Merge pull request nlohmann#44 from nlohmann/develop

Sync Fork from Upstream Repo
GerHobbelt · Apr 30, 2021 · f1cd13d · f1cd13d
2 parents fb9099d + b2e784c
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diff --git a/.github/CONTRIBUTING.md b/.github/CONTRIBUTING.md
@@ -58,7 +58,7 @@ To make changes, you need to edit the following files:
 - 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](https://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.
- - We do not preserve the **insertion order of object elements**. The [JSON standard](https://tools.ietf.org/html/rfc7159.html) defines objects as "an unordered collection of zero or more name/value pairs". To this end, this library does not preserve insertion order of name/value pairs. (In fact, keys will be traversed in alphabetical order as `std::map` with `std::less` is used by default.) Note this behavior conforms to the standard, and we shall not change it to any other order. If you do want to preserve the insertion order, you can specialize the object type with containers like [`tsl::ordered_map`](https://github.com/Tessil/ordered-map) or [`nlohmann::fifo_map`](https://github.com/nlohmann/fifo_map).
+ - We do not preserve the **insertion order of object elements**. The [JSON standard](https://tools.ietf.org/html/rfc8259.html) defines objects as "an unordered collection of zero or more name/value pairs". To this end, this library does not preserve insertion order of name/value pairs. (In fact, keys will be traversed in alphabetical order as `std::map` with `std::less` is used by default.) Note this behavior conforms to the standard, and we shall not change it to any other order. If you do want to preserve the insertion order, you can specialize the object type with containers like [`tsl::ordered_map`](https://github.com/Tessil/ordered-map) or [`nlohmann::fifo_map`](https://github.com/nlohmann/fifo_map).
 
 - Please do not open pull requests that address **multiple issues**.
 

diff --git a/doc/images/json_syntax_number.png b/doc/images/json_syntax_number.png
diff --git a/doc/mkdocs/Makefile b/doc/mkdocs/Makefile
@@ -12,7 +12,7 @@ prepare_files: clean
  # create subfolders
  mkdir docs/images docs/examples
  # copy images
- cp -vr ../json.gif ../images/range-begin-end.svg ../images/range-rbegin-rend.svg ../images/callback_events.png docs/images
+ cp -vr ../json.gif ../images/range-begin-end.svg ../images/range-rbegin-rend.svg ../images/callback_events.png ../images/json_syntax_number.png docs/images
  # copy examples
  cp -vr ../examples/*.cpp ../examples/*.output docs/examples
 

diff --git a/doc/mkdocs/docs/api/basic_json/array_t.md b/doc/mkdocs/docs/api/basic_json/array_t.md
@@ -6,7 +6,7 @@ using array_t = ArrayType<basic_json, AllocatorType<basic_json>>;
 
 The type used to store JSON arrays.
 
-[RFC 7159](http://rfc7159.net/rfc7159) describes JSON arrays as follows:
+[RFC 8259](https://tools.ietf.org/html/rfc8259) describes JSON arrays as follows:
 > An array is an ordered sequence of zero or more values.
 
 To store objects in C++, a type is defined by the template parameters explained below.
@@ -35,7 +35,7 @@ std::vector<
 
 #### Limits
 
-[RFC 7159](http://rfc7159.net/rfc7159) specifies:
+[RFC 8259](https://tools.ietf.org/html/rfc8259) specifies:
 > An implementation may set limits on the maximum depth of nesting.
 
 In this class, the array's limit of nesting is not explicitly constrained. However, a maximum depth of nesting may be

diff --git a/doc/mkdocs/docs/api/basic_json/boolean_t.md b/doc/mkdocs/docs/api/basic_json/boolean_t.md
@@ -6,7 +6,7 @@ using boolean_t = BooleanType;
 
 The type used to store JSON booleans.
 
-[RFC 7159](http://rfc7159.net/rfc7159) implicitly describes a boolean as a type which differentiates the two literals
+[RFC 8259](https://tools.ietf.org/html/rfc8259) implicitly describes a boolean as a type which differentiates the two literals
 `#!json true` and `#!json false`.
 
 To store objects in C++, a type is defined by the template parameter `BooleanType` which chooses the type to use.

diff --git a/doc/mkdocs/docs/api/basic_json/number_float_t.md b/doc/mkdocs/docs/api/basic_json/number_float_t.md
@@ -6,7 +6,7 @@ using number_float_t = NumberFloatType;
 
 The type used to store JSON numbers (floating-point).
 
-[RFC 7159](http://rfc7159.net/rfc7159) describes numbers as follows:
+[RFC 8259](https://tools.ietf.org/html/rfc8259) describes numbers as follows:
 > The representation of numbers is similar to that used in most programming languages. A number is represented in base
 > 10 using decimal digits. It contains an integer component that may be prefixed with an optional minus sign, which may
 > be followed by a fraction part and/or an exponent part. Leading zeros are not allowed. (...) Numeric values that
@@ -35,7 +35,7 @@ With the default values for `NumberFloatType` (`double`), the default value for
 
 #### Limits
 
-[RFC 7159](http://rfc7159.net/rfc7159) states:
+[RFC 8259](https://tools.ietf.org/html/rfc8259) states:
 > This specification allows implementations to set limits on the range and precision of numbers accepted. Since software
 > that implements IEEE 754-2008 binary64 (double precision) numbers is generally available and widely used, good
 > interoperability can be achieved by implementations that expect no more precision or range than these provide, in the

diff --git a/doc/mkdocs/docs/api/basic_json/number_integer_t.md b/doc/mkdocs/docs/api/basic_json/number_integer_t.md
@@ -6,7 +6,7 @@ using number_integer_t = NumberIntegerType;
 
 The type used to store JSON numbers (integers).
 
-[RFC 7159](http://rfc7159.net/rfc7159) describes numbers as follows:
+[RFC 8259](https://tools.ietf.org/html/rfc8259) describes numbers as follows:
 > The representation of numbers is similar to that used in most programming languages. A number is represented in base
 > 10 using decimal digits. It contains an integer component that may be prefixed with an optional minus sign, which may
 > be followed by a fraction part and/or an exponent part. Leading zeros are not allowed. (...) Numeric values that
@@ -36,15 +36,15 @@ With the default values for `NumberIntegerType` (`std::int64_t`), the default va
 
 #### Limits
 
-[RFC 7159](http://rfc7159.net/rfc7159) specifies:
+[RFC 8259](https://tools.ietf.org/html/rfc8259) specifies:
 > An implementation may set limits on the range and precision of numbers.
 
 When the default type is used, the maximal integer number that can be stored is `9223372036854775807` (INT64_MAX) and
 the minimal integer number that can be stored is `-9223372036854775808` (INT64_MIN). Integer numbers that are out of
 range will yield over/underflow when used in a constructor. During deserialization, too large or small integer numbers
 will be automatically be stored as [`number_unsigned_t`](number_unsigned_t.md) or [`number_float_t`](number_float_t.md).
 
-[RFC 7159](http://rfc7159.net/rfc7159) further states:
+[RFC 8259](https://tools.ietf.org/html/rfc8259) further states:
 > Note that when such software is used, numbers that are integers and are in the range \f$[-2^{53}+1, 2^{53}-1]\f$ are
 > interoperable in the sense that implementations will agree exactly on their numeric values.
 

diff --git a/doc/mkdocs/docs/api/basic_json/number_unsigned_t.md b/doc/mkdocs/docs/api/basic_json/number_unsigned_t.md
@@ -6,7 +6,7 @@ using number_unsigned_t = NumberUnsignedType;
 
 The type used to store JSON numbers (unsigned).
 
-[RFC 7159](http://rfc7159.net/rfc7159) describes numbers as follows:
+[RFC 8259](https://tools.ietf.org/html/rfc8259) describes numbers as follows:
 > The representation of numbers is similar to that used in most programming languages. A number is represented in base
 > 10 using decimal digits. It contains an integer component that may be prefixed with an optional minus sign, which may
 > be followed by a fraction part and/or an exponent part. Leading zeros are not allowed. (...) Numeric values that
@@ -36,15 +36,15 @@ With the default values for `NumberUnsignedType` (`std::uint64_t`), the default
 
 #### Limits
 
-[RFC 7159](http://rfc7159.net/rfc7159) specifies:
+[RFC 8259](https://tools.ietf.org/html/rfc8259) specifies:
 > An implementation may set limits on the range and precision of numbers.
 
 When the default type is used, the maximal integer number that can be stored is `18446744073709551615` (UINT64_MAX) and
 the minimal integer number that can be stored is `0`. Integer numbers that are out of range will yield over/underflow
 when used in a constructor. During deserialization, too large or small integer numbers will be automatically be stored
 as [`number_integer_t`](number_integer_t.md) or [`number_float_t`](number_float_t.md).
 
-[RFC 7159](http://rfc7159.net/rfc7159) further states:
+[RFC 8259](https://tools.ietf.org/html/rfc8259) further states:
 > Note that when such software is used, numbers that are integers and are in the range \f$[-2^{53}+1, 2^{53}-1]\f$ are
 > interoperable in the sense that implementations will agree exactly on their numeric values.
 

diff --git a/doc/mkdocs/docs/api/basic_json/object_t.md b/doc/mkdocs/docs/api/basic_json/object_t.md
@@ -9,7 +9,7 @@ using object_t = ObjectType<StringType,
 
 The type used to store JSON objects.
 
-[RFC 7159](http://rfc7159.net/rfc7159) describes JSON objects as follows:
+[RFC 8259](https://tools.ietf.org/html/rfc8259) describes JSON objects as follows:
 > An object is an unordered collection of zero or more name/value pairs, where a name is a string and a value is a
 > string, number, boolean, null, object, or array.
 
@@ -73,7 +73,7 @@ behavior:
 
 #### Limits
 
-[RFC 7159](http://rfc7159.net/rfc7159) specifies:
+[RFC 8259](https://tools.ietf.org/html/rfc8259) specifies:
 > An implementation may set limits on the maximum depth of nesting.
 
 In this class, the object's limit of nesting is not explicitly constrained. However, a maximum depth of nesting may be
@@ -90,7 +90,7 @@ Objects are stored as pointers in a `basic_json` type. That is, for any access t
 The order name/value pairs are added to the object is *not* preserved by the library. Therefore, iterating an object may
 return name/value pairs in a different order than they were originally stored. In fact, keys will be traversed in
 alphabetical order as `std::map` with `std::less` is used by default. Please note this behavior conforms to
-[RFC 7159](http://rfc7159.net/rfc7159), because any order implements the specified "unordered" nature of JSON objects.
+[RFC 8259](https://tools.ietf.org/html/rfc8259), because any order implements the specified "unordered" nature of JSON objects.
 
 ## Version history
 

diff --git a/doc/mkdocs/docs/api/basic_json/string_t.md b/doc/mkdocs/docs/api/basic_json/string_t.md
@@ -6,7 +6,7 @@ using string_t = StringType;
 
 The type used to store JSON strings.
 
-[RFC 7159](http://rfc7159.net/rfc7159) describes JSON strings as follows:
+[RFC 8259](https://tools.ietf.org/html/rfc8259) describes JSON strings as follows:
 > A string is a sequence of zero or more Unicode characters.
 
 To store objects in C++, a type is defined by the template parameter described below. Unicode values are split by the
@@ -31,7 +31,7 @@ the number of bytes in the string rather than the number of characters or glyphs
 
 #### String comparison
 
-[RFC 7159](http://rfc7159.net/rfc7159) states:
+[RFC 8259](https://tools.ietf.org/html/rfc8259) states:
 > Software implementations are typically required to test names of object members for equality. Implementations that
 > transform the textual representation into sequences of Unicode code units and then perform the comparison numerically,
 > code unit by code unit, are interoperable in the sense that implementations will agree in all cases on equality or

diff --git a/doc/mkdocs/docs/features/iterators.md b/doc/mkdocs/docs/features/iterators.md
@@ -10,7 +10,7 @@ As for other containers, `begin()` returns an iterator to the first value and `e
 
 ### Iteration order for objects
 
-When iterating over objects, values are ordered with respect to the `object_comparator_t` type which defaults to `std::less`. See the [types documentation](types.md#key-order) for more information.
+When iterating over objects, values are ordered with respect to the `object_comparator_t` type which defaults to `std::less`. See the [types documentation](types/index.md#key-order) for more information.
 
 ??? example
 

diff --git a/doc/mkdocs/docs/features/macros.md b/doc/mkdocs/docs/features/macros.md
@@ -20,6 +20,10 @@ When enabled, exception messages contain a [JSON Pointer](json_pointer.md) to th
 
 The diagnostics messages can also be controlled with the CMake option `JSON_Diagnostics` (`OFF` by default) which sets `JSON_DIAGNOSTICS` accordingly.
 
+## `JSON_HAS_CPP_11`, `JSON_HAS_CPP_14`, `JSON_HAS_CPP_17`, `JSON_HAS_CPP_20`
+
+The library targets C++11, but also supports some features introduced in later C++ versions (e.g., `std::string_view` support for C++17). For these new features, the library implements some preprocessor checks to determine the C++ standard. By defining any of these symbols, the internal check is overridden and the provided C++ version is unconditionally assumed. This can be helpful for compilers that only implement parts of the standard and would be detected incorrectly.
+
 ## `JSON_NOEXCEPTION`
 
 Exceptions can be switched off by defining the symbol `JSON_NOEXCEPTION`.

diff --git a/doc/mkdocs/docs/features/types.md → doc/mkdocs/docs/features/types/index.md b/doc/mkdocs/docs/features/types.md → doc/mkdocs/docs/features/types/index.md
@@ -1,4 +1,4 @@
-# Types
+# Overview
 
 This page gives an overview how JSON values are stored and how this can be configured.
 
@@ -107,7 +107,7 @@ using binary_t = nlohmann::byte_container_with_subtype<BinaryType>;
 
 ## Objects
 
-[RFC 7159](http://rfc7159.net/rfc7159) describes JSON objects as follows:
+[RFC 8259](https://tools.ietf.org/html/rfc8259) describes JSON objects as follows:
 
 > An object is an unordered collection of zero or more name/value pairs, where a name is a string and a value is a string, number, boolean, null, object, or array.
 
@@ -135,11 +135,11 @@ The choice of `object_t` influences the behavior of the JSON class. With the def
 
 ### Key order
 
-The order name/value pairs are added to the object is *not* preserved by the library. Therefore, iterating an object may return name/value pairs in a different order than they were originally stored. In fact, keys will be traversed in alphabetical order as `std::map` with `std::less` is used by default. Please note this behavior conforms to [RFC 7159](http://rfc7159.net/rfc7159), because any order implements the specified "unordered" nature of JSON objects.
+The order name/value pairs are added to the object is *not* preserved by the library. Therefore, iterating an object may return name/value pairs in a different order than they were originally stored. In fact, keys will be traversed in alphabetical order as `std::map` with `std::less` is used by default. Please note this behavior conforms to [RFC 8259](https://tools.ietf.org/html/rfc8259), because any order implements the specified "unordered" nature of JSON objects.
 
 ### Limits
 
-[RFC 7159](http://rfc7159.net/rfc7159) specifies:
+[RFC 8259](https://tools.ietf.org/html/rfc8259) specifies:
 
 > An implementation may set limits on the maximum depth of nesting.
 
@@ -152,7 +152,7 @@ Objects are stored as pointers in a `basic_json` type. That is, for any access t
 
 ## Arrays
 
-[RFC 7159](http://rfc7159.net/rfc7159) describes JSON arrays as follows:
+[RFC 8259](https://tools.ietf.org/html/rfc8259) describes JSON arrays as follows:
 
 > An array is an ordered sequence of zero or more values.
 
@@ -169,7 +169,7 @@ std::vector<
 
 ### Limits
 
-[RFC 7159](http://rfc7159.net/rfc7159) specifies:
+[RFC 8259](https://tools.ietf.org/html/rfc8259) specifies:
 
 > An implementation may set limits on the maximum depth of nesting.
 
@@ -182,7 +182,7 @@ Arrays are stored as pointers in a `basic_json` type. That is, for any access to
 
 ## Strings
 
-[RFC 7159](http://rfc7159.net/rfc7159) describes JSON strings as follows:
+[RFC 8259](https://tools.ietf.org/html/rfc8259) describes JSON strings as follows:
 
 > A string is a sequence of zero or more Unicode characters.
 
@@ -198,7 +198,7 @@ Strings are stored in UTF-8 encoding. Therefore, functions like `std::string::si
 
 ### String comparison
 
-[RFC 7159](http://rfc7159.net/rfc7159) states:
+[RFC 8259](https://tools.ietf.org/html/rfc8259) states:
 
 > Software implementations are typically required to test names of object members for equality. Implementations that transform the textual representation into sequences of Unicode code units and then perform the comparison numerically, code unit by code unit, are interoperable in the sense that implementations will agree in all cases on equality or inequality of two strings. For example, implementations that compare strings with escaped characters unconverted may incorrectly find that `"a\\b"` and `"a\u005Cb"` are not equal.
 
@@ -211,7 +211,7 @@ String values are stored as pointers in a `basic_json` type. That is, for any ac
 
 ## Booleans
 
-[RFC 7159](http://rfc7159.net/rfc7159) implicitly describes a boolean as a type which differentiates the two literals `true` and `false`.
+[RFC 8259](https://tools.ietf.org/html/rfc8259) implicitly describes a boolean as a type which differentiates the two literals `true` and `false`.
 
 ### Default type
 
@@ -223,7 +223,9 @@ Boolean values are stored directly inside a `basic_json` type.
 
 ## Numbers
 
-[RFC 7159](http://rfc7159.net/rfc7159) describes numbers as follows:
+See the [number handling](number_handling.md) article for a detailed discussion on how numbers are handled by this library.
+
+[RFC 8259](https://tools.ietf.org/html/rfc8259) describes numbers as follows:
 
 > The representation of numbers is similar to that used in most programming languages. A number is represented in base 10 using decimal digits. It contains an integer component that may be prefixed with an optional minus sign, which may be followed by a fraction part and/or an exponent part. Leading zeros are not allowed. (...) Numeric values that cannot be represented in the grammar below (such as Infinity and NaN) are not permitted.
 
@@ -242,21 +244,21 @@ With the default values for *NumberFloatType* (`#!cpp double`), the default valu
 
 ### Limits
 
-[RFC 7159](http://rfc7159.net/rfc7159) specifies:
+[RFC 8259](https://tools.ietf.org/html/rfc8259) specifies:
 
 > An implementation may set limits on the range and precision of numbers.
 
 When the default type is used, the maximal integer number that can be stored is `#!c 9223372036854775807` (`INT64_MAX`) and the minimal integer number that can be stored is `#!c -9223372036854775808` (`INT64_MIN`). Integer numbers that are out of range will yield over/underflow when used in a constructor. During deserialization, too large or small integer numbers will be automatically be stored as `number_unsigned_t` or `number_float_t`.
 
 When the default type is used, the maximal unsigned integer number that can be stored is `#!c 18446744073709551615` (`UINT64_MAX`) and the minimal integer number that can be stored is `#!c 0`. Integer numbers that are out of range will yield over/underflow when used in a constructor. During deserialization, too large or small integer numbers will be automatically be stored as `number_integer_t` or `number_float_t`.
 
-[RFC 7159](http://rfc7159.net/rfc7159) further states:
+[RFC 8259](https://tools.ietf.org/html/rfc8259) further states:
 
 > Note that when such software is used, numbers that are integers and are in the range $[-2^{53}+1, 2^{53}-1]$ are interoperable in the sense that implementations will agree exactly on their numeric values.
 
 As this range is a subrange of the exactly supported range [`INT64_MIN`, `INT64_MAX`], this class's integer type is interoperable.
 
-[RFC 7159](http://rfc7159.net/rfc7159) states:
+[RFC 8259](https://tools.ietf.org/html/rfc8259) states:
 
 > This specification allows implementations to set limits on the range and precision of numbers accepted. Since software that implements IEEE 754-2008 binary64 (double precision) numbers is generally available and widely used, good interoperability can be achieved by implementations that expect no more precision or range than these provide, in the sense that implementations will approximate JSON numbers within the expected precision.