+using end_array_function_t = decltype(std::declval<T &>().end_array());
+
+template <typename T, typename Exception>
+using parse_error_function_t = decltype(std::declval<T &>().parse_error(
+    std::declval<std::size_t>(), std::declval<const std::string &>(),
+    std::declval<const Exception &>()));
+
+template <typename SAX, typename BasicJsonType>
+struct is_sax
+{
+private:
+  static_assert(is_basic_json<BasicJsonType>::value,
+                "BasicJsonType must be of type basic_json<...>");
+
+  using number_integer_t = typename BasicJsonType::number_integer_t;
+  using number_unsigned_t = typename BasicJsonType::number_unsigned_t;
+  using number_float_t = typename BasicJsonType::number_float_t;
+  using string_t = typename BasicJsonType::string_t;
+  using exception_t = typename BasicJsonType::exception;
+
+public:
+  static constexpr bool value =
+      is_detected_exact<bool, null_function_t, SAX>::value &&
+      is_detected_exact<bool, boolean_function_t, SAX>::value &&
+      is_detected_exact<bool, number_integer_function_t, SAX,
+                        number_integer_t>::value &&
+      is_detected_exact<bool, number_unsigned_function_t, SAX,
+                        number_unsigned_t>::value &&
+      is_detected_exact<bool, number_float_function_t, SAX, number_float_t,
+                        string_t>::value &&
+      is_detected_exact<bool, string_function_t, SAX, string_t>::value &&
+      is_detected_exact<bool, start_object_function_t, SAX>::value &&
+      is_detected_exact<bool, key_function_t, SAX, string_t>::value &&
+      is_detected_exact<bool, end_object_function_t, SAX>::value &&
+      is_detected_exact<bool, start_array_function_t, SAX>::value &&
+      is_detected_exact<bool, end_array_function_t, SAX>::value &&
+      is_detected_exact<bool, parse_error_function_t, SAX, exception_t>::value;
+};
+
+template <typename SAX, typename BasicJsonType>
+struct is_sax_static_asserts
+{
+private:
+  static_assert(is_basic_json<BasicJsonType>::value,
+                "BasicJsonType must be of type basic_json<...>");
+
+  using number_integer_t = typename BasicJsonType::number_integer_t;
+  using number_unsigned_t = typename BasicJsonType::number_unsigned_t;
+  using number_float_t = typename BasicJsonType::number_float_t;
+  using string_t = typename BasicJsonType::string_t;
+  using exception_t = typename BasicJsonType::exception;
+
+public:
+  static_assert(is_detected_exact<bool, null_function_t, SAX>::value,
+                "Missing/invalid function: bool null()");
+  static_assert(is_detected_exact<bool, boolean_function_t, SAX>::value,
+                "Missing/invalid function: bool boolean(bool)");
+  static_assert(is_detected_exact<bool, boolean_function_t, SAX>::value,
+                "Missing/invalid function: bool boolean(bool)");
+  static_assert(
+      is_detected_exact<bool, number_integer_function_t, SAX,
+                        number_integer_t>::value,
+      "Missing/invalid function: bool number_integer(number_integer_t)");
+  static_assert(
+      is_detected_exact<bool, number_unsigned_function_t, SAX,
+                        number_unsigned_t>::value,
+      "Missing/invalid function: bool number_unsigned(number_unsigned_t)");
+  static_assert(is_detected_exact<bool, number_float_function_t, SAX,
+                                  number_float_t, string_t>::value,
+                "Missing/invalid function: bool number_float(number_float_t, const string_t&)");
+  static_assert(
+      is_detected_exact<bool, string_function_t, SAX, string_t>::value,
+      "Missing/invalid function: bool string(string_t&)");
+  static_assert(is_detected_exact<bool, start_object_function_t, SAX>::value,
+                "Missing/invalid function: bool start_object(std::size_t)");
+  static_assert(is_detected_exact<bool, key_function_t, SAX, string_t>::value,
+                "Missing/invalid function: bool key(string_t&)");
+  static_assert(is_detected_exact<bool, end_object_function_t, SAX>::value,
+                "Missing/invalid function: bool end_object()");
+  static_assert(is_detected_exact<bool, start_array_function_t, SAX>::value,
+                "Missing/invalid function: bool start_array(std::size_t)");
+  static_assert(is_detected_exact<bool, end_array_function_t, SAX>::value,
+                "Missing/invalid function: bool end_array()");
+  static_assert(
+      is_detected_exact<bool, parse_error_function_t, SAX, exception_t>::value,
+      "Missing/invalid function: bool parse_error(std::size_t, const "
+      "std::string&, const exception&)");
+};
+}
+}

include/nlohmann/detail/meta/type_traits.hpp

@@ -0,0 +1,251 @@
+#pragma once
+
+#include <ciso646> // not
+#include <limits> // numeric_limits
+#include <type_traits> // false_type, is_constructible, is_integral, is_same, true_type
+#include <utility> // declval
+
+#include <nlohmann/json_fwd.hpp>
+#include <nlohmann/detail/meta/cpp_future.hpp>
+#include <nlohmann/detail/meta/detected.hpp>
+#include <nlohmann/detail/macro_scope.hpp>
+
+namespace nlohmann
+{
+/*!
+@brief detail namespace with internal helper functions
+
+This namespace collects functions that should not be exposed,
+implementations of some @ref basic_json methods, and meta-programming helpers.
+
+@since version 2.1.0
+*/
+namespace detail
+{
+/////////////
+// helpers //
+/////////////
+
+template<typename> struct is_basic_json : std::false_type {};
+
+NLOHMANN_BASIC_JSON_TPL_DECLARATION
+struct is_basic_json<NLOHMANN_BASIC_JSON_TPL> : std::true_type {};
+
+//////////////////////////
+// aliases for detected //
+//////////////////////////
+
+template <typename T>
+using mapped_type_t = typename T::mapped_type;
+
+template <typename T>
+using key_type_t = typename T::key_type;
+
+template <typename T>
+using value_type_t = typename T::value_type;
+
+template <typename T>
+using difference_type_t = typename T::difference_type;
+
+template <typename T>
+using pointer_t = typename T::pointer;
+
+template <typename T>
+using reference_t = typename T::reference;
+
+template <typename T>
+using iterator_category_t = typename T::iterator_category;
+
+template <typename T>
+using iterator_t = typename T::iterator;
+
+template <typename T, typename... Args>
+using to_json_function = decltype(T::to_json(std::declval<Args>()...));
+
+template <typename T, typename... Args>
+using from_json_function = decltype(T::from_json(std::declval<Args>()...));
+
+template <typename T, typename U>
+using get_template_function = decltype(std::declval<T>().template get<U>());
+
+///////////////////
+// is_ functions //
+///////////////////
+
+template <typename T, typename = void>
+struct is_iterator_traits : std::false_type {};
+
+template <typename T>
+struct is_iterator_traits<std::iterator_traits<T>>
+{
+  private:
+    using traits = std::iterator_traits<T>;
+
+  public:
+    static constexpr auto value =
+        is_detected<value_type_t, traits>::value &&
+        is_detected<difference_type_t, traits>::value &&
+        is_detected<pointer_t, traits>::value &&
+        is_detected<iterator_category_t, traits>::value &&
+        is_detected<reference_t, traits>::value;
+};
+
+// source: https://stackoverflow.com/a/37193089/4116453
+
+template <typename T, typename = void>
+struct is_complete_type : std::false_type {};
+
+template <typename T>
+struct is_complete_type<T, decltype(void(sizeof(T)))> : std::true_type {};
+
+template <typename BasicJsonType, typename CompatibleObjectType,
+          typename = void>
+struct is_compatible_object_type_impl : std::false_type {};
+
+template <typename BasicJsonType, typename CompatibleObjectType>
+struct is_compatible_object_type_impl <
+    BasicJsonType, CompatibleObjectType,
+    enable_if_t<is_detected<mapped_type_t, CompatibleObjectType>::value and
+    is_detected<key_type_t, CompatibleObjectType>::value >>
+{
+
+    using object_t = typename BasicJsonType::object_t;
+
+    // macOS's is_constructible does not play well with nonesuch...
+    static constexpr bool value =
+        std::is_constructible<typename object_t::key_type,
+        typename CompatibleObjectType::key_type>::value and
+        std::is_constructible<typename object_t::mapped_type,
+        typename CompatibleObjectType::mapped_type>::value;
+};
+
+template <typename BasicJsonType, typename CompatibleObjectType>
+struct is_compatible_object_type
+    : is_compatible_object_type_impl<BasicJsonType, CompatibleObjectType> {};
+
+template <typename BasicJsonType, typename CompatibleStringType,
+          typename = void>
+struct is_compatible_string_type_impl : std::false_type {};
+
+template <typename BasicJsonType, typename CompatibleStringType>
+struct is_compatible_string_type_impl <
+    BasicJsonType, CompatibleStringType,
+    enable_if_t<is_detected_exact<typename BasicJsonType::string_t::value_type,
+    value_type_t, CompatibleStringType>::value >>
+{
+    static constexpr auto value =
+        std::is_constructible<typename BasicJsonType::string_t, CompatibleStringType>::value;
+};
+
+template <typename BasicJsonType, typename CompatibleStringType>
+struct is_compatible_string_type
+    : is_compatible_string_type_impl<BasicJsonType, CompatibleStringType> {};
+
+template <typename BasicJsonType, typename CompatibleArrayType, typename = void>
+struct is_compatible_array_type_impl : std::false_type {};
+
+template <typename BasicJsonType, typename CompatibleArrayType>
+struct is_compatible_array_type_impl <
+    BasicJsonType, CompatibleArrayType,
+    enable_if_t<is_detected<value_type_t, CompatibleArrayType>::value and
+    is_detected<iterator_t, CompatibleArrayType>::value >>
+{
+    // This is needed because json_reverse_iterator has a ::iterator type...
+    // Therefore it is detected as a CompatibleArrayType.
+    // The real fix would be to have an Iterable concept.
+    static constexpr bool value = not is_iterator_traits<std::iterator_traits<CompatibleArrayType>>::value;
+};
+
+template <typename BasicJsonType, typename CompatibleArrayType>
+struct is_compatible_array_type
+    : is_compatible_array_type_impl<BasicJsonType, CompatibleArrayType> {};
+
+template <typename RealIntegerType, typename CompatibleNumberIntegerType,
+          typename = void>
+struct is_compatible_integer_type_impl : std::false_type {};
+
+template <typename RealIntegerType, typename CompatibleNumberIntegerType>
+struct is_compatible_integer_type_impl <
+    RealIntegerType, CompatibleNumberIntegerType,
+    enable_if_t<std::is_integral<RealIntegerType>::value and
+    std::is_integral<CompatibleNumberIntegerType>::value and
+    not std::is_same<bool, CompatibleNumberIntegerType>::value >>
+{
+    // is there an assert somewhere on overflows?
+    using RealLimits = std::numeric_limits<RealIntegerType>;
+    using CompatibleLimits = std::numeric_limits<CompatibleNumberIntegerType>;
+
+    static constexpr auto value =
+        std::is_constructible<RealIntegerType,
+        CompatibleNumberIntegerType>::value and
+        CompatibleLimits::is_integer and
+        RealLimits::is_signed == CompatibleLimits::is_signed;
+};
+
+template <typename RealIntegerType, typename CompatibleNumberIntegerType>
+struct is_compatible_integer_type
+    : is_compatible_integer_type_impl<RealIntegerType,
+      CompatibleNumberIntegerType> {};
+
+// trait checking if JSONSerializer<T>::from_json(json const&, udt&) exists
+template <typename BasicJsonType, typename T, typename = void>
+struct has_from_json : std::false_type {};
+
+template <typename BasicJsonType, typename T>
+struct has_from_json<BasicJsonType, T,
+           enable_if_t<not is_basic_json<T>::value>>
+{
+    using serializer = typename BasicJsonType::template json_serializer<T, void>;
+
+    static constexpr bool value =
+        is_detected_exact<void, from_json_function, serializer,
+        const BasicJsonType&, T&>::value;
+};
+
+// This trait checks if JSONSerializer<T>::from_json(json const&) exists
+// this overload is used for non-default-constructible user-defined-types
+template <typename BasicJsonType, typename T, typename = void>
+struct has_non_default_from_json : std::false_type {};
+
+template<typename BasicJsonType, typename T>
+struct has_non_default_from_json<BasicJsonType, T, enable_if_t<not is_basic_json<T>::value>>
+{
+    using serializer = typename BasicJsonType::template json_serializer<T, void>;
+
+    static constexpr bool value =
+        is_detected_exact<T, from_json_function, serializer,
+        const BasicJsonType&>::value;
+};
+
+// This trait checks if BasicJsonType::json_serializer<T>::to_json exists
+// Do not evaluate the trait when T is a basic_json type, to avoid template instantiation infinite recursion.
+template <typename BasicJsonType, typename T, typename = void>
+struct has_to_json : std::false_type {};
+
+template <typename BasicJsonType, typename T>
+struct has_to_json<BasicJsonType, T, enable_if_t<not is_basic_json<T>::value>>
+{
+    using serializer = typename BasicJsonType::template json_serializer<T, void>;
+
+    static constexpr bool value =
+        is_detected_exact<void, to_json_function, serializer, BasicJsonType&,
+        T>::value;
+};
+
+template <typename BasicJsonType, typename CompatibleType, typename = void>
+struct is_compatible_type_impl: std::false_type {};
+
+template <typename BasicJsonType, typename CompatibleType>
+struct is_compatible_type_impl <
+    BasicJsonType, CompatibleType,
+    enable_if_t<is_complete_type<CompatibleType>::value >>
+{
+    static constexpr bool value =
+        has_to_json<BasicJsonType, CompatibleType>::value;
+};
+
+template <typename BasicJsonType, typename CompatibleType>
+struct is_compatible_type
+    : is_compatible_type_impl<BasicJsonType, CompatibleType> {};
+}
+}

include/nlohmann/detail/meta/void_t.hpp

@@ -0,0 +1,13 @@
+#pragma once
+
+namespace nlohmann
+{
+namespace detail
+{
+template <typename ...Ts> struct make_void
+{
+    using type = void;
+};
+template <typename ...Ts> using void_t = typename make_void<Ts...>::type;
+}
+}

include/nlohmann/detail/output/binary_writer.hpp

@@ -149,9 +149,9 @@ class binary_writer
                 break;
             }
 
-            case value_t::number_float: // Double-Precision Float
+            case value_t::number_float:
             {
-                oa->write_character(static_cast<CharType>(0xFB));
+                oa->write_character(get_cbor_float_prefix(j.m_value.number_float));
                 write_number(j.m_value.number_float);
                 break;
             }
@@ -409,9 +409,9 @@ class binary_writer
                 break;
             }
 
-            case value_t::number_float: // float 64
+            case value_t::number_float:
             {
-                oa->write_character(static_cast<CharType>(0xCB));
+                oa->write_character(get_msgpack_float_prefix(j.m_value.number_float));
                 write_number(j.m_value.number_float);
                 break;
             }
@@ -588,7 +588,7 @@ class binary_writer
                 if (use_type and not j.m_value.array->empty())
                 {
                     assert(use_count);
-                    const char first_prefix = ubjson_prefix(j.front());
+                    const CharType first_prefix = ubjson_prefix(j.front());
                     const bool same_prefix = std::all_of(j.begin() + 1, j.end(),
                                                          [this, first_prefix](const BasicJsonType & v)
                     {
@@ -599,7 +599,7 @@ class binary_writer
                     {
                         prefix_required = false;
                         oa->write_character(static_cast<CharType>('$'));
-                        oa->write_character(static_cast<CharType>(first_prefix));
+                        oa->write_character(first_prefix);
                     }
                 }
 
@@ -633,7 +633,7 @@ class binary_writer
                 if (use_type and not j.m_value.object->empty())
                 {
                     assert(use_count);
-                    const char first_prefix = ubjson_prefix(j.front());
+                    const CharType first_prefix = ubjson_prefix(j.front());
                     const bool same_prefix = std::all_of(j.begin(), j.end(),
                                                          [this, first_prefix](const BasicJsonType & v)
                     {
@@ -644,7 +644,7 @@ class binary_writer
                     {
                         prefix_required = false;
                         oa->write_character(static_cast<CharType>('$'));
-                        oa->write_character(static_cast<CharType>(first_prefix));
+                        oa->write_character(first_prefix);
                     }
                 }
 
@@ -712,7 +712,7 @@ class binary_writer
     {
         if (add_prefix)
         {
-            oa->write_character(static_cast<CharType>('D'));  // float64
+            oa->write_character(get_ubjson_float_prefix(n));
         }
         write_number(n);
     }
@@ -833,7 +833,7 @@ class binary_writer
           write_number_with_ubjson_prefix. Therefore, we return 'L' for any
           value that does not fit the previous limits.
     */
-    char ubjson_prefix(const BasicJsonType& j) const noexcept
+    CharType ubjson_prefix(const BasicJsonType& j) const noexcept
     {
         switch (j.type())
         {
@@ -892,7 +892,7 @@ class binary_writer
             }
 
             case value_t::number_float:
-                return 'D';
+                return get_ubjson_float_prefix(j.m_value.number_float);
 
             case value_t::string:
                 return 'S';
@@ -908,6 +908,36 @@ class binary_writer
         }
     }
 
+    static constexpr CharType get_cbor_float_prefix(float)
+    {
+        return static_cast<CharType>(0xFA);  // Single-Precision Float
+    }
+
+    static constexpr CharType get_cbor_float_prefix(double)
+    {
+        return static_cast<CharType>(0xFB);  // Double-Precision Float
+    }
+
+    static constexpr CharType get_msgpack_float_prefix(float)
+    {
+        return static_cast<CharType>(0xCA);  // float 32
+    }
+
+    static constexpr CharType get_msgpack_float_prefix(double)
+    {
+        return static_cast<CharType>(0xCB);  // float 64
+    }
+
+    static constexpr CharType get_ubjson_float_prefix(float)
+    {
+        return 'd';  // float 32
+    }
+
+    static constexpr CharType get_ubjson_float_prefix(double)
+    {
+        return 'D';  // float 64
+    }
+
   private:
     /// whether we can assume little endianess
     const bool is_little_endian = binary_reader<BasicJsonType>::little_endianess();

include/nlohmann/detail/output/serializer.hpp

@@ -9,17 +9,14 @@
 #include <cstddef> // size_t, ptrdiff_t
 #include <cstdint> // uint8_t
 #include <cstdio> // snprintf
-#include <iomanip> // setfill
-#include <iterator> // next
 #include <limits> // numeric_limits
 #include <string> // string
-#include <sstream> // stringstream
 #include <type_traits> // is_same
 
 #include <nlohmann/detail/exceptions.hpp>
 #include <nlohmann/detail/conversions/to_chars.hpp>
 #include <nlohmann/detail/macro_scope.hpp>
-#include <nlohmann/detail/meta.hpp>
+#include <nlohmann/detail/meta/cpp_future.hpp>
 #include <nlohmann/detail/output/output_adapters.hpp>
 #include <nlohmann/detail/value_t.hpp>
 
@@ -389,9 +386,9 @@ class serializer
 
                 case UTF8_REJECT:  // decode found invalid UTF-8 byte
                 {
-                    std::stringstream ss;
-                    ss << std::setw(2) << std::uppercase << std::setfill('0') << std::hex << static_cast<int>(byte);
-                    JSON_THROW(type_error::create(316, "invalid UTF-8 byte at index " + std::to_string(i) + ": 0x" + ss.str()));
+                    std::string sn(3, '\0');
+                    snprintf(&sn[0], sn.size(), "%.2X", byte);
+                    JSON_THROW(type_error::create(316, "invalid UTF-8 byte at index " + std::to_string(i) + ": 0x" + sn));
                 }
 
                 default:  // decode found yet incomplete multi-byte code point
@@ -417,9 +414,9 @@ class serializer
         else
         {
             // we finish reading, but do not accept: string was incomplete
-            std::stringstream ss;
-            ss << std::setw(2) << std::uppercase << std::setfill('0') << std::hex << static_cast<int>(static_cast<uint8_t>(s.back()));
-            JSON_THROW(type_error::create(316, "incomplete UTF-8 string; last byte: 0x" + ss.str()));
+            std::string sn(3, '\0');
+            snprintf(&sn[0], sn.size(), "%.2X", static_cast<uint8_t>(s.back()));
+            JSON_THROW(type_error::create(316, "incomplete UTF-8 string; last byte: 0x" + sn));
         }
     }
 
@@ -445,7 +442,7 @@ class serializer
             return;
         }
 
-        const bool is_negative = (x <= 0) and (x != 0);  // see issue #755
+        const bool is_negative = not (x >= 0);  // see issue #755
         std::size_t i = 0;
 
         while (x != 0)

include/nlohmann/json_fwd.hpp

@@ -18,10 +18,10 @@ namespace nlohmann
 @brief default JSONSerializer template argument
 
 This serializer ignores the template arguments and uses ADL
-([argument-dependent lookup](http://en.cppreference.com/w/cpp/language/adl))
+([argument-dependent lookup](https://en.cppreference.com/w/cpp/language/adl))
 for serialization.
 */
-template<typename = void, typename = void>
+template<typename T = void, typename SFINAE = void>
 struct adl_serializer;
 
 template<template<typename U, typename V, typename... Args> class ObjectType =

meson.build

@@ -1,7 +1,13 @@
-project('nlohmann_json', 'cpp')
-
-nlohmann_json_inc = include_directories('single_include/nlohmann')
+project('nlohmann_json',
+    'cpp',
+    version : '3.3.0',
+    license : 'MIT',
+)
 
 nlohmann_json_dep = declare_dependency(
-  include_directories : nlohmann_json_inc
+    include_directories: include_directories('single_include')
+)
+
+nlohmann_json_multiple_headers = declare_dependency(
+    include_directories: include_directories('include')
 )

test/CMakeLists.txt

@@ -6,15 +6,14 @@ option(JSON_Coverage "Build test suite with coverage information" OFF)
 if(JSON_Sanitizer)
     message(STATUS "Building test suite with Clang sanitizer")
     if(NOT MSVC)
-        set(CMAKE_CXX_FLAGS "-std=c++11 -g -O2 -fsanitize=address -fsanitize=undefined -fno-omit-frame-pointer")
+        set(CMAKE_CXX_FLAGS "-g -O2 -fsanitize=address -fsanitize=undefined -fno-omit-frame-pointer")
     endif()
 endif()
 
 if(JSON_Valgrind)
     find_program(CMAKE_MEMORYCHECK_COMMAND valgrind)
     message(STATUS "Executing test suite with Valgrind (${CMAKE_MEMORYCHECK_COMMAND})")
-    set(MEMORYCHECK_COMMAND_OPTIONS "--error-exitcode=1 --leak-check=full")
-    set(memcheck_command "${CMAKE_MEMORYCHECK_COMMAND} ${CMAKE_MEMORYCHECK_COMMAND_OPTIONS}")
+    set(memcheck_command "${CMAKE_MEMORYCHECK_COMMAND} ${CMAKE_MEMORYCHECK_COMMAND_OPTIONS} --error-exitcode=1 --leak-check=full")
     separate_arguments(memcheck_command)
 endif()
 
@@ -62,11 +61,10 @@ add_library(catch_main OBJECT
     "src/unit.cpp"
 )
 set_target_properties(catch_main PROPERTIES
-    CXX_STANDARD 11
-    CXX_STANDARD_REQUIRED ON
     COMPILE_DEFINITIONS "$<$<CXX_COMPILER_ID:MSVC>:_SCL_SECURE_NO_WARNINGS>"
     COMPILE_OPTIONS "$<$<CXX_COMPILER_ID:MSVC>:/EHsc;$<$<CONFIG:Release>:/Od>>"
 )
+target_compile_features(catch_main PUBLIC cxx_std_11)
 target_include_directories(catch_main PRIVATE "thirdparty/catch")
 
 # https://stackoverflow.com/questions/2368811/how-to-set-warning-level-in-cmake
@@ -83,6 +81,9 @@ if(MSVC)
 	# Disable warning C4566: character represented by universal-character-name '\uFF01' cannot be represented in the current code page (1252)
 	# Disable warning C4996: 'nlohmann::basic_json<std::map,std::vector,std::string,bool,int64_t,uint64_t,double,std::allocator,nlohmann::adl_serializer>::operator <<': was declared deprecated
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /wd4389 /wd4309 /wd4566 /wd4996")
+	
+	# https://github.com/nlohmann/json/issues/1114
+	set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} /bigobj")
 endif()
 
 #############################################################################
@@ -95,23 +96,21 @@ foreach(file ${files})
     string(REGEX REPLACE "unit-([^$]+)" "test-\\1" testcase ${file_basename})
 
     add_executable(${testcase} $<TARGET_OBJECTS:catch_main> ${file})
-    set_target_properties(${testcase} PROPERTIES
-        CXX_STANDARD 11
-        CXX_STANDARD_REQUIRED ON
-        COMPILE_DEFINITIONS "$<$<CXX_COMPILER_ID:MSVC>:_SCL_SECURE_NO_WARNINGS>"
-        COMPILE_OPTIONS "$<$<CXX_COMPILER_ID:MSVC>:/EHsc;$<$<CONFIG:Release>:/Od>>"
+    target_compile_definitions(${testcase} PRIVATE
+      CATCH_CONFIG_FAST_COMPILE
+      $<$<CXX_COMPILER_ID:MSVC>:_SCL_SECURE_NO_WARNINGS>
+    )
+    target_compile_options(${testcase} PRIVATE
+        $<$<CXX_COMPILER_ID:MSVC>:/EHsc;$<$<CONFIG:Release>:/Od>>
+        $<$<NOT:$<CXX_COMPILER_ID:MSVC>>:-Wno-deprecated;-Wno-float-equal>
+        $<$<CXX_COMPILER_ID:GNU>:-Wno-deprecated-declarations>
+    )
+    target_include_directories(${testcase} PRIVATE
+        thirdparty/catch
+        thirdparty/fifo_map
     )
-
-    target_compile_definitions(${testcase} PRIVATE CATCH_CONFIG_FAST_COMPILE)
-    target_include_directories(${testcase} PRIVATE "thirdparty/catch")
-    target_include_directories(${testcase} PRIVATE "thirdparty/fifo_map")
-    target_include_directories(${testcase} PRIVATE ${NLOHMANN_JSON_INCLUDE_BUILD_DIR})
     target_link_libraries(${testcase} ${NLOHMANN_JSON_TARGET_NAME})
 
-    if(NOT MSVC)
-        set_target_properties(${testcase} PROPERTIES COMPILE_FLAGS "${CMAKE_CXX_FLAGS} -Wno-deprecated -Wno-float-equal")
-    endif()
-
     add_test(NAME "${testcase}_default"
       COMMAND ${testcase} ${CATCH_TEST_FILTER}
       WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}
@@ -131,5 +130,11 @@ foreach(file ${files})
         )
         set_tests_properties("${testcase}_valgrind" PROPERTIES LABELS "valgrind")
     endif()
-
 endforeach()
+
+#############################################################################
+# Test the generated build configs
+#############################################################################
+add_subdirectory(cmake_import)
+add_subdirectory(cmake_import_minver)
+add_subdirectory(cmake_add_subdirectory)

test/Makefile

@@ -42,7 +42,8 @@ SOURCES = src/unit.cpp \
           src/unit-serialization.cpp \
           src/unit-testsuites.cpp \
           src/unit-ubjson.cpp \
-          src/unit-unicode.cpp
+          src/unit-unicode.cpp \
+          src/unit-wstring.cpp
 
 OBJECTS = $(SOURCES:.cpp=.o)
 

test/cmake_add_subdirectory/CMakeLists.txt

@@ -0,0 +1,15 @@
+add_test(NAME cmake_add_subdirectory_configure
+  COMMAND ${CMAKE_COMMAND}
+    -G "${CMAKE_GENERATOR}"
+    -Dnlohmann_json_source=${PROJECT_SOURCE_DIR}
+    ${CMAKE_CURRENT_SOURCE_DIR}/project
+)
+add_test(NAME cmake_add_subdirectory_build
+  COMMAND ${CMAKE_COMMAND} --build .
+)
+set_tests_properties(cmake_add_subdirectory_configure PROPERTIES
+  FIXTURES_SETUP cmake_add_subdirectory
+)
+set_tests_properties(cmake_add_subdirectory_build PROPERTIES
+  FIXTURES_REQUIRED cmake_add_subdirectory
+)