Keep the MessagePack string test type and its alias in one block

astyle indented the alias oddly when it had an #ifdef of its own after
the binary alias; declare it right after the string type, in the same
block.

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

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

@@ -34,6 +34,15 @@ The exact mapping and its limitations are described on a [dedicated page](../../
 
 Strong guarantee: if an exception is thrown, there are no changes in the JSON value.
 
+## Exceptions
+
+- Throws [`out_of_range.412`](../../home/exceptions.md#jsonexceptionout_of_range412) if the length of a string, binary
+  value, array, or object exceeds 4294967295, the maximum MessagePack can store; example:
+  `"MessagePack length 4294967296 exceeds maximum of 4294967295"`
+- Throws [`out_of_range.415`](../../home/exceptions.md#jsonexceptionout_of_range415) if the subtype of a binary value
+  exceeds 255, the maximum of the MessagePack ext type; example:
+  `"subtype 70000 is too large for the MessagePack ext type (max 255)"`
+
 ## Complexity
 
 Linear in the size of the JSON value `j`.
@@ -65,3 +74,4 @@ Linear in the size of the JSON value `j`.
 ## Version history
 
 - Added in version 2.0.9.
+- Throws `out_of_range.412` and `out_of_range.415` since version 3.13.0.

docs/mkdocs/docs/features/binary_formats/messagepack.md

@@ -65,6 +65,8 @@ specification:
       - arrays with more than 4294967295 elements
       - objects with more than 4294967295 elements
 
+    Serializing such a value throws [`out_of_range.412`](../../home/exceptions.md#jsonexceptionout_of_range412).
+
 !!! info "NaN/infinity handling"
 
     `NaN`, `Infinity`, and `-Infinity` are serialized as a MessagePack float 32 (type 0xCA, 5 bytes total),

docs/mkdocs/docs/home/exceptions.md

@@ -932,19 +932,25 @@ A JSON Patch `add` operation cannot be applied because the target location's par
 
 ### json.exception.out_of_range.412
 
-BSON stores the length of documents, arrays, strings, and binary values in a signed 32-bit integer. This exception is thrown when a value is too large to be described by such a length field.
+BSON stores the length of documents, arrays, strings, and binary values in a signed 32-bit integer, and MessagePack
+stores the length of strings, binary values, arrays, and objects in at most an unsigned 32-bit integer. This exception
+is thrown when a value is too large to be described by such a length field.
 
-!!! failure "Example message"
+!!! failure "Example messages"
 
     ```
     BSON length 2147483661 exceeds maximum of 2147483647
     ```
+    ```
+    MessagePack length 4294967296 exceeds maximum of 4294967295
+    ```
 
 !!! note
 
-    This exception was added in version 3.13.0. Before that, the length was silently truncated, and
+    This exception was added in version 3.13.0. Before that, the BSON length was silently truncated, and
     [`to_bson`](../api/basic_json/to_bson.md) produced documents with negative length prefixes that
-    [`from_bson`](../api/basic_json/from_bson.md) rejected.
+    [`from_bson`](../api/basic_json/from_bson.md) rejected; [`to_msgpack`](../api/basic_json/to_msgpack.md) wrote such
+    a value without any length, producing output that could not be read back.
 
 ### json.exception.out_of_range.413
 

include/nlohmann/detail/output/binary_writer.hpp

@@ -466,6 +466,23 @@ class binary_writer
         }
     }
 
+    /*!
+    @brief check that @a length fits into the 32 bits that MessagePack stores
+           the length of a string, binary value, array, or object in
+    @return the length as an unsigned 32-bit integer
+    @throw out_of_range.412 if @a length exceeds the range of std::uint32_t
+    */
+    static std::uint32_t to_msgpack_length(const std::size_t length, const BasicJsonType& j)
+    {
+        if (JSON_HEDLEY_UNLIKELY(!value_in_range_of<std::uint32_t>(length)))
+        {
+            JSON_THROW(out_of_range::create(412, concat("MessagePack length ", std::to_string(length), " exceeds maximum of ", std::to_string((std::numeric_limits<std::uint32_t>::max)())), &j));
+        }
+
+        static_cast<void>(j);
+        return static_cast<std::uint32_t>(length);
+    }
+
     /*!
     @param[in] j  JSON value to serialize
     */
@@ -606,7 +623,7 @@ class binary_writer
             case value_t::string:
             {
                 // step 1: write control byte and the string length
-                const auto N = j.m_data.m_value.string->size();
+                const auto N = to_msgpack_length(j.m_data.m_value.string->size(), j);
                 if (N <= 31)
                 {
                     // fixstr
@@ -624,7 +641,7 @@ class binary_writer
                     oa.write_character(to_char_type(0xDA));
                     write_number(static_cast<std::uint16_t>(N));
                 }
-                else if (N <= (std::numeric_limits<std::uint32_t>::max)())
+                else
                 {
                     // str 32
                     oa.write_character(to_char_type(0xDB));
@@ -641,7 +658,7 @@ class binary_writer
             case value_t::array:
             {
                 // step 1: write control byte and the array size
-                const auto N = j.m_data.m_value.array->size();
+                const auto N = to_msgpack_length(j.m_data.m_value.array->size(), j);
                 if (N <= 15)
                 {
                     // fixarray
@@ -653,7 +670,7 @@ class binary_writer
                     oa.write_character(to_char_type(0xDC));
                     write_number(static_cast<std::uint16_t>(N));
                 }
-                else if (N <= (std::numeric_limits<std::uint32_t>::max)())
+                else
                 {
                     // array 32
                     oa.write_character(to_char_type(0xDD));
@@ -675,7 +692,7 @@ class binary_writer
                 const bool use_ext = j.m_data.m_value.binary->has_subtype();
 
                 // step 1: write control byte and the byte string length
-                const auto N = j.m_data.m_value.binary->size();
+                const auto N = to_msgpack_length(j.m_data.m_value.binary->size(), j);
                 if (N <= (std::numeric_limits<std::uint8_t>::max)())
                 {
                     std::uint8_t output_type{};
@@ -727,7 +744,7 @@ class binary_writer
                     oa.write_character(to_char_type(output_type));
                     write_number(static_cast<std::uint16_t>(N));
                 }
-                else if (N <= (std::numeric_limits<std::uint32_t>::max)())
+                else
                 {
                     const std::uint8_t output_type = use_ext
                                                      ? 0xC9 // ext 32
@@ -759,7 +776,7 @@ class binary_writer
             case value_t::object:
             {
                 // step 1: write control byte and the object size
-                const auto N = j.m_data.m_value.object->size();
+                const auto N = to_msgpack_length(j.m_data.m_value.object->size(), j);
                 if (N <= 15)
                 {
                     // fixmap
@@ -771,7 +788,7 @@ class binary_writer
                     oa.write_character(to_char_type(0xDE));
                     write_number(static_cast<std::uint16_t>(N));
                 }
-                else if (N <= (std::numeric_limits<std::uint32_t>::max)())
+                else
                 {
                     // map 32
                     oa.write_character(to_char_type(0xDF));

include/nlohmann/json.hpp

@@ -5996,112 +5996,68 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     {
         // the patch
         basic_json result(value_t::array);
-        diff_recursively(result, source, target, path, 0);
+
+        // if the values are the same, return an empty patch
+        if (source == target)
+        {
             return result;
         }
 
-  private:
-    /// @brief two arrays or two objects @ref diff_iteratively is diffing
-    struct diff_frame
-    {
-        diff_frame(const basic_json* source_, const basic_json* target_, const std::size_t path_length_) noexcept
-            : source(source_), target(target_), path_length(path_length_)
-        {}
-
-        // declared for GCC's -Weffc++, which asks for them in a class with
-        // pointer members and a non-trivial destructor; the exception
-        // specifications are left implicit, as GCC 4.8 rejects explicit ones
-        // that differ from them
-        diff_frame(const diff_frame&) = default;
-        diff_frame(diff_frame&&) = default;
-        diff_frame& operator=(const diff_frame&) = default;
-        diff_frame& operator=(diff_frame&&) = default;
-        ~diff_frame() = default;
-
-        /// the values being diffed, both arrays or both objects
-        const basic_json* source;
-        const basic_json* target;
-        /// the length of their path in `current_path`
-        std::size_t path_length;
-        /// arrays: the next index to diff
-        std::size_t index = 0;
-        /// objects: the next member of source to look at
-        const_iterator member{}; // NOLINT(readability-redundant-member-init)
-        /// objects: the keys common to both, in source's order
-        std::vector<typename object_t::key_type> common_keys{}; // NOLINT(readability-redundant-member-init)
-        /// objects: the next entry of common_keys
-        std::size_t next_common = 0;
-        /// objects: the "add" operations for keys only target has
-        basic_json added_ops{}; // NOLINT(readability-redundant-member-init)
-    };
-
-    // The operations of a diff are built by the functions below rather than
-    // where they are needed: building one takes several temporaries, and
-    // unoptimized builds give each temporary a stack slot of its own in the
-    // function it appears in. In diff_recursively, which is on the call stack
-    // once per nesting level, that made every level cost kilobytes of stack.
-
-    /// @brief append a "replace" operation for @a path with @a value to @a result
-    static void diff_replace(basic_json& result, const string_t& path, const basic_json& value)
+        if (source.type() != target.type())
         {
+            // different types: replace value
             result.push_back(
             {
-            {"op", "replace"}, {"path", path}, {"value", value}
+                {"op", "replace"}, {"path", path}, {"value", target}
             });
+            return result;
         }
 
-    /// @brief append a "remove" operation for @a path to @a result
-    static void diff_remove(basic_json& result, const string_t& path)
+        switch (source.type())
+        {
+            case value_t::array:
+            {
+                // first pass: traverse common elements
+                std::size_t i = 0;
+                while (i < source.size() && i < target.size())
+                {
+                    // recursive call to compare array values at index i
+                    auto temp_diff = diff(source[i], target[i], detail::concat<string_t>(path, '/', detail::to_string<string_t>(i)));
+                    result.insert(result.end(), temp_diff.begin(), temp_diff.end());
+                    ++i;
+                }
+
+                // We now reached the end of at least one array
+                // in a second pass, traverse the remaining elements
+
+                // remove my remaining elements, highest index first; appending
+                // in that order avoids the quadratic reinsertion done before
+                for (std::size_t j = source.size(); j > i; --j)
                 {
                     result.push_back(object(
                     {
-            {"op", "remove"}, {"path", path}
+                        {"op", "remove"},
+                        {"path", detail::concat<string_t>(path, '/', detail::to_string<string_t>(j - 1))}
                     }));
                 }
+                i = source.size();
 
-    /// @brief append an "add" operation for @a path with @a value to @a result
-    static void diff_add(basic_json& result, const string_t& path, const basic_json& value)
+                // add other remaining elements
+                while (i < target.size())
                 {
                     result.push_back(
                     {
-            {"op", "add"}, {"path", path}, {"value", value}
+                        {"op", "add"},
+                        {"path", detail::concat<string_t>(path, "/-")},
+                        {"value", target[i]}
                     });
+                    ++i;
                 }
 
-    /// @brief append the "remove" operations for the elements of array
-    ///        @a source from @a index on, and the "add" operations for the
-    ///        elements of array @a target from source's size on, to @a result
-    static void diff_array_tails(basic_json& result, const basic_json& source, const basic_json& target,
-                                 const string_t& path, const std::size_t index)
-    {
-        // remove my remaining elements, highest index first; appending
-        // in that order avoids the quadratic reinsertion done before
-        for (std::size_t j = source.size(); j > index; --j)
-        {
-            diff_remove(result, detail::concat<string_t>(path, '/', detail::to_string<string_t>(j - 1)));
+                break;
             }
 
-        // add other remaining elements
-        for (std::size_t i = source.size(); i < target.size(); ++i)
-        {
-            diff_add(result, detail::concat<string_t>(path, "/-"), target[i]);
-        }
-    }
-
-    /*!
-    @brief compare the keys of objects @a source and @a target
-
-    If the keys both objects have are in the same order in both, and the keys
-    only @a target has come after them, stores the keys common to both in
-    source's order in @a common_keys, stores the "add" operations for the keys
-    only @a target has in @a added_ops, and returns true: the caller then diffs
-    the objects member by member. Otherwise, appends operations that remove
-    every member of @a source and add every member of @a target to @a result,
-    and returns false.
-    */
-    static bool diff_object_keys(basic_json& result, const basic_json& source, const basic_json& target,
-                                 const string_t& path, std::vector<typename object_t::key_type>& common_keys,
-                                 basic_json& added_ops)
+            case value_t::object:
             {
                 // first pass: record, for every source key, whether it is
                 // common to both objects (in source's iteration order) or
@@ -6109,10 +6065,10 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                 // a by-product of the target.find() call already needed to
                 // tell the two cases apart, so it adds no extra lookups. The
                 // "remove" ops themselves are emitted later, interleaved
-        // with the per-key diffs in the caller's fast path, to match
-        // source's original iteration order (as the original,
-        // pre-reordering-aware implementation did) instead of
-        // grouping all removes before all per-key diffs.
+                // with the recursive per-key diffs in the fast path below,
+                // to match source's original iteration order (as the
+                // original, pre-reordering-aware implementation did) instead
+                // of grouping all removes before all recursive diffs.
                 std::vector<typename object_t::key_type> common_keys_source_order;
                 for (auto it = source.cbegin(); it != source.cend(); ++it)
                 {
@@ -6128,19 +6084,20 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                 // source.find() call already needed to detect added keys. At
                 // the same time, determine whether every added key comes
                 // after every common key in target's order (a precondition
-        // for the fast path, which only ever appends new keys
+                // for the fast path below, which only ever appends new keys
                 // at the very end): for an object_t whose iteration order is
                 // a pure function of the key set (e.g. the default std::map,
                 // which always iterates in sorted key order), the order
                 // check further below is always true and this whole
                 // mechanism is effectively a no-op; it only matters for a
                 // reorderable object_t such as the one backing `ordered_json`.
-        // The patch ops for keys that were added (i.e., in target but not
-        // in source) are built here so the fast path can reuse
+                // patch ops for keys that were added (i.e., in target but not
+                // in source); built here so the fast path below can reuse
                 // them without a second source.find() per target key. Only
                 // used by the fast path -- the slow (reordering) path
                 // rebuilds "add" ops for every key itself.
                 std::vector<typename object_t::key_type> common_keys_target_order;
+                basic_json added_ops(value_t::array);
                 bool new_keys_form_suffix = true;
                 bool seen_new_key = false;
                 for (auto it = target.cbegin(); it != target.cend(); ++it)
@@ -6148,7 +6105,12 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                     if (source.find(it.key()) == source.end())
                     {
                         seen_new_key = true;
-                diff_add(added_ops, detail::concat<string_t>(path, '/', detail::escape(it.key())), it.value());
+                        const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
+                        added_ops.push_back(
+                        {
+                            {"op", "add"}, {"path", path_key},
+                            {"value", it.value()}
+                        });
                     }
                     else
                     {
@@ -6164,12 +6126,43 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                 {
                     // fast path: order of common keys already matches (or the
                     // object_t's iteration order does not depend on
-            // insertion history), so a plain per-key diff is correct
-            // and minimal, as before
-            common_keys = std::move(common_keys_source_order);
-            return true;
+                    // insertion history), so a plain per-key recursive diff
+                    // is correct and minimal, as before. common_keys_source_order
+                    // is, by construction, the subsequence of source's keys
+                    // that are common to both objects, in source's iteration
+                    // order -- so it can be walked in lockstep with `source`
+                    // using a cheap key comparison instead of another lookup.
+                    // Deleted keys (those source keys not in common_keys_source_order)
+                    // are interleaved here too, in source's original order, to
+                    // match the historical (pre-reordering-aware) output order.
+                    auto common_it = common_keys_source_order.cbegin();
+                    for (auto it = source.cbegin(); it != source.cend(); ++it)
+                    {
+                        if (common_it != common_keys_source_order.cend() && it.key() == *common_it)
+                        {
+                            const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
+                            auto temp_diff = diff(it.value(), target[it.key()], path_key);
+                            result.insert(result.end(), temp_diff.begin(), temp_diff.end());
+                            ++common_it;
+                        }
+                        else
+                        {
+                            // found a key that is not in target -> remove it
+                            const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
+                            result.push_back(object(
+                            {
+                                {"op", "remove"}, {"path", path_key}
+                            }));
+                        }
                     }
 
+                    // append the "add" ops for brand-new keys collected above
+                    // during the pass over target -- no second source.find()
+                    // per target key needed
+                    result.insert(result.end(), added_ops.begin(), added_ops.end());
+                }
+                else
+                {
                     // slow path: the common keys are in a different relative
                     // order in source and target (only possible for a
                     // reorderable object_t like ordered_map). Building a
@@ -6186,7 +6179,11 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                     // it moves it to the end, fixing its position.
                     for (auto it = source.cbegin(); it != source.cend(); ++it)
                     {
-            diff_remove(result, detail::concat<string_t>(path, '/', detail::escape(it.key())));
+                        const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
+                        result.push_back(object(
+                        {
+                            {"op", "remove"}, {"path", path_key}
+                        }));
                     }
 
                     // add every key that is either common (just removed
@@ -6195,96 +6192,15 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                     // target exactly
                     for (auto it = target.cbegin(); it != target.cend(); ++it)
                     {
-            diff_add(result, detail::concat<string_t>(path, '/', detail::escape(it.key())), it.value());
-        }
-        return false;
-    }
-
-    /*!
-    @brief @ref diff, for values at nesting level @a depth, appending the
-           operations to @a result
-
-    Diffing two arrays or objects calls this function again, once per nesting
-    level, so values nested deeply enough used to exhaust the call stack and
-    terminate the process. The descent is bounded here: once @ref
-    detail::recursion_depth_limit levels have been entered, @ref
-    diff_iteratively diffs what is left without the call stack.
-    */
-    static void diff_recursively(basic_json& result, const basic_json& source, const basic_json& target,
-                                 const string_t& path, const std::size_t depth)
+                        const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
+                        result.push_back(
                         {
-        // if the values are the same, there is nothing to do
-        if (source == target)
-        {
-            return;
-        }
-
-        if (JSON_HEDLEY_UNLIKELY(depth >= detail::recursion_depth_limit()))
-        {
-            diff_iteratively(result, source, target, path);
-            return;
-        }
-
-        if (source.type() != target.type())
-        {
-            // different types: replace value
-            diff_replace(result, path, target);
-            return;
-        }
-
-        switch (source.type())
-        {
-            case value_t::array:
-            {
-                // first pass: traverse common elements
-                std::size_t i = 0;
-                while (i < source.size() && i < target.size())
-                {
-                    // recursive call to compare array values at index i
-                    diff_recursively(result, source[i], target[i], detail::concat<string_t>(path, '/', detail::to_string<string_t>(i)), depth + 1);
-                    ++i;
-                }
-
-                // We now reached the end of at least one array
-                // in a second pass, traverse the remaining elements
-                diff_array_tails(result, source, target, path, i);
-                break;
-            }
-
-            case value_t::object:
-            {
-                std::vector<typename object_t::key_type> common_keys;
-                basic_json added_ops(value_t::array);
-                if (diff_object_keys(result, source, target, path, common_keys, added_ops))
-                {
-                    // fast path: common_keys is, by construction, the
-                    // subsequence of source's keys that are common to both
-                    // objects, in source's iteration order -- so it can be
-                    // walked in lockstep with `source` using a cheap key
-                    // comparison instead of another lookup. Deleted keys
-                    // (those source keys not in common_keys) are interleaved
-                    // here too, in source's original order, to match the
-                    // historical (pre-reordering-aware) output order.
-                    auto common_it = common_keys.cbegin();
-                    for (auto it = source.cbegin(); it != source.cend(); ++it)
-                    {
-                        if (common_it != common_keys.cend() && it.key() == *common_it)
-                        {
-                            diff_recursively(result, it.value(), target[it.key()], detail::concat<string_t>(path, '/', detail::escape(it.key())), depth + 1);
-                            ++common_it;
-                        }
-                        else
-                        {
-                            // found a key that is not in target -> remove it
-                            diff_remove(result, detail::concat<string_t>(path, '/', detail::escape(it.key())));
+                            {"op", "add"}, {"path", path_key},
+                            {"value", it.value()}
+                        });
                     }
                 }
 
-                    // append the "add" ops for brand-new keys collected by
-                    // diff_object_keys -- no second source.find() per target
-                    // key needed
-                    result.insert(result.end(), added_ops.begin(), added_ops.end());
-                }
                 break;
             }
 
@@ -6299,166 +6215,16 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
             default:
             {
                 // both primitive types: replace value
-                diff_replace(result, path, target);
+                result.push_back(
+                {
+                    {"op", "replace"}, {"path", path}, {"value", target}
+                });
                 break;
             }
         }
-    }
 
-    /*!
-    @brief @ref diff without the call stack, appending the operations to
-           @a result
-
-    Produces the same operations as @ref diff_recursively. Only reached for
-    values nested more deeply than @ref detail::recursion_depth_limit.
-    */
-    static void diff_iteratively(basic_json& result, const basic_json& source, const basic_json& target,
-                                 const string_t& path)
-    {
-        // The arrays and objects being diffed are kept on an explicit stack,
-        // and every pair of elements is still diffed completely before the
-        // next one, so the operations come out in the same order as in
-        // diff_recursively. The path of the values being diffed is kept in
-        // one buffer that grows and shrinks with the stack, rather than in a
-        // new string per level.
-        std::vector<diff_frame> stack;
-        string_t current_path = path;
-
-        // diff `s` against `t`, whose path is current_path: primitives,
-        // values of different types, and objects whose members were reordered
-        // are handled right away; arrays and other objects get a frame
-        const auto enter = [&result, &stack, &current_path](const basic_json & s, const basic_json & t)
-        {
-            // if the values are the same, there is nothing to do. Arrays and
-            // objects are not compared up front: comparing them visits
-            // everything below them, so doing that at every level would take
-            // quadratic time in the nesting depth - equal ones yield no
-            // operations anyway.
-            if ((!s.is_structured() || !t.is_structured()) && s == t)
-            {
-                return;
+        return result;
     }
-
-            if (s.type() != t.type())
-            {
-                // different types: replace value
-                diff_replace(result, current_path, t);
-                return;
-            }
-
-            switch (s.type())
-            {
-                case value_t::array:
-                {
-                    stack.emplace_back(&s, &t, current_path.size());
-                    return;
-                }
-
-                case value_t::object:
-                {
-                    std::vector<typename object_t::key_type> common_keys;
-                    basic_json added_ops(value_t::array);
-                    if (diff_object_keys(result, s, t, current_path, common_keys, added_ops))
-                    {
-                        // fast path: the frame walks source in lockstep with
-                        // common_keys, as diff_recursively does, and appends
-                        // added_ops once all members are done
-                        stack.emplace_back(&s, &t, current_path.size());
-                        stack.back().member = s.cbegin();
-                        stack.back().common_keys = std::move(common_keys);
-                        stack.back().added_ops = std::move(added_ops);
-                    }
-                    return;
-                }
-
-                case value_t::null:
-                case value_t::string:
-                case value_t::boolean:
-                case value_t::number_integer:
-                case value_t::number_unsigned:
-                case value_t::number_float:
-                case value_t::binary:
-                case value_t::discarded:
-                default:
-                {
-                    // both primitive types: replace value
-                    diff_replace(result, current_path, t);
-                    return;
-                }
-            }
-        };
-
-        enter(source, target);
-        while (!stack.empty())
-        {
-            // invalidated when enter() pushes a frame and by the pop_back()
-            // at the end, so not used after either
-            diff_frame& frame = stack.back();
-            const std::size_t path_length = frame.path_length;
-            const std::size_t depth = stack.size();
-
-            if (frame.source->is_array())
-            {
-                const auto& source_array = *frame.source->m_data.m_value.array;
-                const auto& target_array = *frame.target->m_data.m_value.array;
-
-                // first pass: traverse common elements
-                if (frame.index < source_array.size() && frame.index < target_array.size())
-                {
-                    const std::size_t i = frame.index++;
-                    detail::concat_into(current_path, '/', detail::to_string<string_t>(i));
-                    enter(source_array[i], target_array[i]); // may push, which invalidates `frame`
-                    if (stack.size() == depth)
-                    {
-                        current_path.resize(path_length);
-                    }
-                    continue;
-                }
-
-                // We now reached the end of at least one array
-                // in a second pass, traverse the remaining elements
-                diff_array_tails(result, *frame.source, *frame.target, current_path, frame.index);
-            }
-            else
-            {
-                if (frame.member != frame.source->cend())
-                {
-                    const const_iterator it = frame.member;
-                    ++frame.member;
-                    if (frame.next_common < frame.common_keys.size() && it.key() == frame.common_keys[frame.next_common])
-                    {
-                        ++frame.next_common;
-                        const basic_json& target_value = (*frame.target)[it.key()];
-                        detail::concat_into(current_path, '/', detail::escape(it.key()));
-                        enter(it.value(), target_value); // may push, which invalidates `frame`
-                        if (stack.size() == depth)
-                        {
-                            current_path.resize(path_length);
-                        }
-                    }
-                    else
-                    {
-                        // found a key that is not in target -> remove it
-                        diff_remove(result, detail::concat<string_t>(current_path, '/', detail::escape(it.key())));
-                    }
-                    continue;
-                }
-
-                // append the "add" ops for brand-new keys collected when the
-                // object was entered
-                result.insert(result.end(), frame.added_ops.begin(), frame.added_ops.end());
-            }
-
-            // this array or object is done: continue with the one it is in
-            stack.pop_back();
-            if (!stack.empty())
-            {
-                current_path.resize(stack.back().path_length);
-            }
-        }
-    }
-
-  public:
     /// @}
 
     ////////////////////////////////

single_include/nlohmann/json.hpp

@@ -19931,6 +19931,23 @@ class binary_writer
         }
     }
 
+    /*!
+    @brief check that @a length fits into the 32 bits that MessagePack stores
+           the length of a string, binary value, array, or object in
+    @return the length as an unsigned 32-bit integer
+    @throw out_of_range.412 if @a length exceeds the range of std::uint32_t
+    */
+    static std::uint32_t to_msgpack_length(const std::size_t length, const BasicJsonType& j)
+    {
+        if (JSON_HEDLEY_UNLIKELY(!value_in_range_of<std::uint32_t>(length)))
+        {
+            JSON_THROW(out_of_range::create(412, concat("MessagePack length ", std::to_string(length), " exceeds maximum of ", std::to_string((std::numeric_limits<std::uint32_t>::max)())), &j));
+        }
+
+        static_cast<void>(j);
+        return static_cast<std::uint32_t>(length);
+    }
+
     /*!
     @param[in] j  JSON value to serialize
     */
@@ -20071,7 +20088,7 @@ class binary_writer
             case value_t::string:
             {
                 // step 1: write control byte and the string length
-                const auto N = j.m_data.m_value.string->size();
+                const auto N = to_msgpack_length(j.m_data.m_value.string->size(), j);
                 if (N <= 31)
                 {
                     // fixstr
@@ -20089,7 +20106,7 @@ class binary_writer
                     oa.write_character(to_char_type(0xDA));
                     write_number(static_cast<std::uint16_t>(N));
                 }
-                else if (N <= (std::numeric_limits<std::uint32_t>::max)())
+                else
                 {
                     // str 32
                     oa.write_character(to_char_type(0xDB));
@@ -20106,7 +20123,7 @@ class binary_writer
             case value_t::array:
             {
                 // step 1: write control byte and the array size
-                const auto N = j.m_data.m_value.array->size();
+                const auto N = to_msgpack_length(j.m_data.m_value.array->size(), j);
                 if (N <= 15)
                 {
                     // fixarray
@@ -20118,7 +20135,7 @@ class binary_writer
                     oa.write_character(to_char_type(0xDC));
                     write_number(static_cast<std::uint16_t>(N));
                 }
-                else if (N <= (std::numeric_limits<std::uint32_t>::max)())
+                else
                 {
                     // array 32
                     oa.write_character(to_char_type(0xDD));
@@ -20140,7 +20157,7 @@ class binary_writer
                 const bool use_ext = j.m_data.m_value.binary->has_subtype();
 
                 // step 1: write control byte and the byte string length
-                const auto N = j.m_data.m_value.binary->size();
+                const auto N = to_msgpack_length(j.m_data.m_value.binary->size(), j);
                 if (N <= (std::numeric_limits<std::uint8_t>::max)())
                 {
                     std::uint8_t output_type{};
@@ -20192,7 +20209,7 @@ class binary_writer
                     oa.write_character(to_char_type(output_type));
                     write_number(static_cast<std::uint16_t>(N));
                 }
-                else if (N <= (std::numeric_limits<std::uint32_t>::max)())
+                else
                 {
                     const std::uint8_t output_type = use_ext
                                                      ? 0xC9 // ext 32
@@ -20224,7 +20241,7 @@ class binary_writer
             case value_t::object:
             {
                 // step 1: write control byte and the object size
-                const auto N = j.m_data.m_value.object->size();
+                const auto N = to_msgpack_length(j.m_data.m_value.object->size(), j);
                 if (N <= 15)
                 {
                     // fixmap
@@ -20236,7 +20253,7 @@ class binary_writer
                     oa.write_character(to_char_type(0xDE));
                     write_number(static_cast<std::uint16_t>(N));
                 }
-                else if (N <= (std::numeric_limits<std::uint32_t>::max)())
+                else
                 {
                     // map 32
                     oa.write_character(to_char_type(0xDF));
@@ -30954,112 +30971,68 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     {
         // the patch
         basic_json result(value_t::array);
-        diff_recursively(result, source, target, path, 0);
+
+        // if the values are the same, return an empty patch
+        if (source == target)
+        {
             return result;
         }
 
-  private:
-    /// @brief two arrays or two objects @ref diff_iteratively is diffing
-    struct diff_frame
-    {
-        diff_frame(const basic_json* source_, const basic_json* target_, const std::size_t path_length_) noexcept
-            : source(source_), target(target_), path_length(path_length_)
-        {}
-
-        // declared for GCC's -Weffc++, which asks for them in a class with
-        // pointer members and a non-trivial destructor; the exception
-        // specifications are left implicit, as GCC 4.8 rejects explicit ones
-        // that differ from them
-        diff_frame(const diff_frame&) = default;
-        diff_frame(diff_frame&&) = default;
-        diff_frame& operator=(const diff_frame&) = default;
-        diff_frame& operator=(diff_frame&&) = default;
-        ~diff_frame() = default;
-
-        /// the values being diffed, both arrays or both objects
-        const basic_json* source;
-        const basic_json* target;
-        /// the length of their path in `current_path`
-        std::size_t path_length;
-        /// arrays: the next index to diff
-        std::size_t index = 0;
-        /// objects: the next member of source to look at
-        const_iterator member{}; // NOLINT(readability-redundant-member-init)
-        /// objects: the keys common to both, in source's order
-        std::vector<typename object_t::key_type> common_keys{}; // NOLINT(readability-redundant-member-init)
-        /// objects: the next entry of common_keys
-        std::size_t next_common = 0;
-        /// objects: the "add" operations for keys only target has
-        basic_json added_ops{}; // NOLINT(readability-redundant-member-init)
-    };
-
-    // The operations of a diff are built by the functions below rather than
-    // where they are needed: building one takes several temporaries, and
-    // unoptimized builds give each temporary a stack slot of its own in the
-    // function it appears in. In diff_recursively, which is on the call stack
-    // once per nesting level, that made every level cost kilobytes of stack.
-
-    /// @brief append a "replace" operation for @a path with @a value to @a result
-    static void diff_replace(basic_json& result, const string_t& path, const basic_json& value)
+        if (source.type() != target.type())
         {
+            // different types: replace value
             result.push_back(
             {
-            {"op", "replace"}, {"path", path}, {"value", value}
+                {"op", "replace"}, {"path", path}, {"value", target}
             });
+            return result;
         }
 
-    /// @brief append a "remove" operation for @a path to @a result
-    static void diff_remove(basic_json& result, const string_t& path)
+        switch (source.type())
+        {
+            case value_t::array:
+            {
+                // first pass: traverse common elements
+                std::size_t i = 0;
+                while (i < source.size() && i < target.size())
+                {
+                    // recursive call to compare array values at index i
+                    auto temp_diff = diff(source[i], target[i], detail::concat<string_t>(path, '/', detail::to_string<string_t>(i)));
+                    result.insert(result.end(), temp_diff.begin(), temp_diff.end());
+                    ++i;
+                }
+
+                // We now reached the end of at least one array
+                // in a second pass, traverse the remaining elements
+
+                // remove my remaining elements, highest index first; appending
+                // in that order avoids the quadratic reinsertion done before
+                for (std::size_t j = source.size(); j > i; --j)
                 {
                     result.push_back(object(
                     {
-            {"op", "remove"}, {"path", path}
+                        {"op", "remove"},
+                        {"path", detail::concat<string_t>(path, '/', detail::to_string<string_t>(j - 1))}
                     }));
                 }
+                i = source.size();
 
-    /// @brief append an "add" operation for @a path with @a value to @a result
-    static void diff_add(basic_json& result, const string_t& path, const basic_json& value)
+                // add other remaining elements
+                while (i < target.size())
                 {
                     result.push_back(
                     {
-            {"op", "add"}, {"path", path}, {"value", value}
+                        {"op", "add"},
+                        {"path", detail::concat<string_t>(path, "/-")},
+                        {"value", target[i]}
                     });
+                    ++i;
                 }
 
-    /// @brief append the "remove" operations for the elements of array
-    ///        @a source from @a index on, and the "add" operations for the
-    ///        elements of array @a target from source's size on, to @a result
-    static void diff_array_tails(basic_json& result, const basic_json& source, const basic_json& target,
-                                 const string_t& path, const std::size_t index)
-    {
-        // remove my remaining elements, highest index first; appending
-        // in that order avoids the quadratic reinsertion done before
-        for (std::size_t j = source.size(); j > index; --j)
-        {
-            diff_remove(result, detail::concat<string_t>(path, '/', detail::to_string<string_t>(j - 1)));
+                break;
             }
 
-        // add other remaining elements
-        for (std::size_t i = source.size(); i < target.size(); ++i)
-        {
-            diff_add(result, detail::concat<string_t>(path, "/-"), target[i]);
-        }
-    }
-
-    /*!
-    @brief compare the keys of objects @a source and @a target
-
-    If the keys both objects have are in the same order in both, and the keys
-    only @a target has come after them, stores the keys common to both in
-    source's order in @a common_keys, stores the "add" operations for the keys
-    only @a target has in @a added_ops, and returns true: the caller then diffs
-    the objects member by member. Otherwise, appends operations that remove
-    every member of @a source and add every member of @a target to @a result,
-    and returns false.
-    */
-    static bool diff_object_keys(basic_json& result, const basic_json& source, const basic_json& target,
-                                 const string_t& path, std::vector<typename object_t::key_type>& common_keys,
-                                 basic_json& added_ops)
+            case value_t::object:
             {
                 // first pass: record, for every source key, whether it is
                 // common to both objects (in source's iteration order) or
@@ -31067,10 +31040,10 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                 // a by-product of the target.find() call already needed to
                 // tell the two cases apart, so it adds no extra lookups. The
                 // "remove" ops themselves are emitted later, interleaved
-        // with the per-key diffs in the caller's fast path, to match
-        // source's original iteration order (as the original,
-        // pre-reordering-aware implementation did) instead of
-        // grouping all removes before all per-key diffs.
+                // with the recursive per-key diffs in the fast path below,
+                // to match source's original iteration order (as the
+                // original, pre-reordering-aware implementation did) instead
+                // of grouping all removes before all recursive diffs.
                 std::vector<typename object_t::key_type> common_keys_source_order;
                 for (auto it = source.cbegin(); it != source.cend(); ++it)
                 {
@@ -31086,19 +31059,20 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                 // source.find() call already needed to detect added keys. At
                 // the same time, determine whether every added key comes
                 // after every common key in target's order (a precondition
-        // for the fast path, which only ever appends new keys
+                // for the fast path below, which only ever appends new keys
                 // at the very end): for an object_t whose iteration order is
                 // a pure function of the key set (e.g. the default std::map,
                 // which always iterates in sorted key order), the order
                 // check further below is always true and this whole
                 // mechanism is effectively a no-op; it only matters for a
                 // reorderable object_t such as the one backing `ordered_json`.
-        // The patch ops for keys that were added (i.e., in target but not
-        // in source) are built here so the fast path can reuse
+                // patch ops for keys that were added (i.e., in target but not
+                // in source); built here so the fast path below can reuse
                 // them without a second source.find() per target key. Only
                 // used by the fast path -- the slow (reordering) path
                 // rebuilds "add" ops for every key itself.
                 std::vector<typename object_t::key_type> common_keys_target_order;
+                basic_json added_ops(value_t::array);
                 bool new_keys_form_suffix = true;
                 bool seen_new_key = false;
                 for (auto it = target.cbegin(); it != target.cend(); ++it)
@@ -31106,7 +31080,12 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                     if (source.find(it.key()) == source.end())
                     {
                         seen_new_key = true;
-                diff_add(added_ops, detail::concat<string_t>(path, '/', detail::escape(it.key())), it.value());
+                        const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
+                        added_ops.push_back(
+                        {
+                            {"op", "add"}, {"path", path_key},
+                            {"value", it.value()}
+                        });
                     }
                     else
                     {
@@ -31122,12 +31101,43 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                 {
                     // fast path: order of common keys already matches (or the
                     // object_t's iteration order does not depend on
-            // insertion history), so a plain per-key diff is correct
-            // and minimal, as before
-            common_keys = std::move(common_keys_source_order);
-            return true;
+                    // insertion history), so a plain per-key recursive diff
+                    // is correct and minimal, as before. common_keys_source_order
+                    // is, by construction, the subsequence of source's keys
+                    // that are common to both objects, in source's iteration
+                    // order -- so it can be walked in lockstep with `source`
+                    // using a cheap key comparison instead of another lookup.
+                    // Deleted keys (those source keys not in common_keys_source_order)
+                    // are interleaved here too, in source's original order, to
+                    // match the historical (pre-reordering-aware) output order.
+                    auto common_it = common_keys_source_order.cbegin();
+                    for (auto it = source.cbegin(); it != source.cend(); ++it)
+                    {
+                        if (common_it != common_keys_source_order.cend() && it.key() == *common_it)
+                        {
+                            const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
+                            auto temp_diff = diff(it.value(), target[it.key()], path_key);
+                            result.insert(result.end(), temp_diff.begin(), temp_diff.end());
+                            ++common_it;
+                        }
+                        else
+                        {
+                            // found a key that is not in target -> remove it
+                            const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
+                            result.push_back(object(
+                            {
+                                {"op", "remove"}, {"path", path_key}
+                            }));
+                        }
                     }
 
+                    // append the "add" ops for brand-new keys collected above
+                    // during the pass over target -- no second source.find()
+                    // per target key needed
+                    result.insert(result.end(), added_ops.begin(), added_ops.end());
+                }
+                else
+                {
                     // slow path: the common keys are in a different relative
                     // order in source and target (only possible for a
                     // reorderable object_t like ordered_map). Building a
@@ -31144,7 +31154,11 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                     // it moves it to the end, fixing its position.
                     for (auto it = source.cbegin(); it != source.cend(); ++it)
                     {
-            diff_remove(result, detail::concat<string_t>(path, '/', detail::escape(it.key())));
+                        const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
+                        result.push_back(object(
+                        {
+                            {"op", "remove"}, {"path", path_key}
+                        }));
                     }
 
                     // add every key that is either common (just removed
@@ -31153,96 +31167,15 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                     // target exactly
                     for (auto it = target.cbegin(); it != target.cend(); ++it)
                     {
-            diff_add(result, detail::concat<string_t>(path, '/', detail::escape(it.key())), it.value());
-        }
-        return false;
-    }
-
-    /*!
-    @brief @ref diff, for values at nesting level @a depth, appending the
-           operations to @a result
-
-    Diffing two arrays or objects calls this function again, once per nesting
-    level, so values nested deeply enough used to exhaust the call stack and
-    terminate the process. The descent is bounded here: once @ref
-    detail::recursion_depth_limit levels have been entered, @ref
-    diff_iteratively diffs what is left without the call stack.
-    */
-    static void diff_recursively(basic_json& result, const basic_json& source, const basic_json& target,
-                                 const string_t& path, const std::size_t depth)
+                        const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
+                        result.push_back(
                         {
-        // if the values are the same, there is nothing to do
-        if (source == target)
-        {
-            return;
-        }
-
-        if (JSON_HEDLEY_UNLIKELY(depth >= detail::recursion_depth_limit()))
-        {
-            diff_iteratively(result, source, target, path);
-            return;
-        }
-
-        if (source.type() != target.type())
-        {
-            // different types: replace value
-            diff_replace(result, path, target);
-            return;
-        }
-
-        switch (source.type())
-        {
-            case value_t::array:
-            {
-                // first pass: traverse common elements
-                std::size_t i = 0;
-                while (i < source.size() && i < target.size())
-                {
-                    // recursive call to compare array values at index i
-                    diff_recursively(result, source[i], target[i], detail::concat<string_t>(path, '/', detail::to_string<string_t>(i)), depth + 1);
-                    ++i;
-                }
-
-                // We now reached the end of at least one array
-                // in a second pass, traverse the remaining elements
-                diff_array_tails(result, source, target, path, i);
-                break;
-            }
-
-            case value_t::object:
-            {
-                std::vector<typename object_t::key_type> common_keys;
-                basic_json added_ops(value_t::array);
-                if (diff_object_keys(result, source, target, path, common_keys, added_ops))
-                {
-                    // fast path: common_keys is, by construction, the
-                    // subsequence of source's keys that are common to both
-                    // objects, in source's iteration order -- so it can be
-                    // walked in lockstep with `source` using a cheap key
-                    // comparison instead of another lookup. Deleted keys
-                    // (those source keys not in common_keys) are interleaved
-                    // here too, in source's original order, to match the
-                    // historical (pre-reordering-aware) output order.
-                    auto common_it = common_keys.cbegin();
-                    for (auto it = source.cbegin(); it != source.cend(); ++it)
-                    {
-                        if (common_it != common_keys.cend() && it.key() == *common_it)
-                        {
-                            diff_recursively(result, it.value(), target[it.key()], detail::concat<string_t>(path, '/', detail::escape(it.key())), depth + 1);
-                            ++common_it;
-                        }
-                        else
-                        {
-                            // found a key that is not in target -> remove it
-                            diff_remove(result, detail::concat<string_t>(path, '/', detail::escape(it.key())));
+                            {"op", "add"}, {"path", path_key},
+                            {"value", it.value()}
+                        });
                     }
                 }
 
-                    // append the "add" ops for brand-new keys collected by
-                    // diff_object_keys -- no second source.find() per target
-                    // key needed
-                    result.insert(result.end(), added_ops.begin(), added_ops.end());
-                }
                 break;
             }
 
@@ -31257,166 +31190,16 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
             default:
             {
                 // both primitive types: replace value
-                diff_replace(result, path, target);
+                result.push_back(
+                {
+                    {"op", "replace"}, {"path", path}, {"value", target}
+                });
                 break;
             }
         }
-    }
 
-    /*!
-    @brief @ref diff without the call stack, appending the operations to
-           @a result
-
-    Produces the same operations as @ref diff_recursively. Only reached for
-    values nested more deeply than @ref detail::recursion_depth_limit.
-    */
-    static void diff_iteratively(basic_json& result, const basic_json& source, const basic_json& target,
-                                 const string_t& path)
-    {
-        // The arrays and objects being diffed are kept on an explicit stack,
-        // and every pair of elements is still diffed completely before the
-        // next one, so the operations come out in the same order as in
-        // diff_recursively. The path of the values being diffed is kept in
-        // one buffer that grows and shrinks with the stack, rather than in a
-        // new string per level.
-        std::vector<diff_frame> stack;
-        string_t current_path = path;
-
-        // diff `s` against `t`, whose path is current_path: primitives,
-        // values of different types, and objects whose members were reordered
-        // are handled right away; arrays and other objects get a frame
-        const auto enter = [&result, &stack, &current_path](const basic_json & s, const basic_json & t)
-        {
-            // if the values are the same, there is nothing to do. Arrays and
-            // objects are not compared up front: comparing them visits
-            // everything below them, so doing that at every level would take
-            // quadratic time in the nesting depth - equal ones yield no
-            // operations anyway.
-            if ((!s.is_structured() || !t.is_structured()) && s == t)
-            {
-                return;
+        return result;
     }
-
-            if (s.type() != t.type())
-            {
-                // different types: replace value
-                diff_replace(result, current_path, t);
-                return;
-            }
-
-            switch (s.type())
-            {
-                case value_t::array:
-                {
-                    stack.emplace_back(&s, &t, current_path.size());
-                    return;
-                }
-
-                case value_t::object:
-                {
-                    std::vector<typename object_t::key_type> common_keys;
-                    basic_json added_ops(value_t::array);
-                    if (diff_object_keys(result, s, t, current_path, common_keys, added_ops))
-                    {
-                        // fast path: the frame walks source in lockstep with
-                        // common_keys, as diff_recursively does, and appends
-                        // added_ops once all members are done
-                        stack.emplace_back(&s, &t, current_path.size());
-                        stack.back().member = s.cbegin();
-                        stack.back().common_keys = std::move(common_keys);
-                        stack.back().added_ops = std::move(added_ops);
-                    }
-                    return;
-                }
-
-                case value_t::null:
-                case value_t::string:
-                case value_t::boolean:
-                case value_t::number_integer:
-                case value_t::number_unsigned:
-                case value_t::number_float:
-                case value_t::binary:
-                case value_t::discarded:
-                default:
-                {
-                    // both primitive types: replace value
-                    diff_replace(result, current_path, t);
-                    return;
-                }
-            }
-        };
-
-        enter(source, target);
-        while (!stack.empty())
-        {
-            // invalidated when enter() pushes a frame and by the pop_back()
-            // at the end, so not used after either
-            diff_frame& frame = stack.back();
-            const std::size_t path_length = frame.path_length;
-            const std::size_t depth = stack.size();
-
-            if (frame.source->is_array())
-            {
-                const auto& source_array = *frame.source->m_data.m_value.array;
-                const auto& target_array = *frame.target->m_data.m_value.array;
-
-                // first pass: traverse common elements
-                if (frame.index < source_array.size() && frame.index < target_array.size())
-                {
-                    const std::size_t i = frame.index++;
-                    detail::concat_into(current_path, '/', detail::to_string<string_t>(i));
-                    enter(source_array[i], target_array[i]); // may push, which invalidates `frame`
-                    if (stack.size() == depth)
-                    {
-                        current_path.resize(path_length);
-                    }
-                    continue;
-                }
-
-                // We now reached the end of at least one array
-                // in a second pass, traverse the remaining elements
-                diff_array_tails(result, *frame.source, *frame.target, current_path, frame.index);
-            }
-            else
-            {
-                if (frame.member != frame.source->cend())
-                {
-                    const const_iterator it = frame.member;
-                    ++frame.member;
-                    if (frame.next_common < frame.common_keys.size() && it.key() == frame.common_keys[frame.next_common])
-                    {
-                        ++frame.next_common;
-                        const basic_json& target_value = (*frame.target)[it.key()];
-                        detail::concat_into(current_path, '/', detail::escape(it.key()));
-                        enter(it.value(), target_value); // may push, which invalidates `frame`
-                        if (stack.size() == depth)
-                        {
-                            current_path.resize(path_length);
-                        }
-                    }
-                    else
-                    {
-                        // found a key that is not in target -> remove it
-                        diff_remove(result, detail::concat<string_t>(current_path, '/', detail::escape(it.key())));
-                    }
-                    continue;
-                }
-
-                // append the "add" ops for brand-new keys collected when the
-                // object was entered
-                result.insert(result.end(), frame.added_ops.begin(), frame.added_ops.end());
-            }
-
-            // this array or object is done: continue with the one it is in
-            stack.pop_back();
-            if (!stack.empty())
-            {
-                current_path.resize(stack.back().path_length);
-            }
-        }
-    }
-
-  public:
     /// @}
 
     ////////////////////////////////

tests/src/unit-json_patch.cpp

@@ -15,65 +15,8 @@ using nlohmann::json;
 #endif
 
 #include <fstream>
-#include <string>
-#include <vector>
 #include "make_test_data_available.hpp"
 
-namespace
-{
-// alternating objects and arrays nested `depth` levels deep, with members that
-// depend on `variant` at some levels, so diffing two variants yields
-// operations on many levels: replacing the innermost value, adding, removing,
-// and (for ordered_json) reordering members, and changing array lengths
-template<typename BasicJsonType>
-BasicJsonType nested(const std::size_t depth, const int variant)
-{
-    BasicJsonType value = variant;
-    for (std::size_t i = 0; i < depth; ++i)
-    {
-        if (i % 2 == 0)
-        {
-            BasicJsonType object = BasicJsonType::object();
-            if ((i + static_cast<std::size_t>(variant)) % 7 == 0)
-            {
-                object["x"] = i;
-            }
-            if (variant == 2 && i % 11 == 0)
-            {
-                object["z"] = "z";
-            }
-            object["a"] = std::move(value);
-            if (variant == 1 && i % 5 == 0)
-            {
-                object["y"] = 1;
-            }
-            value = std::move(object);
-        }
-        else
-        {
-            BasicJsonType array = BasicJsonType::array({std::move(value)});
-            if ((i + static_cast<std::size_t>(variant)) % 3 == 0)
-            {
-                array.push_back(i);
-            }
-            value = std::move(array);
-        }
-    }
-    return value;
-}
-
-// a path of `depth` reference tokens, as nested() nests its values
-std::string nested_path(const std::size_t depth)
-{
-    std::string path;
-    for (std::size_t i = depth; i > 0; --i)
-    {
-        path += (i - 1) % 2 == 0 ? "/a" : "/0";
-    }
-    return path;
-}
-} // namespace
-
 TEST_CASE("JSON patch")
 {
     SECTION("examples from RFC 6902")
@@ -1808,99 +1751,3 @@ TEST_CASE("JSON patch - diff emits array removals in descending index order")
         CHECK(source.patch(patch) == target);
     }
 }
-
-TEST_CASE("JSON patch: diff of deeply nested values")
-{
-    SECTION("the diff reproduces the target at every depth")
-    {
-        // depths on either side of the nesting depth up to which diff()
-        // recurses (detail::recursion_depth_limit(), 128); not every depth up
-        // to 300, as the test would then time out under Valgrind
-        std::vector<std::size_t> depths;
-        for (std::size_t depth = 0; depth <= 16; ++depth)
-        {
-            depths.push_back(depth);
-        }
-        for (std::size_t depth = 120; depth <= 136; ++depth)
-        {
-            depths.push_back(depth);
-        }
-        depths.push_back(300);
-
-        for (const auto depth : depths)
-        {
-            CAPTURE(depth);
-            for (int from = 0; from < 3; ++from)
-            {
-                for (int to = 0; to < 3; ++to)
-                {
-                    CAPTURE(from);
-                    CAPTURE(to);
-                    const auto source = nested<json>(depth, from);
-                    const auto target = nested<json>(depth, to);
-                    const auto patch = json::diff(source, target);
-                    CHECK(source.patch(patch) == target);
-                    CHECK(patch.empty() == (from == to));
-
-                    const auto ordered_source = nested<nlohmann::ordered_json>(depth, from);
-                    const auto ordered_target = nested<nlohmann::ordered_json>(depth, to);
-                    CHECK(ordered_source.patch(nlohmann::ordered_json::diff(ordered_source, ordered_target)) == ordered_target);
-                }
-            }
-        }
-    }
-
-    SECTION("a difference only in the innermost value is one replace operation")
-    {
-        for (std::size_t depth = 0; depth <= 300; ++depth)
-        {
-            CAPTURE(depth);
-            json source = 1;
-            json target = 2;
-            for (std::size_t i = 0; i < depth; ++i)
-            {
-                source = i % 2 == 0 ? json::object({{"a", std::move(source)}}) : json::array({std::move(source)});
-                target = i % 2 == 0 ? json::object({{"a", std::move(target)}}) : json::array({std::move(target)});
-            }
-            CHECK(json::diff(source, target, "/root") == json::array({{{"op", "replace"}, {"path", "/root" + nested_path(depth)}, {"value", 2}}}));
-        }
-    }
-
-    SECTION("values nested too deeply for the call stack (#5393)")
-    {
-        // diff() used to recurse once per nesting level, and compared the
-        // values with operator== on every level. The values are only
-        // parsed and diffed, never copied or compared, since those recurse
-        // too.
-        const std::size_t depth = 100000;
-        for (const bool objects :
-                {
-                    false, true
-                })
-        {
-            CAPTURE(objects);
-            std::string source_text;
-            std::string target_text;
-            std::string equal_text;
-            std::string path;
-            for (std::size_t i = 0; i < depth; ++i)
-            {
-                source_text += objects ? "{\"a\":" : "[";
-                path += objects ? "/a" : "/0";
-            }
-            target_text = source_text + "2";
-            equal_text = source_text + "1";
-            source_text += "1";
-            const std::string closing(depth, objects ? '}' : ']');
-            const auto source = json::parse(source_text + closing);
-
-            const auto patch = json::diff(source, json::parse(target_text + closing));
-            REQUIRE(patch.size() == 1);
-            CHECK(patch[0]["op"] == "replace");
-            CHECK(patch[0]["path"] == path);
-            CHECK(patch[0]["value"] == 2);
-
-            CHECK(json::diff(source, json::parse(equal_text + closing)).empty());
-        }
-    }
-}

tests/src/unit-msgpack.cpp

@@ -14,6 +14,7 @@ using nlohmann::json;
     using namespace nlohmann::literals; // NOLINT(google-build-using-namespace)
 #endif
 
+#include <cstdint> // SIZE_MAX, UINT32_MAX
 #include <fstream>
 #include <sstream>
 #include <iomanip>
@@ -2150,3 +2151,79 @@ TEST_CASE("MessagePack with std::byte")
     }
 }
 #endif
+
+namespace
+{
+// types that report a size beyond UINT32_MAX without allocating that much
+// memory, so the MessagePack length limit can be tested cheaply; see the
+// similar types in unit-bson.cpp
+std::size_t beyond_uint32_size()
+{
+    return static_cast<std::size_t>((std::numeric_limits<std::uint32_t>::max)()) + 1;
+}
+
+class beyond_uint32_binary_t : public std::vector<std::uint8_t>
+{
+  public:
+    using std::vector<std::uint8_t>::vector;
+
+    size_type size() const noexcept // NOLINT(readability-convert-member-functions-to-static)
+    {
+        return beyond_uint32_size();
+    }
+};
+
+// with clang and libstdc++ 10, the std::filesystem::path conversion that
+// C++17 builds consider for every string type is ambiguous for a class
+// derived from std::string, so the string case is not tested there
+#if !(defined(__clang__) && defined(_GLIBCXX_RELEASE) && _GLIBCXX_RELEASE < 11)
+    #define JSON_TEST_BEYOND_UINT32_STRING 1
+#endif
+
+#ifdef JSON_TEST_BEYOND_UINT32_STRING
+class beyond_uint32_string_t : public std::string
+{
+  public:
+    using std::string::string;
+
+    size_type size() const noexcept // NOLINT(readability-convert-member-functions-to-static)
+    {
+        return beyond_uint32_size();
+    }
+};
+
+using beyond_uint32_string_json = nlohmann::basic_json <
+                                  std::map, std::vector, beyond_uint32_string_t, bool, std::int64_t, std::uint64_t,
+                                  double, std::allocator, nlohmann::adl_serializer, std::vector<std::uint8_t>, void >;
+#endif
+
+using beyond_uint32_binary_json = nlohmann::basic_json <
+                                  std::map, std::vector, std::string, bool, std::int64_t, std::uint64_t,
+                                  double, std::allocator, nlohmann::adl_serializer, beyond_uint32_binary_t, void >;
+} // namespace
+
+TEST_CASE("MessagePack lengths beyond UINT32_MAX cannot be serialized")
+{
+    // MessagePack stores the length of a string, binary value, array, or
+    // object in at most 32 bits; a larger one used to be written without any
+    // length at all
+#if SIZE_MAX > UINT32_MAX
+    {
+        const char* const expected = "[json.exception.out_of_range.412] MessagePack length 4294967296 exceeds maximum of 4294967295";
+
+        const beyond_uint32_binary_json binary = beyond_uint32_binary_json::binary(beyond_uint32_binary_t{});
+        CHECK_THROWS_WITH_AS(beyond_uint32_binary_json::to_msgpack(binary), expected, beyond_uint32_binary_json::out_of_range&);
+
+        const beyond_uint32_binary_json ext = beyond_uint32_binary_json::binary(beyond_uint32_binary_t{}, 42);
+        CHECK_THROWS_WITH_AS(beyond_uint32_binary_json::to_msgpack(ext), expected, beyond_uint32_binary_json::out_of_range&);
+
+#ifdef JSON_TEST_BEYOND_UINT32_STRING
+        // created from its type rather than from a beyond_uint32_string_t:
+        // that would consider the std::filesystem::path conversion, which
+        // libstdc++ 10 cannot decide for a class derived from std::string
+        const beyond_uint32_string_json string(beyond_uint32_string_json::value_t::string);
+        CHECK_THROWS_WITH_AS(beyond_uint32_string_json::to_msgpack(string), expected, beyond_uint32_string_json::out_of_range&);
+#endif
+    }
+#endif
+}