Merge branch 'develop' into claude/fix-issue-2649-738aba

Conflicts:
- tests/src/unit-alt-string.cpp: kept both new sections (this PR's
  "conversion between basic_json specializations (#2649)" and develop's
  "strict enum" regression test for #5667)

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

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

@@ -272,6 +272,15 @@ basic_json(basic_json&& other) noexcept;
         When used without parentheses around an empty initializer list, `basic_json()` is called instead of this
         function, yielding the JSON `#!json null` value.
 
+- Overload 4:
+
+    !!! info "Implicit conversion"
+
+        The conversion is implicit unless [`JSON_USE_IMPLICIT_CONVERSIONS`](../macros/json_use_implicit_conversions.md)
+        is defined to `0` and `BasicJsonType::string_t` differs from `string_t`. In that case, the constructor is
+        `explicit`, so a JSON value with a different string type is no longer silently converted, for example when it is
+        passed to a function taking `#!cpp const json&`. Write `#!cpp json(other)` or `#!cpp other.get<json>()` instead.
+
 - Overload 7:
 
     !!! info "Preconditions"
@@ -420,7 +429,8 @@ basic_json(basic_json&& other) noexcept;
 1. Since version 1.0.0.
 2. Since version 1.0.0.
 3. Since version 2.1.0.
-4. Since version 3.2.0.
+4. Since version 3.2.0. Explicit for different string types if `JSON_USE_IMPLICIT_CONVERSIONS` is `0` since
+   version 3.13.0.
 5. Since version 1.0.0.
 6. Since version 1.0.0.
 7. Since version 1.0.0. Fixed in version 3.13.0 to also check the iterator range for binary values; before, a range

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

@@ -5,7 +5,9 @@
 ```
 
 When defined to `0`, implicit conversions are switched off. By default, implicit conversions are switched on. The
-value directly affects [`operator ValueType`](../basic_json/operator_ValueType.md).
+value directly affects [`operator ValueType`](../basic_json/operator_ValueType.md) and the
+[converting constructor](../basic_json/basic_json.md) from a `basic_json` specialization with a different string
+type (overload 4).
 
 ## Default definition
 
@@ -57,6 +59,25 @@ By default, implicit conversions are enabled.
     auto s = j.get<std::string>();
     ```
 
+??? example "Conversion between `basic_json` specializations"
+
+    A `basic_json` specialization with a different string type is also no longer converted implicitly when
+    `JSON_USE_IMPLICIT_CONVERSIONS` is defined to `0`:
+
+    ```cpp
+    using wjson = nlohmann::basic_json<std::map, std::vector, std::wstring>;
+
+    void load(const nlohmann::json& j);
+
+    wjson wj = /* ... */;
+    load(wj);                            // error: no implicit conversion
+    load(nlohmann::json(wj));            // OK: explicit conversion
+    load(wj.get<nlohmann::json>());      // OK: explicit conversion
+    ```
+
+    Specializations that share the same string type, such as `json` and `ordered_json`, remain implicitly
+    convertible.
+
 ## See also
 
 - [**operator ValueType**](../basic_json/operator_ValueType.md) - get a value (implicit)
@@ -66,3 +87,4 @@ By default, implicit conversions are enabled.
 ## Version history
 
 - Added in version 3.9.0.
+- Also affects the conversion between `basic_json` specializations with different string types since version 3.13.0.

include/nlohmann/detail/conversions/to_json.hpp

@@ -291,7 +291,9 @@ void to_json(BasicJsonType& j, const std::optional<T>& opt) noexcept(std::is_not
 {
     if (opt.has_value())
     {
-        j = *opt;
+        // explicit construction, as the conversion from a basic_json with a different
+        // string type is explicit if JSON_USE_IMPLICIT_CONVERSIONS is 0 (#2649)
+        j = BasicJsonType(*opt);
     }
     else
     {

include/nlohmann/detail/input/binary_reader.hpp

@@ -8,6 +8,7 @@
 
 #pragma once
 
+#include <algorithm> // generate_n
 #include <array> // array
 #include <cmath> // ldexp
 #include <cstddef> // size_t
@@ -122,26 +123,7 @@ class binary_reader
     ~binary_reader() = default;
 
     /*!
-    @brief parse in the format the constructor was given
-
-    @param[in] sax_    a SAX event processor
-    @param[in] strict  whether to expect the input to be consumed completed
-    @param[in] tag_handler  how to treat CBOR tags
-
-    @return whether parsing was successful
-    */
-    JSON_HEDLEY_NON_NULL(2)
-    bool sax_parse(json_sax_t* sax_,
-                   const bool strict = true,
-                   const cbor_tag_handler_t tag_handler = cbor_tag_handler_t::error)
-    {
-        return sax_parse(input_format, sax_, strict, tag_handler);
-    }
-
-    /*!
-    @param[in] format  the binary format to parse; must equal the format the
-                        constructor was given, since that format is what
-                        every reader function below actually dispatches on
+    @param[in] format  the binary format to parse
     @param[in] sax_    a SAX event processor
     @param[in] strict  whether to expect the input to be consumed completed
     @param[in] tag_handler  how to treat CBOR tags
@@ -154,7 +136,6 @@ class binary_reader
                    const bool strict = true,
                    const cbor_tag_handler_t tag_handler = cbor_tag_handler_t::error)
     {
-        JSON_ASSERT(format == input_format);
         sax = sax_;
         container_stack.clear();
         bon8_pushback_size = 0;
@@ -167,7 +148,7 @@ class binary_reader
                 break;
 
             case input_format_t::cbor:
-                result = parse_cbor_internal(tag_handler);
+                result = parse_cbor_internal(true, tag_handler);
                 break;
 
             case input_format_t::msgpack:
@@ -290,22 +271,6 @@ class binary_reader
         return enter_container(/*is_object*/true, len, type_marker);
     }
 
-    /*!
-    @brief close the innermost open array or object
-
-    Pops the container opened by the matching @ref enter_container call and
-    emits the SAX end event. Every format-specific driver otherwise repeated
-    the same pop-then-dispatch sequence at its own close site.
-
-    @return whether the SAX parser accepted the end event
-    */
-    bool leave_container()
-    {
-        const bool is_object = container_stack.back().is_object;
-        container_stack.pop_back();
-        return is_object ? sax->end_object() : sax->end_array();
-    }
-
     //////////
     // BSON //
     //////////
@@ -390,8 +355,8 @@ class binary_reader
             if (element_type == 0) // end of the innermost document
             {
                 // a copy, not a reference: it must stay valid across the
-                // pop_back() inside leave_container() below, which destroys
-                // the container_stack element it would otherwise alias
+                // pop_back() below, which destroys the container_stack
+                // element it would otherwise alias
                 const container_frame top = container_stack.back();
 
                 if (JSON_HEDLEY_UNLIKELY(!check_bson_document_size(top.start_position, top.declared_size)))
@@ -399,7 +364,8 @@ class binary_reader
                     return false;
                 }
 
-                if (JSON_HEDLEY_UNLIKELY(!leave_container()))
+                container_stack.pop_back();
+                if (JSON_HEDLEY_UNLIKELY(top.is_object ? !sax->end_object() : !sax->end_array()))
                 {
                     return false;
                 }
@@ -894,13 +860,29 @@ class binary_reader
                 return enter_array(conditional_static_cast<std::size_t>(static_cast<unsigned int>(current) & 0x1Fu));
 
             case 0x98: // array (one-byte uint8_t for n follows)
+            {
+                std::uint8_t len{};
+                return get_number(input_format_t::cbor, len) && enter_array(static_cast<std::size_t>(len));
+            }
+
             case 0x99: // array (two-byte uint16_t for n follow)
+            {
+                std::uint16_t len{};
+                return get_number(input_format_t::cbor, len) && enter_array(static_cast<std::size_t>(len));
+            }
+
             case 0x9A: // array (four-byte uint32_t for n follow)
+            {
+                std::uint32_t len{};
+                std::size_t size{};
+                return get_number(input_format_t::cbor, len) && get_cbor_container_size(len, size, "array") && enter_array(size);
+            }
+
             case 0x9B: // array (eight-byte uint64_t for n follow)
             {
                 std::uint64_t len{};
                 std::size_t size{};
-                return get_cbor_argument(len) && get_cbor_container_size(len, size, "array") && enter_array(size);
+                return get_number(input_format_t::cbor, len) && get_cbor_container_size(len, size, "array") && enter_array(size);
             }
 
             case 0x9F: // array (indefinite length)
@@ -934,19 +916,35 @@ class binary_reader
                 return enter_object(conditional_static_cast<std::size_t>(static_cast<unsigned int>(current) & 0x1Fu));
 
             case 0xB8: // map (one-byte uint8_t for n follows)
+            {
+                std::uint8_t len{};
+                return get_number(input_format_t::cbor, len) && enter_object(static_cast<std::size_t>(len));
+            }
+
             case 0xB9: // map (two-byte uint16_t for n follow)
+            {
+                std::uint16_t len{};
+                return get_number(input_format_t::cbor, len) && enter_object(static_cast<std::size_t>(len));
+            }
+
             case 0xBA: // map (four-byte uint32_t for n follow)
+            {
+                std::uint32_t len{};
+                std::size_t size{};
+                return get_number(input_format_t::cbor, len) && get_cbor_container_size(len, size, "map") && enter_object(size);
+            }
+
             case 0xBB: // map (eight-byte uint64_t for n follow)
             {
                 std::uint64_t len{};
                 std::size_t size{};
-                return get_cbor_argument(len) && get_cbor_container_size(len, size, "map") && enter_object(size);
+                return get_number(input_format_t::cbor, len) && get_cbor_container_size(len, size, "map") && enter_object(size);
             }
 
             case 0xBF: // map (indefinite length)
                 return enter_object(detail::unknown_size());
 
-            case 0xC0: // tagged item (tag value 0-23, in the head itself)
+            case 0xC0: // tagged item
             case 0xC1:
             case 0xC2:
             case 0xC3:
@@ -970,22 +968,6 @@ class binary_reader
             case 0xD5:
             case 0xD6:
             case 0xD7:
-            {
-                if (tag_handler == cbor_tag_handler_t::error)
-                {
-                    auto last_token = get_token_string();
-                    return sax->parse_error(chars_read, last_token, parse_error::create(112, chars_read,
-                                            exception_message(input_format_t::cbor, concat("invalid byte: 0x", last_token), "value"), nullptr));
-                }
-
-                // ignore and store: the tag value is already in the head, so
-                // there is nothing left to read here; the tagged value that
-                // follows is read by the loop in parse_cbor_internal() rather
-                // than by recursing here
-                tag_pending = true;
-                return true;
-            }
-
             case 0xD8: // tagged item (1 byte follows)
             case 0xD9: // tagged item (2 bytes follow)
             case 0xDA: // tagged item (4 bytes follow)
@@ -1002,11 +984,47 @@ class binary_reader
 
                     case cbor_tag_handler_t::ignore:
                     {
-                        // ignore the tag's binary subtype argument
-                        std::uint64_t subtype_to_ignore{};
-                        if (!get_cbor_argument(subtype_to_ignore))
+                        // ignore binary subtype
+                        switch (current)
                         {
-                            return false;
+                            case 0xD8:
+                            {
+                                std::uint8_t subtype_to_ignore{};
+                                if (!get_number(input_format_t::cbor, subtype_to_ignore))
+                                {
+                                    return false;
+                                }
+                                break;
+                            }
+                            case 0xD9:
+                            {
+                                std::uint16_t subtype_to_ignore{};
+                                if (!get_number(input_format_t::cbor, subtype_to_ignore))
+                                {
+                                    return false;
+                                }
+                                break;
+                            }
+                            case 0xDA:
+                            {
+                                std::uint32_t subtype_to_ignore{};
+                                if (!get_number(input_format_t::cbor, subtype_to_ignore))
+                                {
+                                    return false;
+                                }
+                                break;
+                            }
+                            case 0xDB:
+                            {
+                                std::uint64_t subtype_to_ignore{};
+                                if (!get_number(input_format_t::cbor, subtype_to_ignore))
+                                {
+                                    return false;
+                                }
+                                break;
+                            }
+                            default:
+                                break;
                         }
                         // the tagged value follows; it is read by the loop in
                         // parse_cbor_internal() rather than by recursing here
@@ -1016,15 +1034,57 @@ class binary_reader
 
                     case cbor_tag_handler_t::store:
                     {
-                        // use binary subtype and store in a binary container
-                        std::uint64_t subtype{};
-                        if (!get_cbor_argument(subtype))
-                        {
-                            return false;
-                        }
                         binary_t b;
-                        b.set_subtype(detail::conditional_static_cast<typename binary_t::subtype_type>(subtype));
-
+                        // use binary subtype and store in a binary container
+                        switch (current)
+                        {
+                            case 0xD8:
+                            {
+                                std::uint8_t subtype{};
+                                if (!get_number(input_format_t::cbor, subtype))
+                                {
+                                    return false;
+                                }
+                                b.set_subtype(detail::conditional_static_cast<typename binary_t::subtype_type>(subtype));
+                                break;
+                            }
+                            case 0xD9:
+                            {
+                                std::uint16_t subtype{};
+                                if (!get_number(input_format_t::cbor, subtype))
+                                {
+                                    return false;
+                                }
+                                b.set_subtype(detail::conditional_static_cast<typename binary_t::subtype_type>(subtype));
+                                break;
+                            }
+                            case 0xDA:
+                            {
+                                std::uint32_t subtype{};
+                                if (!get_number(input_format_t::cbor, subtype))
+                                {
+                                    return false;
+                                }
+                                b.set_subtype(detail::conditional_static_cast<typename binary_t::subtype_type>(subtype));
+                                break;
+                            }
+                            case 0xDB:
+                            {
+                                std::uint64_t subtype{};
+                                if (!get_number(input_format_t::cbor, subtype))
+                                {
+                                    return false;
+                                }
+                                b.set_subtype(detail::conditional_static_cast<typename binary_t::subtype_type>(subtype));
+                                break;
+                            }
+                            default:
+                            {
+                                // as above, the tagged value is read by the caller
+                                tag_pending = true;
+                                return true;
+                            }
+                        }
                         get();
                         // a byte string (the heads accepted by get_cbor_binary) keeps the tag as subtype
                         if ((current >= 0x40 && current <= 0x5B) || current == 0x5F)
@@ -1055,7 +1115,52 @@ class binary_reader
                 return sax->null();
 
             case 0xF9: // Half-Precision Float (two-byte IEEE 754)
-                return get_half_float(input_format_t::cbor, false);
+            {
+                const auto byte1_raw = get();
+                if (JSON_HEDLEY_UNLIKELY(!unexpect_eof(input_format_t::cbor, "number")))
+                {
+                    return false;
+                }
+                const auto byte2_raw = get();
+                if (JSON_HEDLEY_UNLIKELY(!unexpect_eof(input_format_t::cbor, "number")))
+                {
+                    return false;
+                }
+
+                const auto byte1 = static_cast<unsigned char>(byte1_raw);
+                const auto byte2 = static_cast<unsigned char>(byte2_raw);
+
+                // Code from RFC 8949, Appendix D, Figure 3:
+                // As half-precision floating-point numbers were only added
+                // to IEEE 754 in 2008, today's programming platforms often
+                // still only have limited support for them. It is very
+                // easy to include at least decoding support for them even
+                // without such support. An example of a small decoder for
+                // half-precision floating-point numbers in the C language
+                // is shown in Fig. 3.
+                const auto half = static_cast<unsigned int>((byte1 << 8u) + byte2);
+                const double val = [&half]
+                {
+                    const int exp = (half >> 10u) & 0x1Fu;
+                    const unsigned int mant = half & 0x3FFu;
+                    JSON_ASSERT(exp <= 31);
+                    JSON_ASSERT(mant <= 1023);
+                    switch (exp)
+                    {
+                        case 0:
+                            return std::ldexp(mant, -24);
+                        case 31:
+                            return (mant == 0)
+                            ? std::numeric_limits<double>::infinity()
+                            : std::numeric_limits<double>::quiet_NaN();
+                        default:
+                            return std::ldexp(mant + 1024, exp - 25);
+                    }
+                }();
+                return sax->number_float((half & 0x8000u) != 0
+                                         ? static_cast<number_float_t>(-val)
+                                         : static_cast<number_float_t>(val), "");
+            }
 
             case 0xFA: // Single-Precision Float (four-byte IEEE 754)
             {
@@ -1434,73 +1539,6 @@ class binary_reader
         }
     }
 
-    /*!
-    @brief read a CBOR argument (additional information 24-27) of the width
-           @ref current announces
-
-    The lower 5 bits of @a current (0x18-0x1B) select a 1/2/4/8-byte
-    big-endian unsigned integer that follows the head byte; this is shared by
-    every major type that uses this encoding (unsigned/negative integers,
-    strings, arrays, maps, tags). Reading always goes through @ref get_number,
-    so EOF is reported the same way as before this helper existed.
-
-    @param[out] value  the decoded argument
-    @return whether reading succeeded
-    */
-    bool get_cbor_argument(std::uint64_t& value)
-    {
-        switch (current & 0x1F)
-        {
-            case 0x18: // 1 byte
-            {
-                std::uint8_t n{};
-                if (JSON_HEDLEY_UNLIKELY(!get_number(input_format_t::cbor, n)))
-                {
-                    return false;
-                }
-                value = n;
-                return true;
-            }
-
-            case 0x19: // 2 bytes
-            {
-                std::uint16_t n{};
-                if (JSON_HEDLEY_UNLIKELY(!get_number(input_format_t::cbor, n)))
-                {
-                    return false;
-                }
-                value = n;
-                return true;
-            }
-
-            case 0x1A: // 4 bytes
-            {
-                std::uint32_t n{};
-                if (JSON_HEDLEY_UNLIKELY(!get_number(input_format_t::cbor, n)))
-                {
-                    return false;
-                }
-                value = n;
-                return true;
-            }
-
-            case 0x1B: // 8 bytes
-            {
-                std::uint64_t n{};
-                if (JSON_HEDLEY_UNLIKELY(!get_number(input_format_t::cbor, n)))
-                {
-                    return false;
-                }
-                value = n;
-                return true;
-            }
-
-            default:                 // LCOV_EXCL_LINE
-                JSON_ASSERT(false); // NOLINT(cert-dcl03-c,hicpp-static-assert,misc-static-assert) LCOV_EXCL_LINE
-                return false;        // LCOV_EXCL_LINE
-        }
-    }
-
     /*!
     @brief narrow a definite CBOR array/map length to std::size_t
 
@@ -1533,15 +1571,19 @@ class binary_reader
     enclosing container after each element, so that the nesting depth of the
     input costs heap rather than native stack (see #5104).
 
+    @param[in] get_char  whether a new character should be retrieved from the
+                         input (true) or whether the last read character
+                         @a current should be considered instead
     @param[in] tag_handler how CBOR tags should be treated
 
     @return whether reading the value succeeded
     */
-    bool parse_cbor_internal(const cbor_tag_handler_t tag_handler)
+    bool parse_cbor_internal(const bool get_char,
+                             const cbor_tag_handler_t tag_handler)
     {
         // whether the next value starts at a fresh byte or at the one already
         // read into `current`
-        bool fetch = true;
+        bool fetch = get_char;
 
         // the key currently being read; hoisted out of the loop so that its
         // capacity is reused across elements and across nesting levels
@@ -1584,7 +1626,8 @@ class binary_reader
 
                 if (at_end)
                 {
-                    if (JSON_HEDLEY_UNLIKELY(!leave_container()))
+                    container_stack.pop_back();
+                    if (JSON_HEDLEY_UNLIKELY(top.is_object ? !sax->end_object() : !sax->end_array()))
                     {
                         return false;
                     }
@@ -1633,6 +1676,9 @@ class binary_reader
     // MsgPack //
     /////////////
 
+    /*!
+    @return whether a valid MessagePack value was passed to the SAX parser
+    */
     /*!
     @brief read one MessagePack value
 
@@ -2331,7 +2377,8 @@ class binary_reader
 
                 if (container_stack.back().remaining == 0)
                 {
-                    if (JSON_HEDLEY_UNLIKELY(!leave_container()))
+                    container_stack.pop_back();
+                    if (JSON_HEDLEY_UNLIKELY(is_object ? !sax->end_object() : !sax->end_array()))
                     {
                         return false;
                     }
@@ -2376,16 +2423,20 @@ class binary_reader
     ////////////
 
     /*!
+    @param[in] get_char  whether a new character should be retrieved from the
+                         input (true, default) or whether the last read
+                         character should be considered instead
+
     @return whether a valid UBJSON value was passed to the SAX parser
     */
-    bool parse_ubjson_internal()
+    bool parse_ubjson_internal(const bool get_char = true)
     {
         // the key currently being read; hoisted out of the loop so that its
         // capacity is reused across elements and across nesting levels
         string_t key;
 
         // the type marker of the value to read next
-        char_int_type prefix = get_ignore_noop();
+        char_int_type prefix = get_char ? get_ignore_noop() : current;
 
         while (true)
         {
@@ -2460,7 +2511,8 @@ class binary_reader
                     break;
                 }
 
-                if (JSON_HEDLEY_UNLIKELY(!leave_container()))
+                container_stack.pop_back();
+                if (JSON_HEDLEY_UNLIKELY(top.is_object ? !sax->end_object() : !sax->end_array()))
                 {
                     return false;
                 }
@@ -2668,42 +2720,6 @@ class binary_reader
         return true;
     }
 
-    /*!
-    @brief read a UBJSON/BJData optimized-container count of a signed marker
-           type ('i', 'I', 'l', 'L') and narrow it to std::size_t
-
-    Every signed count marker rejects a negative value the same way (error
-    113); the value_in_range_of check additionally needed for 'L' is only
-    ever live when @a SignedType is std::int64_t on a target where
-    std::size_t is narrower (e.g. 32-bit), since 'i'/'I'/'l' can never exceed
-    std::size_t there.
-
-    @tparam SignedType  std::int8_t, std::int16_t, std::int32_t or std::int64_t
-    @param[out] result  the count narrowed to std::size_t
-    @return whether reading and validating succeeded
-    */
-    template<typename SignedType>
-    bool get_ubjson_signed_count(std::size_t& result)
-    {
-        SignedType number{};
-        if (JSON_HEDLEY_UNLIKELY(!get_number(input_format, number)))
-        {
-            return false;
-        }
-        if (JSON_HEDLEY_UNLIKELY(number < 0))
-        {
-            return sax->parse_error(chars_read, get_token_string(), parse_error::create(113, chars_read,
-                                    exception_message(input_format, "count in an optimized container must be positive", "size"), nullptr));
-        }
-        if (JSON_HEDLEY_UNLIKELY(!value_in_range_of<std::size_t>(number)))
-        {
-            return sax->parse_error(chars_read, get_token_string(), out_of_range::create(408,
-                                    exception_message(input_format, "integer value overflow", "size"), nullptr));
-        }
-        result = static_cast<std::size_t>(number); // NOLINT(bugprone-signed-char-misuse,cert-str34-c): number is not a char
-        return true;
-    }
-
     /*!
     @param[out] result  determined size
     @param[in,out] is_ndarray  for input, `true` means already inside an ndarray vector
@@ -2736,16 +2752,73 @@ class binary_reader
             }
 
             case 'i':
-                return get_ubjson_signed_count<std::int8_t>(result);
+            {
+                std::int8_t number{};
+                if (JSON_HEDLEY_UNLIKELY(!get_number(input_format, number)))
+                {
+                    return false;
+                }
+                if (number < 0)
+                {
+                    return sax->parse_error(chars_read, get_token_string(), parse_error::create(113, chars_read,
+                                            exception_message(input_format, "count in an optimized container must be positive", "size"), nullptr));
+                }
+                result = static_cast<std::size_t>(number); // NOLINT(bugprone-signed-char-misuse,cert-str34-c): number is not a char
+                return true;
+            }
 
             case 'I':
-                return get_ubjson_signed_count<std::int16_t>(result);
+            {
+                std::int16_t number{};
+                if (JSON_HEDLEY_UNLIKELY(!get_number(input_format, number)))
+                {
+                    return false;
+                }
+                if (number < 0)
+                {
+                    return sax->parse_error(chars_read, get_token_string(), parse_error::create(113, chars_read,
+                                            exception_message(input_format, "count in an optimized container must be positive", "size"), nullptr));
+                }
+                result = static_cast<std::size_t>(number);
+                return true;
+            }
 
             case 'l':
-                return get_ubjson_signed_count<std::int32_t>(result);
+            {
+                std::int32_t number{};
+                if (JSON_HEDLEY_UNLIKELY(!get_number(input_format, number)))
+                {
+                    return false;
+                }
+                if (number < 0)
+                {
+                    return sax->parse_error(chars_read, get_token_string(), parse_error::create(113, chars_read,
+                                            exception_message(input_format, "count in an optimized container must be positive", "size"), nullptr));
+                }
+                result = static_cast<std::size_t>(number);
+                return true;
+            }
 
             case 'L':
-                return get_ubjson_signed_count<std::int64_t>(result);
+            {
+                std::int64_t number{};
+                if (JSON_HEDLEY_UNLIKELY(!get_number(input_format, number)))
+                {
+                    return false;
+                }
+                if (number < 0)
+                {
+                    return sax->parse_error(chars_read, get_token_string(), parse_error::create(113, chars_read,
+                                            exception_message(input_format, "count in an optimized container must be positive", "size"), nullptr));
+                }
+                if (!value_in_range_of<std::size_t>(number))
+                {
+                    return sax->parse_error(chars_read, get_token_string(), out_of_range::create(408,
+                                            exception_message(input_format, "integer value overflow", "size"), nullptr));
+                }
+                result = static_cast<std::size_t>(number);
+                return true;
+            }
 
             case 'u':
             {
@@ -2836,23 +2909,16 @@ class binary_reader
                     result = 1;
                     for (auto i : dim)
                     {
-                        // Pre-multiplication overflow check: since the loop above
-                        // already rejected any zero dimension, i is always > 0
-                        // here, so result > SIZE_MAX/i means result*i would
-                        // overflow. This check must happen before multiplication
-                        // since overflow detection after the fact is unreliable,
-                        // as modular arithmetic can produce any value, not just 0
-                        // or SIZE_MAX.
-                        if (JSON_HEDLEY_UNLIKELY(result > (std::numeric_limits<std::size_t>::max)() / i))
+                        // Pre-multiplication overflow check: if i > 0 and result > SIZE_MAX/i, then result*i would overflow.
+                        // This check must happen before multiplication since overflow detection after the fact is unreliable
+                        // as modular arithmetic can produce any value, not just 0 or SIZE_MAX.
+                        if (JSON_HEDLEY_UNLIKELY(i > 0 && result > (std::numeric_limits<std::size_t>::max)() / i))
                         {
                             return sax->parse_error(chars_read, get_token_string(), out_of_range::create(408, exception_message(input_format, "excessive ndarray size caused overflow", "size"), nullptr));
                         }
                         result *= i;
-                        // the pre-check above already rules out result becoming 0
-                        // by overflow; the only value it cannot rule out is an
-                        // exact match with npos, the sentinel reserved for an
-                        // unknown-size container (see get_ubjson_size_type())
-                        if (result == npos)
+                        // Additional post-multiplication check to catch any edge cases the pre-check might miss
+                        if (result == 0 || result == npos)
                         {
                             return sax->parse_error(chars_read, get_token_string(), out_of_range::create(408, exception_message(input_format, "excessive ndarray size caused overflow", "size"), nullptr));
                         }
@@ -2913,7 +2979,7 @@ class binary_reader
         {
             result.second = get();  // must not ignore 'N', because 'N' maybe the type
             if (input_format == input_format_t::bjdata
-                    && JSON_HEDLEY_UNLIKELY(is_bjd_excluded_optimized_type(result.second)))
+                    && JSON_HEDLEY_UNLIKELY(std::binary_search(bjd_optimized_type_markers.begin(), bjd_optimized_type_markers.end(), result.second)))
             {
                 auto last_token = get_token_string();
                 return sax->parse_error(chars_read, last_token, parse_error::create(112, chars_read,
@@ -3057,7 +3123,50 @@ class binary_reader
                 {
                     break;
                 }
-                return get_half_float(input_format, true);
+                const auto byte1_raw = get();
+                if (JSON_HEDLEY_UNLIKELY(!unexpect_eof(input_format, "number")))
+                {
+                    return false;
+                }
+                const auto byte2_raw = get();
+                if (JSON_HEDLEY_UNLIKELY(!unexpect_eof(input_format, "number")))
+                {
+                    return false;
+                }
+
+                const auto byte1 = static_cast<unsigned char>(byte1_raw);
+                const auto byte2 = static_cast<unsigned char>(byte2_raw);
+
+                // Code from RFC 8949, Appendix D, Figure 3:
+                // As half-precision floating-point numbers were only added
+                // to IEEE 754 in 2008, today's programming platforms often
+                // still only have limited support for them. It is very
+                // easy to include at least decoding support for them even
+                // without such support. An example of a small decoder for
+                // half-precision floating-point numbers in the C language
+                // is shown in Fig. 3.
+                const auto half = static_cast<unsigned int>((byte2 << 8u) + byte1);
+                const double val = [&half]
+                {
+                    const int exp = (half >> 10u) & 0x1Fu;
+                    const unsigned int mant = half & 0x3FFu;
+                    JSON_ASSERT(exp <= 31);
+                    JSON_ASSERT(mant <= 1023);
+                    switch (exp)
+                    {
+                        case 0:
+                            return std::ldexp(mant, -24);
+                        case 31:
+                            return (mant == 0)
+                            ? std::numeric_limits<double>::infinity()
+                            : std::numeric_limits<double>::quiet_NaN();
+                        default:
+                            return std::ldexp(mant + 1024, exp - 25);
+                    }
+                }();
+                return sax->number_float((half & 0x8000u) != 0
+                                         ? static_cast<number_float_t>(-val)
+                                         : static_cast<number_float_t>(val), "");
             }
 
             case 'd':
@@ -3130,16 +3239,19 @@ class binary_reader
         if (input_format == input_format_t::bjdata && size_and_type.first != npos && (size_and_type.second & (1 << 8)) != 0)
         {
             size_and_type.second &= ~(static_cast<char_int_type>(1) << 8);  // use bit 8 to indicate ndarray, here we remove the bit to restore the type marker
-            const char* type_name = bjd_type_name(size_and_type.second);
+            auto it = std::lower_bound(bjd_types_map.begin(), bjd_types_map.end(), size_and_type.second, [](const bjd_type & p, char_int_type t)
+            {
+                return p.first < t;
+            });
             string_t key = "_ArrayType_";
-            if (JSON_HEDLEY_UNLIKELY(type_name == nullptr))
+            if (JSON_HEDLEY_UNLIKELY(it == bjd_types_map.end() || it->first != size_and_type.second))
             {
                 auto last_token = get_token_string();
                 return sax->parse_error(chars_read, last_token, parse_error::create(112, chars_read,
                                         exception_message(input_format, "invalid byte: 0x" + last_token, "type"), nullptr));
             }
 
-            string_t type = type_name; // sax->string() takes a reference
+            string_t type = it->second; // sax->string() takes a reference
             if (JSON_HEDLEY_UNLIKELY(!sax->key(key) || !sax->string(type)))
             {
                 return false;
@@ -3431,7 +3543,8 @@ class binary_reader
 
                 if (at_end)
                 {
-                    if (JSON_HEDLEY_UNLIKELY(!leave_container()))
+                    container_stack.pop_back();
+                    if (JSON_HEDLEY_UNLIKELY(top.is_object ? !sax->end_object() : !sax->end_array()))
                     {
                         return false;
                     }
@@ -3970,68 +4083,6 @@ class binary_reader
         return true;
     }
 
-    /*!
-    @brief read and decode an IEEE 754 half-precision (16-bit) float
-
-    Used by CBOR (big endian) and BJData (little endian); the two formats
-    only differ in the byte order of the two bytes that make up the half.
-
-    @param[in] format       the current format (for diagnostics)
-    @param[in] little_endian whether the two bytes are little endian (BJData)
-                             or big endian (CBOR)
-
-    @return whether reading and decoding succeeded
-    */
-    bool get_half_float(const input_format_t format, const bool little_endian)
-    {
-        const auto byte1_raw = get();
-        if (JSON_HEDLEY_UNLIKELY(!unexpect_eof(format, "number")))
-        {
-            return false;
-        }
-        const auto byte2_raw = get();
-        if (JSON_HEDLEY_UNLIKELY(!unexpect_eof(format, "number")))
-        {
-            return false;
-        }
-
-        const auto byte1 = static_cast<unsigned char>(byte1_raw);
-        const auto byte2 = static_cast<unsigned char>(byte2_raw);
-
-        // Code from RFC 8949, Appendix D, Figure 3:
-        // As half-precision floating-point numbers were only added
-        // to IEEE 754 in 2008, today's programming platforms often
-        // still only have limited support for them. It is very
-        // easy to include at least decoding support for them even
-        // without such support. An example of a small decoder for
-        // half-precision floating-point numbers in the C language
-        // is shown in Fig. 3.
-        const auto half = little_endian
-                          ? static_cast<unsigned int>((byte2 << 8u) + byte1)
-                          : static_cast<unsigned int>((byte1 << 8u) + byte2);
-        const double val = [&half]
-        {
-            const int exp = (half >> 10u) & 0x1Fu;
-            const unsigned int mant = half & 0x3FFu;
-            JSON_ASSERT(exp <= 31);
-            JSON_ASSERT(mant <= 1023);
-            switch (exp)
-            {
-                case 0:
-                    return std::ldexp(mant, -24);
-                case 31:
-                    return (mant == 0)
-                    ? std::numeric_limits<double>::infinity()
-                    : std::numeric_limits<double>::quiet_NaN();
-                default:
-                    return std::ldexp(mant + 1024, exp - 25);
-            }
-        }();
-        return sax->number_float((half & 0x8000u) != 0
-                                 ? static_cast<number_float_t>(-val)
-                                 : static_cast<number_float_t>(val), "");
-    }
-
     /*!
     @brief create a string by reading characters from the input
 
@@ -4257,61 +4308,38 @@ class binary_reader
     /// BON8: number of bytes in @ref bon8_pushback
     std::size_t bon8_pushback_size = 0;
 
+    // excluded markers in bjdata optimized type
+#define JSON_BINARY_READER_MAKE_BJD_OPTIMIZED_TYPE_MARKERS_ \
+    make_array<char_int_type>('F', 'H', 'N', 'S', 'T', 'Z', '[', '{')
+
+#define JSON_BINARY_READER_MAKE_BJD_TYPES_MAP_ \
+    make_array<bjd_type>(                      \
+    bjd_type{'B', "byte"},                     \
+    bjd_type{'C', "char"},                     \
+    bjd_type{'D', "double"},                   \
+    bjd_type{'I', "int16"},                    \
+    bjd_type{'L', "int64"},                    \
+    bjd_type{'M', "uint64"},                   \
+    bjd_type{'U', "uint8"},                    \
+    bjd_type{'d', "single"},                   \
+    bjd_type{'i', "int8"},                     \
+    bjd_type{'l', "int32"},                    \
+    bjd_type{'m', "uint32"},                   \
+    bjd_type{'u', "uint16"})
+
   JSON_PRIVATE_UNLESS_TESTED:
-    /*!
-    @brief whether @a marker is excluded from BJData's optimized ND-array types
-    @return whether @a marker is one of 'F', 'H', 'N', 'S', 'T', 'Z', '[', '{'
+    // lookup tables
+    // NOLINTNEXTLINE(cppcoreguidelines-non-private-member-variables-in-classes)
+    const decltype(JSON_BINARY_READER_MAKE_BJD_OPTIMIZED_TYPE_MARKERS_) bjd_optimized_type_markers =
+        JSON_BINARY_READER_MAKE_BJD_OPTIMIZED_TYPE_MARKERS_;
 
-    Mirrors binary_writer's @ref binary_writer::is_bjdata_excluded_type_marker
-    "is_bjdata_excluded_type_marker()`, which encodes the same list the other
-    way; keep the two in sync.
-    */
-    static constexpr bool is_bjd_excluded_optimized_type(const char_int_type marker) noexcept
-    {
-        return marker == '[' || marker == '{' || marker == 'S' || marker == 'H'
-               || marker == 'T' || marker == 'F' || marker == 'N' || marker == 'Z';
-    }
+    using bjd_type = std::pair<char_int_type, string_t>;
+    // NOLINTNEXTLINE(cppcoreguidelines-non-private-member-variables-in-classes)
+    const decltype(JSON_BINARY_READER_MAKE_BJD_TYPES_MAP_) bjd_types_map =
+        JSON_BINARY_READER_MAKE_BJD_TYPES_MAP_;
 
-    /*!
-    @brief look up the ND-array element type name for a BJData dtype marker
-    @return the type name ("uint8", "int8", ...), or nullptr if @a marker does
-            not name a known dtype
-
-    A C++11 `constexpr` function cannot contain a `switch`, so this is a
-    plain (non-constexpr) switch instead.
-    */
-    static const char* bjd_type_name(const char_int_type marker)
-    {
-        switch (marker)
-        {
-            case 'B':
-                return "byte";
-            case 'C':
-                return "char";
-            case 'D':
-                return "double";
-            case 'I':
-                return "int16";
-            case 'L':
-                return "int64";
-            case 'M':
-                return "uint64";
-            case 'U':
-                return "uint8";
-            case 'd':
-                return "single";
-            case 'i':
-                return "int8";
-            case 'l':
-                return "int32";
-            case 'm':
-                return "uint32";
-            case 'u':
-                return "uint16";
-            default:
-                return nullptr;
-        }
-    }
+#undef JSON_BINARY_READER_MAKE_BJD_OPTIMIZED_TYPE_MARKERS_
+#undef JSON_BINARY_READER_MAKE_BJD_TYPES_MAP_
 };
 
 #ifndef JSON_HAS_CPP_17

include/nlohmann/detail/meta/cpp_future.hpp

@@ -9,6 +9,7 @@
 
 #pragma once
 
+#include <array> // array
 #include <cstddef> // size_t
 #include <type_traits> // conditional, enable_if, false_type, integral_constant, is_constructible, is_integral, is_same, remove_cv, remove_reference, true_type
 #include <utility> // index_sequence, make_index_sequence, index_sequence_for
@@ -160,5 +161,11 @@ struct static_const
     constexpr T static_const<T>::value;
 #endif
 
+template<typename T, typename... Args>
+constexpr std::array<T, sizeof...(Args)> make_array(Args&& ... args)
+{
+    return std::array<T, sizeof...(Args)> {{static_cast<T>(std::forward<Args>(args))...}};
+}
+
 }  // namespace detail
 NLOHMANN_JSON_NAMESPACE_END

include/nlohmann/json.hpp

@@ -1606,12 +1606,42 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         assert_invariant();
     }
 
+  private:
+    /// whether a basic_json specialization can be converted implicitly into this one;
+    /// with JSON_USE_IMPLICIT_CONVERSIONS set to 0, this is only the case if both share
+    /// the same string type (see https://github.com/nlohmann/json/issues/2649)
+    template<typename BasicJsonType>
+    using is_implicitly_convertible_basic_json = std::integral_constant < bool,
+          (JSON_USE_IMPLICIT_CONVERSIONS != 0)
+          || std::is_same<typename BasicJsonType::string_t, string_t>::value >;
+
+    /// tag to select the constructor that performs the conversion from another basic_json specialization
+    struct convert_basic_json_tag {};
+
+  public:
     /// @brief create a JSON value from an existing one
     /// @sa https://json.nlohmann.me/api/basic_json/basic_json/
     template < typename BasicJsonType,
                detail::enable_if_t <
-                   detail::is_basic_json<BasicJsonType>::value&& !std::is_same<basic_json, BasicJsonType>::value, int > = 0 >
+                   detail::is_basic_json<BasicJsonType>::value&& !std::is_same<basic_json, BasicJsonType>::value
+                   && is_implicitly_convertible_basic_json<BasicJsonType>::value, int > = 0 >
     basic_json(const BasicJsonType& val)
+        : basic_json(val, convert_basic_json_tag{})
+    {}
+
+    /// @brief create a JSON value from an existing one
+    /// @sa https://json.nlohmann.me/api/basic_json/basic_json/
+    template < typename BasicJsonType,
+               detail::enable_if_t <
+                   detail::is_basic_json<BasicJsonType>::value&& !std::is_same<basic_json, BasicJsonType>::value
+                   && !is_implicitly_convertible_basic_json<BasicJsonType>::value, int > = 0 >
+    explicit basic_json(const BasicJsonType& val)
+        : basic_json(val, convert_basic_json_tag{})
+    {}
+
+  private:
+    template<typename BasicJsonType>
+    basic_json(const BasicJsonType& val, convert_basic_json_tag /*unused*/)
 #if JSON_DIAGNOSTIC_POSITIONS
         : start_position(val.start_pos()),
           end_position(val.end_pos())
@@ -1667,6 +1697,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         assert_invariant();
     }
 
+  public:
     /// @brief create a container (array or object) from an initializer list
     /// @sa https://json.nlohmann.me/api/basic_json/basic_json/
     basic_json(initializer_list_t init,
@@ -2433,7 +2464,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                    int > = 0 >
     BasicJsonType get_impl(detail::priority_tag<2> /*unused*/) const
     {
-        return *this;
+        return BasicJsonType(*this);
     }
 
     /*!
@@ -2572,7 +2603,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                  int> = 0>
     ValueType & get_to(ValueType& v) const
     {
-        v = *this;
+        v = ValueType(*this);
         return v;
     }
 
@@ -5034,7 +5065,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         auto ia = detail::input_adapter(std::forward<InputType>(i));
         return format == input_format_t::json
                ? parser(std::move(ia), nullptr, true, ignore_comments, ignore_trailing_commas).sax_parse(sax, strict)
-               : detail::binary_reader<basic_json, decltype(ia), SAX>(std::move(ia), format).sax_parse(sax, strict);
+               : detail::binary_reader<basic_json, decltype(ia), SAX>(std::move(ia), format).sax_parse(format, sax, strict);
     }
 
     /// @brief generate SAX events (iterator pair, or iterator+sentinel pair for C++20 ranges support)
@@ -5051,7 +5082,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         auto ia = detail::input_adapter(std::move(first), std::move(last));
         return format == input_format_t::json
                ? parser(std::move(ia), nullptr, true, ignore_comments, ignore_trailing_commas).sax_parse(sax, strict)
-               : detail::binary_reader<basic_json, decltype(ia), SAX>(std::move(ia), format).sax_parse(sax, strict);
+               : detail::binary_reader<basic_json, decltype(ia), SAX>(std::move(ia), format).sax_parse(format, sax, strict);
     }
 
     /// @brief generate SAX events
@@ -5073,7 +5104,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                // NOLINTNEXTLINE(hicpp-move-const-arg,performance-move-const-arg)
                ? parser(std::move(ia), nullptr, true, ignore_comments, ignore_trailing_commas).sax_parse(sax, strict)
                // NOLINTNEXTLINE(hicpp-move-const-arg,performance-move-const-arg)
-               : detail::binary_reader<basic_json, decltype(ia), SAX>(std::move(ia), format).sax_parse(sax, strict);
+               : detail::binary_reader<basic_json, decltype(ia), SAX>(std::move(ia), format).sax_parse(format, sax, strict);
     }
 #ifndef JSON_NO_IO
     /// @brief deserialize from stream
@@ -5371,7 +5402,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         basic_json result;
         auto ia = detail::input_adapter(std::forward<InputType>(i));
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
-        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::cbor).sax_parse(&sdp, strict, tag_handler)) // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::cbor).sax_parse(input_format_t::cbor, &sdp, strict, tag_handler)) // cppcheck-suppress[accessMoved]
         {
             result = value_t::discarded;
         }
@@ -5391,7 +5422,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         basic_json result;
         auto ia = detail::input_adapter(std::move(first), std::move(last));
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
-        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::cbor).sax_parse(&sdp, strict, tag_handler)) // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::cbor).sax_parse(input_format_t::cbor, &sdp, strict, tag_handler)) // cppcheck-suppress[accessMoved]
         {
             result = value_t::discarded;
         }
@@ -5420,7 +5451,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         auto ia = i.get();
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
         // NOLINTNEXTLINE(hicpp-move-const-arg,performance-move-const-arg)
-        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::cbor).sax_parse(&sdp, strict, tag_handler)) // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::cbor).sax_parse(input_format_t::cbor, &sdp, strict, tag_handler)) // cppcheck-suppress[accessMoved]
         {
             result = value_t::discarded;
         }
@@ -5438,7 +5469,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         basic_json result;
         auto ia = detail::input_adapter(std::forward<InputType>(i));
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
-        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::msgpack).sax_parse(&sdp, strict)) // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::msgpack).sax_parse(input_format_t::msgpack, &sdp, strict)) // cppcheck-suppress[accessMoved]
         {
             result = value_t::discarded;
         }
@@ -5457,7 +5488,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         basic_json result;
         auto ia = detail::input_adapter(std::move(first), std::move(last));
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
-        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::msgpack).sax_parse(&sdp, strict)) // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::msgpack).sax_parse(input_format_t::msgpack, &sdp, strict)) // cppcheck-suppress[accessMoved]
         {
             result = value_t::discarded;
         }
@@ -5484,7 +5515,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         auto ia = i.get();
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
         // NOLINTNEXTLINE(hicpp-move-const-arg,performance-move-const-arg)
-        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::msgpack).sax_parse(&sdp, strict)) // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::msgpack).sax_parse(input_format_t::msgpack, &sdp, strict)) // cppcheck-suppress[accessMoved]
         {
             result = value_t::discarded;
         }
@@ -5502,7 +5533,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         basic_json result;
         auto ia = detail::input_adapter(std::forward<InputType>(i));
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
-        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::ubjson).sax_parse(&sdp, strict)) // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::ubjson).sax_parse(input_format_t::ubjson, &sdp, strict)) // cppcheck-suppress[accessMoved]
         {
             result = value_t::discarded;
         }
@@ -5521,7 +5552,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         basic_json result;
         auto ia = detail::input_adapter(std::move(first), std::move(last));
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
-        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::ubjson).sax_parse(&sdp, strict)) // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::ubjson).sax_parse(input_format_t::ubjson, &sdp, strict)) // cppcheck-suppress[accessMoved]
         {
             result = value_t::discarded;
         }
@@ -5548,7 +5579,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         auto ia = i.get();
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
         // NOLINTNEXTLINE(hicpp-move-const-arg,performance-move-const-arg)
-        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::ubjson).sax_parse(&sdp, strict)) // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::ubjson).sax_parse(input_format_t::ubjson, &sdp, strict)) // cppcheck-suppress[accessMoved]
         {
             result = value_t::discarded;
         }
@@ -5566,7 +5597,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         basic_json result;
         auto ia = detail::input_adapter(std::forward<InputType>(i));
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
-        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::bjdata).sax_parse(&sdp, strict)) // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::bjdata).sax_parse(input_format_t::bjdata, &sdp, strict)) // cppcheck-suppress[accessMoved]
         {
             result = value_t::discarded;
         }
@@ -5585,7 +5616,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         basic_json result;
         auto ia = detail::input_adapter(std::move(first), std::move(last));
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
-        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::bjdata).sax_parse(&sdp, strict)) // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::bjdata).sax_parse(input_format_t::bjdata, &sdp, strict)) // cppcheck-suppress[accessMoved]
         {
             result = value_t::discarded;
         }
@@ -5603,7 +5634,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         basic_json result;
         auto ia = detail::input_adapter(std::forward<InputType>(i));
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
-        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::bon8).sax_parse(&sdp, strict)) // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::bon8).sax_parse(input_format_t::bon8, &sdp, strict)) // cppcheck-suppress[accessMoved]
         {
             result = value_t::discarded;
         }
@@ -5622,7 +5653,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         basic_json result;
         auto ia = detail::input_adapter(std::move(first), std::move(last));
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
-        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::bon8).sax_parse(&sdp, strict)) // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::bon8).sax_parse(input_format_t::bon8, &sdp, strict)) // cppcheck-suppress[accessMoved]
         {
             result = value_t::discarded;
         }
@@ -5640,7 +5671,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         basic_json result;
         auto ia = detail::input_adapter(std::forward<InputType>(i));
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
-        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::bson).sax_parse(&sdp, strict)) // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::bson).sax_parse(input_format_t::bson, &sdp, strict)) // cppcheck-suppress[accessMoved]
         {
             result = value_t::discarded;
         }
@@ -5659,7 +5690,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         basic_json result;
         auto ia = detail::input_adapter(std::move(first), std::move(last));
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
-        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::bson).sax_parse(&sdp, strict)) // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::bson).sax_parse(input_format_t::bson, &sdp, strict)) // cppcheck-suppress[accessMoved]
         {
             result = value_t::discarded;
         }
@@ -5686,7 +5717,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         auto ia = i.get();
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
         // NOLINTNEXTLINE(hicpp-move-const-arg,performance-move-const-arg)
-        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::bson).sax_parse(&sdp, strict)) // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::bson).sax_parse(input_format_t::bson, &sdp, strict)) // cppcheck-suppress[accessMoved]
         {
             result = value_t::discarded;
         }

tests/src/unit-alt-string.cpp

@@ -13,6 +13,7 @@
 
 #include <cstdint>
 #include <string>
+#include <type_traits>
 #include <utility>
 #include <vector>
 
@@ -419,6 +420,41 @@ TEST_CASE("alternative string type")
         CHECK(j2.dump() == R"({"/foo/0":"bar","/foo/1":"baz"})");
     }
 
+    SECTION("conversion between basic_json specializations (#2649)")
+    {
+        // explicit conversions are always possible
+        CHECK(std::is_constructible<nlohmann::json, alt_json>::value);
+        CHECK(std::is_constructible<alt_json, nlohmann::json>::value);
+        CHECK(std::is_constructible<nlohmann::json, nlohmann::ordered_json>::value);
+        CHECK(std::is_constructible<nlohmann::ordered_json, nlohmann::json>::value);
+
+        // specializations with the same string type are implicitly convertible
+        CHECK(std::is_convertible<nlohmann::ordered_json, nlohmann::json>::value);
+        CHECK(std::is_convertible<nlohmann::json, nlohmann::ordered_json>::value);
+
+        // specializations with different string types are only implicitly convertible
+        // if implicit conversions are enabled
+#if JSON_USE_IMPLICIT_CONVERSIONS
+        CHECK(std::is_convertible<alt_json, nlohmann::json>::value);
+        CHECK(std::is_convertible<nlohmann::json, alt_json>::value);
+#else
+        CHECK_FALSE(std::is_convertible<alt_json, nlohmann::json>::value);
+        CHECK_FALSE(std::is_convertible<nlohmann::json, alt_json>::value);
+#endif
+
+        // get<BasicJsonType>() works in either case
+        const nlohmann::json j = {{"foo", 1}, {"bar", true}};
+        CHECK(j.get<nlohmann::ordered_json>() == nlohmann::ordered_json(j));
+        // (only a number is converted here, as objects and strings are affected by #3425)
+        CHECK(nlohmann::json(42).get<alt_json>() == 42);
+        CHECK(alt_json(nlohmann::json(42)) == 42);
+
+        // get_to() also works in either case
+        alt_json a;
+        nlohmann::json(42).get_to(a);
+        CHECK(a == 42);
+    }
+
     SECTION("strict enum")
     {
         // regression test for #5667: NLOHMANN_JSON_SERIALIZE_ENUM_STRICT's from_json

tests/src/unit-bjdata.cpp

@@ -210,42 +210,15 @@ TEST_CASE_TEMPLATE_INVOKE(value_in_range_of_test, \
 
 TEST_CASE("BJData")
 {
-    SECTION("binary_reader BJData lookup tables")
+    SECTION("binary_reader BJData LUT arrays are sorted")
     {
         std::vector<std::uint8_t> const data;
         auto ia = nlohmann::detail::input_adapter(data);
         // NOLINTNEXTLINE(hicpp-move-const-arg,performance-move-const-arg)
         nlohmann::detail::binary_reader<json, decltype(ia)> const br{std::move(ia), json::input_format_t::bjdata};
 
-        // the excluded optimized-type markers must match binary_writer's
-        // is_bjdata_excluded_type_marker(), which encodes the same 8 markers
-        for (const char marker :
-                {'[', '{', 'S', 'H', 'T', 'F', 'N', 'Z'
-                })
-        {
-            CHECK(br.is_bjd_excluded_optimized_type(marker));
-        }
-        for (const char marker :
-                {'U', 'i', 'u', 'I', 'm', 'l', 'M', 'L', 'd', 'D', 'C', 'B', 'x'
-                })
-        {
-            CHECK(!br.is_bjd_excluded_optimized_type(marker));
-        }
-
-        // every dtype marker must round-trip to its ND-array type name
-        const std::vector<std::pair<char, std::string>> types
-        {
-            {'B', "byte"}, {'C', "char"}, {'D', "double"}, {'I', "int16"},
-            {'L', "int64"}, {'M', "uint64"}, {'U', "uint8"}, {'d', "single"},
-            {'i', "int8"}, {'l', "int32"}, {'m', "uint32"}, {'u', "uint16"}
-        };
-        for (const auto& type : types)
-        {
-            const char* name = br.bjd_type_name(type.first);
-            REQUIRE(name != nullptr);
-            CHECK(std::string(name) == type.second);
-        }
-        CHECK(br.bjd_type_name('x') == nullptr);
+        CHECK(std::is_sorted(br.bjd_optimized_type_markers.begin(), br.bjd_optimized_type_markers.end()));
+        CHECK(std::is_sorted(br.bjd_types_map.begin(), br.bjd_types_map.end()));
     }
 
     SECTION("individual values")

tests/src/unit-ubjson.cpp

@@ -3033,224 +3033,3 @@ TEST_CASE("UBJSON optimized array of unsigned integers beyond int64")
     CHECK(json::to_ubjson(j, true, true) == expected);
     CHECK(json::from_ubjson(expected) == j);
 }
-
-namespace
-{
-// the bytes that follow the marker of an integer: the value in the width of
-// the marker (big endian for UBJSON, little endian for BJData), or, for a
-// high-precision number, the length and the decimal digits
-std::vector<std::uint8_t> integer_payload(const char marker, const json& value, const bool little_endian)
-{
-    std::size_t width = 0;
-    switch (marker)
-    {
-        case 'i':
-        case 'U':
-            width = 1;
-            break;
-        case 'I':
-        case 'u':
-            width = 2;
-            break;
-        case 'l':
-        case 'm':
-            width = 4;
-            break;
-        case 'L':
-        case 'M':
-            width = 8;
-            break;
-        default:
-        {
-            const std::string digits = value.dump();
-            std::vector<std::uint8_t> result = {'i', static_cast<std::uint8_t>(digits.size())};
-            for (const char c : digits)
-            {
-                result.push_back(static_cast<std::uint8_t>(c));
-            }
-            return result;
-        }
-    }
-
-    const std::uint64_t bits = value.is_number_unsigned()
-                               ? value.get<std::uint64_t>()
-                               : static_cast<std::uint64_t>(value.get<std::int64_t>());
-    std::vector<std::uint8_t> result(width);
-    for (std::size_t i = 0; i < width; ++i)
-    {
-        result[little_endian ? i : width - 1 - i] = static_cast<std::uint8_t>(bits >> (8 * i));
-    }
-    return result;
-}
-
-json i64(const std::int64_t v)
-{
-    return v;
-}
-
-json u64(const std::uint64_t v)
-{
-    return v;
-}
-} // namespace
-
-TEST_CASE("UBJSON and BJData integer markers at every range edge")
-{
-    // An optimized container announces the marker of its values after `$` and
-    // then writes every value without a marker, so the marker the writer
-    // announces and the width it writes must match for every value. This
-    // checks both for the values around each edge of the integer types, as
-    // scalars and as the values of optimized arrays and objects.
-    struct integer_case
-    {
-        json value;
-        char ubjson; // expected UBJSON marker
-        char bjdata; // expected BJData marker
-    };
-
-    const std::int64_t int64_min = (std::numeric_limits<std::int64_t>::min)();
-    const std::int64_t int64_max = (std::numeric_limits<std::int64_t>::max)();
-    const std::uint64_t uint64_max = (std::numeric_limits<std::uint64_t>::max)();
-
-    const std::vector<integer_case> cases =
-    {
-        // int8
-        {i64(-129), 'I', 'I'},
-        {i64(-128), 'i', 'i'},
-        {i64(-127), 'i', 'i'},
-        {i64(-1), 'i', 'i'},
-        {i64(0), 'i', 'i'},
-        {u64(0), 'i', 'i'},
-        {i64(126), 'i', 'i'},
-        {i64(127), 'i', 'i'},
-        {u64(127), 'i', 'i'},
-        {i64(128), 'U', 'U'},
-        {u64(128), 'U', 'U'},
-        // uint8
-        {i64(254), 'U', 'U'},
-        {i64(255), 'U', 'U'},
-        {u64(255), 'U', 'U'},
-        {i64(256), 'I', 'I'},
-        {u64(256), 'I', 'I'},
-        // int16
-        {i64(-32769), 'l', 'l'},
-        {i64(-32768), 'I', 'I'},
-        {i64(-32767), 'I', 'I'},
-        {i64(32766), 'I', 'I'},
-        {i64(32767), 'I', 'I'},
-        {u64(32767), 'I', 'I'},
-        {i64(32768), 'l', 'u'},
-        {u64(32768), 'l', 'u'},
-        // uint16 (BJData only)
-        {i64(65534), 'l', 'u'},
-        {i64(65535), 'l', 'u'},
-        {u64(65535), 'l', 'u'},
-        {i64(65536), 'l', 'l'},
-        {u64(65536), 'l', 'l'},
-        // int32
-        {i64(-2147483649LL), 'L', 'L'},
-        {i64(-2147483648LL), 'l', 'l'},
-        {i64(-2147483647LL), 'l', 'l'},
-        {i64(2147483646LL), 'l', 'l'},
-        {i64(2147483647LL), 'l', 'l'},
-        {u64(2147483647ULL), 'l', 'l'},
-        {i64(2147483648LL), 'L', 'm'},
-        {u64(2147483648ULL), 'L', 'm'},
-        // uint32 (BJData only)
-        {i64(4294967294LL), 'L', 'm'},
-        {i64(4294967295LL), 'L', 'm'},
-        {u64(4294967295ULL), 'L', 'm'},
-        {i64(4294967296LL), 'L', 'L'},
-        {u64(4294967296ULL), 'L', 'L'},
-        // int64
-        {i64(int64_min), 'L', 'L'},
-        {i64(int64_min + 1), 'L', 'L'},
-        {i64(int64_max - 1), 'L', 'L'},
-        {i64(int64_max), 'L', 'L'},
-        {u64(static_cast<std::uint64_t>(int64_max)), 'L', 'L'},
-        // uint64 (BJData only; UBJSON writes a high-precision number)
-        {u64(static_cast<std::uint64_t>(int64_max) + 1), 'H', 'M'},
-        {u64(uint64_max - 1), 'H', 'M'},
-        {u64(uint64_max), 'H', 'M'},
-    };
-
-    for (const auto& c : cases)
-    {
-        for (const bool bjdata :
-                {
-                    false, true
-                })
-        {
-            const char marker = bjdata ? c.bjdata : c.ubjson;
-            const std::vector<std::uint8_t> payload = integer_payload(marker, c.value, bjdata);
-            const auto to_binary = [bjdata](const json & j, const bool use_size, const bool use_type)
-            {
-                return bjdata ? json::to_bjdata(j, use_size, use_type) : json::to_ubjson(j, use_size, use_type);
-            };
-            const auto from_binary = [bjdata](const std::vector<std::uint8_t>& v)
-            {
-                return bjdata ? json::from_bjdata(v) : json::from_ubjson(v);
-            };
-            INFO("value = " << c.value.dump() << (c.value.is_number_unsigned() ? " (unsigned)" : "") << ", format = " << (bjdata ? "BJData" : "UBJSON"));
-
-            // scalar
-            std::vector<std::uint8_t> expected = {static_cast<std::uint8_t>(marker)};
-            expected.insert(expected.end(), payload.begin(), payload.end());
-            for (const bool use_size :
-                    {
-                        false, true
-                    })
-            {
-                CHECK(to_binary(c.value, use_size, false) == expected);
-            }
-            CHECK(from_binary(expected) == c.value);
-
-            const json arr = {c.value, c.value, c.value};
-
-            // array without count or type: every value has its marker
-            expected = {'['};
-            for (int i = 0; i < 3; ++i)
-            {
-                expected.push_back(static_cast<std::uint8_t>(marker));
-                expected.insert(expected.end(), payload.begin(), payload.end());
-            }
-            expected.push_back(']');
-            CHECK(to_binary(arr, false, false) == expected);
-            CHECK(from_binary(expected) == arr);
-
-            // array with count: every value has its marker
-            expected = {'[', '#', 'i', 3};
-            for (int i = 0; i < 3; ++i)
-            {
-                expected.push_back(static_cast<std::uint8_t>(marker));
-                expected.insert(expected.end(), payload.begin(), payload.end());
-            }
-            CHECK(to_binary(arr, true, false) == expected);
-            CHECK(from_binary(expected) == arr);
-
-            // array with type and count: the marker once, then the payloads
-            expected = {'[', '$', static_cast<std::uint8_t>(marker), '#', 'i', 3};
-            for (int i = 0; i < 3; ++i)
-            {
-                expected.insert(expected.end(), payload.begin(), payload.end());
-            }
-            CHECK(to_binary(arr, true, true) == expected);
-            CHECK(from_binary(expected) == arr);
-
-            // object with type and count: the marker once, then key and payload
-            const json obj = {{"a", c.value}, {"b", c.value}};
-            expected = {'{', '$', static_cast<std::uint8_t>(marker), '#', 'i', 2};
-            for (const char key :
-                    {'a', 'b'
-                    })
-            {
-                expected.push_back('i');
-                expected.push_back(1);
-                expected.push_back(static_cast<std::uint8_t>(key));
-                expected.insert(expected.end(), payload.begin(), payload.end());
-            }
-            CHECK(to_binary(obj, true, true) == expected);
-            CHECK(from_binary(expected) == obj);
-        }
-    }
-}