Merge branch 'develop' into json-view/02b-float-parser

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

# Conflicts:
#	tests/src/unit-class_lexer.cpp

README.md

@@ -1396,7 +1396,7 @@ THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR I
 - The class contains a slightly modified version of the Grisu2 algorithm from Florian Loitsch which is licensed under the [MIT License](https://opensource.org/licenses/MIT) (see above). Copyright © 2009 [Florian Loitsch](https://florian.loitsch.com/)
 - The class contains a copy of [Hedley](https://nemequ.github.io/hedley/) from Evan Nemerson which is licensed as [CC0-1.0](https://creativecommons.org/publicdomain/zero/1.0/).
 - The class contains parts of [Google Abseil](https://github.com/abseil/abseil-cpp) which is licensed under the [Apache 2.0 License](https://opensource.org/licenses/Apache-2.0).
-- The class contains an adapted version of the Eisel-Lemire algorithm and its table of powers of five from [fast_float](https://github.com/fastfloat/fast_float) by Daniel Lemire and contributors, which is available under the [MIT License](https://opensource.org/licenses/MIT) (used here), the Apache 2.0 License, and the Boost Software License. Copyright © 2021 The fast_float authors
+- The class contains an adapted version of the Eisel-Lemire algorithm, its table of powers of five, and its digit comparison for long numbers from [fast_float](https://github.com/fastfloat/fast_float) by Daniel Lemire and contributors, which is available under the [MIT License](https://opensource.org/licenses/MIT) (used here), the Apache 2.0 License, and the Boost Software License. Copyright © 2021 The fast_float authors
 
 <img align="right" src="https://git.fsfe.org/reuse/reuse-ci/raw/branch/master/reuse-horizontal.png" alt="REUSE Software">
 

docs/mkdocs/docs/api/basic_json/number_float_t.md

@@ -23,9 +23,10 @@ type to use.
 ## Template parameters
 
 `NumberFloatType`
-:   the type to store floating-point numbers. Parsing and serialization are implemented in terms of
+:   the type to store floating-point numbers. The parser converts `#!cpp float`, `#!cpp double`, and a
-    `#!cpp std::strtof`/`#!cpp std::strtod`/`#!cpp std::strtold` and `#!cpp std::snprintf`, so the type must be
+    `#!cpp long double` that is IEEE 754 binary64 itself and other `#!cpp long double` formats with
-    `#!cpp float`, `#!cpp double`, or `#!cpp long double`. The
+    `#!cpp std::from_chars` or `#!cpp std::strtold`, and serialization falls back to `#!cpp std::snprintf`, so the
+    type must be `#!cpp float`, `#!cpp double`, or `#!cpp long double`. The
     [binary formats](../../features/binary_formats/index.md) additionally require `#!cpp float` or `#!cpp double`,
     because they have no encoding for `#!cpp long double`. See
     [Template Parameter Requirements](../../features/types/template_parameters.md#numberfloattype).

docs/mkdocs/docs/api/macros/json_use_implicit_conversions.md

@@ -67,7 +67,7 @@ By default, implicit conversions are enabled.
     `JSON_USE_IMPLICIT_CONVERSIONS` is defined to `0`:
 
     ```cpp
-    using wjson = nlohmann::basic_json<std::map, std::vector, std::wstring>;
+    using wjson = nlohmann::json::with_string_t<std::wstring>;
 
     void load(const nlohmann::json& j);
 

docs/mkdocs/docs/examples/custom_array_type.cpp

@@ -1,11 +1,10 @@
 #include <iostream>
-#include <map>
 
 #include <nlohmann/json.hpp>
 
 #include "custom_array_type.hpp"
 
-using custom_json = nlohmann::basic_json<std::map, custom_array_type>;
+using custom_json = nlohmann::json::with_array_t<custom_array_type>;
 
 int main()
 {

docs/mkdocs/docs/examples/custom_binary_type.cpp

@@ -1,16 +1,10 @@
-#include <cstdint>
 #include <iostream>
-#include <map>
-#include <string>
-#include <vector>
 
 #include <nlohmann/json.hpp>
 
 #include "custom_binary_type.hpp"
 
-using custom_json = nlohmann::basic_json<std::map, std::vector, std::string, bool,
+using custom_json = nlohmann::json::with_binary_t<custom_binary_type>;
-      std::int64_t, std::uint64_t, double, std::allocator,
-      nlohmann::adl_serializer, custom_binary_type>;
 
 int main()
 {

docs/mkdocs/docs/examples/custom_object_type.cpp

@@ -1,12 +1,11 @@
 #include <iostream>
 #include <type_traits>
-#include <vector>
 
 #include <nlohmann/json.hpp>
 
 #include "custom_object_type.hpp"
 
-using custom_json = nlohmann::basic_json<custom_object_type, std::vector>;
+using custom_json = nlohmann::json::with_object_t<custom_object_type>;
 
 int main()
 {

docs/mkdocs/docs/examples/custom_string_type.cpp

@@ -1,12 +1,10 @@
 #include <iostream>
-#include <map>
-#include <vector>
 
 #include <nlohmann/json.hpp>
 
 #include "custom_string_type.hpp"
 
-using custom_json = nlohmann::basic_json<std::map, std::vector, custom_string_type>;
+using custom_json = nlohmann::json::with_string_t<custom_string_type>;
 
 int main()
 {

docs/mkdocs/docs/features/types/number_handling.md

@@ -82,12 +82,13 @@ flowchart TD
 
     - Numbers with a decimal digit or scientific notation are always stored as `#!c double`.
     - The number types can be changed, see [Template number types](#template-number-types). 
-    - Integers are converted by the library's own digit parser. Floating-point numbers are converted with
+    - The library converts integers and floating-point numbers itself, independent of the locale. Floating-point
-      [`std::from_chars`](https://en.cppreference.com/w/cpp/utility/from_chars) if the library is compiled with C++17
+      numbers are correctly rounded (to nearest, ties to even). Only a `#!c long double` that is not IEEE 754 binary64
-      and the standard library supports it, then with an exact fast path for `#!c double` values with few significant
+      (e.g., the 80-bit x87 format) is converted with `#!cpp std::from_chars` where available, or else with
-      digits, and otherwise with the locale-aware
+      [`std::strtold`](https://en.cppreference.com/w/cpp/string/byte/strtof). For that call, the library temporarily
-      [`std::strtod`](https://en.cppreference.com/w/cpp/string/byte/strtof) (`std::strtof`/`std::strtold` for the
+      replaces the `.` with the decimal point of the current locale (which may be longer than one byte, e.g., in
-      other floating-point types). Before version 3.13.0, the conversion was realized by
+      `fa_IR.UTF-8`), so the result does not depend on the locale either. Changing the locale in another thread during
+      parsing is undefined behavior of the C library, though. Before version 3.13.0, the conversion was realized by
       [`std::strtoull`](https://en.cppreference.com/w/cpp/string/byte/strtoul),
       [`std::strtoll`](https://en.cppreference.com/w/cpp/string/byte/strtol), and `std::strtod`, respectively.
 
@@ -100,10 +101,10 @@ flowchart TD
 ### Number limits
 
 - Any 64-bit signed or unsigned integer can be stored without loss of precision.
-- Numbers exceeding the limits of `#!c double` (i.e., numbers that after conversion via
+- Numbers exceeding the limits of `#!c double` (i.e., numbers whose rounded value is not satisfying
-[`std::strtod`](https://en.cppreference.com/w/cpp/string/byte/strtof) are not satisfying
 [`std::isfinite`](https://en.cppreference.com/w/cpp/numeric/math/isfinite) such as `#!c 1E400`) will throw exception
-[`json.exception.out_of_range.406`](../../home/exceptions.md#jsonexceptionout_of_range406) during parsing.
+[`json.exception.out_of_range.406`](../../home/exceptions.md#jsonexceptionout_of_range406) during parsing. Numbers too
+small for `#!c double` (such as `#!c 1E-400`) become zero, with the sign of the number.
 - Floating-point numbers are rounded to the next number representable as `double`. For instance
 `#!c 3.141592653589793238462643383279` is stored as [`0x400921fb54442d18`](https://float.exposed/0x400921fb54442d18).
 This is the same behavior as the code `#!c double x = 3.141592653589793238462643383279;`.
@@ -351,9 +352,8 @@ The number types can be changed with template parameters.
 
     A `basic_json` type that uses `#!c long double` as floating-point type.
 
-    ```cpp hl_lines="2"
+    ```cpp hl_lines="1"
-    using json_ld = nlohmann::basic_json<std::map, std::vector, std::string, bool,
+    using json_ld = nlohmann::json::with_float_t<long double>;
-                                         std::int64_t, std::uint64_t, long double>;
     ```
 
     Note values should then be parsed with `json_ld::parse` rather than `json::parse` as the latter would parse

docs/mkdocs/docs/features/types/template_parameters.md

@@ -8,6 +8,10 @@ these requirements so they do not have to be discovered by trial and error. Each
 that are known to work for that parameter and the ones that do not, checked against Boost 1.83, Abseil 20250127.0,
 Folly, EASTL 3.21, `ankerl::unordered_dense`, `phmap`, `gtl`, `robin_hood`, `tsl::ordered_map`, and Qt 6.
 
+To change a single template parameter and keep the others, use the member alias templates
+[`with_*_t`](../../api/basic_json/with_t.md); for instance, `nlohmann::json::with_float_t<long double>` is `json` with
+`#!cpp long double` as [`number_float_t`](../../api/basic_json/number_float_t.md).
+
 ## How to read this page
 
 Requirements are split into two groups:
@@ -26,9 +30,9 @@ Requirements are split into two groups:
     diagnosed with dedicated error messages, and violating most of them results in a compiler error somewhere inside
     the library. Four violations are not caught at compile time at all:
 
-    - A [`StringType`](#stringtype) whose `data()` is not null-terminated compiles and can silently misparse
+    - A [`StringType`](#stringtype) whose `data()` is not null-terminated compiles and silently misparses numbers
-      floating-point numbers, because the lexer may hand the buffer to `#!cpp std::strtod`, which reads up to the
+      stored as a `#!cpp long double` that is not IEEE 754 binary64 (e.g., the 80-bit x87 format), because the lexer
-      terminating null character.
+      hands the buffer to `#!cpp std::strtold`.
     - A stateful [`AllocatorType`](#allocatortype) compiles and silently ignores its state: allocation, deallocation,
       and [`get_allocator()`](../../api/basic_json/get_allocator.md) each use a different default-constructed instance.
     - The two [cross-specialization conversions](#cross-specialization-conversions) below. These abort on an assertion
@@ -143,7 +147,7 @@ struct unordered_map_object
     using base_t::base_t;
 };
 
-using unordered_json = nlohmann::basic_json<unordered_map_object>;
+using unordered_json = nlohmann::json::with_object_t<unordered_map_object>;
 ```
 
 Whether `#!cpp std::unordered_map` can be instantiated at all depends on the standard library: `object_t` is formed
@@ -176,7 +180,7 @@ struct flat_hash_object
     using base_t::base_t;
 };
 
-using flat_hash_json = nlohmann::basic_json<flat_hash_object>;
+using flat_hash_json = nlohmann::json::with_object_t<flat_hash_object>;
 ```
 
 `absl::node_hash_map` keeps references to the mapped values valid across insertions; `absl::flat_hash_map` does not,
@@ -537,9 +541,10 @@ therefore silently changes parse results rather than raising an error. See
 
 `NumberFloatType` must be one of `#!cpp float`, `#!cpp double`, or `#!cpp long double`:
 
-- The [parser](../parsing/index.md) converts number literals with `#!cpp std::from_chars` or, as a fallback, with
+- The [parser](../parsing/index.md) converts number literals to `#!cpp float`, `#!cpp double`, and a
-  `#!cpp std::strtof`, `#!cpp std::strtod`, or `#!cpp std::strtold`; the library provides overloads for exactly these
+  `#!cpp long double` that is IEEE 754 binary64 itself; other `#!cpp long double` formats are converted with
-  three types.
+  `#!cpp std::from_chars` where available, or with `#!cpp std::strtold`. The library provides overloads for exactly
+  these three types.
 - [`dump`](../../api/basic_json/dump.md) falls back to `#!cpp std::snprintf` with the `%g` and `%Lg` conversion
   specifiers, for which the library likewise provides only `#!cpp double` and `#!cpp long double` overloads
   (`#!cpp float` is promoted to `#!cpp double`).

docs/mkdocs/docs/home/license.md

@@ -20,4 +20,4 @@ The class contains a slightly modified version of the Grisu2 algorithm from Flor
 
 The class contains a copy of [Hedley](https://nemequ.github.io/hedley/) from Evan Nemerson which is licensed as [CC0-1.0](https://creativecommons.org/publicdomain/zero/1.0/).
 
-The class contains an adapted version of the Eisel-Lemire algorithm and its table of powers of five from [fast_float](https://github.com/fastfloat/fast_float) by Daniel Lemire and contributors, which is available under the [MIT License](https://opensource.org/licenses/MIT) (used here), the Apache 2.0 License, and the Boost Software License. Copyright © 2021 The fast_float authors
+The class contains an adapted version of the Eisel-Lemire algorithm, its table of powers of five, and its digit comparison for long numbers from [fast_float](https://github.com/fastfloat/fast_float) by Daniel Lemire and contributors, which is available under the [MIT License](https://opensource.org/licenses/MIT) (used here), the Apache 2.0 License, and the Boost Software License. Copyright © 2021 The fast_float authors

docs/mkdocs/docs/integration/migration_guide.md

@@ -116,7 +116,7 @@ function to use instead.
     === "Deprecated"
   
           ```cpp
-          using my_json = nlohmann::basic_json<std::map, std::vector, my_string_type>;
+          using my_json = nlohmann::json::with_string_t<my_string_type>;
           nlohmann::json_pointer<my_json> ptr("/foo/bar/1");
           ```
   

include/nlohmann/detail/bit_ops.hpp

@@ -9,12 +9,15 @@
 #pragma once
 
 #include <cstdint> // uint64_t
+#if !defined(__SIZEOF_INT128__) && defined(_MSC_VER) && (defined(_M_X64) || defined(_M_ARM64))
+    #include <intrin0.h> // __umulh, _umul128
+#endif
 
 #include <nlohmann/detail/abi_macros.hpp>
 
 // Portable bit-level helpers for the number and string scanners. They use
-// compiler builtins where available and plain C++ otherwise, so they need no
+// compiler builtins or platform-specific intrinsics where available and plain
-// platform headers and work regardless of byte order.
+// C++ otherwise, so they work regardless of byte order.
 
 NLOHMANN_JSON_NAMESPACE_BEGIN
 namespace detail
@@ -39,6 +42,25 @@ inline int count_leading_zeros(std::uint64_t x) noexcept
 #endif
 }
 
+/// number of trailing zero bits of x (x != 0)
+inline int count_trailing_zeros(std::uint64_t x) noexcept
+{
+#if defined(__GNUC__) || defined(__clang__)
+    return __builtin_ctzll(x);
+#else
+    int n = 0;
+    for (int shift = 32; shift != 0; shift >>= 1)
+    {
+        if ((x << (64 - shift)) == 0)
+        {
+            n += shift;
+            x >>= shift;
+        }
+    }
+    return n;
+#endif
+}
+
 /// the 128-bit product of two 64-bit numbers
 struct uint128_parts
 {
@@ -52,6 +74,12 @@ inline uint128_parts full_multiplication(std::uint64_t a, std::uint64_t b) noexc
     __extension__ using uint128 = unsigned __int128;
     const uint128 r = static_cast<uint128>(a) * b;
     return {static_cast<std::uint64_t>(r), static_cast<std::uint64_t>(r >> 64u)};
+#elif defined(_MSC_VER) && defined(_M_X64)
+    std::uint64_t high = 0;
+    const std::uint64_t low = _umul128(a, b, &high);
+    return {low, high};
+#elif defined(_MSC_VER) && defined(_M_ARM64)
+    return {a * b, __umulh(a, b)};
 #else
     const std::uint64_t a_lo = a & 0xFFFFFFFFu;
     const std::uint64_t a_hi = a >> 32u;
@@ -68,14 +96,19 @@ inline uint128_parts full_multiplication(std::uint64_t a, std::uint64_t b) noexc
 
 /// eight bytes as a little-endian word (compilers fold this into one load on
 /// little-endian targets)
-inline std::uint64_t read_eight_bytes(const char* p) noexcept
+inline std::uint64_t read_eight_bytes(const unsigned char* b) noexcept
 {
-    const auto* b = reinterpret_cast<const unsigned char*>(p); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
     return static_cast<std::uint64_t>(b[0]) | (static_cast<std::uint64_t>(b[1]) << 8u)
            | (static_cast<std::uint64_t>(b[2]) << 16u) | (static_cast<std::uint64_t>(b[3]) << 24u)
            | (static_cast<std::uint64_t>(b[4]) << 32u) | (static_cast<std::uint64_t>(b[5]) << 40u)
            | (static_cast<std::uint64_t>(b[6]) << 48u) | (static_cast<std::uint64_t>(b[7]) << 56u);
 }
 
+/// eight bytes as a little-endian word
+inline std::uint64_t read_eight_bytes(const char* p) noexcept
+{
+    return read_eight_bytes(reinterpret_cast<const unsigned char*>(p)); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
+}
+
 }  // namespace detail
 NLOHMANN_JSON_NAMESPACE_END

include/nlohmann/detail/input/lexer.hpp

@@ -221,6 +221,44 @@ class lexer : public lexer_base<BasicJsonType>
     // scan functions
     /////////////////////
 
+    /// contiguous input: try to decode the 4 hex digits following `\\u`
+    /// directly from the input buffer via hex_codepoint(), instead of 4 calls
+    /// to get(). On success, advances the adapter and the position counters
+    /// exactly as those 4 get() calls would (a hex digit is never '\n', so
+    /// only the flat counters move) and leaves @a current holding the last of
+    /// the 4 digits, just as the last such get() would; the codepoint is
+    /// written to @a out. Makes no state change and returns false - for a
+    /// pending unget, fewer than 4 remaining bytes, or any of the 4 bytes not
+    /// being a hex digit - so the caller falls back unchanged to the
+    /// per-character loop, which then reports the same diagnostic (stopping
+    /// at the first invalid digit) as before this optimization.
+    bool get_codepoint_bulk(std::true_type /*bulk*/, int& out)
+    {
+        if (next_unget || ia.bulk_remaining() < 4)
+        {
+            return false;
+        }
+        const char_type* const raw = ia.bulk_data();
+        const int codepoint = hex_codepoint(reinterpret_cast<const unsigned char*>(raw));
+        if (codepoint < 0)
+        {
+            return false;
+        }
+        ia.bulk_skip(4);
+        // a hex digit is never a newline, so only the flat counters advance
+        position.chars_read_total += 4;
+        position.chars_read_current_line += 4;
+        current = char_traits<char_type>::to_int_type(raw[3]);
+        out = codepoint;
+        return true;
+    }
+
+    /// streaming input: no bulk fast path
+    bool get_codepoint_bulk(std::false_type /*bulk*/, int& /*out*/) const noexcept
+    {
+        return false;
+    }
+
     /*!
     @brief get codepoint from 4 hex characters following `\\u`
 
@@ -240,6 +278,14 @@ class lexer : public lexer_base<BasicJsonType>
     {
         // this function only makes sense after reading `\u`
         JSON_ASSERT(current == 'u');
+
+        // contiguous input: decode all 4 hex digits directly from the buffer
+        int fast_codepoint = 0;
+        if (get_codepoint_bulk(std::integral_constant<bool, bulk_scan> {}, fast_codepoint))
+        {
+            return fast_codepoint;
+        }
+
         int codepoint = 0;
 
         const auto factors = { 12u, 8u, 4u, 0u };
@@ -1044,9 +1090,11 @@ class lexer : public lexer_base<BasicJsonType>
             token_type::parse_error otherwise
 
     @note The scanner is independent of the current locale: token_buffer
-          always holds `.`. Only the std::strtod fallback of convert_number()
+          always holds `.`. The conversion of float and double does not use
-          depends on the locale, and it looks up the decimal point right
+          the locale either. Only the std::strtold fallback of
-          before converting (see detail::convert_float_locale_aware()).
+          convert_number() for long double formats other than binary64
+          depends on it, and it looks up the decimal point right before
+          converting (see detail::convert_float_locale_aware()).
     */
     token_type scan_number()  // lgtm [cpp/use-of-goto] `goto` is used in this function to implement the number-parsing state machine described above. By design, any finite input will eventually reach the "done" state or return token_type::parse_error. In each intermediate state, 1 byte of the input is appended to the token_buffer vector, and only the already initialized variables token_buffer, number_type, and error_message are manipulated.
     {
@@ -1059,7 +1107,7 @@ class lexer : public lexer_base<BasicJsonType>
 
         // offset just past the last mantissa byte in token_buffer (i.e. the
         // index of 'e'/'E', or the whole token when there is no exponent).
-        // convert_number() uses it to count significant digits; npos means
+        // convert_number() uses it to split the token; npos means
         // "not seen an exponent yet" and is resolved at scan_number_done
         std::size_t mantissa_end = std::string::npos;
 
@@ -1389,8 +1437,8 @@ scan_number_done:
     @param[in] mantissa_end  offset just past the last mantissa byte in
                              token_buffer (the index of 'e'/'E', or
                              token_buffer.size() when there is no exponent);
-                             used to skip Clinger's fast path when it cannot
+                             with decimal_point_position, it locates the parts
-                             possibly succeed - see detail::mantissa_fits_clinger()
+                             of a float token without scanning it again
     */
     token_type convert_number(token_type number_type, std::size_t mantissa_end)
     {
@@ -1444,10 +1492,11 @@ scan_number_done:
         }
 
         // this code is reached if we parse a floating-point number or if an
-        // integer conversion above overflowed. Prefer std::from_chars
+        // integer conversion above overflowed. float and double (and long
-        // (Eisel-Lemire, locale-independent, correctly rounded) when available;
+        // double where it is binary64) are converted by the library itself,
-        // otherwise the exact Clinger fast path (double only); otherwise the
+        // correctly rounded and independent of the locale; other long double
-        // locale-aware strtof/strtod/strtold.
+        // formats use std::from_chars when available, otherwise the
+        // locale-aware strtold.
         if (convert_float_fast(num_begin, num_end, decimal_point_position, mantissa_end, value_float))
         {
             return token_type::value_float;

include/nlohmann/detail/input/pow5_table.hpp

@@ -22,6 +22,10 @@ namespace detail
 constexpr std::int64_t pow5_128_smallest_power = -342;
 constexpr std::int64_t pow5_128_largest_power = 308;
 
+// every entry of pow5_128() holds two 64-bit halves of 5^q, one per covered power of 5
+static_assert((pow5_128_largest_power - pow5_128_smallest_power + 1) * 2 == 1302,
+              "pow5_128_smallest_power/pow5_128_largest_power must match the size of the pow5_128() table");
+
 /*!
 @brief 128-bit approximations of 5^q for q in [-342, 308]
 

include/nlohmann/detail/input/string_scan.hpp

@@ -8,10 +8,12 @@
 
 #pragma once
 
+#include <array> // array
 #include <cstddef> // size_t
-#include <cstdint> // uint64_t
+#include <cstdint> // uint64_t, uint8_t
 #include <cstring> // memcpy
 
+#include <nlohmann/detail/bit_ops.hpp>
 #include <nlohmann/detail/macro_scope.hpp>
 
 // Optional SIMD backend for bulk UTF-8 validation. This is an opt-in external
@@ -69,18 +71,12 @@ inline std::size_t find_string_special(const unsigned char* data, std::size_t n)
     std::size_t i = 0;
     for (; i + 8 <= n; i += 8)
     {
-        std::uint64_t word = 0;
+        const std::uint64_t special = swar_string_special(read_eight_bytes(data + i));
-        std::memcpy(&word, data + i, sizeof(word));
+        if (special != 0)
-        if (swar_string_special(word) != 0)
         {
-            // a special byte is in this word; locate it (endian-agnostic)
+            // the lowest flagged byte is the first special one: the borrows of
-            for (std::size_t j = 0; j < 8; ++j)
+            // the subtractions can only flag bytes above a true hit
-            {
+            return i + (static_cast<std::size_t>(count_trailing_zeros(special)) / 8);
-                if (is_string_special(data[i + j]))
-                {
-                    return i + j;
-                }
-            }
         }
     }
     for (; i < n; ++i)
@@ -114,8 +110,7 @@ inline std::size_t find_ascii_copyable_run(const unsigned char* data, std::size_
     std::size_t i = 0;
     for (; i + 8 <= n; i += 8)
     {
-        std::uint64_t v = 0;
+        const std::uint64_t v = read_eight_bytes(data + i);
-        std::memcpy(&v, data + i, sizeof(v));
         const std::uint64_t q = v ^ 0x2222222222222222ull; // '"'  (0x22)
         const std::uint64_t b = v ^ 0x5C5C5C5C5C5C5C5Cull; // '\\' (0x5C)
         const std::uint64_t d = v ^ 0x7F7F7F7F7F7F7F7Full; // DEL  (0x7F)
@@ -126,7 +121,9 @@ inline std::size_t find_ascii_copyable_run(const unsigned char* data, std::size_
                                    | (v & high);               // >= 0x80
         if (stop != 0)
         {
-            break;
+            // the lowest flagged byte is the first one to stop at (see
+            // find_string_special())
+            return i + (static_cast<std::size_t>(count_trailing_zeros(stop)) / 8);
         }
     }
     for (; i < n; ++i)
@@ -253,13 +250,19 @@ inline std::size_t scalar_string_bulk_run(const unsigned char* data, std::size_t
         {
             break; // end of buffer, or a quote/escape/control byte
         }
+        // a run of multi-byte sequences (e.g. CJK text) is validated sequence
+        // by sequence without searching for the next special byte in between
+        do
+        {
             const std::size_t seq = validate_one_utf8(data + pos, n - pos);
             if (seq == 0)
             {
-            break; // ill-formed or truncated: let the byte path diagnose it
+                return pos; // ill-formed or truncated: let the byte path diagnose it
             }
             pos += seq;
         }
+        while (pos < n && data[pos] >= 0x80u);
+    }
     return pos;
 }
 
@@ -273,8 +276,7 @@ inline std::size_t find_string_delimiter(const unsigned char* data, std::size_t
     std::size_t i = 0;
     for (; i + 8 <= n; i += 8)
     {
-        std::uint64_t v = 0;
+        const std::uint64_t v = read_eight_bytes(data + i);
-        std::memcpy(&v, data + i, sizeof(v));
         const std::uint64_t q = v ^ 0x2222222222222222ull;
         const std::uint64_t b = v ^ 0x5C5C5C5C5C5C5C5Cull;
         const std::uint64_t hit = ((q - ones) & ~q & high)
@@ -282,14 +284,8 @@ inline std::size_t find_string_delimiter(const unsigned char* data, std::size_t
                                   | ((v - 0x2020202020202020ull) & ~v & high);
         if (hit != 0)
         {
-            for (std::size_t j = 0; j < 8; ++j)
+            // the lowest flagged byte is the first delimiter (see find_string_special())
-            {
+            return i + (static_cast<std::size_t>(count_trailing_zeros(hit)) / 8);
-                const unsigned char c = data[i + j];
-                if (c == '\"' || c == '\\' || c < 0x20u)
-                {
-                    return i + j;
-                }
-            }
         }
     }
     for (; i < n; ++i)
@@ -320,5 +316,50 @@ inline std::size_t string_bulk_run(const unsigned char* data, std::size_t n) noe
     return scalar_string_bulk_run(data, n);
 }
 
+// Decode the 4 hex digits at [data, data+4) - the digits following a `\u`
+// escape - into a codepoint 0x0000..0xFFFF via one table lookup per byte
+// (after yyjson's read_hex_u16), or return -1 if any of the 4 bytes is not a
+// hex digit ('0'..'9', 'A'..'F', 'a'..'f'). The caller must already have
+// checked that 4 bytes are available; used by lexer::get_codepoint()'s
+// contiguous fast path. On -1 it falls back to the byte-at-a-time loop, which
+// stops at the first invalid digit, so the reported error and position are
+// unaffected by this fast path.
+inline int hex_codepoint(const unsigned char* data) noexcept
+{
+    static const std::array<std::uint8_t, 256> hex_digit_table = // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)
+    {
+        {
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 00..0F
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 10..1F
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 20..2F
+            0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 30..3F ('0'..'9')
+            0xFF, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 40..4F ('A'..'F')
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 50..5F
+            0xFF, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 60..6F ('a'..'f')
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 70..7F
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 80..8F
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 90..9F
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // A0..AF
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // B0..BF
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // C0..CF
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // D0..DF
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // E0..EF
+            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF  // F0..FF
+        }
+    };
+
+    const std::uint8_t d0 = hex_digit_table[data[0]];
+    const std::uint8_t d1 = hex_digit_table[data[1]];
+    const std::uint8_t d2 = hex_digit_table[data[2]];
+    const std::uint8_t d3 = hex_digit_table[data[3]];
+    // every valid digit is <= 0xF; the combined OR only exceeds it if at
+    // least one of the four bytes was not a hex digit (looked up as 0xFF)
+    if ((d0 | d1 | d2 | d3) > 0x0F)
+    {
+        return -1;
+    }
+    return (d0 << 12) | (d1 << 8) | (d2 << 4) | d3;
+}
+
 }  // namespace detail
 NLOHMANN_JSON_NAMESPACE_END

tests/src/float_hard_cases.hpp

@@ -0,0 +1,599 @@
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  JSON for Modern C++ (supporting code)
+// |  |  |__   |  |  | | | |  version 3.12.0
+// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
+//
+// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
+// SPDX-License-Identifier: MIT
+
+#pragma once
+
+#include <array> // array
+#include <cstdint> // uint32_t, uint64_t
+
+// Number tokens that are hard to round correctly, with the IEEE-754 binary64
+// and binary32 bits of their correctly rounded values (ties to even; infinity
+// for an overflow, a signed zero for an underflow).
+//
+// For doubles and floats around 0, the smallest normal number, 1, 2^24, 2^53,
+// 0.1, and the largest finite number, and for random ones, the exact midpoint
+// m to the next number gives: m, m with one unit more and less in the last
+// digit, m with "01" and "0...01" appended, m with trailing zeros, and m cut
+// after 17 to 30 digits (rounded down and up, so that the rounding is decided
+// after the 19th digit), in fixed and exponent notation, 30% of them negative.
+// Tokens longer than 80 characters are left out, except for four of 700 digits
+// and more. Zeros, underflow, overflow, huge exponents, and integers beyond 64
+// bits complete the set. Of the 508 tokens, 134 (as double) and 150 (as
+// float) need the exact comparison with the midpoint (detail::digit_comparison()).
+//
+// The expected bits were computed with exact rational arithmetic in Python
+// (fractions.Fraction) and cross-checked with Python's float(); strtod_l and
+// strtof_l of Apple's libc and of glibc agree. Generated by
+// compact_hard_cases.py 5 (with hard_cases.py), see the pull request that
+// added this file.
+
+namespace float_hard_cases
+{
+
+struct hard_case
+{
+    const char* token;
+    std::uint64_t bits64;
+    std::uint32_t bits32;
+};
+
+inline const std::array<hard_case, 508>& cases()
+{
+    static const std::array<hard_case, 508> table =
+    {
+        {
+            {"-2.4703282292062327e-324", 0x8000000000000000u, 0x80000000u},
+            {"24703282292062328e-340", 0x0000000000000001u, 0x00000000u},
+            {"247032822920623272e-341", 0x0000000000000000u, 0x00000000u},
+            {"-0.2470328229206232721e-323", 0x8000000000000001u, 0x80000000u},
+            {"-0.24703282292062327208e-323", 0x8000000000000000u, 0x80000000u},
+            {"-2.4703282292062327209e-324", 0x8000000000000001u, 0x80000000u},
+            {"2.47032822920623272088e-324", 0x0000000000000000u, 0x00000000u},
+            {"247032822920623272089e-344", 0x0000000000000001u, 0x00000000u},
+            {"-247032822920623272088284396434e-353", 0x8000000000000000u, 0x80000000u},
+            {"0.247032822920623272088284396435e-323", 0x0000000000000001u, 0x00000000u},
+            {"-74109846876186981e-340", 0x8000000000000001u, 0x80000000u},
+            {"0.74109846876186982e-323", 0x0000000000000002u, 0x00000000u},
+            {"-0.7410984687618698162e-323", 0x8000000000000001u, 0x80000000u},
+            {"-7.410984687618698163e-324", 0x8000000000000002u, 0x80000000u},
+            {"7.4109846876186981626e-324", 0x0000000000000001u, 0x00000000u},
+            {"-74109846876186981627e-343", 0x8000000000000002u, 0x80000000u},
+            {"-741098468761869816264e-344", 0x8000000000000001u, 0x80000000u},
+            {"0.741098468761869816265e-323", 0x0000000000000002u, 0x00000000u},
+            {"0.741098468761869816264853189302e-323", 0x0000000000000001u, 0x00000000u},
+            {"-7.41098468761869816264853189303e-324", 0x8000000000000002u, 0x80000000u},
+            {"0.22250738585072006e-307", 0x000FFFFFFFFFFFFEu, 0x00000000u},
+            {"2.2250738585072007e-308", 0x000FFFFFFFFFFFFFu, 0x00000000u},
+            {"2.225073858507200641e-308", 0x000FFFFFFFFFFFFEu, 0x00000000u},
+            {"-2225073858507200642e-326", 0x800FFFFFFFFFFFFFu, 0x80000000u},
+            {"22250738585072006419e-327", 0x000FFFFFFFFFFFFEu, 0x00000000u},
+            {"0.2225073858507200642e-307", 0x000FFFFFFFFFFFFFu, 0x00000000u},
+            {"0.222507385850720064199e-307", 0x000FFFFFFFFFFFFEu, 0x00000000u},
+            {"2.225073858507200642e-308", 0x000FFFFFFFFFFFFFu, 0x00000000u},
+            {"-2.22507385850720064199176395546e-308", 0x800FFFFFFFFFFFFEu, 0x80000000u},
+            {"222507385850720064199176395547e-337", 0x000FFFFFFFFFFFFFu, 0x00000000u},
+            {"-2.2250738585072011e-308", 0x800FFFFFFFFFFFFFu, 0x80000000u},
+            {"-22250738585072012e-324", 0x8010000000000000u, 0x80000000u},
+            {"-2225073858507201136e-326", 0x800FFFFFFFFFFFFFu, 0x80000000u},
+            {"0.2225073858507201137e-307", 0x0010000000000000u, 0x00000000u},
+            {"0.2225073858507201136e-307", 0x000FFFFFFFFFFFFFu, 0x00000000u},
+            {"-2.2250738585072011361e-308", 0x8010000000000000u, 0x80000000u},
+            {"2.22507385850720113605e-308", 0x000FFFFFFFFFFFFFu, 0x00000000u},
+            {"222507385850720113606e-328", 0x0010000000000000u, 0x00000000u},
+            {"22250738585072011360574097967e-336", 0x000FFFFFFFFFFFFFu, 0x00000000u},
+            {"0.222507385850720113605740979671e-307", 0x0010000000000000u, 0x00000000u},
+            {"22250738585072016e-324", 0x0010000000000000u, 0x00000000u},
+            {"0.22250738585072017e-307", 0x0010000000000001u, 0x00000000u},
+            {"0.222507385850720163e-307", 0x0010000000000000u, 0x00000000u},
+            {"2.225073858507201631e-308", 0x0010000000000001u, 0x00000000u},
+            {"-2.2250738585072016301e-308", 0x8010000000000000u, 0x80000000u},
+            {"22250738585072016302e-327", 0x0010000000000001u, 0x00000000u},
+            {"-222507385850720163012e-328", 0x8010000000000000u, 0x80000000u},
+            {"0.222507385850720163013e-307", 0x0010000000000001u, 0x00000000u},
+            {"0.222507385850720163012305563795e-307", 0x0010000000000000u, 0x00000000u},
+            {"-2.22507385850720163012305563796e-308", 0x8010000000000001u, 0x80000000u},
+            {"0.17976931348623156E+309", 0x7FEFFFFFFFFFFFFEu, 0x7F800000u},
+            {"1.7976931348623157e308", 0x7FEFFFFFFFFFFFFFu, 0x7F800000u},
+            {"1.797693134862315608e308", 0x7FEFFFFFFFFFFFFEu, 0x7F800000u},
+            {"-1797693134862315609e290", 0xFFEFFFFFFFFFFFFFu, 0xFF800000u},
+            {"-17976931348623156083e289", 0xFFEFFFFFFFFFFFFEu, 0xFF800000u},
+            {"-0.17976931348623156084E+309", 0xFFEFFFFFFFFFFFFFu, 0xFF800000u},
+            {"0.179769313486231560835E+309", 0x7FEFFFFFFFFFFFFEu, 0x7F800000u},
+            {"-1.79769313486231560836e308", 0xFFEFFFFFFFFFFFFFu, 0xFF800000u},
+            {"1.79769313486231560835325876058e308", 0x7FEFFFFFFFFFFFFEu, 0x7F800000u},
+            {"179769313486231560835325876059e279", 0x7FEFFFFFFFFFFFFFu, 0x7F800000u},
+            {"1.7976931348623158e308", 0x7FEFFFFFFFFFFFFFu, 0x7F800000u},
+            {"17976931348623159e292", 0x7FF0000000000000u, 0x7F800000u},
+            {"1797693134862315807e290", 0x7FEFFFFFFFFFFFFFu, 0x7F800000u},
+            {"0.1797693134862315808E+309", 0x7FF0000000000000u, 0x7F800000u},
+            {"0.17976931348623158079E+309", 0x7FEFFFFFFFFFFFFFu, 0x7F800000u},
+            {"-1.797693134862315808e308", 0xFFF0000000000000u, 0xFF800000u},
+            {"1.79769313486231580793e308", 0x7FEFFFFFFFFFFFFFu, 0x7F800000u},
+            {"179769313486231580794e288", 0x7FF0000000000000u, 0x7F800000u},
+            {"179769313486231580793728971405e279", 0x7FEFFFFFFFFFFFFFu, 0x7F800000u},
+            {"-0.179769313486231580793728971406E+309", 0xFFF0000000000000u, 0xFF800000u},
+            {"100000000000000011102230246251565404236316680908203125e-53", 0x3FF0000000000000u, 0x3F800000u},
+            {"-1.00000000000000011102230246251565404236316680908203126", 0xBFF0000000000001u, 0xBF800000u},
+            {"1.00000000000000011102230246251565404236316680908203124e0", 0x3FF0000000000000u, 0x3F800000u},
+            {"10000000000000001110223024625156540423631668090820312501e-55", 0x3FF0000000000001u, 0x3F800000u},
+            {"1.00000000000000011102230246251565404236316680908203125000000000000000000001", 0x3FF0000000000001u, 0x3F800000u},
+            {"10000000000000001e-16", 0x3FF0000000000000u, 0x3F800000u},
+            {"1.0000000000000002", 0x3FF0000000000001u, 0x3F800000u},
+            {"1.000000000000000111", 0x3FF0000000000000u, 0x3F800000u},
+            {"1.000000000000000112e0", 0x3FF0000000000001u, 0x3F800000u},
+            {"1.000000000000000111e0", 0x3FF0000000000000u, 0x3F800000u},
+            {"-10000000000000001111e-19", 0xBFF0000000000001u, 0xBF800000u},
+            {"-100000000000000011102e-20", 0xBFF0000000000000u, 0xBF800000u},
+            {"-1.00000000000000011103", 0xBFF0000000000001u, 0xBF800000u},
+            {"1.00000000000000011102230246251", 0x3FF0000000000000u, 0x3F800000u},
+            {"1.00000000000000011102230246252e0", 0x3FF0000000000001u, 0x3F800000u},
+            {"-0.999999999999999944488848768742172978818416595458984375", 0xBFF0000000000000u, 0xBF800000u},
+            {"-9.99999999999999944488848768742172978818416595458984376e-1", 0xBFF0000000000000u, 0xBF800000u},
+            {"999999999999999944488848768742172978818416595458984374e-54", 0x3FEFFFFFFFFFFFFFu, 0x3F800000u},
+            {"0.99999999999999994448884876874217297881841659545898437501", 0x3FF0000000000000u, 0x3F800000u},
+            {"9.99999999999999944488848768742172978818416595458984375000000000000000000001e-1", 0x3FF0000000000000u, 0x3F800000u},
+            {"-0.99999999999999994", 0xBFEFFFFFFFFFFFFFu, 0xBF800000u},
+            {"9.9999999999999995e-1", 0x3FF0000000000000u, 0x3F800000u},
+            {"9.999999999999999444e-1", 0x3FEFFFFFFFFFFFFFu, 0x3F800000u},
+            {"9999999999999999445e-19", 0x3FF0000000000000u, 0x3F800000u},
+            {"99999999999999994448e-20", 0x3FEFFFFFFFFFFFFFu, 0x3F800000u},
+            {"-0.99999999999999994449", 0xBFF0000000000000u, 0xBF800000u},
+            {"0.999999999999999944488", 0x3FEFFFFFFFFFFFFFu, 0x3F800000u},
+            {"-9.99999999999999944489e-1", 0xBFF0000000000000u, 0xBF800000u},
+            {"9.99999999999999944488848768742e-1", 0x3FEFFFFFFFFFFFFFu, 0x3F800000u},
+            {"999999999999999944488848768743e-30", 0x3FF0000000000000u, 0x3F800000u},
+            {"-9.007199254740993e15", 0xC340000000000000u, 0xDA000000u},
+            {"9007199254740994e0", 0x4340000000000001u, 0x5A000000u},
+            {"9007199254740992", 0x4340000000000000u, 0x5A000000u},
+            {"9.00719925474099301e15", 0x4340000000000001u, 0x5A000000u},
+            {"9007199254740993000000000000000000001e-21", 0x4340000000000001u, 0x5A000000u},
+            {"-9007199254740993.000000000000000000000000000000", 0xC340000000000000u, 0xDA000000u},
+            {"90071992547409915e-1", 0x4340000000000000u, 0x5A000000u},
+            {"-9007199254740991.6", 0xC340000000000000u, 0xDA000000u},
+            {"9.0071992547409914e15", 0x433FFFFFFFFFFFFFu, 0x5A000000u},
+            {"-9007199254740991501e-3", 0xC340000000000000u, 0xDA000000u},
+            {"9007199254740991.5000000000000000000001", 0x4340000000000000u, 0x5A000000u},
+            {"9.0071992547409915000000000000000000000000000000e15", 0x4340000000000000u, 0x5A000000u},
+            {"0.100000000000000012490009027033011079765856266021728515625", 0x3FB999999999999Au, 0x3DCCCCCDu},
+            {"1.00000000000000012490009027033011079765856266021728515626e-1", 0x3FB999999999999Bu, 0x3DCCCCCDu},
+            {"100000000000000012490009027033011079765856266021728515624e-57", 0x3FB999999999999Au, 0x3DCCCCCDu},
+            {"0.10000000000000001249000902703301107976585626602172851562501", 0x3FB999999999999Bu, 0x3DCCCCCDu},
+            {"0.10000000000000001", 0x3FB999999999999Au, 0x3DCCCCCDu},
+            {"1.0000000000000002e-1", 0x3FB999999999999Bu, 0x3DCCCCCDu},
+            {"-1.000000000000000124e-1", 0xBFB999999999999Au, 0xBDCCCCCDu},
+            {"1000000000000000125e-19", 0x3FB999999999999Bu, 0x3DCCCCCDu},
+            {"-10000000000000001249e-20", 0xBFB999999999999Au, 0xBDCCCCCDu},
+            {"0.1000000000000000125", 0x3FB999999999999Bu, 0x3DCCCCCDu},
+            {"0.10000000000000001249", 0x3FB999999999999Au, 0x3DCCCCCDu},
+            {"1.00000000000000012491e-1", 0x3FB999999999999Bu, 0x3DCCCCCDu},
+            {"1.00000000000000012490009027033e-1", 0x3FB999999999999Au, 0x3DCCCCCDu},
+            {"100000000000000012490009027034e-30", 0x3FB999999999999Bu, 0x3DCCCCCDu},
+            {"2.45134755833537796875e14", 0x42EBDE5C4164D83Au, 0x575EF2E2u},
+            {"-245134755833537796876e-6", 0xC2EBDE5C4164D83Au, 0xD75EF2E2u},
+            {"-245134755833537.796874", 0xC2EBDE5C4164D839u, 0xD75EF2E2u},
+            {"2.4513475583353779687501e14", 0x42EBDE5C4164D83Au, 0x575EF2E2u},
+            {"245134755833537796875000000000000000000001e-27", 0x42EBDE5C4164D83Au, 0x575EF2E2u},
+            {"245134755833537.796875000000000000000000000000000000", 0x42EBDE5C4164D83Au, 0x575EF2E2u},
+            {"2.4513475583353779e14", 0x42EBDE5C4164D839u, 0x575EF2E2u},
+            {"2451347558335378e-1", 0x42EBDE5C4164D83Au, 0x575EF2E2u},
+            {"2451347558335377968e-4", 0x42EBDE5C4164D839u, 0x575EF2E2u},
+            {"245134755833537.7969", 0x42EBDE5C4164D83Au, 0x575EF2E2u},
+            {"245134755833537.79687", 0x42EBDE5C4164D839u, 0x575EF2E2u},
+            {"2.4513475583353779688e14", 0x42EBDE5C4164D83Au, 0x575EF2E2u},
+            {"181510327827821147441864013671875e-23", 0x41DB0C11CB91CE38u, 0x4ED8608Eu},
+            {"-1815103278.27821147441864013671876", 0xC1DB0C11CB91CE38u, 0xCED8608Eu},
+            {"1.81510327827821147441864013671874e9", 0x41DB0C11CB91CE37u, 0x4ED8608Eu},
+            {"18151032782782114744186401367187501e-25", 0x41DB0C11CB91CE38u, 0x4ED8608Eu},
+            {"1815103278.27821147441864013671875000000000000000000001", 0x41DB0C11CB91CE38u, 0x4ED8608Eu},
+            {"-1.81510327827821147441864013671875000000000000000000000000000000e9", 0xC1DB0C11CB91CE38u, 0xCED8608Eu},
+            {"18151032782782114e-7", 0x41DB0C11CB91CE37u, 0x4ED8608Eu},
+            {"1815103278.2782115", 0x41DB0C11CB91CE38u, 0x4ED8608Eu},
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+            {"10000000521540641784e-20", 0x3FB99999B0000000u, 0x3DCCCCCDu},
+            {"0.10000000521540641785", 0x3FB99999B0000000u, 0x3DCCCCCEu},
+            {"0.100000005215406417846", 0x3FB99999B0000000u, 0x3DCCCCCDu},
+            {"1.00000005215406417847e-1", 0x3FB99999B0000000u, 0x3DCCCCCEu},
+            {"5.429001220703125e3", 0x40B5350050000000u, 0x45A9A802u},
+            {"-5429001220703126e-12", 0xC0B5350050000001u, 0xC5A9A803u},
+            {"-5429.001220703124", 0xC0B535004FFFFFFFu, 0xC5A9A802u},
+            {"5.42900122070312501e3", 0x40B5350050000000u, 0x45A9A803u},
+            {"5429001220703125000000000000000000001e-33", 0x40B5350050000000u, 0x45A9A803u},
+            {"-5429.001220703125000000000000000000000000000000", 0xC0B5350050000000u, 0xC5A9A802u},
+            {"503719056e0", 0x41BE062490000000u, 0x4DF03124u},
+            {"503719057", 0x41BE062491000000u, 0x4DF03125u},
+            {"5.03719055e8", 0x41BE06248F000000u, 0x4DF03124u},
+            {"50371905601e-2", 0x41BE062490028F5Cu, 0x4DF03125u},
+            {"503719056.000000000000000000001", 0x41BE062490000000u, 0x4DF03125u},
+            {"5.03719056000000000000000000000000000000e8", 0x41BE062490000000u, 0x4DF03124u},
+            {"-92331620", 0xC196037990000000u, 0xCCB01BCCu},
+            {"9.233163e7", 0x41960379B8000000u, 0x4CB01BCEu},
+            {"9233161e1", 0x4196037968000000u, 0x4CB01BCBu},
+            {"92331620.1", 0x4196037990666666u, 0x4CB01BCDu},
+            {"9.233162000000000000000000001e7", 0x4196037990000000u, 0x4CB01BCDu},
+            {"9233162000000000000000000000000000000e-29", 0x4196037990000000u, 0x4CB01BCCu},
+            {"3.002458625e6", 0x4146E82D50000000u, 0x4A37416Au},
+            {"3002458626e-3", 0x4146E82D5020C49Cu, 0x4A37416Bu},
+            {"3002458.624", 0x4146E82D4FDF3B64u, 0x4A37416Au},
+            {"-3.00245862501e6", 0xC146E82D500053E3u, 0xCA37416Bu},
+            {"3002458625000000000000000000001e-24", 0x4146E82D50000000u, 0x4A37416Bu},
+            {"3002458.625000000000000000000000000000000", 0x4146E82D50000000u, 0x4A37416Au},
+            {"-1095485584696182596504479582065262592e1", 0xC7A07BA830000000u, 0xFD03DD42u},
+            {"10954855846961825965044795820652625930", 0x47A07BA830000000u, 0x7D03DD42u},
+            {"1.095485584696182596504479582065262591e37", 0x47A07BA830000000u, 0x7D03DD41u},
+            {"109548558469618259650447958206526259201e-1", 0x47A07BA830000000u, 0x7D03DD42u},
+            {"-10954855846961825965044795820652625920.00000000000000000001", 0xC7A07BA830000000u, 0xFD03DD42u},
+            {"1.095485584696182596504479582065262592000000000000000000000000000000e37", 0x47A07BA830000000u, 0x7D03DD42u},
+            {"10954855846961825e21", 0x47A07BA830000000u, 0x7D03DD41u},
+            {"10954855846961826000000000000000000000", 0x47A07BA830000000u, 0x7D03DD42u},
+            {"10954855846961825960000000000000000000", 0x47A07BA830000000u, 0x7D03DD41u},
+            {"1.095485584696182597e37", 0x47A07BA830000000u, 0x7D03DD42u},
+            {"1.0954855846961825965e37", 0x47A07BA830000000u, 0x7D03DD41u},
+            {"-10954855846961825966e18", 0xC7A07BA830000000u, 0xFD03DD42u},
+            {"10954855846961825965e18", 0x47A07BA830000000u, 0x7D03DD41u},
+            {"10954855846961825965100000000000000000", 0x47A07BA830000000u, 0x7D03DD42u},
+            {"10954855846961825965044795820600000000", 0x47A07BA830000000u, 0x7D03DD41u},
+            {"-1.09548558469618259650447958207e37", 0xC7A07BA830000000u, 0xFD03DD42u},
+            {"1.6449216019182103706535606608388384863861375606575165875256061553955078126e-21", 0x3B9F125A50000000u, 0x1CF892D3u},
+            {"-16449216019182103706535606608388384863861375606575165875256061553955078124e-94", 0xBB9F125A50000000u, 0x9CF892D2u},
+            {"-0.0000000000000000000016449216019182103", 0xBB9F125A50000000u, 0x9CF892D2u},
+            {"-1.6449216019182104e-21", 0xBB9F125A50000000u, 0x9CF892D3u},
+            {"-1.64492160191821037e-21", 0xBB9F125A50000000u, 0x9CF892D2u},
+            {"-1644921601918210371e-39", 0xBB9F125A50000000u, 0x9CF892D3u},
+            {"-16449216019182103706e-40", 0xBB9F125A50000000u, 0x9CF892D2u},
+            {"0.0000000000000000000016449216019182103707", 0x3B9F125A50000000u, 0x1CF892D3u},
+            {"0.00000000000000000000164492160191821037065", 0x3B9F125A50000000u, 0x1CF892D2u},
+            {"1.64492160191821037066e-21", 0x3B9F125A50000000u, 0x1CF892D3u},
+            {"1.64492160191821037065356066083e-21", 0x3B9F125A50000000u, 0x1CF892D2u},
+            {"164492160191821037065356066084e-50", 0x3B9F125A50000000u, 0x1CF892D3u},
+            {"6.565061509609222412109375e-1", 0x3FE5021930000000u, 0x3F2810CAu},
+            {"6565061509609222412109376e-25", 0x3FE5021930000000u, 0x3F2810CAu},
+            {"0.6565061509609222412109374", 0x3FE5021930000000u, 0x3F2810C9u},
+            {"6.56506150960922241210937501e-1", 0x3FE5021930000000u, 0x3F2810CAu},
+            {"6565061509609222412109375000000000000000000001e-46", 0x3FE5021930000000u, 0x3F2810CAu},
+            {"-0.6565061509609222412109375000000000000000000000000000000", 0xBFE5021930000000u, 0xBF2810CAu},
+            {"6.5650615096092224e-1", 0x3FE5021930000000u, 0x3F2810C9u},
+            {"-65650615096092225e-17", 0xBFE5021930000000u, 0xBF2810CAu},
+            {"6565061509609222412e-19", 0x3FE5021930000000u, 0x3F2810C9u},
+            {"0.6565061509609222413", 0x3FE5021930000000u, 0x3F2810CAu},
+            {"0.65650615096092224121", 0x3FE5021930000000u, 0x3F2810C9u},
+            {"6.5650615096092224122e-1", 0x3FE5021930000000u, 0x3F2810CAu},
+            {"-6.5650615096092224121e-1", 0xBFE5021930000000u, 0xBF2810C9u},
+            {"656506150960922241211e-21", 0x3FE5021930000000u, 0x3F2810CAu},
+            {"18014627239033005156980393746124491372029297053813934326171875e-77", 0x3CA9F63970000000u, 0x254FB1CCu},
+            {"0.00000000000000018014627239033005156980393746124491372029297053813934326171876", 0x3CA9F63970000000u, 0x254FB1CCu},
+            {"-1.8014627239033005156980393746124491372029297053813934326171874e-16", 0xBCA9F63970000000u, 0xA54FB1CBu},
+            {"1801462723903300515698039374612449137202929705381393432617187501e-79", 0x3CA9F63970000000u, 0x254FB1CCu},
+            {"18014627239033005e-32", 0x3CA9F63970000000u, 0x254FB1CBu},
+            {"0.00000000000000018014627239033006", 0x3CA9F63970000000u, 0x254FB1CCu},
+            {"0.0000000000000001801462723903300515", 0x3CA9F63970000000u, 0x254FB1CBu},
+            {"-1.801462723903300516e-16", 0xBCA9F63970000000u, 0xA54FB1CCu},
+            {"-1.8014627239033005156e-16", 0xBCA9F63970000000u, 0xA54FB1CBu},
+            {"18014627239033005157e-35", 0x3CA9F63970000000u, 0x254FB1CCu},
+            {"180146272390330051569e-36", 0x3CA9F63970000000u, 0x254FB1CBu},
+            {"-0.00000000000000018014627239033005157", 0xBCA9F63970000000u, 0xA54FB1CCu},
+            {"0.000000000000000180146272390330051569803937461", 0x3CA9F63970000000u, 0x254FB1CBu},
+            {"1.80146272390330051569803937462e-16", 0x3CA9F63970000000u, 0x254FB1CCu},
+            {"0.05534819327294826507568359375", 0x3FAC569930000000u, 0x3D62B4CAu},
+            {"-5.534819327294826507568359376e-2", 0xBFAC569930000000u, 0xBD62B4CAu},
+            {"5534819327294826507568359374e-29", 0x3FAC569930000000u, 0x3D62B4C9u},
+            {"-0.0553481932729482650756835937501", 0xBFAC569930000000u, 0xBD62B4CAu},
+            {"5.534819327294826507568359375000000000000000000001e-2", 0x3FAC569930000000u, 0x3D62B4CAu},
+            {"5534819327294826507568359375000000000000000000000000000000e-59", 0x3FAC569930000000u, 0x3D62B4CAu},
+            {"0.055348193272948265", 0x3FAC569930000000u, 0x3D62B4C9u},
+            {"5.5348193272948266e-2", 0x3FAC569930000000u, 0x3D62B4CAu},
+            {"5.534819327294826507e-2", 0x3FAC569930000000u, 0x3D62B4C9u},
+            {"5534819327294826508e-20", 0x3FAC569930000000u, 0x3D62B4CAu},
+            {"55348193272948265075e-21", 0x3FAC569930000000u, 0x3D62B4C9u},
+            {"-0.055348193272948265076", 0xBFAC569930000000u, 0xBD62B4CAu},
+            {"0.0553481932729482650756", 0x3FAC569930000000u, 0x3D62B4C9u},
+            {"-5.53481932729482650757e-2", 0xBFAC569930000000u, 0xBD62B4CAu},
+            {"5.179692133247783258005389047985340416e36", 0x478F2C9450000000u, 0x7C7964A2u},
+            {"5179692133247783258005389047985340417e0", 0x478F2C9450000000u, 0x7C7964A3u},
+            {"5179692133247783258005389047985340415", 0x478F2C9450000000u, 0x7C7964A2u},
+            {"-5.17969213324778325800538904798534041601e36", 0xC78F2C9450000000u, 0xFC7964A3u},
+            {"-5179692133247783258005389047985340416000000000000000000001e-21", 0xC78F2C9450000000u, 0xFC7964A3u},
+            {"-5179692133247783258005389047985340416.000000000000000000000000000000", 0xC78F2C9450000000u, 0xFC7964A2u},
+            {"5.1796921332477832e36", 0x478F2C9450000000u, 0x7C7964A2u},
+            {"51796921332477833e20", 0x478F2C9450000000u, 0x7C7964A3u},
+            {"-5179692133247783258e18", 0xC78F2C9450000000u, 0xFC7964A2u},
+            {"5179692133247783259000000000000000000", 0x478F2C9450000000u, 0x7C7964A3u},
+            {"5179692133247783258000000000000000000", 0x478F2C9450000000u, 0x7C7964A2u},
+            {"5.1796921332477832581e36", 0x478F2C9450000000u, 0x7C7964A3u},
+            {"-5.179692133247783258e36", 0xC78F2C9450000000u, 0xFC7964A2u},
+            {"-517969213324778325801e16", 0xC78F2C9450000000u, 0xFC7964A3u},
+            {"517969213324778325800538904798e7", 0x478F2C9450000000u, 0x7C7964A2u},
+            {"5179692133247783258005389047990000000", 0x478F2C9450000000u, 0x7C7964A3u},
+            {
+                "0.22250738585072011360574097967091319759348195463516456480234261097248222220210769455165295239081350"
+                "8791414915891303962110687008643869459464552765720740782062174337998814106326732925355228688137214901"
+                "2981122451451889849057222307285255133155755015914397476397983411801999323962548289017107081850690630"
+                "6666559949382757725720157630626906633326475653000092458883164330377797918696120494973903778297049050"
+                "5108060994073026293712895895000358379996720725430436028407889577179615094551674824347103070260914462"
+                "1572289880258182545180325707018860872113128079512233426288368622321503775666622503982534335974568884"
+                "4239002654981983854879482922068947216898310996983658468140228542433306603398508864458040010349339704"
+                "2756718644338377048603786162277173854562306587467901408672332763671875e-307", 0x0010000000000000u, 0x00000000u
+            },
+            {
+                "2.22507385850720113605740979670913197593481954635164564802342610972482222202107694551652952390813508"
+                "7914149158913039621106870086438694594645527657207407820621743379988141063267329253552286881372149012"
+                "9811224514518898490572223072852551331557550159143974763979834118019993239625482890171070818506906306"
+                "6665599493827577257201576306269066333264756530000924588831643303777979186961204949739037782970490505"
+                "1080609940730262937128958950003583799967207254304360284078895771796150945516748243471030702609144621"
+                "5722898802581825451803257070188608721131280795122334262883686223215037756666225039825343359745688844"
+                "2390026549819838548794829220689472168983109969836584681402285424333066033985088644580400103493397042"
+                "756718644338377048603786162277173854562306587467901408672332763671875000000000000000000001e-308", 0x0010000000000000u, 0x00000000u
+            },
+            {
+                "0.11754942807573642917278829910357665133228589927589904276829631184250030649651730385585324256680905"
+                "8189392089843750000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+                "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+                "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+                "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+                "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+                "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+                "00000000000000000000000000000000000000000000000000000000000000000e-37", 0x380FFFFFE0000000u, 0x00800000u
+            },
+            {
+                "1175494280757364291727882991035766513322858992758990427682963118425003064965173038558532425668090581"
+                "8939208984375000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+                "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+                "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+                "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+                "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+                "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+                "00000000000001e-751", 0x380FFFFFE0000000u, 0x00800000u
+            },
+            {"0", 0x0000000000000000u, 0x00000000u},
+            {"-0", 0x8000000000000000u, 0x80000000u},
+            {"0.0", 0x0000000000000000u, 0x00000000u},
+            {"-0.0", 0x8000000000000000u, 0x80000000u},
+            {"0e999999999999999999999", 0x0000000000000000u, 0x00000000u},
+            {"-0.000e-99999", 0x8000000000000000u, 0x80000000u},
+            {"1e-400", 0x0000000000000000u, 0x00000000u},
+            {"-1e-400", 0x8000000000000000u, 0x80000000u},
+            {"1e400", 0x7FF0000000000000u, 0x7F800000u},
+            {"-1e400", 0xFFF0000000000000u, 0xFF800000u},
+            {"1e-50", 0x358DEE7A4AD4B81Fu, 0x00000000u},
+            {"-1e-50", 0xB58DEE7A4AD4B81Fu, 0x80000000u},
+            {"1e39", 0x48078287F49C4A1Du, 0x7F800000u},
+            {"-1e39", 0xC8078287F49C4A1Du, 0xFF800000u},
+            {"1e99999999999999999999999999", 0x7FF0000000000000u, 0x7F800000u},
+            {"1e-99999999999999999999999999", 0x0000000000000000u, 0x00000000u},
+            {"1e0000000000000000000000000000000000000000308", 0x7FE1CCF385EBC8A0u, 0x7F800000u},
+            {"123456789012345678901234567890e-30", 0x3FBF9ADD3746F65Fu, 0x3DFCD6EAu},
+            {"18446744073709551615", 0x43F0000000000000u, 0x5F800000u},
+            {"18446744073709551616", 0x43F0000000000000u, 0x5F800000u},
+            {"-9223372036854775808", 0xC3E0000000000000u, 0xDF000000u},
+            {"-9223372036854775809", 0xC3E0000000000000u, 0xDF000000u},
+        }
+    };
+    return table;
+}
+
+} // namespace float_hard_cases

tests/src/unit-allocator.cpp

@@ -370,14 +370,7 @@ TEST_CASE("copy of a deeply nested value survives a failing allocation (#5640)")
 #if !(defined(_ITERATOR_DEBUG_LEVEL) && _ITERATOR_DEBUG_LEVEL > 0)
     SECTION("std::map-backed object_t")
     {
-        using bad_alloc_json = nlohmann::basic_json<std::map,
+        using bad_alloc_json = nlohmann::json::with_allocator_t<nth_alloc_fails_allocator>;
-              std::vector,
-              std::string,
-              bool,
-              std::int64_t,
-              std::uint64_t,
-              double,
-              nth_alloc_fails_allocator>;
 
         check_deep_copy_survives_failing_allocation<bad_alloc_json>(false);
         check_deep_copy_survives_failing_allocation<bad_alloc_json>(true);
@@ -385,14 +378,7 @@ TEST_CASE("copy of a deeply nested value survives a failing allocation (#5640)")
 
     SECTION("ordered_map-backed object_t")
     {
-        using bad_alloc_ordered_json = nlohmann::basic_json<nlohmann::ordered_map,
+        using bad_alloc_ordered_json = nlohmann::ordered_json::with_allocator_t<nth_alloc_fails_allocator>;
-              std::vector,
-              std::string,
-              bool,
-              std::int64_t,
-              std::uint64_t,
-              double,
-              nth_alloc_fails_allocator>;
 
         check_deep_copy_survives_failing_allocation<bad_alloc_ordered_json>(false);
         check_deep_copy_survives_failing_allocation<bad_alloc_ordered_json>(true);
@@ -450,14 +436,7 @@ struct scratch_counting_allocator : std::allocator<T>
 
 TEST_CASE("deep copy uses the provided allocator")
 {
-    using counting_json = nlohmann::basic_json<std::map,
+    using counting_json = nlohmann::json::with_allocator_t<scratch_counting_allocator>;
-          std::vector,
-          std::string,
-          bool,
-          std::int64_t,
-          std::uint64_t,
-          double,
-          scratch_counting_allocator>;
 
     // deeper than the 128 levels the copy constructor descends into, so the
     // innermost objects are copied by the iterative deep copy
@@ -516,14 +495,7 @@ TEST_CASE("converting a deeply nested value from another specialization fails cl
     // the allocator in noexcept constructors, so a failing construction crashes
     // the program there instead of throwing std::bad_alloc. Nothing to check.
 #if !(defined(_MSC_VER) && _MSC_VER < 1910 && defined(_ITERATOR_DEBUG_LEVEL) && _ITERATOR_DEBUG_LEVEL > 0)
-    using countdown_json = nlohmann::basic_json<std::map,
+    using countdown_json = nlohmann::json::with_allocator_t<countdown_allocator>;
-          std::vector,
-          std::string,
-          bool,
-          std::int64_t,
-          std::uint64_t,
-          double,
-          countdown_allocator>;
 
     // deeper than the 128 levels the converting constructor descends into, so
     // that failures land on both sides of the bound - or, built with
@@ -631,14 +603,7 @@ TEST_CASE("destructor performs no allocation, only deallocation")
     // Since that stack could itself throw bad_alloc from inside the
     // noexcept destructor (#5135), destroy() no longer allocates anything:
     // it only ever frees what is already there.
-    using counting_json = nlohmann::basic_json<std::map,
+    using counting_json = nlohmann::json::with_allocator_t<counting_allocator>;
-          std::vector,
-          std::string,
-          bool,
-          std::int64_t,
-          std::uint64_t,
-          double,
-          counting_allocator>;
 
     SECTION("array")
     {
@@ -683,14 +648,7 @@ TEST_CASE("destructor performs no allocation, only deallocation")
 TEST_CASE("a failed allocation leaves the value unchanged")
 {
     // create JSON type using the throwing allocator
-    using my_json = nlohmann::basic_json<std::map,
+    using my_json = nlohmann::json::with_allocator_t<my_allocator>;
-          std::vector,
-          std::string,
-          bool,
-          std::int64_t,
-          std::uint64_t,
-          double,
-          my_allocator>;
 
     // Each of these creates a string, array, object, or binary value. The
     // value must be created before the type is changed: otherwise, a failed

tests/src/unit-binary_formats.cpp

@@ -237,7 +237,7 @@ namespace
 // the binary formats as function pointers for "Binary formats with narrow number types";
 // named functions rather than lambdas, because clang 3.5 cannot convert a lambda
 // to a function pointer in the braced initializer of the format table
-using narrow_json = nlohmann::basic_json<std::map, std::vector, std::string, bool, std::int32_t, std::uint32_t, float>;
+using narrow_json = nlohmann::json::with_integers_t<std::int32_t, std::uint32_t>::with_float_t<float>;
 using bytes = std::vector<std::uint8_t>;
 
 bytes encode_cbor(const json& j)

tests/src/unit-class_lexer.cpp

@@ -13,15 +13,20 @@
 using nlohmann::json;
 
 #include <array> // array
-#include <cfloat> // FLT_EVAL_METHOD
 #include <cstdint> // uint32_t, uint64_t
+#include <cstdio> // snprintf
 #include <cstdlib> // strtod
 #include <cstring> // memcpy
+#include <limits> // numeric_limits
+#include <map> // map
+#include <random> // mt19937
 #include <sstream> // stringstream
 #include <string> // string
 #include <utility> // pair
 #include <vector> // vector
 
+#include "float_hard_cases.hpp"
+
 namespace
 {
 // shortcut to scan a string literal
@@ -257,7 +262,7 @@ TEST_CASE("lexer number fast path")
             "123456789012345678901234567890",  // huge -> float
             "0.30000000000000004", "2.2250738585072014e-308", "1e308",
             // high-precision / wide-exponent values that exercise the
-            // std::from_chars (Eisel-Lemire) path beyond the Clinger subset
+            // Eisel-Lemire path beyond the Clinger subset
             "1.7976931348623157e308", "1.2345678901234567e-250",
             "9007199254740993", "5e-324", "1e-320"
         };
@@ -279,20 +284,18 @@ TEST_CASE("lexer number fast path")
         }
     }
 
-    SECTION("significant-digit gate for the Clinger fast path")
+    SECTION("significant digits around Clinger's fast path")
     {
-        // Clinger's fast path needs a significand below 2^53, so it cannot
+        // Clinger's fast path needs a significand of at most 2^53, which
-        // succeed once the mantissa has 17 or more significant digits (the
+        // tokens with 17 or more significant digits exceed. The conversion
-        // significand would be at least 10^16). The lexer skips the attempt
+        // splits the token at the positions the scanners recorded, so leading
-        // there. That is only allowed to save work: every value must still come
+        // zeros must not count as digits - "0.1234567890123456" has 16
-        // out bit-exactly, and both scanners must agree. In particular the gate
+        // significant digits, not 17 - and both scanners must agree.
-        // must not fire for tokens whose leading zeros merely look like extra
-        // digits - "0.1234567890123456" has 16 significant digits, not 17.
         const std::vector<std::string> numbers =
         {
             "1234567890123456",                  // 16 significant digits
-            "12345678901234567",                 // 17 -> attempt skipped
+            "12345678901234567",                 // 17
-            "123456789012345678",                // 18 -> attempt skipped
+            "123456789012345678",                // 18
             "0.1234567890123456",                // 16: the leading "0" is not significant
             "0.12345678901234567",               // 17
             "0.00000000000000001",               // 1, in a long token
@@ -663,46 +666,323 @@ TEST_CASE("lexer string fast path")
     }
 }
 
-TEST_CASE("parse_float_fast declines what it cannot convert exactly")
+TEST_CASE("lexer escape fast path")
 {
-    // The lexer only hands well-formed numbers to parse_float_fast, so the
+    // json::accept() never throws, so this section stays covered without
-    // malformed ones below can only be passed to it directly. Declining is
+    // exceptions; it pins which of the cases below are valid/invalid and
-    // always safe: the caller then falls back to a slower, exact conversion.
+    // checks the contiguous and streaming paths agree on that classification.
-    const auto fast = [](const std::string & s, double & out)
+    SECTION("accept() parity")
     {
-        return nlohmann::detail::parse_float_fast(s.data(), s.data() + s.size(), out);
+        const std::vector<std::pair<std::string, bool>> cases =
+        {
+            {"\\u0041", true}, {"\\u00e4", true}, {"\\u00E4", true},
+            {"\\uD83D\\uDE00", true},
+            {"\\u12", false}, {"\\u12G4", false}, {"\\uXYZW", false},
+            {"\\uD800", false}, {"\\uD800A", false}, {"\\uD800\\u0041", false},
+            {"\\uDC00", false}, {"\\u", false}
         };
-    double out = 0;
 
-#if defined(FLT_EVAL_METHOD) && FLT_EVAL_METHOD != 0
+        for (const auto& c : cases)
-    // without true double precision, the fast path declines everything
+        {
-    CHECK_FALSE(fast("1.5", out));
+            for (const std::size_t offset :
-#else
+                    {
-    CHECK(fast("1.5", out));
+                        std::size_t{0}, std::size_t{9}
-    CHECK(out == 1.5);
+                    })
-    CHECK(fast("+2.5e1", out));
+            {
-    CHECK(out == 25.0);
+                const std::string doc = "[\"" + std::string(offset, 'a') + c.first + "\"]";
-    CHECK(fast("-25E-1", out));
+                CAPTURE(doc)
-    CHECK(out == -2.5);
+                CHECK(json::accept(doc) == c.second);
-    CHECK(fast("1e", out));
+                std::stringstream ss(doc);
-    CHECK(out == 1.0);
+                CHECK(json::accept(ss) == c.second);
+            }
+        }
+    }
+
+#if !defined(JSON_NOEXCEPTION)
+    // the full outcome of parsing @a doc: the parsed value, or the exact
+    // error message, so a mismatch in either is caught
+    const auto outcome = [](const std::string & doc, bool streaming) -> std::string
+    {
+        try
+        {
+            if (streaming)
+            {
+                std::stringstream ss(doc);
+                const json j = json::parse(ss);
+                return j.dump();
+            }
+            const json j = json::parse(doc);
+            return j.dump();
+        }
+        catch (const json::exception& e)
+        {
+            return {e.what()};
+        }
+    };
+
+    SECTION("contiguous vs streaming parity")
+    {
+        const std::vector<std::string> escapes =
+        {
+            "\\u0041",             // "A"
+            "\\u00e4",             // "ä" (lowercase hex)
+            "\\u00E4",             // "ä" (uppercase hex)
+            "\\uD83D\\uDE00",      // valid surrogate pair (an emoji)
+            "\\u12",               // truncated: only 2 hex digits before the closing quote
+            "\\u12G4",             // invalid hex digit at the 3rd position
+            "\\uXYZW",             // all 4 bytes invalid
+            "\\uD800",             // lone high surrogate, string ends right after
+            "\\uD800A",            // high surrogate not followed by another \u escape
+            "\\uD800\\u0041",      // high surrogate followed by \u, but not a low surrogate
+            "\\uDC00",             // lone low surrogate
+            "\\u",                 // '\u' with nothing after (closing quote right away)
+        };
+
+        // once at the start of the string and once past the first 8-byte SWAR
+        // word of the outer string_bulk_run, so the escape is reached both
+        // right after the opening quote and mid-run
+        for (const auto& escape : escapes)
+        {
+            for (const std::size_t offset :
+                    {
+                        std::size_t{0}, std::size_t{9}
+                    })
+            {
+                const std::string doc = "[\"" + std::string(offset, 'a') + escape + "\"]";
+                CAPTURE(doc)
+                CHECK(outcome(doc, false) == outcome(doc, true));
+            }
+
+            // the escape is the last thing before end of input: no closing
+            // quote at all
+            const std::string truncated_doc = "[\"" + escape;
+            CAPTURE(truncated_doc)
+            CHECK(outcome(truncated_doc, false) == outcome(truncated_doc, true));
+        }
+    }
+
+    SECTION("truncated \\u escape at every distance from the end of input")
+    {
+        // ia.bulk_remaining() must correctly report fewer than 4 bytes for
+        // every possible count of trailing hex-looking bytes (0, 1, 2, or 3)
+        // before end of input, so the fast path declines and the byte path
+        // alone reports the "must be followed by 4 hex digits" error, at the
+        // same position, in every case
+        for (const std::string& tail :
+                {
+                    std::string{}, std::string("1"), std::string("12"), std::string("123")
+                })
+        {
+            const std::string doc = "[\"\\u" + tail;
+            CAPTURE(doc)
+            CHECK(outcome(doc, false) == outcome(doc, true));
+            CHECK(outcome(doc, false).find("must be followed by 4 hex digits") != std::string::npos);
+        }
+    }
+
+    SECTION("invalid hex digit at every position of the 4")
+    {
+        // the fast path must decline for *any* invalid byte among the 4, not
+        // just the first, and the byte path must then stop at exactly that
+        // position - same as it always has
+        for (std::size_t bad_pos = 0; bad_pos < 4; ++bad_pos)
+        {
+            std::string digits = "1234";
+            digits[bad_pos] = 'g'; // not a hex digit
+            const std::string doc = "[\"\\u" + digits + "\"]";
+            CAPTURE(doc)
+            CHECK(outcome(doc, false) == outcome(doc, true));
+            CHECK(outcome(doc, false).find("must be followed by 4 hex digits") != std::string::npos);
+        }
+    }
+
+    SECTION("random escapes")
+    {
+        // A seeded PRNG builds the 4 bytes following `\u` from a mix of hex
+        // digits and non-hex bytes, at varying distances from the start of
+        // the string, to compare the two scanners on many more shapes than
+        // are practical to enumerate by hand.
+        std::mt19937 gen(7654321); // NOLINT(cert-msc32-c,cert-msc51-cpp,bugprone-random-generator-seed)
+        const std::string hex_alphabet = "0123456789AaBbCcDdEeFf";
+        std::uniform_int_distribution<std::size_t> pick_hex(0, hex_alphabet.size() - 1);
+        std::uniform_int_distribution<int> pick_byte(1, 255); // never NUL
+        std::uniform_int_distribution<int> pick_is_hex(0, 4); // 4-in-5 chance of a hex digit
+        std::uniform_int_distribution<std::size_t> pick_offset(0, 12);
+
+        std::vector<std::string> mismatches;
+        for (int iter = 0; iter < 3000; ++iter)
+        {
+            std::string digits;
+            for (int i = 0; i < 4; ++i)
+            {
+                if (pick_is_hex(gen) != 0)
+                {
+                    digits += hex_alphabet[pick_hex(gen)];
+                }
+                else
+                {
+                    char c = static_cast<char>(pick_byte(gen));
+                    if (c == '"' || c == '\\')
+                    {
+                        // keep the string well-formed apart from the escape
+                        // itself, so any mismatch is attributable to the \u
+                        // handling and not to an unrelated quote/escape
+                        c = 'z';
+                    }
+                    digits += c;
+                }
+            }
+            const std::string doc = "[\"" + std::string(pick_offset(gen), 'a') + "\\u" + digits + "\"]";
+            if (outcome(doc, false) != outcome(doc, true))
+            {
+                mismatches.push_back(doc);
+            }
+        }
+        CAPTURE(mismatches)
+        CHECK(mismatches.empty());
+    }
 #endif
+}
 
-    // not a number
+namespace
-    CHECK_FALSE(fast("", out));
+{
-    CHECK_FALSE(fast("-", out));
+// the index of the decimal point (or npos) and of the end of the mantissa of a
-    CHECK_FALSE(fast(".", out));
+// number token, which the lexer records while scanning it
-    CHECK_FALSE(fast("1.2.3", out));
+std::pair<std::size_t, std::size_t> float_token_layout(const std::string& s)
-    CHECK_FALSE(fast("1x", out));
+{
-    CHECK_FALSE(fast("1e+", out));
+    std::size_t dot = std::string::npos;
-    CHECK_FALSE(fast("1e1x", out));
+    std::size_t mantissa_end = s.size();
+    for (std::size_t i = 0; i < s.size(); ++i)
+    {
+        if (s[i] == '.')
+        {
+            dot = i;
+        }
+        else if (s[i] == 'e' || s[i] == 'E')
+        {
+            mantissa_end = i;
+            break;
+        }
+    }
+    return {dot, mantissa_end};
+}
 
-    // numbers that are not represented exactly on the fast path
+template<typename FloatType>
-    CHECK_FALSE(fast("12345678901234567890", out));
+FloatType parse_native(const std::string& s)
-    CHECK_FALSE(fast("1e10000", out));
+{
-    CHECK_FALSE(fast("9007199254740993", out));
+    const auto layout = float_token_layout(s);
-    CHECK_FALSE(fast("1e23", out));
+    return nlohmann::detail::parse_float_native<FloatType>(s.data(), s.data() + s.size(), layout.first, layout.second);
-    CHECK_FALSE(fast("1e-23", out));
+}
+
+std::uint64_t bits_of(double d)
+{
+    std::uint64_t b = 0;
+    std::memcpy(&b, &d, sizeof(b));
+    return b;
+}
+
+std::uint32_t bits_of(float f)
+{
+    std::uint32_t b = 0;
+    std::memcpy(&b, &f, sizeof(b));
+    return b;
+}
+
+std::uint64_t native_bits64(const std::string& s)
+{
+    return bits_of(parse_native<double>(s));
+}
+
+std::uint32_t native_bits32(const std::string& s)
+{
+    return bits_of(parse_native<float>(s));
+}
+} // namespace
+
+TEST_CASE("parse_float_native rounds correctly")
+{
+    SECTION("double")
+    {
+        CHECK(native_bits64("1.5") == 0x3FF8000000000000u);
+        CHECK(native_bits64("0.1") == 0x3FB999999999999Au);
+        CHECK(native_bits64("-0.0") == 0x8000000000000000u);
+        CHECK(native_bits64("0e999999999999999999999") == 0u);
+        // 2^53 + 1 is exactly between two doubles: ties to even, unless more digits follow
+        CHECK(native_bits64("9007199254740993") == 0x4340000000000000u);
+        CHECK(native_bits64("9007199254740993.0000000000000000001") == 0x4340000000000001u);
+        CHECK(native_bits64("9007199254740992.9999999999999999999") == 0x4340000000000000u);
+        // 1 + 2^-53 exactly (a tie), and one unit in the 55th digit around it
+        CHECK(native_bits64("1.00000000000000011102230246251565404236316680908203125") == 0x3FF0000000000000u);
+        CHECK(native_bits64("1.00000000000000011102230246251565404236316680908203126") == 0x3FF0000000000001u);
+        CHECK(native_bits64("1.00000000000000011102230246251565404236316680908203124") == 0x3FF0000000000000u);
+        // subnormal and overflow boundaries
+        CHECK(native_bits64("2.4703282292062327e-324") == 0u);
+        CHECK(native_bits64("2.4703282292062328e-324") == 1u);
+        CHECK(native_bits64("2.2250738585072011e-308") == 0x000FFFFFFFFFFFFFu);
+        CHECK(native_bits64("2.2250738585072012e-308") == 0x0010000000000000u);
+        CHECK(native_bits64("1.7976931348623157e308") == 0x7FEFFFFFFFFFFFFFu);
+        CHECK(native_bits64("1.7976931348623159e308") == 0x7FF0000000000000u);
+        CHECK(native_bits64("-1e400") == 0xFFF0000000000000u);
+        CHECK(native_bits64("-1e-400") == 0x8000000000000000u);
+        // exponents and zeros far beyond the range cancel out
+        CHECK(native_bits64("0." + std::string(1000, '0') + "1e1001") == 0x3FF0000000000000u);
+        CHECK(native_bits64("1" + std::string(1000, '0') + "e-1000") == 0x3FF0000000000000u);
+        CHECK(native_bits64("1e-99999999999999999999999") == 0u);
+        CHECK(native_bits64("1E+99999999999999999999999") == 0x7FF0000000000000u);
+        // more digits than any midpoint has (769): only whether a nonzero digit follows matters
+        const std::string tie = "1.00000000000000011102230246251565404236316680908203125";
+        CHECK(native_bits64(tie + std::string(800, '0')) == 0x3FF0000000000000u);
+        CHECK(native_bits64(tie + std::string(800, '0') + "1") == 0x3FF0000000000001u);
+    }
+
+    SECTION("float")
+    {
+        CHECK(native_bits32("1.5") == 0x3FC00000u);
+        CHECK(native_bits32("0.1") == 0x3DCCCCCDu);
+        CHECK(native_bits32("-0.0") == 0x80000000u);
+        // 2^24 + 1 is exactly between two floats
+        CHECK(native_bits32("16777217") == 0x4B800000u);
+        CHECK(native_bits32("16777217.000000000000000000001") == 0x4B800001u);
+        CHECK(native_bits32("16777218.999999999999999999999") == 0x4B800001u);
+        CHECK(native_bits32("16777219") == 0x4B800002u);
+        // subnormal and overflow boundaries
+        CHECK(native_bits32("3.4028235677973366e38") == 0x7F7FFFFFu);
+        CHECK(native_bits32("3.4028235677973367e38") == 0x7F800000u);
+        CHECK(native_bits32("7.006492321624085e-46") == 0u);
+        CHECK(native_bits32("7.006492321624086e-46") == 1u);
+        CHECK(native_bits32("1.1754942e-38") == 0x007FFFFFu);
+        CHECK(native_bits32("-1.17549435e-38") == 0x80800000u);
+        CHECK(native_bits32("1e39") == 0x7F800000u);
+        CHECK(native_bits32("-1e-50") == 0x80000000u);
+        // not rounded through double: its double would round to another float
+        CHECK(native_bits32("1.00000005960464477539062500000000001") == 0x3F800001u);
+        CHECK(native_bits32("9007199254740993") == 0x5A000000u);
+    }
+
+    SECTION("the conversion shared with other parsers")
+    {
+        // convert_float() gives the lexer's results, for every type
+        const std::vector<std::string> tokens =
+        {
+            "0", "-0.0", "1.5", "0.1", "1e-400", "-2.5E+3", "123456789012345678901234567890",
+            "9007199254740993.0000000000000000001", "4.9406564584124654e-324"
+        };
+        using float_json = nlohmann::basic_json<std::map, std::vector, std::string, bool, std::int64_t, std::uint64_t, float>;
+        using long_double_json = nlohmann::basic_json<std::map, std::vector, std::string, bool, std::int64_t, std::uint64_t, long double>;
+        for (const auto& t : tokens)
+        {
+            CAPTURE(t)
+            const auto layout = float_token_layout(t);
+            const char* const first = t.data();
+            const char* const last = first + t.size();
+            const auto d = nlohmann::detail::convert_float<double>(first, last, layout.first, layout.second);
+            const auto f = nlohmann::detail::convert_float<float>(first, last, layout.first, layout.second);
+            const auto ld = nlohmann::detail::convert_float<long double>(first, last, layout.first, layout.second);
+            CHECK(bits_of(d) == bits_of(json::parse(t).get<double>()));
+            CHECK(bits_of(f) == bits_of(float_json::parse(t).get<float>()));
+            CHECK(ld == long_double_json::parse(t).get<long double>());
+        }
+    }
 }
 
 namespace
@@ -806,40 +1086,6 @@ std::size_t big_bit_length(const big_uint& a)
     }
     return n;
 }
-
-std::uint64_t bits_of(double d)
-{
-    std::uint64_t b = 0;
-    std::memcpy(&b, &d, sizeof(b));
-    return b;
-}
-
-bool eisel_lemire(const std::string& s, double& out)
-{
-    return nlohmann::detail::parse_float_eisel_lemire(s.data(), s.data() + s.size(), out);
-}
-
-// significant digits of a token, without trailing zeros
-std::size_t significant_digits(const std::string& s)
-{
-    std::string digits;
-    for (const char c : s)
-    {
-        if (c == 'e' || c == 'E')
-        {
-            break;
-        }
-        if (c >= '0' && c <= '9' && !(digits.empty() && c == '0'))
-        {
-            digits += c;
-        }
-    }
-    while (!digits.empty() && digits.back() == '0')
-    {
-        digits.pop_back();
-    }
-    return digits.size();
-}
 } // namespace
 
 TEST_CASE("Eisel-Lemire float conversion")
@@ -891,8 +1137,39 @@ TEST_CASE("Eisel-Lemire float conversion")
 
     SECTION("128-bit products and leading zeros")
     {
+        const auto check_product = [](std::uint64_t a, std::uint64_t b)
+        {
+            const auto product = nlohmann::detail::full_multiplication(a, b);
+            CHECK(big_from(product.high, product.low) == big_mul(big_from(0, a), big_from(0, b)));
+        };
+
+        const std::uint64_t max = (std::numeric_limits<std::uint64_t>::max)();
+        const std::array<std::pair<std::uint64_t, std::uint64_t>, 13> edge_cases =
+        {
+            {
+                {0, 0},
+                {0, 1},
+                {1, 1},
+                {1, max},
+                {0xFFFFFFFFu, 0x100000000u},
+                {0x100000000u, 0x100000000u},
+                {0x100000001u, 0x100000001u},
+                {max, max},
+                {max, 2},
+                {0xFFFFFFFF00000000u, 0x100000001u},
+                {0x100000001u, 0xFFFFFFFF00000000u},
+                {max, 1},
+                {2, max},
+            }
+        };
+
+        for (const auto& test : edge_cases)
+        {
+            check_product(test.first, test.second);
+        }
+
         // whichever implementation the compiler gets (with or without a
-        // 128-bit integer type or a builtin)
+        // 128-bit integer type or a builtin / intrinsic)
         std::uint64_t state = 42;
         for (int i = 0; i < 10000; ++i)
         {
@@ -901,8 +1178,7 @@ TEST_CASE("Eisel-Lemire float conversion")
             state ^= state << 17u;
             const std::uint64_t a = state;
             const std::uint64_t b = (state * 0x9E3779B97F4A7C15u) >> (i % 64);
-            const auto product = nlohmann::detail::full_multiplication(a, b);
+            check_product(a, b);
-            CHECK(big_from(product.high, product.low) == big_mul(big_from(0, a), big_from(0, b)));
 
             const int k = i % 64;
             const std::uint64_t x = (std::uint64_t{1} << k) | (a & ((std::uint64_t{1} << k) - 1));
@@ -1237,26 +1513,33 @@ TEST_CASE("Eisel-Lemire float conversion")
         for (const auto& c : known)
         {
             CAPTURE(c.first)
-            double out = 0;
+            CHECK(native_bits64(c.first) == c.second);
-            if (eisel_lemire(c.first, out))
+        }
+    }
+
+    SECTION("binary32")
     {
-                CHECK(bits_of(out) == c.second);
+        using binary32 = nlohmann::detail::ieee_binary_format<24>;
-            }
+        CHECK(nlohmann::detail::eisel_lemire<binary32>(0, 1) == 0x3F800000u);
-            else
+        CHECK(nlohmann::detail::eisel_lemire<binary32>(-1, 1) == 0x3DCCCCCDu);
-            {
+        CHECK(nlohmann::detail::eisel_lemire<binary32>(-1, 15) == 0x3FC00000u);
-                // only tokens with more than 19 significant digits are left to
+        CHECK(nlohmann::detail::eisel_lemire<binary32>(0, 16777217) == 0x4B800000u); // tie, to even
-                // strtod: those whose value lies too close to a tie
+        CHECK(nlohmann::detail::eisel_lemire<binary32>(0, 16777219) == 0x4B800002u); // tie, to even
-                CHECK(significant_digits(c.first) > 19);
+        CHECK(nlohmann::detail::eisel_lemire<binary32>(-45, 1) == 0x00000001u);
-            }
+        CHECK(nlohmann::detail::eisel_lemire<binary32>(-46, 7) == 0x00000000u);
-        }
+        CHECK(nlohmann::detail::eisel_lemire<binary32>(-46, 8) == 0x00000001u);
+        CHECK(nlohmann::detail::eisel_lemire<binary32>(-65, 9999999999999999999u) == 0x00000000u);
+        CHECK(nlohmann::detail::eisel_lemire<binary32>(20, 3402823466385288598u) == 0x7F7FFFFFu);
+        CHECK(nlohmann::detail::eisel_lemire<binary32>(20, 3402823669209384635u) == 0x7F800000u);
+        CHECK(nlohmann::detail::eisel_lemire<binary32>(39, 1) == 0x7F800000u);
+        CHECK(nlohmann::detail::eisel_lemire<binary32>(-5, 0) == 0x00000000u);
     }
 
     SECTION("round trip")
     {
-        // every double written by to_chars and read back, also with trailing
+        // every double written by to_chars and read back, and its 17-digit
-        // digits that make the token longer than 19 digits
+        // form with trailing digits that make the token longer than 19 digits
         std::uint64_t state = 5295;
-        std::size_t declined = 0;
         for (int i = 0; i < 200000; ++i)
         {
             state ^= state << 13u;
@@ -1278,30 +1561,51 @@ TEST_CASE("Eisel-Lemire float conversion")
             const char* end = nlohmann::detail::to_chars(buffer.data(), buffer.data() + buffer.size(), d);
             const std::string token(buffer.data(), static_cast<std::size_t>(end - buffer.data()));
             CAPTURE(token)
-            double out = 0;
+            CHECK(native_bits64(token) == b);
-            REQUIRE(eisel_lemire(token, out));
-            CHECK(bits_of(out) == b);
 
-            // insert digits before the exponent: the value moves by far less
+            // insert digits before the exponent of the 17-digit form: that
-            // than the distance to the rounding boundary, so it must not change
+            // form lies strictly inside the rounding interval of the double
-            std::string longer = token;
+            // (the shortest one may lie on its boundary), and the digits move
+            // it by far less than the distance to the boundary, so the value
+            // must not change
+            std::array<char, 64> digits17{};
+            static_cast<void>(std::snprintf(digits17.data(), digits17.size(), "%.17g", d)); // NOLINT(cppcoreguidelines-pro-type-vararg,hicpp-vararg)
+            std::string longer = digits17.data();
             const std::size_t e = longer.find('e');
             const std::size_t dot = longer.find('.');
             const std::string extra = dot == std::string::npos ? ".000000000000000000001" : "000000000000000000001";
             longer.insert(e == std::string::npos ? longer.size() : e, extra);
             CAPTURE(longer)
-            if (eisel_lemire(longer, out))
+            CHECK(native_bits64(longer) == b);
+        }
+    }
+
+    SECTION("round trip, binary32")
     {
-                CHECK(bits_of(out) == b);
+        std::uint32_t state = 5295;
-            }
+        for (int i = 0; i < 100000; ++i)
-            else
         {
-                // w and w + 1 round differently: only when the value is very
+            state ^= state << 13u;
-                // close to a rounding boundary
+            state ^= state >> 17u;
-                ++declined;
+            state ^= state << 5u;
+            std::uint32_t b = state;
+            if ((b & 0x7F800000u) == 0x7F800000u)
+            {
+                continue; // infinity or NaN
             }
+            if (i % 4 == 0)
+            {
+                b &= 0x807FFFFFu; // subnormals
+            }
+            float f = 0;
+            std::memcpy(&f, &b, sizeof(f));
+
+            std::array<char, 64> buffer{};
+            const char* end = nlohmann::detail::to_chars(buffer.data(), buffer.data() + buffer.size(), f);
+            const std::string token(buffer.data(), static_cast<std::size_t>(end - buffer.data()));
+            CAPTURE(token)
+            CHECK(native_bits32(token) == b);
         }
-        CHECK(declined < 1000); // 107 of the 200,000
     }
 
     SECTION("used by the lexer")
@@ -1315,3 +1619,177 @@ TEST_CASE("Eisel-Lemire float conversion")
                              "[json.exception.out_of_range.406] number overflow parsing '1.7976931348623159e308'", json::out_of_range&);
     }
 }
+
+namespace
+{
+using float_json = nlohmann::basic_json<std::map, std::vector, std::string, bool, std::int64_t, std::uint64_t, float>;
+
+// the bits of the float that parse() gives for a token, via both scanners;
+// the value must be the same for both
+template<typename Json, typename Bits>
+void check_parse(const std::string& token, Bits expected, Bits infinity)
+{
+    std::stringstream stream(token);
+    if ((expected & ~(Bits{1} << ((8 * sizeof(Bits)) - 1))) == infinity)
+    {
+        Json _;
+        CHECK_THROWS_WITH_AS(_ = Json::parse(token), ("[json.exception.out_of_range.406] number overflow parsing '" + token + "'").c_str(), typename Json::out_of_range&);
+        CHECK_THROWS_WITH_AS(_ = Json::parse(stream), ("[json.exception.out_of_range.406] number overflow parsing '" + token + "'").c_str(), typename Json::out_of_range&);
+        return;
+    }
+    const Json contiguous = Json::parse(token);
+    const Json streamed = Json::parse(stream);
+    if (contiguous.is_number_float()) // not an integer that fits
+    {
+        CHECK(bits_of(contiguous.template get<typename Json::number_float_t>()) == expected);
+        CHECK(bits_of(streamed.template get<typename Json::number_float_t>()) == expected);
+    }
+    else
+    {
+        CHECK(streamed.is_number_integer());
+    }
+}
+} // namespace
+
+TEST_CASE("float conversion of hard cases")
+{
+    // see float_hard_cases.hpp
+    for (const auto& c : float_hard_cases::cases())
+    {
+        const std::string token = c.token;
+        CAPTURE(token)
+        CHECK(native_bits64(token) == c.bits64);
+        CHECK(native_bits32(token) == c.bits32);
+        check_parse<json>(token, c.bits64, std::uint64_t{0x7FF0000000000000u});
+        check_parse<float_json>(token, c.bits32, std::uint32_t{0x7F800000u});
+    }
+}
+
+TEST_CASE("float overflow and underflow in the parser")
+{
+    SECTION("double")
+    {
+        check_parse<json>("1.7976931348623157e308", std::uint64_t{0x7FEFFFFFFFFFFFFFu}, std::uint64_t{0x7FF0000000000000u});
+        check_parse<json>("1.7976931348623159e308", std::uint64_t{0x7FF0000000000000u}, std::uint64_t{0x7FF0000000000000u});
+        check_parse<json>("-1e309", std::uint64_t{0xFFF0000000000000u}, std::uint64_t{0x7FF0000000000000u});
+        check_parse<json>("1" + std::string(400, '0'), std::uint64_t{0x7FF0000000000000u}, std::uint64_t{0x7FF0000000000000u});
+        check_parse<json>("1e99999999999999999999", std::uint64_t{0x7FF0000000000000u}, std::uint64_t{0x7FF0000000000000u});
+        // an underflow gives a zero with the sign of the token
+        check_parse<json>("1e-400", std::uint64_t{0}, std::uint64_t{0x7FF0000000000000u});
+        check_parse<json>("-1e-400", std::uint64_t{0x8000000000000000u}, std::uint64_t{0x7FF0000000000000u});
+        check_parse<json>("-2.4703282292062327e-324", std::uint64_t{0x8000000000000000u}, std::uint64_t{0x7FF0000000000000u});
+        check_parse<json>("0." + std::string(400, '0') + "1", std::uint64_t{0}, std::uint64_t{0x7FF0000000000000u});
+    }
+
+    SECTION("float")
+    {
+        check_parse<float_json>("3.4028234e38", std::uint32_t{0x7F7FFFFFu}, std::uint32_t{0x7F800000u});
+        check_parse<float_json>("3.4028236e38", std::uint32_t{0x7F800000u}, std::uint32_t{0x7F800000u});
+        check_parse<float_json>("-1e39", std::uint32_t{0xFF800000u}, std::uint32_t{0x7F800000u});
+        check_parse<float_json>("1e-46", std::uint32_t{0}, std::uint32_t{0x7F800000u});
+        check_parse<float_json>("-1e-46", std::uint32_t{0x80000000u}, std::uint32_t{0x7F800000u});
+        check_parse<float_json>("-7.006492321624085e-46", std::uint32_t{0x80000000u}, std::uint32_t{0x7F800000u});
+        check_parse<float_json>("-7.006492321624086e-46", std::uint32_t{0x80000001u}, std::uint32_t{0x7F800000u});
+    }
+}
+
+TEST_CASE("string scanning kernels")
+{
+    // the word-at-a-time kernels must stop exactly where a byte-by-byte scan
+    // stops, for any content, length, and alignment
+    const auto reference_special = [](const unsigned char* data, std::size_t n)
+    {
+        std::size_t i = 0;
+        while (i < n && !nlohmann::detail::is_string_special(data[i]))
+        {
+            ++i;
+        }
+        return i;
+    };
+    const auto reference_copyable = [](const unsigned char* data, std::size_t n)
+    {
+        std::size_t i = 0;
+        while (i < n && nlohmann::detail::is_ascii_copyable(data[i]))
+        {
+            ++i;
+        }
+        return i;
+    };
+    const auto reference_bulk_run = [](const unsigned char* data, std::size_t n)
+    {
+        std::size_t i = 0;
+        while (i < n)
+        {
+            if (data[i] < 0x80u)
+            {
+                if (nlohmann::detail::is_string_special(data[i]))
+                {
+                    break;
+                }
+                ++i;
+                continue;
+            }
+            const std::size_t seq = nlohmann::detail::validate_one_utf8(data + i, n - i);
+            if (seq == 0)
+            {
+                break;
+            }
+            i += seq;
+        }
+        return i;
+    };
+
+    // pieces: ordinary ASCII, stops, DEL, well-formed sequences of every
+    // length, and ill-formed or truncated ones
+    const std::vector<std::string> pieces =
+    {
+        "a", "Z", " ", "~", "0123456789", "\"", "\\", std::string(1, '\0'), "\n", "\x1F", "\x7F",
+        "\xC3\xA4", "\xE2\x82\xAC", "\xE6\x97\xA5\xE6\x9C\xAC", "\xF0\x9F\x98\x80", "\xED\x9F\xBF",
+        "\x80", "\xC0\x80", "\xC3", "\xE2\x82", "\xED\xA0\x80", "\xF4\x90\x80\x80", "\xFF",
+    };
+    std::uint64_t state = 5295;
+    const auto next = [&state]()
+    {
+        state ^= state << 13u;
+        state ^= state >> 7u;
+        state ^= state << 17u;
+        return state;
+    };
+    // the upper half as a 32-bit value: converts to std::size_t implicitly on
+    // every platform (a cast of std::uint64_t is useless where both are the
+    // same type, and required where std::size_t is 32 bits wide)
+    const auto next_small = [&next]()
+    {
+        return static_cast<std::uint32_t>(next() >> 32u);
+    };
+    for (int round = 0; round < 100000; ++round)
+    {
+        // mostly ordinary text, so that runs span several words
+        std::string text(next_small() % 8u, '.');
+        const std::size_t count = next_small() % 12u;
+        for (std::size_t k = 0; k < count; ++k)
+        {
+            const std::size_t p = (next() % 4 == 0) ? next_small() % pieces.size() : 0;
+            text += pieces[p];
+            text += std::string(next_small() % 10u, 'x');
+        }
+        const auto* data = reinterpret_cast<const unsigned char*>(text.data()); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
+        for (std::size_t offset = 0; offset < 3 && offset <= text.size(); ++offset)
+        {
+            const std::size_t n = text.size() - offset;
+            CAPTURE(text)
+            CAPTURE(offset)
+            CHECK(nlohmann::detail::find_string_special(data + offset, n) == reference_special(data + offset, n));
+            CHECK(nlohmann::detail::find_ascii_copyable_run(data + offset, n) == reference_copyable(data + offset, n));
+            CHECK(nlohmann::detail::scalar_string_bulk_run(data + offset, n) == reference_bulk_run(data + offset, n));
+        }
+    }
+
+    // the trailing-zero count, whichever implementation the compiler gets
+    for (int k = 0; k < 64; ++k)
+    {
+        const std::uint64_t bit = std::uint64_t{1} << k;
+        CHECK(nlohmann::detail::count_trailing_zeros(bit) == k);
+        CHECK(nlohmann::detail::count_trailing_zeros(bit | (bit << 1u) | 0x8000000000000000u) == k);
+    }
+}

tests/src/unit-comparison.cpp

@@ -824,7 +824,7 @@ struct unordered_object_t : std::map<Key, Value, directed_less<Key>, Allocator>
         return !(lhs == rhs);
     }
 };
-using unordered_json = nlohmann::basic_json<unordered_object_t>;
+using unordered_json = nlohmann::json::with_object_t<unordered_object_t>;
 
 // the entries "0" to "9", enumerated in ascending or in descending order
 unordered_json make_unordered_object(const bool descending)
@@ -875,7 +875,7 @@ struct key_case_less
 
 template<class Key, class Value, class /*Compare*/, class Allocator>
 using key_case_map = std::map<Key, Value, key_case_less, Allocator>;
-using key_case_json = nlohmann::basic_json<key_case_map>;
+using key_case_json = nlohmann::json::with_object_t<key_case_map>;
 
 // the innermost value of a chain of single-element arrays
 template<typename Json>
@@ -905,7 +905,7 @@ struct case_insensitive_less
 
 template<class Key, class Value, class /*Compare*/, class Allocator>
 using case_insensitive_map = std::map<Key, Value, case_insensitive_less, Allocator>;
-using ci_json = nlohmann::basic_json<case_insensitive_map>;
+using ci_json = nlohmann::json::with_object_t<case_insensitive_map>;
 } // namespace
 
 TEST_CASE("equality of objects whose entries have no fixed order")

tests/src/unit-custom-array-type.cpp

@@ -22,7 +22,7 @@ namespace
 
 // std::deque has no capacity() member function, which the library only needs
 // to detect a reallocation for JSON_DIAGNOSTICS
-using deque_json = nlohmann::basic_json<std::map, std::deque>;
+using deque_json = nlohmann::json::with_array_t<std::deque>;
 
 // a std::vector whose at() is hidden: the library performs its own bounds
 // check and must not fall back to the container's checked accessor
@@ -39,7 +39,7 @@ class vector_without_at : public std::vector<T, Allocator>
     void at() = delete;
 };
 
-using no_at_json = nlohmann::basic_json<std::map, vector_without_at>;
+using no_at_json = nlohmann::json::with_array_t<vector_without_at>;
 
 } // namespace
 

tests/src/unit-custom-object-type.cpp

@@ -179,7 +179,7 @@ class no_key_compare_map
     }
 };
 
-using no_key_compare_json = nlohmann::basic_json<no_key_compare_map>;
+using no_key_compare_json = nlohmann::json::with_object_t<no_key_compare_map>;
 
 // An ObjectType whose erase(iterator) returns void rather than the following
 // iterator, as for instance Abseil's hash maps do
@@ -196,7 +196,7 @@ struct void_erase_map : std::map<Key, T, Compare, Allocator>
     }
 };
 
-using void_erase_json = nlohmann::basic_json<void_erase_map>;
+using void_erase_json = nlohmann::json::with_object_t<void_erase_map>;
 
 // wraps an iterator, but only offers the LegacyForwardIterator operations,
 // like the iterators of std::unordered_map and other hash maps
@@ -388,7 +388,7 @@ class forward_only_map
     }
 };
 
-using forward_only_json = nlohmann::basic_json<forward_only_map>;
+using forward_only_json = nlohmann::json::with_object_t<forward_only_map>;
 
 } // namespace
 

tests/src/unit-hash.cpp

@@ -157,13 +157,13 @@ TEST_CASE("hash<nlohmann::json>")
     // the ends of the integer ranges, which equal floats exactly
     const auto int_min = (std::numeric_limits<json::number_integer_t>::min)();
     const auto int_max = (std::numeric_limits<json::number_integer_t>::max)();
-    const auto two_63 = json::number_unsigned_t(1) << 63U;
+    const auto two_63 = static_cast<json::number_unsigned_t>(1) << 63U;
     CHECK(json(int_min) == json(-9223372036854775808.0));
     CHECK(std::hash<json> {}(json(int_min)) == std::hash<json> {}(json(-9223372036854775808.0)));
     CHECK(json(two_63) == json(9223372036854775808.0));
     CHECK(std::hash<json> {}(json(two_63)) == std::hash<json> {}(json(9223372036854775808.0)));
-    CHECK(json(json::number_unsigned_t(int_max)) == json(int_max));
+    CHECK(json(static_cast<json::number_unsigned_t>(int_max)) == json(int_max));
-    CHECK(std::hash<json> {}(json(json::number_unsigned_t(int_max))) == std::hash<json> {}(json(int_max)));
+    CHECK(std::hash<json> {}(json(static_cast<json::number_unsigned_t>(int_max))) == std::hash<json> {}(json(int_max)));
 }
 
 TEST_CASE("hash<nlohmann::ordered_json>")

tests/src/unit-large_json.cpp

@@ -426,7 +426,7 @@ TEST_CASE("issue #5392 - binary writers on deeply nested values")
     {
         for (std::size_t depth = 120; depth <= 140; ++depth)
         {
-            CAPTURE(depth);
+            CAPTURE(depth)
 
             const json array = nested_array(depth, json(7));
             CHECK(json::from_cbor(json::to_cbor(array)) == array);
@@ -464,7 +464,7 @@ TEST_CASE("issue #5392 - binary writers on deeply nested values")
                     nlohmann::detail::recursion_depth_limit() + 1, nlohmann::detail::recursion_depth_limit() + 2
                 })
         {
-            CAPTURE(depth);
+            CAPTURE(depth)
             const json array = nested_array(depth, json(0));
 
             std::vector<std::uint8_t> expected_cbor(depth, 0x81);
@@ -505,10 +505,22 @@ TEST_CASE("issue #5392 - binary writers on deeply nested values")
         const json discarded_leaf(json::value_t::discarded);
         const json deep_discarded = nested_array(depth, discarded_leaf);
 
-        CHECK_THROWS_WITH_AS(json::to_cbor(deep_discarded), "[json.exception.type_error.321] cannot serialize discarded value to CBOR", json::type_error);
+        // with diagnostics, the message names the path to the discarded leaf
-        CHECK_THROWS_WITH_AS(json::to_msgpack(deep_discarded), "[json.exception.type_error.321] cannot serialize discarded value to MessagePack", json::type_error);
+#if JSON_DIAGNOSTICS
-        CHECK_THROWS_WITH_AS(json::to_ubjson(deep_discarded), "[json.exception.type_error.321] cannot serialize discarded value to UBJSON", json::type_error);
+        std::string path;
-        CHECK_THROWS_WITH_AS(json::to_bjdata(deep_discarded), "[json.exception.type_error.321] cannot serialize discarded value to BJData", json::type_error);
+        for (std::size_t i = 0; i < depth; ++i)
+        {
+            path += "/0";
+        }
+        const std::string prefix = "[json.exception.type_error.321] (" + path + ") ";
+#else
+        const std::string prefix = "[json.exception.type_error.321] ";
+#endif
+
+        CHECK_THROWS_WITH_AS(json::to_cbor(deep_discarded), (prefix + "cannot serialize discarded value to CBOR").c_str(), json::type_error);
+        CHECK_THROWS_WITH_AS(json::to_msgpack(deep_discarded), (prefix + "cannot serialize discarded value to MessagePack").c_str(), json::type_error);
+        CHECK_THROWS_WITH_AS(json::to_ubjson(deep_discarded), (prefix + "cannot serialize discarded value to UBJSON").c_str(), json::type_error);
+        CHECK_THROWS_WITH_AS(json::to_bjdata(deep_discarded), (prefix + "cannot serialize discarded value to BJData").c_str(), json::type_error);
     }
 
     SECTION("does not overflow the C++ stack")

tests/src/unit-locale-cpp.cpp

@@ -172,7 +172,7 @@ TEST_CASE("locale-dependent test (LC_NUMERIC=de_DE)")
             // a floating-point type that is not a float or a double is written
             // with snprintf, whose locale-specific decimal point and thousands
             // separator are undone afterwards
-            using long_double_json = nlohmann::basic_json<std::map, std::vector, std::string, bool, std::int64_t, std::uint64_t, long double>;
+            using long_double_json = nlohmann::json::with_float_t<long double>;
             CHECK(long_double_json(12345.5L).dump() == "12345.5");
             CHECK(long_double_json(1.0L).dump() == "1.0");
             CHECK(long_double_json(-0.25L).dump() == "-0.25");
@@ -260,10 +260,11 @@ struct LocaleSwitchingSax final: public nlohmann::json_sax<json>
 
 TEST_CASE("locale changes between lexer construction and number conversion (#5198)")
 {
-    // The numbers are chosen so that the conversion also takes the strtod
+    // float and double are converted without the locale. A long double that
-    // fallback, which honors the locale that is current at conversion time:
+    // is not binary64 can take the strtold fallback, which honors the locale
-    // too many significant digits for Clinger's fast path, an underflow that
+    // that is current at conversion time. The numbers are chosen so that it
-    // std::from_chars rejects, and a plain value.
+    // does: too many significant digits for Clinger's fast path, an underflow
+    // that std::from_chars rejects, and a plain value.
     const std::vector<std::string> numbers = {"3.14159265358979323846", "1.5e-400", "12.34", "-0.000123456789012345678"};
     std::string text = "[";
     for (const auto& n : numbers)
@@ -272,7 +273,7 @@ TEST_CASE("locale changes between lexer construction and number conversion (#519
     }
     text += "]";
 
-    using long_double_json = nlohmann::basic_json<std::map, std::vector, std::string, bool, std::int64_t, std::uint64_t, long double>;
+    using long_double_json = nlohmann::json::with_float_t<long double>;
 
     // reference values, parsed without a locale switch
     REQUIRE(std::setlocale(LC_NUMERIC, "C") != nullptr);
@@ -327,7 +328,8 @@ TEST_CASE("locale changes between lexer construction and number conversion (#519
             }
         }
 
-        // a long double goes through std::strtold unless std::from_chars supports it
+        // a long double goes through std::strtold unless it is binary64 or
+        // std::from_chars supports it
         {
             bool switched = false;
             const auto cb = [&](int /*depth*/, long_double_json::parse_event_t event, long_double_json& /*parsed*/) noexcept
@@ -353,8 +355,15 @@ TEST_CASE("locale with a multi-byte decimal point")
 {
     // Some locales use a decimal point that is not a single character, e.g.
     // U+066B ARABIC DECIMAL SEPARATOR (two bytes in UTF-8). It cannot be
-    // substituted in place for '.', so the strtod fallback stops early. The
+    // substituted in place for '.', so the strtold fallback (only for long
-    // conversion must still terminate rather than retry forever.
+    // double formats other than binary64) converts a copy of the token with
+    // the whole decimal point instead (#5660). The values must be those of the
+    // "C" locale.
+    using long_double_json = nlohmann::basic_json<std::map, std::vector, std::string, bool, std::int64_t, std::uint64_t, long double>;
+    const char* const long_double_numbers = "[3.14159265358979323846, 1.5e-400, -0.000123456789012345678]";
+    REQUIRE(std::setlocale(LC_NUMERIC, "C") != nullptr);
+    const long_double_json expected_long_double = long_double_json::parse(long_double_numbers);
+
     const std::array<const char*, 6> names = {{"ar_EG.UTF-8", "ar_SA.UTF-8", "fa_IR.UTF-8", "ps_AF.UTF-8", "ar_EG", "fa_IR"}};
     bool tested = false;
     for (const char* name : names)
@@ -372,12 +381,20 @@ TEST_CASE("locale with a multi-byte decimal point")
         tested = true;
 
         // too many significant digits for Clinger's fast path, and an underflow
-        // that std::from_chars rejects: both reach the strtod fallback
+        // that std::from_chars rejects: double does not depend on the locale
         json j;
         CHECK_NOTHROW(j = json::parse("[3.14159265358979323846, 1.5e-400, -0.000123456789012345678]"));
         CHECK(j.is_array());
+        CHECK(j[0] == 3.14159265358979323846);
+        CHECK(j[1] == 0.0);
+        CHECK(j[2] == -0.000123456789012345678);
         CHECK(json::accept("3.14159265358979323846"));
 
+        // a long double that reaches the strtold fallback is not truncated
+        long_double_json ld;
+        CHECK_NOTHROW(ld = long_double_json::parse(long_double_numbers));
+        CHECK(ld == expected_long_double);
+
         // a value the locale-independent paths convert is not affected
         CHECK(json::parse("12.5") == 12.5);
     }
@@ -432,7 +449,7 @@ TEST_CASE("locale changes during a single dump() (#5709 item 3)")
     // long double on 64-bit Arm, where it is IEEE-754 double) takes the
     // locale-independent to_chars() path instead, and this test is a no-op
     // there.
-    using long_double_json = nlohmann::basic_json<std::map, std::vector, std::string, bool, std::int64_t, std::uint64_t, long double>;
+    using long_double_json = nlohmann::json::with_float_t<long double>;
     using ld_limits = std::numeric_limits<long_double_json::number_float_t>;
     const bool is_ieee_single_or_double =
         (ld_limits::is_iec559 && ld_limits::digits == 24 && ld_limits::max_exponent == 128) ||

tests/src/unit-msgpack.cpp

@@ -2432,8 +2432,8 @@ TEST_CASE("MessagePack numbers use the active union member (see #5644)")
     // used to read the union member that was not the active one, writing
     // wrong bytes for some values; std::int64_t/std::uint64_t (the default
     // types, where both members have the same width) were not affected
-    using int32_json = nlohmann::basic_json<std::map, std::vector, std::string, bool, std::int32_t, std::uint64_t, double>;
+    using int32_json = nlohmann::json::with_integers_t<std::int32_t, std::uint64_t>;
-    using int16_json = nlohmann::basic_json<std::map, std::vector, std::string, bool, std::int16_t, std::uint64_t, double>;
+    using int16_json = nlohmann::json::with_integers_t<std::int16_t, std::uint64_t>;
 
     SECTION("number_integer_t = std::int32_t")
     {

tests/src/unit-regression1.cpp

@@ -39,7 +39,7 @@ using nlohmann::json;
 
 template<class K, class V, class dummy_compare, class A>
 using my_workaround_fifo_map = nlohmann::fifo_map<K, V, nlohmann::fifo_map_compare<K>, A>;
-using my_json = nlohmann::basic_json<my_workaround_fifo_map>;
+using my_json = nlohmann::json::with_object_t<my_workaround_fifo_map>;
 
 /////////////////////////////////////////////////////////////////////
 // for #977
@@ -86,8 +86,7 @@ struct foo_serializer < T, typename std::enable_if < !std::is_same<foo, T>::valu
 };
 } // namespace ns
 
-using foo_json = nlohmann::basic_json<std::map, std::vector, std::string, bool, std::int64_t,
+using foo_json = nlohmann::json::with_json_serializer_t<ns::foo_serializer>;
-      std::uint64_t, double, std::allocator, ns::foo_serializer, std::vector<std::uint8_t>>;
 
 /////////////////////////////////////////////////////////////////////
 // for #805
@@ -254,7 +253,7 @@ TEST_CASE("regression tests 1")
     {
         // create JSON class with nonstandard integer number type
         using custom_json =
-            nlohmann::basic_json<std::map, std::vector, std::string, bool, int32_t, uint32_t, float>;
+            nlohmann::json::with_integers_t<std::int32_t, std::uint32_t>::with_float_t<float>;
         custom_json j;
         j["int_1"] = 1;
         CHECK(j["int_1"] == 1);
@@ -470,18 +469,17 @@ TEST_CASE("regression tests 1")
         // create JSON class with nonstandard float number type
 
         // float
-        nlohmann::basic_json<std::map, std::vector, std::string, bool, int32_t, uint32_t, float> const j_float =
+        nlohmann::json::with_integers_t<std::int32_t, std::uint32_t>::with_float_t<float> const j_float =
             1.23e25f;
         CHECK(j_float.get<float>() == 1.23e25f);
 
         // double
-        nlohmann::basic_json<std::map, std::vector, std::string, bool, int64_t, uint64_t, double> const j_double =
+        nlohmann::json const j_double =
             1.23e35;
         CHECK(j_double.get<double>() == 1.23e35);
 
         // long double
-        nlohmann::basic_json<std::map, std::vector, std::string, bool, int64_t, uint64_t, long double>
+        nlohmann::json::with_float_t<long double> const j_long_double = 1.23e45L;
-        const j_long_double = 1.23e45L;
         CHECK(j_long_double.get<long double>() == 1.23e45L);
     }
 

tests/src/unit-regression2.cpp

@@ -64,18 +64,7 @@ using ordered_json = nlohmann::ordered_json;
     /////////////////////////////////////////////////////////////////////
     // for #4804
     /////////////////////////////////////////////////////////////////////
-    using json_4804 = nlohmann::basic_json<std::map,        // ObjectType
+    using json_4804 = nlohmann::json::with_binary_t<std::vector<std::byte>>;
-    std::vector,     // ArrayType
-    std::string,     // StringType
-    bool,            // BooleanType
-    std::int64_t,    // NumberIntegerType
-    std::uint64_t,   // NumberUnsignedType
-    double,          // NumberFloatType
-    std::allocator,  // AllocatorType
-    nlohmann::adl_serializer,  // JSONSerializer
-    std::vector<std::byte>,    // BinaryType
-    void                       // CustomBaseClass
-    >;
 #endif
 
 #ifdef JSON_HAS_CPP_20
@@ -107,7 +96,7 @@ DOCTEST_CLANG_SUPPRESS_WARNING("-Wexit-time-destructors")
 // for #1021
 /////////////////////////////////////////////////////////////////////
 
-using float_json = nlohmann::basic_json<std::map, std::vector, std::string, bool, std::int64_t, std::uint64_t, float>;
+using float_json = nlohmann::json::with_float_t<float>;
 
 #if (defined(__cpp_exceptions) || defined(__EXCEPTIONS) || defined(_CPPUNWIND)) && !defined(JSON_NOEXCEPTION)
 namespace
@@ -155,10 +144,8 @@ struct failing_allocator : std::allocator<T>
     };
 };
 
-using failing_json = nlohmann::basic_json<std::map, std::vector, std::string, bool,
+using failing_json = nlohmann::json::with_allocator_t<failing_allocator>;
-      std::int64_t, std::uint64_t, double, failing_allocator>;
+using failing_ordered_json = nlohmann::ordered_json::with_allocator_t<failing_allocator>;
-using failing_ordered_json = nlohmann::basic_json<nlohmann::ordered_map, std::vector, std::string, bool,
-      std::int64_t, std::uint64_t, double, failing_allocator>;
 
 // builds `depth` levels of nesting around a scalar, iteratively (never
 // recursing: each wrap only moves the previous, already-built value, which

tests/src/unit-regression3.cpp

@@ -62,18 +62,7 @@ using ordered_json = nlohmann::ordered_json;
     /////////////////////////////////////////////////////////////////////
     // for #4804
     /////////////////////////////////////////////////////////////////////
-    using json_4804 = nlohmann::basic_json<std::map,        // ObjectType
+    using json_4804 = nlohmann::json::with_binary_t<std::vector<std::byte>>;
-    std::vector,     // ArrayType
-    std::string,     // StringType
-    bool,            // BooleanType
-    std::int64_t,    // NumberIntegerType
-    std::uint64_t,   // NumberUnsignedType
-    double,          // NumberFloatType
-    std::allocator,  // AllocatorType
-    nlohmann::adl_serializer,  // JSONSerializer
-    std::vector<std::byte>,    // BinaryType
-    void                       // CustomBaseClass
-    >;
 #endif
 
 #ifdef JSON_HAS_CPP_20
@@ -930,7 +919,7 @@ TEST_CASE("regression test #5476 - array type without reserve()")
 {
     // the capacity reserved for definite-length arrays must not require the
     // array type to have a reserve() member function
-    using deque_json = nlohmann::basic_json<std::map, std::deque>;
+    using deque_json = nlohmann::json::with_array_t<std::deque>;
 
     SECTION("std::deque")
     {

tests/src/unit-serialization.cpp

@@ -367,8 +367,7 @@ TEST_CASE("dump for basic_json with long double number_float_t")
     // serializer::dump_float(x, std::false_type). That branch must use the
     // "%.*Lg" format specifier; using "%.*g" with a long double argument is
     // undefined behavior and corrupts the output.
-    using long_double_json = nlohmann::basic_json<std::map, std::vector, std::string,
+    using long_double_json = nlohmann::json::with_float_t<long double>;
-          bool, std::int64_t, std::uint64_t, long double>;
 
     SECTION("round-trip dump/parse")
     {