Test that destroy() performs no allocation, even under memory pressure

Update the #4842 regression test: it used to check that destroying a nested array/object made at least one allocation through the provided allocator (the old flattening stack). Now that destroy() does not allocate at all, assert the opposite: zero allocations, deallocations only. Rework the #5135 regression test to use a dedicated failing/counting allocator instead of overriding the process-wide ::operator new and ::operator delete, which affected every allocation in the whole unit-regression2 binary rather than just the values under test. Keep the original small repro as one case, and add deep (100000 levels) and wide-and-deep nested array/object/ordered_json cases, all destroyed while every further allocation is made to fail: the destructor must complete without allocating, without throwing, and without leaking. Co-authored-by: Michael Sam <9461037+michaelsam94@users.noreply.github.com> Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Make json_value::destroy() non-recursive and allocation-free
2026-10-05 06:00:29 +00:00 · 2026-10-04 22:22:17 +02:00 · 2026-10-04 22:22:06 +02:00 · 2026-10-04 18:11:25 +02:00 · 2026-10-04 18:00:22 +02:00 · 2026-10-04 18:00:21 +02:00
34 changed files with 512 additions and 963 deletions
@@ -107,7 +107,7 @@ jobs:
    container: ubuntu:24.04
    strategy:
      matrix:
-        target: [ci_cmake_flags, ci_test_diagnostics, ci_test_diagnostic_positions, ci_test_noexceptions, ci_test_noimplicitconversions, ci_test_legacycomparison, ci_test_noglobaludls, ci_test_disableenumserialization, ci_test_disabletuplereferenceconversion, ci_test_skiplibraryversioncheck, ci_test_simdutf, ci_test_strict_nul_handling, ci_test_delete_deprecated_functions, ci_test_no_thread_local]
+        target: [ci_cmake_flags, ci_test_diagnostics, ci_test_diagnostic_positions, ci_test_noexceptions, ci_test_noimplicitconversions, ci_test_legacycomparison, ci_test_noglobaludls, ci_test_disableenumserialization, ci_test_disabletuplereferenceconversion, ci_test_skiplibraryversioncheck, ci_test_simdutf, ci_test_strict_nul_handling, ci_test_no_thread_local]
    steps:
      - name: Install build-essential
        run: apt-get update ; apt-get install -y build-essential unzip wget git
@@ -62,7 +62,6 @@ option(JSON_MultipleHeaders                "Use non-amalgamated version of the l
 option(JSON_SystemInclude                  "Include as system headers (skip for clang-tidy)." OFF)
 option(JSON_StrictNulHandling              "Build with strict NUL-byte handling enabled." OFF)
 option(JSON_StrictBinaryUTF8               "Build with UTF-8 checks in the CBOR, UBJSON, BJData, and BSON writers enabled." OFF)
-option(JSON_DeleteDeprecatedFunctions      "Delete the deprecated functions instead of only deprecating them." OFF)

 if (JSON_CI)
    include(ci)
@@ -124,10 +123,6 @@ if (JSON_StrictBinaryUTF8)
    message(STATUS "Strict UTF-8 checks in binary writers enabled (JSON_STRICT_BINARY_UTF8=1)")
 endif()

-if (JSON_DeleteDeprecatedFunctions)
-    message(STATUS "Deprecated functions are deleted (JSON_DELETE_DEPRECATED_FUNCTIONS=1)")
-endif()
-
 if (JSON_Diagnostic_Positions)
    message(STATUS "Diagnostic positions enabled (JSON_DIAGNOSTIC_POSITIONS=1)")
 endif()
@@ -164,7 +159,6 @@ target_compile_definitions(
    $<$<BOOL:${JSON_LegacyDiscardedValueComparison}>:JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON=1>
    $<$<BOOL:${JSON_StrictNulHandling}>:JSON_STRICT_NUL_HANDLING=1>
    $<$<BOOL:${JSON_StrictBinaryUTF8}>:JSON_STRICT_BINARY_UTF8=1>
-    $<$<BOOL:${JSON_DeleteDeprecatedFunctions}>:JSON_DELETE_DEPRECATED_FUNCTIONS=1>
 )

 target_include_directories(
@@ -249,20 +249,6 @@ add_custom_target(ci_test_strict_nul_handling
    COMMENT "Compile and test with strict NUL-byte handling enabled"
 )

-###############################################################################
-# Delete the deprecated functions.
-###############################################################################
-
-add_custom_target(ci_test_delete_deprecated_functions
-    COMMAND ${CMAKE_COMMAND}
-    -DCMAKE_BUILD_TYPE=Debug -GNinja
-    -DJSON_BuildTests=ON -DJSON_FastTests=ON -DJSON_DeleteDeprecatedFunctions=ON
-    -S${PROJECT_SOURCE_DIR} -B${PROJECT_BINARY_DIR}/build_delete_deprecated_functions
-    COMMAND ${CMAKE_COMMAND} --build ${PROJECT_BINARY_DIR}/build_delete_deprecated_functions
-    COMMAND cd ${PROJECT_BINARY_DIR}/build_delete_deprecated_functions && ${CMAKE_CTEST_COMMAND} --parallel ${N} --output-on-failure
-    COMMENT "Compile and test with the deprecated functions deleted"
-)
-
 ###############################################################################
 # Disable global UDLs.
 ###############################################################################
@@ -719,7 +705,7 @@ ci_get_cmake(4.0.0  CMAKE_4_0_0_BINARY)
 # the tests require CMake 3.13 or later, so they are excluded for CMake 3.5.0
 set(JSON_CMAKE_FLAGS_3_5_0 JSON_Diagnostics JSON_Diagnostic_Positions JSON_GlobalUDLs JSON_ImplicitConversions JSON_DisableEnumSerialization
    JSON_LegacyDiscardedValueComparison JSON_Install JSON_MultipleHeaders JSON_SystemInclude JSON_Valgrind
-    JSON_StrictNulHandling JSON_StrictBinaryUTF8 JSON_DeleteDeprecatedFunctions)
+    JSON_StrictNulHandling JSON_StrictBinaryUTF8)
 set(JSON_CMAKE_FLAGS_3_31_6 JSON_BuildTests ${JSON_CMAKE_FLAGS_3_5_0})
 set(JSON_CMAKE_FLAGS_4_0_0 JSON_BuildTests ${JSON_CMAKE_FLAGS_3_5_0})

@@ -219,7 +219,6 @@ INSERT INTO searchIndex(name, type, path) VALUES ('Supported Macros', 'Guide', '
 INSERT INTO searchIndex(name, type, path) VALUES ('JSON_ASSERT', 'Macro', 'api/macros/json_assert/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('JSON_BRACE_INIT_COPY_SEMANTICS', 'Macro', 'api/macros/json_brace_init_copy_semantics/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('JSON_CATCH_USER', 'Macro', 'api/macros/json_throw_user/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('JSON_DELETE_DEPRECATED_FUNCTIONS', 'Macro', 'api/macros/json_delete_deprecated_functions/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('JSON_DIAGNOSTICS', 'Macro', 'api/macros/json_diagnostics/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('JSON_DIAGNOSTIC_POSITIONS', 'Macro', 'api/macros/json_diagnostic_positions/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('JSON_DISABLE_ENUM_SERIALIZATION', 'Macro', 'api/macros/json_disable_enum_serialization/index.html');
@@ -8,7 +8,7 @@ static basic_json diff(const basic_json& source,
 Creates a [JSON Patch](http://jsonpatch.com) so that value `source` can be changed into the value `target` by calling
 [`patch`](patch.md) function.

-For two JSON values `source` and `target`, the following code always yields `#!cpp true`:
+For two JSON values `source` and `target`, the following code yields always `#!cpp true`:
 ```cpp
 source.patch(diff(source, target)) == target;
 ```
@@ -27,7 +27,7 @@ a JSON patch to convert the `source` to `target`

 ## Exception safety

-Strong guarantee: `source` and `target` are never modified.
+Strong guarantee: if an exception is thrown, there are no changes in the JSON value.

 ## Complexity

@@ -120,12 +120,3 @@ Linear in the size of the input.
 - Extended container support (1) to include types with lvalue-only ADL `begin`/`end` (matching `std::begin`/`std::end` semantics) in version 3.13.0.
 - Extended overload (2) to accept heterogeneous iterator+sentinel pairs (C++20 ranges support) in version 3.13.0.
 - Added `error_handler` parameter in version 3.13.0.
-
-!!! warning "Deprecation"
-
-    - Overload (2) replaces calls to `from_bjdata` with a pointer and a length as first two parameters, which has been
-      deprecated in version 3.13.0. This overload will be removed in version 4.0.0. Please replace all calls like
-      `#!cpp from_bjdata(ptr, len, ...);` with `#!cpp from_bjdata(ptr, ptr+len, ...);`.
-
-    You should be warned by your compiler with a `-Wdeprecated-declarations` warning if you are using a deprecated
-    function.
@@ -106,12 +106,3 @@ Linear in the size of the input.
 ## Version history

 - Added in version 3.13.0.
-
-!!! warning "Deprecation"
-
-    - Overload (2) replaces calls to `from_bon8` with a pointer and a length as first two parameters, which has been
-      deprecated in version 3.13.0. This overload will be removed in version 4.0.0. Please replace all calls like
-      `#!cpp from_bon8(ptr, len, ...);` with `#!cpp from_bon8(ptr, ptr+len, ...);`.
-
-    You should be warned by your compiler with a `-Wdeprecated-declarations` warning if you are using a deprecated
-    function.
@@ -61,11 +61,6 @@ header. See also the [macro overview page](../../features/macros.md).
 - [**JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS**](json_use_objects_for_enum_keyed_maps.md) - opt in to storing maps with enum
  keys as objects

-## Deprecated functions
-
- [**JSON_DELETE_DEPRECATED_FUNCTIONS**](json_delete_deprecated_functions.md) - opt in to deleting the deprecated
-  functions ahead of their removal in version 4.0.0
-
 ## Comparison behavior

 - [**JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON**](json_use_legacy_discarded_value_comparison.md) -
@@ -1,96 +0,0 @@
-# JSON_DELETE_DEPRECATED_FUNCTIONS
-
-```cpp
-#define JSON_DELETE_DEPRECATED_FUNCTIONS /* value */
-```
-
-When defined to `1`, all [deprecated functions](../../community/roadmap.md#removal-of-deprecated-functions) of the
-library are declared as deleted (`= delete`) instead of only being marked as deprecated. Code that still calls one of
-them no longer compiles. This way, you can find all calls that need to be replaced before version 4.0.0 removes these
-functions; the [migration guide](../../integration/migration_guide.md#replace-deprecated-functions) describes how.
-
-A deleted function, unlike a removed one, still takes part in overload resolution. A call that would select it
-therefore fails to compile instead of silently selecting another overload. This matters for the deprecated
-`from_*(ptr, len)` overloads of [`from_cbor`](../basic_json/from_cbor.md), [`from_msgpack`](../basic_json/from_msgpack.md),
-[`from_ubjson`](../basic_json/from_ubjson.md), [`from_bjdata`](../basic_json/from_bjdata.md),
-[`from_bon8`](../basic_json/from_bon8.md), and [`from_bson`](../basic_json/from_bson.md): without them, a call like
-`from_cbor(ptr, len)` would compile, read `ptr` as a NUL-terminated string, and convert `len` to the `strict` parameter.
-
-The macro does not affect the deprecated legacy comparison of discarded values, which is controlled by
-[`JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON`](json_use_legacy_discarded_value_comparison.md).
-
-## Default definition
-
-The default value is `0` (disabled, the deprecated functions can still be called, and the compiler warns about it).
-
-```cpp
-#define JSON_DELETE_DEPRECATED_FUNCTIONS 0
-```
-
-## Notes
-
-!!! info "CMake option"
-
-    The macro can also be set with the CMake option
-    [`JSON_DeleteDeprecatedFunctions`](../../integration/cmake.md#json_deletedeprecatedfunctions) (`OFF` by default).
-
-!!! warning "Opt-in only"
-
-    This macro must be defined **before** including `<nlohmann/json.hpp>`. Defining it after the include has no
-    effect. Define it for the whole project to avoid different declarations of the same class in different
-    translation units.
-
-!!! note "ABI compatibility"
-
-    The macro only turns calls that compile into calls that do not; it does not change the layout or the behavior of
-    any type. Its value is therefore not encoded in the [namespace](../../features/namespace.md).
-
-## Examples
-
-??? example "Example: default behavior (macro not defined)"
-
-    Without the macro, the deprecated overload is called, and the compiler warns about it:
-
-    ```cpp
-    #include <nlohmann/json.hpp>
-
-    using json = nlohmann::json;
-
-    int main()
-    {
-        const std::vector<std::uint8_t> v = {0x82, 0x01, 0x02};
-        auto j = json::from_cbor(v.data(), v.size());
-        // warning: 'from_cbor' is deprecated: Since 3.8.0; use from_cbor(ptr, ptr + len)
-    }
-    ```
-
-??? example "Example: deleted deprecated functions (macro defined to 1)"
-
-    With the macro, the call does not compile:
-
-    ```cpp
-    #define JSON_DELETE_DEPRECATED_FUNCTIONS 1
-    #include <nlohmann/json.hpp>
-
-    using json = nlohmann::json;
-
-    int main()
-    {
-        const std::vector<std::uint8_t> v = {0x82, 0x01, 0x02};
-        auto j = json::from_cbor(v.data(), v.size());
-        // error: call to deleted function 'from_cbor'
-    }
-    ```
-
-## See also
-
- [Roadmap: removal of deprecated functions](../../community/roadmap.md#removal-of-deprecated-functions) - the
-  deprecated functions and the version they were deprecated in
- [Migration guide: replace deprecated functions](../../integration/migration_guide.md#replace-deprecated-functions) -
-  how to replace each deprecated function
-
-## Version history
-
- Added in version 3.13.0.
- Planned to be removed in version 4.0.0, which removes the deprecated functions. The deprecated `from_*(ptr, len)`
-  overloads stay deleted in version 4.0.0.
@@ -112,4 +112,3 @@ The default value is `0` (disabled — existing behavior is preserved).
 ## Version history

 - Added in version 3.13.0.
- Planned to become the default (with the macro removed) in version 4.0.0.
@@ -44,7 +44,7 @@ By default, implicit conversions are enabled.

 ## Examples

-??? example "Example: implicit and explicit conversions"
+??? example "Example: implicit conversion"

    This is an example for an implicit conversion:

@@ -64,8 +64,6 @@ The following macros guard changes that are planned to become the default in ver
 | [`JSON_PRECISE_STREAM_POSITION`](../api/macros/json_precise_stream_position.md)                                  | `0`         | `1`: reading from a stream does not consume the character after a number                                                      | –                                                                                                                  | 3.13.0 |
 | [`JSON_STRICT_NUL_HANDLING`](../api/macros/json_strict_nul_handling.md)                                          | `0`         | `1`: a NUL byte in the input is a parse error instead of the end of input                                                     | [`JSON_StrictNulHandling`](../integration/cmake.md#json_strictnulhandling)                                         | 3.13.0 |
 | [`JSON_STRICT_BINARY_UTF8`](../api/macros/json_strict_binary_utf8.md)                                            | `0`         | `1`: `to_cbor`, `to_ubjson`, `to_bjdata`, and `to_bson` throw for strings that are not valid UTF-8 by default                 | [`JSON_StrictBinaryUTF8`](../integration/cmake.md#json_strictbinaryutf8)                                           | 3.13.0 |
-| [`JSON_DISABLE_TUPLE_REFERENCE_CONVERSION`](../api/macros/json_disable_tuple_reference_conversion.md)            | `0`         | `1`: a `basic_json` value can no longer be created from a one-element tuple of a reference to it, such as `std::forward_as_tuple(j)`| [`JSON_DisableTupleReferenceConversion`](../integration/cmake.md#json_disabletuplereferenceconversion)             | 3.13.0 |
-| [`JSON_DELETE_DEPRECATED_FUNCTIONS`](../api/macros/json_delete_deprecated_functions.md)                          | `0`         | removed: the deprecated functions are removed (see below); the `from_*(ptr, len)` overloads stay deleted                      | [`JSON_DeleteDeprecatedFunctions`](../integration/cmake.md#json_deletedeprecatedfunctions)                         | 3.13.0 |

 For example, the following makes a 3.x release behave like version 4.0 with respect to these changes:

@@ -77,8 +75,6 @@ For example, the following makes a 3.x release behave like version 4.0 with resp
 #define JSON_PRECISE_STREAM_POSITION 1
 #define JSON_STRICT_NUL_HANDLING 1
 #define JSON_STRICT_BINARY_UTF8 1
-#define JSON_DISABLE_TUPLE_REFERENCE_CONVERSION 1
-#define JSON_DELETE_DEPRECATED_FUNCTIONS 1
 #include <nlohmann/json.hpp>
 ```

@@ -88,13 +84,8 @@ way to achieve this.
 ### Removal of deprecated functions

 Version 4.0 will remove all deprecated functions. Compiling with deprecation warnings enabled shows which of them your
-code still uses. Defining [`JSON_DELETE_DEPRECATED_FUNCTIONS`](../api/macros/json_delete_deprecated_functions.md) to
-`1` turns these warnings into errors, as the deprecated functions are then deleted. The
-[migration guide](../integration/migration_guide.md#replace-deprecated-functions) shows how to replace each of them.
-
-The `from_*` overloads taking a pointer and a length are not removed in version 4.0, but stay deleted. Without them, a
-call like `from_cbor(ptr, len)` would still compile: it would read `ptr` as a NUL-terminated string and convert `len`
-to the `strict` parameter.
+code still uses. The [migration guide](../integration/migration_guide.md#replace-deprecated-functions) shows how to
+replace each of them.

 | Deprecated                                                                                                                                                                                                                                         | Since  | Migration                                                                        |
 |----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------|----------------------------------------------------------------------------------|
@@ -106,7 +97,6 @@ to the `strict` parameter.
 | [`json_pointer::operator string_t`](../api/json_pointer/operator_string_t.md)                                                                                                                                                                      | 3.11.0 | [JSON Pointers](../integration/migration_guide.md#json-pointers)                 |
 | [`json_pointer`](../api/json_pointer/index.md) with a `basic_json` type as template argument, and the overloads of `value`, `contains`, `operator[]`, and `at` accepting such a pointer                                                           | 3.11.0 | [JSON Pointers](../integration/migration_guide.md#json-pointers)                 |
 | Comparing a [`json_pointer`](../api/json_pointer/index.md) with a string via [`operator==`](../api/json_pointer/operator_eq.md) or [`operator!=`](../api/json_pointer/operator_ne.md)                                                              | 3.11.2 | [JSON Pointers](../integration/migration_guide.md#json-pointers)                 |
-| [`from_bjdata`](../api/basic_json/from_bjdata.md) and [`from_bon8`](../api/basic_json/from_bon8.md) with `(ptr, len)`                                                                                                                              | 3.13.0 | [Parsing](../integration/migration_guide.md#parsing)                             |

 The deprecated legacy comparison of discarded values is controlled by a macro and therefore listed in the table above.

@@ -23,17 +23,6 @@ This macro overrides [`#!cpp catch`](https://en.cppreference.com/w/cpp/language/

 See [full documentation of `JSON_CATCH_USER(exception)`](../api/macros/json_throw_user.md).

-## `JSON_DELETE_DEPRECATED_FUNCTIONS`
-
-When defined to `1`, all deprecated functions are declared as deleted instead of only being marked as deprecated, so
-code that still calls them no longer compiles. This way, you can find all calls that need to be replaced before version
-4.0.0 removes these functions.
-
-The macro can also be set with the CMake option
-[`JSON_DeleteDeprecatedFunctions`](../integration/cmake.md#json_deletedeprecatedfunctions) (`OFF` by default).
-
-See [full documentation of `JSON_DELETE_DEPRECATED_FUNCTIONS`](../api/macros/json_delete_deprecated_functions.md).
-
 ## `JSON_DIAGNOSTICS`

 This macro enables extended diagnostics for exception messages. Possible values are `1` to enable or `0` to disable
@@ -97,8 +86,7 @@ See [full documentation of `JSON_DISABLE_ENUM_SERIALIZATION`](../api/macros/json
 ## `JSON_DISABLE_TUPLE_REFERENCE_CONVERSION`

 When defined to `1`, a JSON value can no longer be created from a one-element `std::tuple` holding a reference to a JSON
-value, such as the result of `std::forward_as_tuple(j)`. This lets `std::tuple` convert such tuples element-wise. This
-is planned to become the default in version 4.0.0.
+value, such as the result of `std::forward_as_tuple(j)`. This lets `std::tuple` convert such tuples element-wise.

 See [full documentation of `JSON_DISABLE_TUPLE_REFERENCE_CONVERSION`](../api/macros/json_disable_tuple_reference_conversion.md).

@@ -132,12 +132,6 @@ Build the unit tests when [`BUILD_TESTING`](https://cmake.org/cmake/help/latest/

 Enable CI build targets. The exact targets are used during the several CI steps and are subject to change without notice. This option is `OFF` by default.

-### `JSON_DeleteDeprecatedFunctions`
-
-Delete the deprecated functions instead of only deprecating them by defining the macro
-[`JSON_DELETE_DEPRECATED_FUNCTIONS`](../api/macros/json_delete_deprecated_functions.md). This option is `OFF` by
-default.
-
 ### `JSON_Diagnostics`

 Enable [extended diagnostic messages](../home/exceptions.md#extended-diagnostic-messages) by defining macro [`JSON_DIAGNOSTICS`](../api/macros/json_diagnostics.md). This option is `OFF` by default.
@@ -14,13 +14,6 @@ deprecations are annotated with
 [`HEDLEY_DEPRECATED_FOR`](https://nemequ.github.io/hedley/api-reference.html#HEDLEY_DEPRECATED_FOR) to report which
 function to use instead.

-!!! tip "Find all calls of deprecated functions"
-
-    Define [`JSON_DELETE_DEPRECATED_FUNCTIONS`](../api/macros/json_delete_deprecated_functions.md) to `1` (or set the
-    CMake option [`JSON_DeleteDeprecatedFunctions`](cmake.md#json_deletedeprecatedfunctions)) to delete all deprecated
-    functions. Every remaining call then fails to compile, even if deprecation warnings are disabled, so your code is
-    ready for version 4.0.0 once it compiles with the macro.
-
 ### Parsing

 - Function `friend std::istream& operator<<(basic_json&, std::istream&)` is deprecated since 3.0.0. Please use
@@ -48,10 +41,8 @@ function to use instead.
  [`from_ubjson`](../api/basic_json/from_ubjson.md), and [`from_bson`](../api/basic_json/from_bson.md)) via initializer
  lists is deprecated since 3.8.0. Instead, pass two iterators; for instance, call `from_cbor(ptr, ptr+len)` instead of
  `from_cbor({ptr, len})`. Likewise, passing a pointer and a length as two separate arguments to `from_cbor`,
-  `from_msgpack`, `from_ubjson`, and `from_bson` is deprecated since 3.8.0, and to
-  [`from_bjdata`](../api/basic_json/from_bjdata.md) and [`from_bon8`](../api/basic_json/from_bon8.md) since 3.13.0; call
-  `from_cbor(ptr, ptr+len)` instead of `from_cbor(ptr, len)`. These overloads will not be removed in version 4.0.0, but
-  deleted, so a call like `from_cbor(ptr, len)` cannot compile and convert `len` to the `strict` parameter.
+  `from_msgpack`, `from_ubjson`, and `from_bson` is deprecated since 3.8.0; call `from_cbor(ptr, ptr+len)` instead of
+  `from_cbor(ptr, len)`.

    === "Deprecated"
  
@@ -292,7 +292,6 @@ nav:
          - 'JSON_BRACE_INIT_COPY_SEMANTICS': api/macros/json_brace_init_copy_semantics.md
          - 'JSON_CATCH_USER, JSON_THROW_USER, JSON_TRY_USER': api/macros/json_throw_user.md
          - 'JSON_DIAGNOSTICS': api/macros/json_diagnostics.md
-          - 'JSON_DELETE_DEPRECATED_FUNCTIONS': api/macros/json_delete_deprecated_functions.md
          - 'JSON_DIAGNOSTIC_POSITIONS': api/macros/json_diagnostic_positions.md
          - 'JSON_DISABLE_ENUM_SERIALIZATION': api/macros/json_disable_enum_serialization.md
          - 'JSON_DISABLE_TUPLE_REFERENCE_CONVERSION': api/macros/json_disable_tuple_reference_conversion.md
@@ -81,13 +81,9 @@ class json_pointer
    /// @sa https://json.nlohmann.me/api/json_pointer/operator_string_t/
    JSON_HEDLEY_DEPRECATED_FOR(3.11.0, to_string())
    operator string_t() const
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-        = delete;
-#else
    {
        return to_string();
    }
-#endif

 #ifndef JSON_NO_IO
    /// @brief write string representation of the JSON pointer to stream
@@ -1026,13 +1022,9 @@ class json_pointer
    /// @sa https://json.nlohmann.me/api/json_pointer/operator_eq/
    JSON_HEDLEY_DEPRECATED_FOR(3.11.2, operator==(json_pointer))
    bool operator==(const string_t& rhs) const
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-        = delete;
-#else
    {
        return *this == json_pointer(rhs);
    }
-#endif

    /// @brief 3-way compares two JSON pointers
    template<typename RefStringTypeRhs>
@@ -1110,26 +1102,18 @@ template<typename RefStringTypeLhs,
 JSON_HEDLEY_DEPRECATED_FOR(3.11.2, operator==(json_pointer, json_pointer))
 inline bool operator==(const json_pointer<RefStringTypeLhs>& lhs,
                       const StringType& rhs)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
 {
    return lhs == json_pointer<RefStringTypeLhs>(rhs);
 }
-#endif

 template<typename RefStringTypeRhs,
         typename StringType = typename json_pointer<RefStringTypeRhs>::string_t>
 JSON_HEDLEY_DEPRECATED_FOR(3.11.2, operator==(json_pointer, json_pointer))
 inline bool operator==(const StringType& lhs,
                       const json_pointer<RefStringTypeRhs>& rhs)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
 {
    return json_pointer<RefStringTypeRhs>(lhs) == rhs;
 }
-#endif

 template<typename RefStringTypeLhs, typename RefStringTypeRhs>
 inline bool operator!=(const json_pointer<RefStringTypeLhs>& lhs,
@@ -1143,26 +1127,18 @@ template<typename RefStringTypeLhs,
 JSON_HEDLEY_DEPRECATED_FOR(3.11.2, operator!=(json_pointer, json_pointer))
 inline bool operator!=(const json_pointer<RefStringTypeLhs>& lhs,
                       const StringType& rhs)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
 {
    return !(lhs == rhs);
 }
-#endif

 template<typename RefStringTypeRhs,
         typename StringType = typename json_pointer<RefStringTypeRhs>::string_t>
 JSON_HEDLEY_DEPRECATED_FOR(3.11.2, operator!=(json_pointer, json_pointer))
 inline bool operator!=(const StringType& lhs,
                       const json_pointer<RefStringTypeRhs>& rhs)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
 {
    return !(lhs == rhs);
 }
-#endif

 template<typename RefStringTypeLhs, typename RefStringTypeRhs>
 inline bool operator<(const json_pointer<RefStringTypeLhs>& lhs,
@@ -888,10 +888,6 @@
    #define JSON_DISABLE_ENUM_SERIALIZATION 0
 #endif

-#ifndef JSON_DELETE_DEPRECATED_FUNCTIONS
-    #define JSON_DELETE_DEPRECATED_FUNCTIONS 0
-#endif
-
 #ifndef JSON_DISABLE_TUPLE_REFERENCE_CONVERSION
    #define JSON_DISABLE_TUPLE_REFERENCE_CONVERSION 0
 #endif
@@ -43,7 +43,6 @@
    #undef JSON_PRECISE_STREAM_POSITION
    #undef JSON_STRICT_NUL_HANDLING
    #undef JSON_STRICT_BINARY_UTF8
-    #undef JSON_DELETE_DEPRECATED_FUNCTIONS
    #undef JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS
 #endif

@@ -612,6 +612,68 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
        /// constructor for rvalue binary arrays (internal type)
        json_value(binary_t&& value) : binary(create<binary_t>(std::move(value))) {}

+        // raw, allocation-free transfer of m_data from src to dst: no
+        // set_parents()/assert_invariant() (the former is O(#children) per
+        // call under JSON_DIAGNOSTICS, which would make the walk below
+        // quadratic); dst takes ownership, src is left as value_t::null.
+        static void take(basic_json& dst, basic_json& src) noexcept
+        {
+            dst.m_data.m_type = src.m_data.m_type;
+            dst.m_data.m_value = src.m_data.m_value;
+            src.m_data.m_type = value_t::null;
+        }
+
+        static bool is_empty_container(const basic_json& v) noexcept
+        {
+            return v.m_data.m_type == value_t::array
+                   ? v.m_data.m_value.array->empty()
+                   : v.m_data.m_value.object->empty();
+        }
+
+        static basic_json& last_child(basic_json& v)
+        {
+            return v.m_data.m_type == value_t::array
+                   ? v.m_data.m_value.array->back()
+                   : std::prev(v.m_data.m_value.object->end())->second;
+        }
+
+        // removes the last child of a non-empty array/object v; this never
+        // allocates, and since it is only ever called when that child is a
+        // scalar or an already-empty array/object, destroying it never
+        // recurses more than one level deep (see destroy() below)
+        static void pop_last_child(basic_json& v)
+        {
+            if (v.m_data.m_type == value_t::array)
+            {
+                v.m_data.m_value.array->pop_back();
+            }
+            else
+            {
+                v.m_data.m_value.object->erase(std::prev(v.m_data.m_value.object->end()));
+            }
+        }
+
+        // deallocates the (already empty) array/object held by v; this is
+        // the same allocator-based free the old recursive implementation
+        // used, just factored out so every level of the walk in destroy()
+        // can share it
+        static void free_container(basic_json& v) noexcept
+        {
+            if (v.m_data.m_type == value_t::array)
+            {
+                AllocatorType<array_t> alloc;
+                std::allocator_traits<decltype(alloc)>::destroy(alloc, v.m_data.m_value.array);
+                std::allocator_traits<decltype(alloc)>::deallocate(alloc, v.m_data.m_value.array, 1);
+            }
+            else
+            {
+                AllocatorType<object_t> alloc;
+                std::allocator_traits<decltype(alloc)>::destroy(alloc, v.m_data.m_value.object);
+                std::allocator_traits<decltype(alloc)>::deallocate(alloc, v.m_data.m_value.object, 1);
+            }
+            v.m_data.m_type = value_t::null; // avoid a double free if v is later destructed
+        }
+
        void destroy(value_t t)
        {
            if (
@@ -626,71 +688,88 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
            }
            if (t == value_t::array || t == value_t::object)
            {
-                // flatten the current json_value to a heap-allocated stack
-                std::vector<basic_json> stack;
-
-                // move the top-level items to stack
+                // Destroy the tree without recursing per nesting level and
+                // without any heap allocation: a heap-allocated flattening
+                // stack (the previous implementation) can itself throw
+                // bad_alloc, which would escape this noexcept destructor and
+                // terminate the program (#5135).
+                //
+                // Instead, walk down the "last child" chain, reversing links
+                // as we go: cur is the container currently being emptied,
+                // and prev is its parent (value_t::null when there is none).
+                // Each parent's last child slot doubles as storage for that
+                // parent's own parent link while we are below it, so no
+                // extra memory is needed. We only ever remove a child once
+                // it is a scalar or an empty array/object, which neither
+                // allocates nor recurses more than one level deep.
+                //
+                // This json_value is not itself a basic_json, so the
+                // top-level container is first moved into a local stand-in
+                // ("cur"); this union's own pointer is cleared so it is
+                // never looked at or freed a second time.
+                basic_json cur;
+                cur.m_data.m_type = t;
+                cur.m_data.m_value = *this;
                if (t == value_t::array)
                {
-                    stack.reserve(array->size());
-                    std::move(array->begin(), array->end(), std::back_inserter(stack));
+                    array = nullptr;
                }
                else
                {
-                    stack.reserve(object->size());
-                    for (auto&& it : *object)
-                    {
-                        stack.push_back(std::move(it.second));
-                    }
+                    object = nullptr;
                }

-                while (!stack.empty())
+                basic_json prev; // value_t::null: no parent
+
+                while (true)
                {
-                    // move the last item to a local variable to be processed
-                    basic_json current_item(std::move(stack.back()));
-                    stack.pop_back();
-
-                    // if current_item is array/object, move
-                    // its children to the stack to be processed later
-                    if (current_item.is_array())
+                    if (is_empty_container(cur))
                    {
-                        std::move(current_item.m_data.m_value.array->begin(), current_item.m_data.m_value.array->end(), std::back_inserter(stack));
-
-                        current_item.m_data.m_value.array->clear();
-                    }
-                    else if (current_item.is_object())
-                    {
-                        for (auto&& it : *current_item.m_data.m_value.object)
+                        if (prev.m_data.m_type == value_t::null)
                        {
-                            stack.push_back(std::move(it.second));
+                            break; // back at the top with nothing left to do
                        }

-                        current_item.m_data.m_value.object->clear();
+                        // ascend: detach the grandparent link from prev's
+                        // last slot, drop that (now null) slot, free cur
+                        // (it is empty), then move up one level
+                        basic_json gp;
+                        take(gp, last_child(prev));
+                        pop_last_child(prev);
+
+                        free_container(cur);
+
+                        take(cur, prev);
+                        take(prev, gp);
+                        continue;
                    }

-                    // it's now safe that current_item gets destructed
-                    // since it doesn't have any children
+                    basic_json& last = last_child(cur);
+                    const bool last_is_container = last.m_data.m_type == value_t::array || last.m_data.m_type == value_t::object;
+
+                    if (!last_is_container || is_empty_container(last))
+                    {
+                        // scalar, or already-empty array/object
+                        pop_last_child(cur);
+                        continue;
+                    }
+
+                    // descend into the non-empty last child, reversing the
+                    // link: its slot takes over prev, and the child becomes
+                    // the new cur
+                    basic_json tmp;
+                    take(tmp, last);
+                    take(last, prev);
+                    take(prev, cur);
+                    take(cur, tmp);
                }
+
+                free_container(cur);
+                return;
            }

            switch (t)
            {
-                case value_t::object:
-                {
-                    AllocatorType<object_t> alloc;
-                    std::allocator_traits<decltype(alloc)>::destroy(alloc, object);
-                    std::allocator_traits<decltype(alloc)>::deallocate(alloc, object, 1);
-                    break;
-                }
-
-                case value_t::array:
-                {
-                    AllocatorType<array_t> alloc;
-                    std::allocator_traits<decltype(alloc)>::destroy(alloc, array);
-                    std::allocator_traits<decltype(alloc)>::deallocate(alloc, array, 1);
-                    break;
-                }
-
                case value_t::string:
                {
                    AllocatorType<string_t> alloc;
@@ -3492,13 +3571,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                   && !std::is_same<value_t, detail::uncvref_t<ValueType>>::value, int > = 0 >
    JSON_HEDLEY_DEPRECATED_FOR(3.11.0, basic_json::json_pointer or nlohmann::json_pointer<basic_json::string_t>) // NOLINT(readability/alt_tokens)
    ValueType value(const ::nlohmann::json_pointer<BasicJsonType>& ptr, const ValueType& default_value) const
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
    {
        return value(ptr.convert(), default_value);
    }
-#endif

    template < class ValueType, class BasicJsonType, class ReturnType = typename value_return_type<ValueType>::type,
               detail::enable_if_t <
@@ -3507,13 +3582,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                   && !std::is_same<value_t, detail::uncvref_t<ValueType>>::value, int > = 0 >
    JSON_HEDLEY_DEPRECATED_FOR(3.11.0, basic_json::json_pointer or nlohmann::json_pointer<basic_json::string_t>) // NOLINT(readability/alt_tokens)
    ReturnType value(const ::nlohmann::json_pointer<BasicJsonType>& ptr, ValueType && default_value) const
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
    {
        return value(ptr.convert(), std::forward<ValueType>(default_value));
    }
-#endif

    /// @brief access the first element
    /// @sa https://json.nlohmann.me/api/basic_json/front/
@@ -3871,13 +3942,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    JSON_HEDLEY_WARN_UNUSED_RESULT
    JSON_HEDLEY_DEPRECATED_FOR(3.11.0, basic_json::json_pointer or nlohmann::json_pointer<basic_json::string_t>) // NOLINT(readability/alt_tokens)
    bool contains(const typename ::nlohmann::json_pointer<BasicJsonType>& ptr) const
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
    {
        return ptr.contains(this);
    }
-#endif

    /// @}

@@ -3988,13 +4055,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    ///             that is, replace `json::iterator_wrapper(j)` with `j.items()`.
    JSON_HEDLEY_DEPRECATED_FOR(3.1.0, items())
    static iteration_proxy<iterator> iterator_wrapper(reference ref) noexcept
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-        = delete;
-#else
    {
        return ref.items();
    }
-#endif

    /// @brief wrapper to access iterator member functions in range-based for
    /// @sa https://json.nlohmann.me/api/basic_json/items/
@@ -4003,13 +4066,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    ///         that is, replace `json::iterator_wrapper(j)` with `j.items()`.
    JSON_HEDLEY_DEPRECATED_FOR(3.1.0, items())
    static iteration_proxy<const_iterator> iterator_wrapper(const_reference ref) noexcept
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-        = delete;
-#else
    {
        return ref.items();
    }
-#endif

    /// @brief helper to access iterator member functions in range-based for
    /// @sa https://json.nlohmann.me/api/basic_json/items/
@@ -5327,13 +5386,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    ///             replace calls like `j >> o;` with `o << j;`.
    JSON_HEDLEY_DEPRECATED_FOR(3.0.0, operator<<(std::ostream&, const basic_json&))
    friend std::ostream& operator>>(const basic_json& j, std::ostream& o)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-        = delete;
-#else
    {
        return o << j;
    }
-#endif
 #endif  // JSON_NO_IO
    /// @}

@@ -5385,16 +5440,12 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                            const bool allow_exceptions = true,
                            const bool ignore_comments = false,
                            const bool ignore_trailing_commas = false)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-        = delete;
-#else
    {
        basic_json result;
        auto p = parser(i.get(), std::move(cb), allow_exceptions, ignore_comments, ignore_trailing_commas);
        p.parse(true, result);
        return result;
    }
-#endif

    /// @brief check if the input is valid JSON
    /// @sa https://json.nlohmann.me/api/basic_json/accept/
@@ -5424,13 +5475,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    static bool accept(detail::span_input_adapter&& i,
                       const bool ignore_comments = false,
                       const bool ignore_trailing_commas = false)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-        = delete;
-#else
    {
        return parser(i.get(), nullptr, false, ignore_comments, ignore_trailing_commas, true).accept(true);
    }
-#endif

    /// @brief generate SAX events
    /// @sa https://json.nlohmann.me/api/basic_json/sax_parse/
@@ -5491,9 +5538,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                          const bool strict = true,
                          const bool ignore_comments = false,
                          const bool ignore_trailing_commas = false)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
    {
        auto ia = i.get();
        return format == input_format_t::json
@@ -5502,7 +5546,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
               // 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);
    }
-#endif
 #if defined(__clang__)
 #pragma clang diagnostic pop
 #endif
@@ -5515,13 +5558,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    ///             replace calls like `j << i;` with `i >> j;`.
    JSON_HEDLEY_DEPRECATED_FOR(3.0.0, operator>>(std::istream&, basic_json&))
    friend std::istream& operator<<(basic_json& j, std::istream& i)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-        = delete;
-#else
    {
        return operator>>(i, j);
    }
-#endif

    /// @brief deserialize from stream
    /// @sa https://json.nlohmann.me/api/operator_gtgt/
@@ -5869,13 +5908,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                                const bool strict = true,
                                const bool allow_exceptions = true,
                                const cbor_tag_handler_t tag_handler = cbor_tag_handler_t::error)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
    {
        return from_cbor(ptr, ptr + len, strict, allow_exceptions, tag_handler);
    }
-#endif

    JSON_HEDLEY_WARN_UNUSED_RESULT
    JSON_HEDLEY_DEPRECATED_FOR(3.8.0, from_cbor(ptr, ptr + len))
@@ -5883,13 +5918,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                                const bool strict = true,
                                const bool allow_exceptions = true,
                                const cbor_tag_handler_t tag_handler = cbor_tag_handler_t::error)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-        = delete;
-#else
    {
        return from_binary_impl(i.get(), input_format_t::cbor, strict, allow_exceptions, error_handler_t::keep, tag_handler);
    }
-#endif

    /// @brief create a JSON value from an input in MessagePack format
    /// @sa https://json.nlohmann.me/api/basic_json/from_msgpack/
@@ -5922,26 +5953,18 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    static basic_json from_msgpack(const T* ptr, std::size_t len,
                                   const bool strict = true,
                                   const bool allow_exceptions = true)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
    {
        return from_msgpack(ptr, ptr + len, strict, allow_exceptions);
    }
-#endif

    JSON_HEDLEY_WARN_UNUSED_RESULT
    JSON_HEDLEY_DEPRECATED_FOR(3.8.0, from_msgpack(ptr, ptr + len))
    static basic_json from_msgpack(detail::span_input_adapter&& i,
                                   const bool strict = true,
                                   const bool allow_exceptions = true)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-        = delete;
-#else
    {
        return from_binary_impl(i.get(), input_format_t::msgpack, strict, allow_exceptions);
    }
-#endif

    /// @brief create a JSON value from an input in UBJSON format
    /// @sa https://json.nlohmann.me/api/basic_json/from_ubjson/
@@ -5974,26 +5997,18 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    static basic_json from_ubjson(const T* ptr, std::size_t len,
                                  const bool strict = true,
                                  const bool allow_exceptions = true)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
    {
        return from_ubjson(ptr, ptr + len, strict, allow_exceptions);
    }
-#endif

    JSON_HEDLEY_WARN_UNUSED_RESULT
    JSON_HEDLEY_DEPRECATED_FOR(3.8.0, from_ubjson(ptr, ptr + len))
    static basic_json from_ubjson(detail::span_input_adapter&& i,
                                  const bool strict = true,
                                  const bool allow_exceptions = true)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-        = delete;
-#else
    {
        return from_binary_impl(i.get(), input_format_t::ubjson, strict, allow_exceptions);
    }
-#endif

    /// @brief create a JSON value from an input in BJData format
    /// @sa https://json.nlohmann.me/api/basic_json/from_bjdata/
@@ -6020,20 +6035,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
        return from_binary_impl(detail::input_adapter(std::move(first), std::move(last)), input_format_t::bjdata, strict, allow_exceptions, error_handler);
    }

-    template<typename T>
-    JSON_HEDLEY_WARN_UNUSED_RESULT
-    JSON_HEDLEY_DEPRECATED_FOR(3.13.0, from_bjdata(ptr, ptr + len))
-    static basic_json from_bjdata(const T* ptr, std::size_t len,
-                                  const bool strict = true,
-                                  const bool allow_exceptions = true)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
-    {
-        return from_bjdata(ptr, ptr + len, strict, allow_exceptions);
-    }
-#endif
-
    /// @brief create a JSON value from an input in BON8 format
    /// @sa https://json.nlohmann.me/api/basic_json/from_bon8/
    template<typename InputType>
@@ -6057,20 +6058,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
        return from_binary_impl(detail::input_adapter(std::move(first), std::move(last)), input_format_t::bon8, strict, allow_exceptions);
    }

-    template<typename T>
-    JSON_HEDLEY_WARN_UNUSED_RESULT
-    JSON_HEDLEY_DEPRECATED_FOR(3.13.0, from_bon8(ptr, ptr + len))
-    static basic_json from_bon8(const T* ptr, std::size_t len,
-                                const bool strict = true,
-                                const bool allow_exceptions = true)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
-    {
-        return from_bon8(ptr, ptr + len, strict, allow_exceptions);
-    }
-#endif
-
    /// @brief create a JSON value from an input in BSON format
    /// @sa https://json.nlohmann.me/api/basic_json/from_bson/
    template<typename InputType>
@@ -6102,26 +6089,18 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    static basic_json from_bson(const T* ptr, std::size_t len,
                                const bool strict = true,
                                const bool allow_exceptions = true)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
    {
        return from_bson(ptr, ptr + len, strict, allow_exceptions);
    }
-#endif

    JSON_HEDLEY_WARN_UNUSED_RESULT
    JSON_HEDLEY_DEPRECATED_FOR(3.8.0, from_bson(ptr, ptr + len))
    static basic_json from_bson(detail::span_input_adapter&& i,
                                const bool strict = true,
                                const bool allow_exceptions = true)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-        = delete;
-#else
    {
        return from_binary_impl(i.get(), input_format_t::bson, strict, allow_exceptions);
    }
-#endif
    /// @}

    //////////////////////////
@@ -6141,13 +6120,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    template<typename BasicJsonType, detail::enable_if_t<detail::is_basic_json<BasicJsonType>::value, int> = 0>
    JSON_HEDLEY_DEPRECATED_FOR(3.11.0, basic_json::json_pointer or nlohmann::json_pointer<basic_json::string_t>) // NOLINT(readability/alt_tokens)
    reference operator[](const ::nlohmann::json_pointer<BasicJsonType>& ptr)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
    {
        return ptr.get_unchecked(this);
    }
-#endif

    /// @brief access specified element via JSON Pointer
    /// @sa https://json.nlohmann.me/api/basic_json/operator%5B%5D/
@@ -6159,13 +6134,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    template<typename BasicJsonType, detail::enable_if_t<detail::is_basic_json<BasicJsonType>::value, int> = 0>
    JSON_HEDLEY_DEPRECATED_FOR(3.11.0, basic_json::json_pointer or nlohmann::json_pointer<basic_json::string_t>) // NOLINT(readability/alt_tokens)
    const_reference operator[](const ::nlohmann::json_pointer<BasicJsonType>& ptr) const
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
    {
        return ptr.get_unchecked(this);
    }
-#endif

    /// @brief access specified element via JSON Pointer
    /// @sa https://json.nlohmann.me/api/basic_json/at/
@@ -6177,13 +6148,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    template<typename BasicJsonType, detail::enable_if_t<detail::is_basic_json<BasicJsonType>::value, int> = 0>
    JSON_HEDLEY_DEPRECATED_FOR(3.11.0, basic_json::json_pointer or nlohmann::json_pointer<basic_json::string_t>) // NOLINT(readability/alt_tokens)
    reference at(const ::nlohmann::json_pointer<BasicJsonType>& ptr)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
    {
        return ptr.get_checked(this);
    }
-#endif

    /// @brief access specified element via JSON Pointer
    /// @sa https://json.nlohmann.me/api/basic_json/at/
@@ -6195,13 +6162,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    template<typename BasicJsonType, detail::enable_if_t<detail::is_basic_json<BasicJsonType>::value, int> = 0>
    JSON_HEDLEY_DEPRECATED_FOR(3.11.0, basic_json::json_pointer or nlohmann::json_pointer<basic_json::string_t>) // NOLINT(readability/alt_tokens)
    const_reference at(const ::nlohmann::json_pointer<BasicJsonType>& ptr) const
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
    {
        return ptr.get_checked(this);
    }
-#endif

    /// @brief return flattened JSON value
    /// @sa https://json.nlohmann.me/api/basic_json/flatten/
@@ -3225,10 +3225,6 @@ JSON_HEDLEY_DIAGNOSTIC_POP
    #define JSON_DISABLE_ENUM_SERIALIZATION 0
 #endif

-#ifndef JSON_DELETE_DEPRECATED_FUNCTIONS
-    #define JSON_DELETE_DEPRECATED_FUNCTIONS 0
-#endif
-
 #ifndef JSON_DISABLE_TUPLE_REFERENCE_CONVERSION
    #define JSON_DISABLE_TUPLE_REFERENCE_CONVERSION 0
 #endif
@@ -19934,13 +19930,9 @@ class json_pointer
    /// @sa https://json.nlohmann.me/api/json_pointer/operator_string_t/
    JSON_HEDLEY_DEPRECATED_FOR(3.11.0, to_string())
    operator string_t() const
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-        = delete;
-#else
    {
        return to_string();
    }
-#endif

 #ifndef JSON_NO_IO
    /// @brief write string representation of the JSON pointer to stream
@@ -20879,13 +20871,9 @@ class json_pointer
    /// @sa https://json.nlohmann.me/api/json_pointer/operator_eq/
    JSON_HEDLEY_DEPRECATED_FOR(3.11.2, operator==(json_pointer))
    bool operator==(const string_t& rhs) const
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-        = delete;
-#else
    {
        return *this == json_pointer(rhs);
    }
-#endif

    /// @brief 3-way compares two JSON pointers
    template<typename RefStringTypeRhs>
@@ -20963,26 +20951,18 @@ template<typename RefStringTypeLhs,
 JSON_HEDLEY_DEPRECATED_FOR(3.11.2, operator==(json_pointer, json_pointer))
 inline bool operator==(const json_pointer<RefStringTypeLhs>& lhs,
                       const StringType& rhs)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
 {
    return lhs == json_pointer<RefStringTypeLhs>(rhs);
 }
-#endif

 template<typename RefStringTypeRhs,
         typename StringType = typename json_pointer<RefStringTypeRhs>::string_t>
 JSON_HEDLEY_DEPRECATED_FOR(3.11.2, operator==(json_pointer, json_pointer))
 inline bool operator==(const StringType& lhs,
                       const json_pointer<RefStringTypeRhs>& rhs)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
 {
    return json_pointer<RefStringTypeRhs>(lhs) == rhs;
 }
-#endif

 template<typename RefStringTypeLhs, typename RefStringTypeRhs>
 inline bool operator!=(const json_pointer<RefStringTypeLhs>& lhs,
@@ -20996,26 +20976,18 @@ template<typename RefStringTypeLhs,
 JSON_HEDLEY_DEPRECATED_FOR(3.11.2, operator!=(json_pointer, json_pointer))
 inline bool operator!=(const json_pointer<RefStringTypeLhs>& lhs,
                       const StringType& rhs)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
 {
    return !(lhs == rhs);
 }
-#endif

 template<typename RefStringTypeRhs,
         typename StringType = typename json_pointer<RefStringTypeRhs>::string_t>
 JSON_HEDLEY_DEPRECATED_FOR(3.11.2, operator!=(json_pointer, json_pointer))
 inline bool operator!=(const StringType& lhs,
                       const json_pointer<RefStringTypeRhs>& rhs)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
 {
    return !(lhs == rhs);
 }
-#endif

 template<typename RefStringTypeLhs, typename RefStringTypeRhs>
 inline bool operator<(const json_pointer<RefStringTypeLhs>& lhs,
@@ -27762,6 +27734,68 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
        /// constructor for rvalue binary arrays (internal type)
        json_value(binary_t&& value) : binary(create<binary_t>(std::move(value))) {}

+        // raw, allocation-free transfer of m_data from src to dst: no
+        // set_parents()/assert_invariant() (the former is O(#children) per
+        // call under JSON_DIAGNOSTICS, which would make the walk below
+        // quadratic); dst takes ownership, src is left as value_t::null.
+        static void take(basic_json& dst, basic_json& src) noexcept
+        {
+            dst.m_data.m_type = src.m_data.m_type;
+            dst.m_data.m_value = src.m_data.m_value;
+            src.m_data.m_type = value_t::null;
+        }
+
+        static bool is_empty_container(const basic_json& v) noexcept
+        {
+            return v.m_data.m_type == value_t::array
+                   ? v.m_data.m_value.array->empty()
+                   : v.m_data.m_value.object->empty();
+        }
+
+        static basic_json& last_child(basic_json& v)
+        {
+            return v.m_data.m_type == value_t::array
+                   ? v.m_data.m_value.array->back()
+                   : std::prev(v.m_data.m_value.object->end())->second;
+        }
+
+        // removes the last child of a non-empty array/object v; this never
+        // allocates, and since it is only ever called when that child is a
+        // scalar or an already-empty array/object, destroying it never
+        // recurses more than one level deep (see destroy() below)
+        static void pop_last_child(basic_json& v)
+        {
+            if (v.m_data.m_type == value_t::array)
+            {
+                v.m_data.m_value.array->pop_back();
+            }
+            else
+            {
+                v.m_data.m_value.object->erase(std::prev(v.m_data.m_value.object->end()));
+            }
+        }
+
+        // deallocates the (already empty) array/object held by v; this is
+        // the same allocator-based free the old recursive implementation
+        // used, just factored out so every level of the walk in destroy()
+        // can share it
+        static void free_container(basic_json& v) noexcept
+        {
+            if (v.m_data.m_type == value_t::array)
+            {
+                AllocatorType<array_t> alloc;
+                std::allocator_traits<decltype(alloc)>::destroy(alloc, v.m_data.m_value.array);
+                std::allocator_traits<decltype(alloc)>::deallocate(alloc, v.m_data.m_value.array, 1);
+            }
+            else
+            {
+                AllocatorType<object_t> alloc;
+                std::allocator_traits<decltype(alloc)>::destroy(alloc, v.m_data.m_value.object);
+                std::allocator_traits<decltype(alloc)>::deallocate(alloc, v.m_data.m_value.object, 1);
+            }
+            v.m_data.m_type = value_t::null; // avoid a double free if v is later destructed
+        }
+
        void destroy(value_t t)
        {
            if (
@@ -27776,71 +27810,88 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
            }
            if (t == value_t::array || t == value_t::object)
            {
-                // flatten the current json_value to a heap-allocated stack
-                std::vector<basic_json> stack;
-
-                // move the top-level items to stack
+                // Destroy the tree without recursing per nesting level and
+                // without any heap allocation: a heap-allocated flattening
+                // stack (the previous implementation) can itself throw
+                // bad_alloc, which would escape this noexcept destructor and
+                // terminate the program (#5135).
+                //
+                // Instead, walk down the "last child" chain, reversing links
+                // as we go: cur is the container currently being emptied,
+                // and prev is its parent (value_t::null when there is none).
+                // Each parent's last child slot doubles as storage for that
+                // parent's own parent link while we are below it, so no
+                // extra memory is needed. We only ever remove a child once
+                // it is a scalar or an empty array/object, which neither
+                // allocates nor recurses more than one level deep.
+                //
+                // This json_value is not itself a basic_json, so the
+                // top-level container is first moved into a local stand-in
+                // ("cur"); this union's own pointer is cleared so it is
+                // never looked at or freed a second time.
+                basic_json cur;
+                cur.m_data.m_type = t;
+                cur.m_data.m_value = *this;
                if (t == value_t::array)
                {
-                    stack.reserve(array->size());
-                    std::move(array->begin(), array->end(), std::back_inserter(stack));
+                    array = nullptr;
                }
                else
                {
-                    stack.reserve(object->size());
-                    for (auto&& it : *object)
-                    {
-                        stack.push_back(std::move(it.second));
-                    }
+                    object = nullptr;
                }

-                while (!stack.empty())
+                basic_json prev; // value_t::null: no parent
+
+                while (true)
                {
-                    // move the last item to a local variable to be processed
-                    basic_json current_item(std::move(stack.back()));
-                    stack.pop_back();
-
-                    // if current_item is array/object, move
-                    // its children to the stack to be processed later
-                    if (current_item.is_array())
+                    if (is_empty_container(cur))
                    {
-                        std::move(current_item.m_data.m_value.array->begin(), current_item.m_data.m_value.array->end(), std::back_inserter(stack));
-
-                        current_item.m_data.m_value.array->clear();
-                    }
-                    else if (current_item.is_object())
-                    {
-                        for (auto&& it : *current_item.m_data.m_value.object)
+                        if (prev.m_data.m_type == value_t::null)
                        {
-                            stack.push_back(std::move(it.second));
+                            break; // back at the top with nothing left to do
                        }

-                        current_item.m_data.m_value.object->clear();
+                        // ascend: detach the grandparent link from prev's
+                        // last slot, drop that (now null) slot, free cur
+                        // (it is empty), then move up one level
+                        basic_json gp;
+                        take(gp, last_child(prev));
+                        pop_last_child(prev);
+
+                        free_container(cur);
+
+                        take(cur, prev);
+                        take(prev, gp);
+                        continue;
                    }

-                    // it's now safe that current_item gets destructed
-                    // since it doesn't have any children
+                    basic_json& last = last_child(cur);
+                    const bool last_is_container = last.m_data.m_type == value_t::array || last.m_data.m_type == value_t::object;
+
+                    if (!last_is_container || is_empty_container(last))
+                    {
+                        // scalar, or already-empty array/object
+                        pop_last_child(cur);
+                        continue;
+                    }
+
+                    // descend into the non-empty last child, reversing the
+                    // link: its slot takes over prev, and the child becomes
+                    // the new cur
+                    basic_json tmp;
+                    take(tmp, last);
+                    take(last, prev);
+                    take(prev, cur);
+                    take(cur, tmp);
                }
+
+                free_container(cur);
+                return;
            }

            switch (t)
            {
-                case value_t::object:
-                {
-                    AllocatorType<object_t> alloc;
-                    std::allocator_traits<decltype(alloc)>::destroy(alloc, object);
-                    std::allocator_traits<decltype(alloc)>::deallocate(alloc, object, 1);
-                    break;
-                }
-
-                case value_t::array:
-                {
-                    AllocatorType<array_t> alloc;
-                    std::allocator_traits<decltype(alloc)>::destroy(alloc, array);
-                    std::allocator_traits<decltype(alloc)>::deallocate(alloc, array, 1);
-                    break;
-                }
-
                case value_t::string:
                {
                    AllocatorType<string_t> alloc;
@@ -30642,13 +30693,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                   && !std::is_same<value_t, detail::uncvref_t<ValueType>>::value, int > = 0 >
    JSON_HEDLEY_DEPRECATED_FOR(3.11.0, basic_json::json_pointer or nlohmann::json_pointer<basic_json::string_t>) // NOLINT(readability/alt_tokens)
    ValueType value(const ::nlohmann::json_pointer<BasicJsonType>& ptr, const ValueType& default_value) const
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
    {
        return value(ptr.convert(), default_value);
    }
-#endif

    template < class ValueType, class BasicJsonType, class ReturnType = typename value_return_type<ValueType>::type,
               detail::enable_if_t <
@@ -30657,13 +30704,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                   && !std::is_same<value_t, detail::uncvref_t<ValueType>>::value, int > = 0 >
    JSON_HEDLEY_DEPRECATED_FOR(3.11.0, basic_json::json_pointer or nlohmann::json_pointer<basic_json::string_t>) // NOLINT(readability/alt_tokens)
    ReturnType value(const ::nlohmann::json_pointer<BasicJsonType>& ptr, ValueType && default_value) const
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
    {
        return value(ptr.convert(), std::forward<ValueType>(default_value));
    }
-#endif

    /// @brief access the first element
    /// @sa https://json.nlohmann.me/api/basic_json/front/
@@ -31021,13 +31064,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    JSON_HEDLEY_WARN_UNUSED_RESULT
    JSON_HEDLEY_DEPRECATED_FOR(3.11.0, basic_json::json_pointer or nlohmann::json_pointer<basic_json::string_t>) // NOLINT(readability/alt_tokens)
    bool contains(const typename ::nlohmann::json_pointer<BasicJsonType>& ptr) const
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
    {
        return ptr.contains(this);
    }
-#endif

    /// @}

@@ -31138,13 +31177,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    ///             that is, replace `json::iterator_wrapper(j)` with `j.items()`.
    JSON_HEDLEY_DEPRECATED_FOR(3.1.0, items())
    static iteration_proxy<iterator> iterator_wrapper(reference ref) noexcept
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-        = delete;
-#else
    {
        return ref.items();
    }
-#endif

    /// @brief wrapper to access iterator member functions in range-based for
    /// @sa https://json.nlohmann.me/api/basic_json/items/
@@ -31153,13 +31188,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    ///         that is, replace `json::iterator_wrapper(j)` with `j.items()`.
    JSON_HEDLEY_DEPRECATED_FOR(3.1.0, items())
    static iteration_proxy<const_iterator> iterator_wrapper(const_reference ref) noexcept
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-        = delete;
-#else
    {
        return ref.items();
    }
-#endif

    /// @brief helper to access iterator member functions in range-based for
    /// @sa https://json.nlohmann.me/api/basic_json/items/
@@ -32477,13 +32508,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    ///             replace calls like `j >> o;` with `o << j;`.
    JSON_HEDLEY_DEPRECATED_FOR(3.0.0, operator<<(std::ostream&, const basic_json&))
    friend std::ostream& operator>>(const basic_json& j, std::ostream& o)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-        = delete;
-#else
    {
        return o << j;
    }
-#endif
 #endif  // JSON_NO_IO
    /// @}

@@ -32535,16 +32562,12 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                            const bool allow_exceptions = true,
                            const bool ignore_comments = false,
                            const bool ignore_trailing_commas = false)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-        = delete;
-#else
    {
        basic_json result;
        auto p = parser(i.get(), std::move(cb), allow_exceptions, ignore_comments, ignore_trailing_commas);
        p.parse(true, result);
        return result;
    }
-#endif

    /// @brief check if the input is valid JSON
    /// @sa https://json.nlohmann.me/api/basic_json/accept/
@@ -32574,13 +32597,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    static bool accept(detail::span_input_adapter&& i,
                       const bool ignore_comments = false,
                       const bool ignore_trailing_commas = false)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-        = delete;
-#else
    {
        return parser(i.get(), nullptr, false, ignore_comments, ignore_trailing_commas, true).accept(true);
    }
-#endif

    /// @brief generate SAX events
    /// @sa https://json.nlohmann.me/api/basic_json/sax_parse/
@@ -32641,9 +32660,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                          const bool strict = true,
                          const bool ignore_comments = false,
                          const bool ignore_trailing_commas = false)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
    {
        auto ia = i.get();
        return format == input_format_t::json
@@ -32652,7 +32668,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
               // 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);
    }
-#endif
 #if defined(__clang__)
 #pragma clang diagnostic pop
 #endif
@@ -32665,13 +32680,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    ///             replace calls like `j << i;` with `i >> j;`.
    JSON_HEDLEY_DEPRECATED_FOR(3.0.0, operator>>(std::istream&, basic_json&))
    friend std::istream& operator<<(basic_json& j, std::istream& i)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-        = delete;
-#else
    {
        return operator>>(i, j);
    }
-#endif

    /// @brief deserialize from stream
    /// @sa https://json.nlohmann.me/api/operator_gtgt/
@@ -33019,13 +33030,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                                const bool strict = true,
                                const bool allow_exceptions = true,
                                const cbor_tag_handler_t tag_handler = cbor_tag_handler_t::error)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
    {
        return from_cbor(ptr, ptr + len, strict, allow_exceptions, tag_handler);
    }
-#endif

    JSON_HEDLEY_WARN_UNUSED_RESULT
    JSON_HEDLEY_DEPRECATED_FOR(3.8.0, from_cbor(ptr, ptr + len))
@@ -33033,13 +33040,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                                const bool strict = true,
                                const bool allow_exceptions = true,
                                const cbor_tag_handler_t tag_handler = cbor_tag_handler_t::error)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-        = delete;
-#else
    {
        return from_binary_impl(i.get(), input_format_t::cbor, strict, allow_exceptions, error_handler_t::keep, tag_handler);
    }
-#endif

    /// @brief create a JSON value from an input in MessagePack format
    /// @sa https://json.nlohmann.me/api/basic_json/from_msgpack/
@@ -33072,26 +33075,18 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    static basic_json from_msgpack(const T* ptr, std::size_t len,
                                   const bool strict = true,
                                   const bool allow_exceptions = true)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
    {
        return from_msgpack(ptr, ptr + len, strict, allow_exceptions);
    }
-#endif

    JSON_HEDLEY_WARN_UNUSED_RESULT
    JSON_HEDLEY_DEPRECATED_FOR(3.8.0, from_msgpack(ptr, ptr + len))
    static basic_json from_msgpack(detail::span_input_adapter&& i,
                                   const bool strict = true,
                                   const bool allow_exceptions = true)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-        = delete;
-#else
    {
        return from_binary_impl(i.get(), input_format_t::msgpack, strict, allow_exceptions);
    }
-#endif

    /// @brief create a JSON value from an input in UBJSON format
    /// @sa https://json.nlohmann.me/api/basic_json/from_ubjson/
@@ -33124,26 +33119,18 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    static basic_json from_ubjson(const T* ptr, std::size_t len,
                                  const bool strict = true,
                                  const bool allow_exceptions = true)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
    {
        return from_ubjson(ptr, ptr + len, strict, allow_exceptions);
    }
-#endif

    JSON_HEDLEY_WARN_UNUSED_RESULT
    JSON_HEDLEY_DEPRECATED_FOR(3.8.0, from_ubjson(ptr, ptr + len))
    static basic_json from_ubjson(detail::span_input_adapter&& i,
                                  const bool strict = true,
                                  const bool allow_exceptions = true)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-        = delete;
-#else
    {
        return from_binary_impl(i.get(), input_format_t::ubjson, strict, allow_exceptions);
    }
-#endif

    /// @brief create a JSON value from an input in BJData format
    /// @sa https://json.nlohmann.me/api/basic_json/from_bjdata/
@@ -33170,20 +33157,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
        return from_binary_impl(detail::input_adapter(std::move(first), std::move(last)), input_format_t::bjdata, strict, allow_exceptions, error_handler);
    }

-    template<typename T>
-    JSON_HEDLEY_WARN_UNUSED_RESULT
-    JSON_HEDLEY_DEPRECATED_FOR(3.13.0, from_bjdata(ptr, ptr + len))
-    static basic_json from_bjdata(const T* ptr, std::size_t len,
-                                  const bool strict = true,
-                                  const bool allow_exceptions = true)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
-    {
-        return from_bjdata(ptr, ptr + len, strict, allow_exceptions);
-    }
-#endif
-
    /// @brief create a JSON value from an input in BON8 format
    /// @sa https://json.nlohmann.me/api/basic_json/from_bon8/
    template<typename InputType>
@@ -33207,20 +33180,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
        return from_binary_impl(detail::input_adapter(std::move(first), std::move(last)), input_format_t::bon8, strict, allow_exceptions);
    }

-    template<typename T>
-    JSON_HEDLEY_WARN_UNUSED_RESULT
-    JSON_HEDLEY_DEPRECATED_FOR(3.13.0, from_bon8(ptr, ptr + len))
-    static basic_json from_bon8(const T* ptr, std::size_t len,
-                                const bool strict = true,
-                                const bool allow_exceptions = true)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
-    {
-        return from_bon8(ptr, ptr + len, strict, allow_exceptions);
-    }
-#endif
-
    /// @brief create a JSON value from an input in BSON format
    /// @sa https://json.nlohmann.me/api/basic_json/from_bson/
    template<typename InputType>
@@ -33252,26 +33211,18 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    static basic_json from_bson(const T* ptr, std::size_t len,
                                const bool strict = true,
                                const bool allow_exceptions = true)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
    {
        return from_bson(ptr, ptr + len, strict, allow_exceptions);
    }
-#endif

    JSON_HEDLEY_WARN_UNUSED_RESULT
    JSON_HEDLEY_DEPRECATED_FOR(3.8.0, from_bson(ptr, ptr + len))
    static basic_json from_bson(detail::span_input_adapter&& i,
                                const bool strict = true,
                                const bool allow_exceptions = true)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-        = delete;
-#else
    {
        return from_binary_impl(i.get(), input_format_t::bson, strict, allow_exceptions);
    }
-#endif
    /// @}

    //////////////////////////
@@ -33291,13 +33242,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    template<typename BasicJsonType, detail::enable_if_t<detail::is_basic_json<BasicJsonType>::value, int> = 0>
    JSON_HEDLEY_DEPRECATED_FOR(3.11.0, basic_json::json_pointer or nlohmann::json_pointer<basic_json::string_t>) // NOLINT(readability/alt_tokens)
    reference operator[](const ::nlohmann::json_pointer<BasicJsonType>& ptr)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
    {
        return ptr.get_unchecked(this);
    }
-#endif

    /// @brief access specified element via JSON Pointer
    /// @sa https://json.nlohmann.me/api/basic_json/operator%5B%5D/
@@ -33309,13 +33256,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    template<typename BasicJsonType, detail::enable_if_t<detail::is_basic_json<BasicJsonType>::value, int> = 0>
    JSON_HEDLEY_DEPRECATED_FOR(3.11.0, basic_json::json_pointer or nlohmann::json_pointer<basic_json::string_t>) // NOLINT(readability/alt_tokens)
    const_reference operator[](const ::nlohmann::json_pointer<BasicJsonType>& ptr) const
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
    {
        return ptr.get_unchecked(this);
    }
-#endif

    /// @brief access specified element via JSON Pointer
    /// @sa https://json.nlohmann.me/api/basic_json/at/
@@ -33327,13 +33270,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    template<typename BasicJsonType, detail::enable_if_t<detail::is_basic_json<BasicJsonType>::value, int> = 0>
    JSON_HEDLEY_DEPRECATED_FOR(3.11.0, basic_json::json_pointer or nlohmann::json_pointer<basic_json::string_t>) // NOLINT(readability/alt_tokens)
    reference at(const ::nlohmann::json_pointer<BasicJsonType>& ptr)
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
    {
        return ptr.get_checked(this);
    }
-#endif

    /// @brief access specified element via JSON Pointer
    /// @sa https://json.nlohmann.me/api/basic_json/at/
@@ -33345,13 +33284,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    template<typename BasicJsonType, detail::enable_if_t<detail::is_basic_json<BasicJsonType>::value, int> = 0>
    JSON_HEDLEY_DEPRECATED_FOR(3.11.0, basic_json::json_pointer or nlohmann::json_pointer<basic_json::string_t>) // NOLINT(readability/alt_tokens)
    const_reference at(const ::nlohmann::json_pointer<BasicJsonType>& ptr) const
-#if JSON_DELETE_DEPRECATED_FUNCTIONS
-    = delete;
-#else
    {
        return ptr.get_checked(this);
    }
-#endif

    /// @brief return flattened JSON value
    /// @sa https://json.nlohmann.me/api/basic_json/flatten/
@@ -34511,7 +34446,6 @@ struct formatter<nlohmann::NLOHMANN_BASIC_JSON_TPL, char> // NOLINT(cert-dcl58-c
    #undef JSON_PRECISE_STREAM_POSITION
    #undef JSON_STRICT_NUL_HANDLING
    #undef JSON_STRICT_BINARY_UTF8
-    #undef JSON_DELETE_DEPRECATED_FUNCTIONS
    #undef JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS
 #endif

@@ -602,3 +602,72 @@ TEST_CASE("bad my_allocator::construct")
        j["test"].push_back("should not leak");
    }
 }
+
+namespace
+{
+std::size_t counting_allocator_allocations = 0;
+std::size_t counting_allocator_deallocations = 0;
+
+template<class T>
+struct counting_allocator : std::allocator<T>
+{
+    using std::allocator<T>::allocator;
+
+    T* allocate(std::size_t n)
+    {
+        ++counting_allocator_allocations;
+        return std::allocator<T>::allocate(n);
+    }
+
+    void deallocate(T* p, std::size_t n)
+    {
+        ++counting_allocator_deallocations;
+        std::allocator<T>::deallocate(p, n);
+    }
+
+    template <class U>
+    struct rebind
+    {
+        using other = counting_allocator<U>;
+    };
+};
+} // namespace
+
+TEST_CASE("destructor performs no allocation, only deallocation")
+{
+    // see https://github.com/nlohmann/json/issues/4842 and
+    // https://github.com/nlohmann/json/issues/5135: destroying nested
+    // arrays/objects used to allocate a temporary stack (first with
+    // std::allocator, later - after #4842 - with the provided allocator).
+    // Since that stack could itself throw bad_alloc from inside the
+    // noexcept destructor (#5135), destroy() no longer allocates anything:
+    // it only ever frees what is already there.
+    using counting_json = nlohmann::basic_json<std::map,
+          std::vector,
+          std::string,
+          bool,
+          std::int64_t,
+          std::uint64_t,
+          double,
+          counting_allocator>;
+
+    SECTION("array")
+    {
+        auto* j = new counting_json({1, {2, {3, 4}}, 5}); // NOLINT(cppcoreguidelines-owning-memory)
+        const auto allocations_before = counting_allocator_allocations;
+        const auto deallocations_before = counting_allocator_deallocations;
+        delete j; // NOLINT(cppcoreguidelines-owning-memory)
+        CHECK(counting_allocator_allocations == allocations_before);
+        CHECK(counting_allocator_deallocations > deallocations_before);
+    }
+
+    SECTION("object")
+    {
+        auto* j = new counting_json({{"a", {{"b", {1, 2}}}}, {"c", 3}}); // NOLINT(cppcoreguidelines-owning-memory)
+        const auto allocations_before = counting_allocator_allocations;
+        const auto deallocations_before = counting_allocator_deallocations;
+        delete j; // NOLINT(cppcoreguidelines-owning-memory)
+        CHECK(counting_allocator_allocations == allocations_before);
+        CHECK(counting_allocator_deallocations > deallocations_before);
+    }
+}
@@ -9,14 +9,6 @@
 #include "doctest_compatibility.h"

 #define JSON_TESTS_PRIVATE
-// capture whether JSON_DELETE_DEPRECATED_FUNCTIONS was enabled on the command
-// line *before* including json.hpp, since the library #undefs it once the header
-// has been fully processed (see include/nlohmann/detail/macro_unscope.hpp); the
-// tests of deprecated functions are skipped if these functions are deleted
-#if defined(JSON_DELETE_DEPRECATED_FUNCTIONS) && (JSON_DELETE_DEPRECATED_FUNCTIONS == 1)
-    #define JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
-#endif
-
 #include <nlohmann/json.hpp>
 using nlohmann::json;

@@ -4498,33 +4490,3 @@ TEST_CASE("BJData roundtrips" * doctest::skip())
        }
    }
 }
-
-TEST_CASE("issue #5648 - from_bjdata(ptr, len) must read len bytes, not treat ptr as a C string")
-{
-    // to_bjdata() encodes the integer 0 as the two bytes 'i' 0x00 (a BJData
-    // type marker followed by the value byte 0x00), so the packed data
-    // below contains a 0x00 byte before its end.
-    const json j = {{"a", 0}};
-    const std::vector<std::uint8_t> packed = json::to_bjdata(j);
-    bool contains_nul = false;
-    for (const auto byte : packed)
-    {
-        contains_nul |= (byte == 0x00);
-    }
-    REQUIRE(contains_nul);
-
-#ifndef JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
-    // before the fix, from_bjdata had no (ptr, len) overload, so this call
-    // bound to from_bjdata(InputType&&, bool strict) instead: ptr was read
-    // as a NUL-terminated C string (stopping at the embedded 0x00 byte), and
-    // len was silently converted to the strict flag. The deprecated
-    // overload added for this issue forwards to from_bjdata(ptr, ptr + len,
-    // ...) instead, like from_ubjson's deprecated (ptr, len) overload does.
-    json result;
-    CHECK_NOTHROW(result = json::from_bjdata(packed.data(), packed.size()));
-    CHECK(result == j);
-
-    // len must not collapse into the strict flag either
-    CHECK(json::from_bjdata(packed.data(), packed.size(), false) == j);
-#endif
-}
@@ -8,14 +8,6 @@

 #include "doctest_compatibility.h"

-// capture whether JSON_DELETE_DEPRECATED_FUNCTIONS was enabled on the command
-// line *before* including json.hpp, since the library #undefs it once the header
-// has been fully processed (see include/nlohmann/detail/macro_unscope.hpp); the
-// tests of deprecated functions are skipped if these functions are deleted
-#if defined(JSON_DELETE_DEPRECATED_FUNCTIONS) && (JSON_DELETE_DEPRECATED_FUNCTIONS == 1)
-    #define JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
-#endif
-
 #include <nlohmann/json.hpp>
 using nlohmann::json;
 #ifdef JSON_TEST_NO_GLOBAL_UDLS
@@ -1022,36 +1014,6 @@ TEST_CASE("BON8 roundtrips" * doctest::skip())
    }
 }

-TEST_CASE("issue #5648 - from_bon8(ptr, len) must read len bytes, not treat ptr as a C string")
-{
-    // to_bon8() encodes the integer 40 as the two bytes 0xC2 0x00 (a BON8
-    // lead byte followed by a continuation byte of 0x00), so the packed data
-    // below contains a 0x00 byte before its end.
-    const json j = {{"a", 40}, {"b", "x"}};
-    const std::vector<std::uint8_t> packed = json::to_bon8(j);
-    bool contains_nul = false;
-    for (const auto byte : packed)
-    {
-        contains_nul |= (byte == 0x00);
-    }
-    REQUIRE(contains_nul);
-
-#ifndef JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
-    // before the fix, from_bon8 had no (ptr, len) overload, so this call
-    // bound to from_bon8(InputType&&, bool strict) instead: ptr was read as
-    // a NUL-terminated C string (stopping at the embedded 0x00 byte), and
-    // len was silently converted to the strict flag. The deprecated
-    // overload added for this issue forwards to from_bon8(ptr, ptr + len,
-    // ...) instead, like from_cbor's deprecated (ptr, len) overload does.
-    json result;
-    CHECK_NOTHROW(result = json::from_bon8(packed.data(), packed.size()));
-    CHECK(result == j);
-
-    // len must not collapse into the strict flag either
-    CHECK(json::from_bon8(packed.data(), packed.size(), false) == j);
-#endif
-}
-
 #ifdef JSON_HAS_CPP_17
 TEST_CASE("BON8 with std::byte")
 {
@@ -8,14 +8,6 @@

 #include "doctest_compatibility.h"

-// capture whether JSON_DELETE_DEPRECATED_FUNCTIONS was enabled on the command
-// line *before* including json.hpp, since the library #undefs it once the header
-// has been fully processed (see include/nlohmann/detail/macro_unscope.hpp); the
-// tests of deprecated functions are skipped if these functions are deleted
-#if defined(JSON_DELETE_DEPRECATED_FUNCTIONS) && (JSON_DELETE_DEPRECATED_FUNCTIONS == 1)
-    #define JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
-#endif
-
 #include <nlohmann/json.hpp>
 using nlohmann::json;

@@ -1269,10 +1261,8 @@ TEST_CASE("BSON input that cannot be read is discarded by every overload")
    CHECK_THROWS_AS(_ = json::from_bson(input.begin(), input.end()), json::parse_error&);
    CHECK(json::from_bson(input, true, false).is_discarded());
    CHECK(json::from_bson(input.begin(), input.end(), true, false).is_discarded());
-#ifndef JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
    CHECK(json::from_bson(input.data(), input.size(), true, false).is_discarded());
    CHECK(json::from_bson({input.data(), input.size()}, true, false).is_discarded());
-#endif
 }

 TEST_CASE("BSON SAX parsing stops at every event")
@@ -1750,7 +1740,6 @@ TEST_CASE("BSON roundtrips" * doctest::skip())
                CHECK(j1 == j2);
            }

-#ifndef JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
            {
                INFO_WITH_TEMP(filename + ": uint8_t* and size");
                // parse JSON file
@@ -1765,7 +1754,6 @@ TEST_CASE("BSON roundtrips" * doctest::skip())
                // compare parsed JSON values
                CHECK(j1 == j2);
            }
-#endif

            {
                INFO_WITH_TEMP(filename + ": output to output adapters");
@@ -8,14 +8,6 @@

 #include "doctest_compatibility.h"

-// capture whether JSON_DELETE_DEPRECATED_FUNCTIONS was enabled on the command
-// line *before* including json.hpp, since the library #undefs it once the header
-// has been fully processed (see include/nlohmann/detail/macro_unscope.hpp); the
-// tests of deprecated functions are skipped if these functions are deleted
-#if defined(JSON_DELETE_DEPRECATED_FUNCTIONS) && (JSON_DELETE_DEPRECATED_FUNCTIONS == 1)
-    #define JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
-#endif
-
 #include <nlohmann/json.hpp>
 using nlohmann::json;

@@ -2223,10 +2215,8 @@ TEST_CASE("CBOR input that cannot be read is discarded by every overload")
    CHECK_THROWS_AS(_ = json::from_cbor(input.begin(), input.end()), json::parse_error&);
    CHECK(json::from_cbor(input, true, false).is_discarded());
    CHECK(json::from_cbor(input.begin(), input.end(), true, false).is_discarded());
-#ifndef JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
    CHECK(json::from_cbor(input.data(), input.size(), true, false).is_discarded());
    CHECK(json::from_cbor({input.data(), input.size()}, true, false).is_discarded());
-#endif

    // a string that ends early, read through iterators that are not
    // contiguous and have to be copied from one element at a time
@@ -2623,14 +2613,12 @@ TEST_CASE("CBOR roundtrips" * doctest::skip())
                CHECK(j1 == j2);
            }

-#ifndef JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
            {
                INFO_WITH_TEMP(filename + ": uint8_t* and size");
                json j2;
                CHECK_NOTHROW(j2 = json::from_cbor({packed.data(), packed.size()}));
                CHECK(j1 == j2);
            }
-#endif

            {
                INFO_WITH_TEMP(filename + ": output to output adapters");
@@ -1,214 +0,0 @@
-//     __ _____ _____ _____
-//  __|  |   __|     |   | |  JSON for Modern C++ (supporting code)
-// |  |  |__   |  |  | | | |  version 3.12.0
-// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
-//
-// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
-// SPDX-License-Identifier: MIT
-
-#include "doctest_compatibility.h"
-
-// This file tests the opt-in JSON_DELETE_DEPRECATED_FUNCTIONS, so it defines the
-// macro itself instead of relying on the build configuration.
-#ifdef JSON_DELETE_DEPRECATED_FUNCTIONS
-    #undef JSON_DELETE_DEPRECATED_FUNCTIONS
-#endif
-#define JSON_DELETE_DEPRECATED_FUNCTIONS 1
-
-#include <nlohmann/json.hpp>
-using nlohmann::json;
-
-#include <cstddef>
-#include <cstdint>
-#include <istream>
-#include <ostream>
-#include <string>
-#include <type_traits>
-#include <utility>
-
-namespace
-{
-template<typename...>
-struct make_void
-{
-    using type = void;
-};
-
-template<typename... Ts>
-using void_t = typename make_void<Ts...>::type;
-
-// A deleted function is still found by overload resolution, but naming it in an
-// unevaluated operand is ill-formed, so each of the following traits is false
-// exactly if the expression selects a deleted (or no) function.
-#define JSON_TEST_DETECT(name, expr)                                 \
-    template<typename J, typename = void>                            \
-    struct name : std::false_type {};                                \
-    template<typename J>                                             \
-    struct name<J, void_t<decltype(expr)>> : std::true_type {}
-
-using ptr_t = const std::uint8_t*;
-
-JSON_TEST_DETECT(from_cbor_ptr_len, J::from_cbor(std::declval<ptr_t>(), std::declval<std::size_t>()));
-JSON_TEST_DETECT(from_msgpack_ptr_len, J::from_msgpack(std::declval<ptr_t>(), std::declval<std::size_t>()));
-JSON_TEST_DETECT(from_ubjson_ptr_len, J::from_ubjson(std::declval<ptr_t>(), std::declval<std::size_t>()));
-JSON_TEST_DETECT(from_bjdata_ptr_len, J::from_bjdata(std::declval<ptr_t>(), std::declval<std::size_t>()));
-JSON_TEST_DETECT(from_bon8_ptr_len, J::from_bon8(std::declval<ptr_t>(), std::declval<std::size_t>()));
-JSON_TEST_DETECT(from_bson_ptr_len, J::from_bson(std::declval<ptr_t>(), std::declval<std::size_t>()));
-
-JSON_TEST_DETECT(from_cbor_ptr_ptr, J::from_cbor(std::declval<ptr_t>(), std::declval<ptr_t>()));
-JSON_TEST_DETECT(from_msgpack_ptr_ptr, J::from_msgpack(std::declval<ptr_t>(), std::declval<ptr_t>()));
-JSON_TEST_DETECT(from_ubjson_ptr_ptr, J::from_ubjson(std::declval<ptr_t>(), std::declval<ptr_t>()));
-JSON_TEST_DETECT(from_bjdata_ptr_ptr, J::from_bjdata(std::declval<ptr_t>(), std::declval<ptr_t>()));
-JSON_TEST_DETECT(from_bon8_ptr_ptr, J::from_bon8(std::declval<ptr_t>(), std::declval<ptr_t>()));
-JSON_TEST_DETECT(from_bson_ptr_ptr, J::from_bson(std::declval<ptr_t>(), std::declval<ptr_t>()));
-
-JSON_TEST_DETECT(from_cbor_init_list, J::from_cbor({std::declval<ptr_t>(), std::declval<std::size_t>()}));
-JSON_TEST_DETECT(from_msgpack_init_list, J::from_msgpack({std::declval<ptr_t>(), std::declval<std::size_t>()}));
-JSON_TEST_DETECT(from_ubjson_init_list, J::from_ubjson({std::declval<ptr_t>(), std::declval<std::size_t>()}));
-JSON_TEST_DETECT(from_bson_init_list, J::from_bson({std::declval<ptr_t>(), std::declval<std::size_t>()}));
-
-JSON_TEST_DETECT(parse_init_list, J::parse({std::declval<ptr_t>(), std::declval<std::size_t>()}));
-JSON_TEST_DETECT(accept_init_list, J::accept({std::declval<ptr_t>(), std::declval<std::size_t>()}));
-JSON_TEST_DETECT(sax_parse_init_list, J::sax_parse({std::declval<ptr_t>(), std::declval<std::size_t>()}, std::declval<nlohmann::json_sax<J>*>()));
-JSON_TEST_DETECT(parse_ptr_ptr, J::parse(std::declval<ptr_t>(), std::declval<ptr_t>()));
-
-JSON_TEST_DETECT(iterator_wrapper, J::iterator_wrapper(std::declval<J&>()));
-JSON_TEST_DETECT(iterator_wrapper_const, J::iterator_wrapper(std::declval<const J&>()));
-JSON_TEST_DETECT(items, std::declval<J&>().items());
-
-JSON_TEST_DETECT(json_ltlt_istream, std::declval<J&>() << std::declval<std::istream&>());
-JSON_TEST_DETECT(istream_gtgt_json, std::declval<std::istream&>() >> std::declval<J&>());
-JSON_TEST_DETECT(json_gtgt_ostream, std::declval<const J&>() >> std::declval<std::ostream&>());
-JSON_TEST_DETECT(ostream_ltlt_json, std::declval<std::ostream&>() << std::declval<const J&>());
-
-JSON_TEST_DETECT(ptr_eq_ptr, std::declval<const typename J::json_pointer&>() == std::declval<const typename J::json_pointer&>());
-JSON_TEST_DETECT(ptr_ne_ptr, std::declval<const typename J::json_pointer&>() != std::declval<const typename J::json_pointer&>());
-JSON_TEST_DETECT(ptr_eq_string, std::declval<const typename J::json_pointer&>() == std::declval<const std::string&>());
-JSON_TEST_DETECT(string_eq_ptr, std::declval<const std::string&>() == std::declval<const typename J::json_pointer&>());
-JSON_TEST_DETECT(ptr_eq_c_string, std::declval<const typename J::json_pointer&>() == std::declval<const char*>());
-JSON_TEST_DETECT(c_string_eq_ptr, std::declval<const char*>() == std::declval<const typename J::json_pointer&>());
-JSON_TEST_DETECT(ptr_ne_string, std::declval<const typename J::json_pointer&>() != std::declval<const std::string&>());
-JSON_TEST_DETECT(string_ne_ptr, std::declval<const std::string&>() != std::declval<const typename J::json_pointer&>());
-JSON_TEST_DETECT(ptr_to_string, std::declval<const typename J::json_pointer&>().to_string());
-
-// json_pointer with a basic_json type as template argument
-template<typename J>
-using legacy_ptr_t = const nlohmann::json_pointer<J>& ;
-JSON_TEST_DETECT(legacy_ptr_value, std::declval<const J&>().value(std::declval<legacy_ptr_t<J>>(), 0));
-JSON_TEST_DETECT(legacy_ptr_value_rvalue, std::declval<const J&>().value(std::declval<legacy_ptr_t<J>>(), std::string()));
-JSON_TEST_DETECT(legacy_ptr_contains, std::declval<const J&>().contains(std::declval<legacy_ptr_t<J>>()));
-JSON_TEST_DETECT(legacy_ptr_subscript, std::declval<J&>()[std::declval<legacy_ptr_t<J>>()]);
-JSON_TEST_DETECT(legacy_ptr_subscript_const, std::declval<const J&>()[std::declval<legacy_ptr_t<J>>()]);
-JSON_TEST_DETECT(legacy_ptr_at, std::declval<J&>().at(std::declval<legacy_ptr_t<J>>()));
-JSON_TEST_DETECT(legacy_ptr_at_const, std::declval<const J&>().at(std::declval<legacy_ptr_t<J>>()));
-JSON_TEST_DETECT(ptr_value, std::declval<const J&>().value(std::declval<const typename J::json_pointer&>(), 0));
-JSON_TEST_DETECT(ptr_at, std::declval<J&>().at(std::declval<const typename J::json_pointer&>()));
-
-#undef JSON_TEST_DETECT
-} // namespace
-
-TEST_CASE("JSON_DELETE_DEPRECATED_FUNCTIONS")
-{
-    SECTION("from_* with a pointer and a length")
-    {
-        // the overloads are deleted rather than removed, so the length cannot
-        // silently bind to the strict parameter of from_*(InputType&&, bool)
-        CHECK_FALSE(from_cbor_ptr_len<json>::value);
-        CHECK_FALSE(from_msgpack_ptr_len<json>::value);
-        CHECK_FALSE(from_ubjson_ptr_len<json>::value);
-        CHECK_FALSE(from_bjdata_ptr_len<json>::value);
-        CHECK_FALSE(from_bon8_ptr_len<json>::value);
-        CHECK_FALSE(from_bson_ptr_len<json>::value);
-
-        // the replacement
-        CHECK(from_cbor_ptr_ptr<json>::value);
-        CHECK(from_msgpack_ptr_ptr<json>::value);
-        CHECK(from_ubjson_ptr_ptr<json>::value);
-        CHECK(from_bjdata_ptr_ptr<json>::value);
-        CHECK(from_bon8_ptr_ptr<json>::value);
-        CHECK(from_bson_ptr_ptr<json>::value);
-    }
-
-    SECTION("initializer lists of a pointer and a length")
-    {
-        CHECK_FALSE(from_cbor_init_list<json>::value);
-        CHECK_FALSE(from_msgpack_init_list<json>::value);
-        CHECK_FALSE(from_ubjson_init_list<json>::value);
-        CHECK_FALSE(from_bson_init_list<json>::value);
-        CHECK_FALSE(parse_init_list<json>::value);
-        CHECK_FALSE(accept_init_list<json>::value);
-        CHECK_FALSE(sax_parse_init_list<json>::value);
-
-        // the replacement
-        CHECK(parse_ptr_ptr<json>::value);
-    }
-
-    SECTION("iterator_wrapper")
-    {
-        CHECK_FALSE(iterator_wrapper<json>::value);
-        CHECK_FALSE(iterator_wrapper_const<json>::value);
-
-        // the replacement
-        CHECK(items<json>::value);
-    }
-
-    SECTION("stream operators with reversed operands")
-    {
-        CHECK_FALSE(json_ltlt_istream<json>::value);
-        CHECK_FALSE(json_gtgt_ostream<json>::value);
-
-        // the replacement
-        CHECK(istream_gtgt_json<json>::value);
-        CHECK(ostream_ltlt_json<json>::value);
-    }
-
-    SECTION("json_pointer")
-    {
-        // conversion to a string
-        CHECK_FALSE(std::is_constructible<std::string, json::json_pointer>::value);
-        CHECK_FALSE(std::is_convertible<json::json_pointer, std::string>::value);
-
-        // comparison with a string
-        CHECK_FALSE(ptr_eq_string<json>::value);
-        CHECK_FALSE(string_eq_ptr<json>::value);
-        CHECK_FALSE(ptr_eq_c_string<json>::value);
-        CHECK_FALSE(c_string_eq_ptr<json>::value);
-        CHECK_FALSE(ptr_ne_string<json>::value);
-        CHECK_FALSE(string_ne_ptr<json>::value);
-
-        // the replacement
-        CHECK(ptr_to_string<json>::value);
-        CHECK(ptr_eq_ptr<json>::value);
-        CHECK(ptr_ne_ptr<json>::value);
-    }
-
-    SECTION("json_pointer with a basic_json type as template argument")
-    {
-        CHECK_FALSE(legacy_ptr_value<json>::value);
-        CHECK_FALSE(legacy_ptr_value_rvalue<json>::value);
-        CHECK_FALSE(legacy_ptr_contains<json>::value);
-        CHECK_FALSE(legacy_ptr_subscript<json>::value);
-        CHECK_FALSE(legacy_ptr_subscript_const<json>::value);
-        CHECK_FALSE(legacy_ptr_at<json>::value);
-        CHECK_FALSE(legacy_ptr_at_const<json>::value);
-
-        // the replacement
-        CHECK(ptr_value<json>::value);
-        CHECK(ptr_at<json>::value);
-    }
-
-    SECTION("the non-deprecated functions still work")
-    {
-        const json j = {{"a", {1, 2}}};
-        const auto cbor = json::to_cbor(j);
-        CHECK(json::from_cbor(cbor.data(), cbor.data() + cbor.size()) == j);
-
-        const json::json_pointer ptr("/a/1");
-        CHECK(ptr == json::json_pointer("/a/1"));
-        CHECK(ptr.to_string() == "/a/1");
-        CHECK(j[ptr] == 2);
-        CHECK(j.at(ptr) == 2);
-        CHECK(j.value(ptr, 0) == 2);
-        CHECK(j.contains(ptr));
-    }
-}
@@ -16,14 +16,6 @@
    #define JSON_TEST_STRICT_NUL_HANDLING_ENABLED 1
 #endif

-// capture whether JSON_DELETE_DEPRECATED_FUNCTIONS was enabled on the command
-// line *before* including json.hpp, since the library #undefs it once the header
-// has been fully processed (see include/nlohmann/detail/macro_unscope.hpp); the
-// tests of deprecated functions are skipped if these functions are deleted
-#if defined(JSON_DELETE_DEPRECATED_FUNCTIONS) && (JSON_DELETE_DEPRECATED_FUNCTIONS == 1)
-    #define JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
-#endif
-
 #include <nlohmann/json.hpp>
 using nlohmann::json;
 #ifdef JSON_TEST_NO_GLOBAL_UDLS
@@ -299,7 +291,6 @@ TEST_CASE("deserialization")
            }));
        }

-#ifndef JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
        SECTION("operator<<")
        {
            std::stringstream ss;
@@ -308,7 +299,6 @@ TEST_CASE("deserialization")
            j << ss;
            CHECK(j == json({"foo", 1, 2, 3, false, {{"one", 1}}}));
        }
-#endif

        SECTION("operator>>")
        {
@@ -433,7 +423,6 @@ TEST_CASE("deserialization")
            CHECK_THROWS_WITH_AS(_ = json::parse(nullptr), "[json.exception.parse_error.101] parse error: attempting to parse an empty input; check that your input string or stream contains the expected JSON", json::parse_error&);
        }

-#ifndef JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
        SECTION("operator<<")
        {
            std::stringstream ss;
@@ -441,7 +430,6 @@ TEST_CASE("deserialization")
            json j;
            CHECK_THROWS_WITH_AS(j << ss, "[json.exception.parse_error.101] parse error at line 1, column 29: syntax error while parsing array - unexpected end of input; expected ']'", json::parse_error&);
        }
-#endif

        SECTION("operator>>")
        {
@@ -1160,9 +1148,9 @@ TEST_CASE("deserialization")
        {
            std::istringstream s(bom + "123 456");
            json j;
-            s >> j;
+            j << s;
            CHECK(j == 123);
-            s >> j;
+            j << s;
            CHECK(j == 456);
        }
    }
@@ -8,14 +8,6 @@

 #include "doctest_compatibility.h"

-// capture whether JSON_DELETE_DEPRECATED_FUNCTIONS was enabled on the command
-// line *before* including json.hpp, since the library #undefs it once the header
-// has been fully processed (see include/nlohmann/detail/macro_unscope.hpp); the
-// tests of deprecated functions are skipped if these functions are deleted
-#if defined(JSON_DELETE_DEPRECATED_FUNCTIONS) && (JSON_DELETE_DEPRECATED_FUNCTIONS == 1)
-    #define JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
-#endif
-
 #include <nlohmann/json.hpp>
 using nlohmann::json;

@@ -27,7 +19,6 @@ DOCTEST_GCC_SUPPRESS_WARNING_PUSH
 DOCTEST_CLANG_SUPPRESS_WARNING_PUSH
 DOCTEST_CLANG_SUPPRESS_WARNING("-Wrange-loop-construct")

-#ifndef JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
 TEST_CASE("iterator_wrapper")
 {
    SECTION("object")
@@ -724,7 +715,6 @@ TEST_CASE("iterator_wrapper")
        }
    }
 }
-#endif

 TEST_CASE("items()")
 {
@@ -9,14 +9,6 @@
 #include "doctest_compatibility.h"

 #define JSON_TESTS_PRIVATE
-// capture whether JSON_DELETE_DEPRECATED_FUNCTIONS was enabled on the command
-// line *before* including json.hpp, since the library #undefs it once the header
-// has been fully processed (see include/nlohmann/detail/macro_unscope.hpp); the
-// tests of deprecated functions are skipped if these functions are deleted
-#if defined(JSON_DELETE_DEPRECATED_FUNCTIONS) && (JSON_DELETE_DEPRECATED_FUNCTIONS == 1)
-    #define JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
-#endif
-
 #include <nlohmann/json.hpp>
 using nlohmann::json;
 #ifdef JSON_TEST_NO_GLOBAL_UDLS
@@ -572,9 +564,7 @@ TEST_CASE("JSON pointers")
            std::stringstream ss;
            ss << ptr;
            CHECK(ptr.to_string() == ptr_str);
-#ifndef JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
            CHECK(std::string(ptr) == ptr_str);
-#endif
            CHECK(ss.str() == ptr_str);
        }
    }
@@ -754,6 +744,8 @@ TEST_CASE("JSON pointers")

    SECTION("equality comparison")
    {
+        const char* ptr_cpstring = "/foo/bar";
+        const char ptr_castring[] = "/foo/bar"; // NOLINT(misc-const-correctness,hicpp-avoid-c-arrays,modernize-avoid-c-arrays,cppcoreguidelines-avoid-c-arrays)
        std::string ptr_string{"/foo/bar"};
        auto ptr1 = json::json_pointer(ptr_string);
        auto ptr2 = json::json_pointer(ptr_string);
@@ -763,12 +755,6 @@ TEST_CASE("JSON pointers")

        CHECK(ptr1 == ptr2);

-        CHECK_FALSE(ptr1 != ptr2);
-
-#ifndef JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
-        const char* ptr_cpstring = "/foo/bar";
-        const char ptr_castring[] = "/foo/bar"; // NOLINT(misc-const-correctness,hicpp-avoid-c-arrays,modernize-avoid-c-arrays,cppcoreguidelines-avoid-c-arrays)
-
        CHECK(ptr1 == "/foo/bar");
        CHECK(ptr1 == ptr_cpstring);
        CHECK(ptr1 == ptr_castring);
@@ -779,6 +765,8 @@ TEST_CASE("JSON pointers")
        CHECK(ptr_castring == ptr1);
        CHECK(ptr_string == ptr1);

+        CHECK_FALSE(ptr1 != ptr2);
+
        CHECK_FALSE(ptr1 != "/foo/bar");
        CHECK_FALSE(ptr1 != ptr_cpstring);
        CHECK_FALSE(ptr1 != ptr_castring);
@@ -800,7 +788,6 @@ TEST_CASE("JSON pointers")
            CHECK_THROWS_WITH_AS("/~~" == ptr1,
                                 "[json.exception.parse_error.108] parse error: escape character '~' must be followed with '0' or '1'", json::parse_error&);
        }
-#endif
    }

    SECTION("less-than comparison")
@@ -852,7 +839,6 @@ TEST_CASE("JSON pointers")
        json_ptr_j ptr_j{ptr_string};
        json_ptr_oj ptr_oj{ptr_string};

-#ifndef JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
        CHECK(j.contains(ptr));
        CHECK(j.contains(ptr_j));
        CHECK(j.contains(ptr_oj));
@@ -865,7 +851,6 @@ TEST_CASE("JSON pointers")

        CHECK(j.value(ptr, "x") == j.value(ptr_j, "x"));
        CHECK(j.value(ptr, "x") == j.value(ptr_oj, "x"));
-#endif

        CHECK(ptr == ptr_j);
        CHECK(ptr == ptr_oj);
@@ -8,14 +8,6 @@

 #include "doctest_compatibility.h"

-// capture whether JSON_DELETE_DEPRECATED_FUNCTIONS was enabled on the command
-// line *before* including json.hpp, since the library #undefs it once the header
-// has been fully processed (see include/nlohmann/detail/macro_unscope.hpp); the
-// tests of deprecated functions are skipped if these functions are deleted
-#if defined(JSON_DELETE_DEPRECATED_FUNCTIONS) && (JSON_DELETE_DEPRECATED_FUNCTIONS == 1)
-    #define JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
-#endif
-
 #include <nlohmann/json.hpp>
 using nlohmann::json;
 #ifdef JSON_TEST_NO_GLOBAL_UDLS
@@ -1803,10 +1795,8 @@ TEST_CASE("MessagePack input that cannot be read is discarded by every overload"
    CHECK_THROWS_AS(_ = json::from_msgpack(input.begin(), input.end()), json::parse_error&);
    CHECK(json::from_msgpack(input, true, false).is_discarded());
    CHECK(json::from_msgpack(input.begin(), input.end(), true, false).is_discarded());
-#ifndef JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
    CHECK(json::from_msgpack(input.data(), input.size(), true, false).is_discarded());
    CHECK(json::from_msgpack({input.data(), input.size()}, true, false).is_discarded());
-#endif
 }

 TEST_CASE("MessagePack SAX parsing stops at every event")
@@ -2109,14 +2099,12 @@ TEST_CASE("MessagePack roundtrips" * doctest::skip())
                CHECK(j1 == j2);
            }

-#ifndef JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
            {
                INFO_WITH_TEMP(filename + ": uint8_t* and size");
                json j2;
                CHECK_NOTHROW(j2 = json::from_msgpack({packed.data(), packed.size()}));
                CHECK(j1 == j2);
            }
-#endif

            {
                INFO_WITH_TEMP(filename + ": output to output adapters");
@@ -40,7 +40,9 @@ using ordered_json = nlohmann::ordered_json;
 #endif

 #include <cstdio>
+#include <cstdlib>
 #include <list>
+#include <new>
 #include <tuple>
 #include <type_traits>
 #include <utility>
@@ -107,6 +109,84 @@ DOCTEST_CLANG_SUPPRESS_WARNING("-Wexit-time-destructors")

 using float_json = nlohmann::basic_json<std::map, std::vector, std::string, bool, std::int64_t, std::uint64_t, float>;

+#if (defined(__cpp_exceptions) || defined(__EXCEPTIONS) || defined(_CPPUNWIND)) && !defined(JSON_NOEXCEPTION)
+namespace
+{
+// An allocator whose allocate() can be told to fail on demand, so tests can
+// check that ~basic_json() tolerates - in fact, after #5135, never even
+// triggers - an allocation failure. This replaces an earlier version of
+// this test that overrode the process-wide ::operator new/::operator
+// delete, which affected every allocation in the whole unit-regression2
+// binary rather than just the values under test.
+std::size_t failing_allocator_allocations = 0;
+std::size_t failing_allocator_deallocations = 0;
+bool fail_next_allocation = false;
+
+template<class T>
+struct failing_allocator : std::allocator<T>
+{
+    using std::allocator<T>::allocator;
+
+    failing_allocator() noexcept = default;
+    template<class U>
+    failing_allocator(const failing_allocator<U>& /*unused*/) noexcept {} // NOLINT(google-explicit-constructor)
+
+    T* allocate(std::size_t n)
+    {
+        if (fail_next_allocation)
+        {
+            fail_next_allocation = false;
+            throw std::bad_alloc();
+        }
+        ++failing_allocator_allocations;
+        return std::allocator<T>::allocate(n);
+    }
+
+    void deallocate(T* p, std::size_t n)
+    {
+        ++failing_allocator_deallocations;
+        std::allocator<T>::deallocate(p, n);
+    }
+
+    template<class U>
+    struct rebind
+    {
+        using other = failing_allocator<U>;
+    };
+};
+
+using failing_json = nlohmann::basic_json<std::map, std::vector, std::string, bool,
+      std::int64_t, std::uint64_t, double, failing_allocator>;
+using failing_ordered_json = nlohmann::basic_json<nlohmann::ordered_map, std::vector, std::string, bool,
+      std::int64_t, std::uint64_t, double, failing_allocator>;
+
+// builds `depth` levels of nesting around a scalar, iteratively (never
+// recursing: each wrap only moves the previous, already-built value, which
+// is O(1)), each level an array or an object depending on `nest_objects`
+template<class BasicJsonType>
+BasicJsonType make_deep_nest(std::size_t depth, bool nest_objects)
+{
+    BasicJsonType v = 0;
+    for (std::size_t i = 0; i < depth; ++i)
+    {
+        if (nest_objects)
+        {
+            BasicJsonType wrapper = BasicJsonType::object();
+            wrapper["x"] = std::move(v);
+            v = std::move(wrapper);
+        }
+        else
+        {
+            BasicJsonType wrapper = BasicJsonType::array();
+            wrapper.push_back(std::move(v));
+            v = std::move(wrapper);
+        }
+    }
+    return v;
+}
+} // namespace
+#endif
+
 /////////////////////////////////////////////////////////////////////
 // for #1647
 /////////////////////////////////////////////////////////////////////
@@ -569,7 +649,7 @@ TEST_CASE("regression tests 2")
    SECTION("issue #2067 - cannot serialize binary data to text JSON")
    {
        const std::array<unsigned char, 23> data = {{0x81, 0xA4, 0x64, 0x61, 0x74, 0x61, 0xC4, 0x0F, 0x33, 0x30, 0x30, 0x32, 0x33, 0x34, 0x30, 0x31, 0x30, 0x37, 0x30, 0x35, 0x30, 0x31, 0x30}};
-        const json j = json::from_msgpack(data.begin(), data.end());
+        const json j = json::from_msgpack(data.data(), data.size());
        // dump() is nodiscard; this only checks that dumping does not throw
        CHECK_NOTHROW(
            utils::ignore_return_value(
@@ -940,4 +1020,100 @@ TEST_CASE("regression test - excessive binary container size honors allow_except
    CHECK(json::from_cbor(std::vector<std::uint8_t> {0x9b, 0, 0, 0, 0, 0, 0, 0, 0x02}, true, false).is_discarded());
 }

+#if (defined(__cpp_exceptions) || defined(__EXCEPTIONS) || defined(_CPPUNWIND)) && !defined(JSON_NOEXCEPTION)
+TEST_CASE("regression test #5135 - destructor never allocates, even under memory pressure")
+{
+    // Before the fix, ~basic_json() flattened a nested array/object into a
+    // heap-allocated std::vector to avoid recursing; that allocation could
+    // itself throw bad_alloc, which escapes a noexcept destructor and
+    // terminates the program. destroy() no longer allocates anything, so
+    // none of the sections below ever observe fail_next_allocation being
+    // consumed: CHECK(fail_next_allocation) confirms it was never touched.
+
+    SECTION("the original report: a small, mixed array/object nest")
+    {
+        failing_allocator_allocations = 0;
+        failing_allocator_deallocations = 0;
+        {
+            failing_json j = failing_json::array(
+            {
+                failing_json::array({1, 2}),
+                failing_json::object({{"key", failing_json::array({3})}})
+            });
+            fail_next_allocation = true;
+        } // j is destroyed here, with every further allocation set to fail
+
+        CHECK(fail_next_allocation);
+        fail_next_allocation = false;
+        CHECK(failing_allocator_deallocations > 0);
+    }
+
+    SECTION("100000-deep nested array")
+    {
+        std::size_t allocations_before = 0;
+        {
+            failing_json j = make_deep_nest<failing_json>(100000, false);
+            allocations_before = failing_allocator_allocations;
+            fail_next_allocation = true;
+        }
+
+        CHECK(fail_next_allocation);
+        fail_next_allocation = false;
+        CHECK(failing_allocator_allocations == allocations_before);
+    }
+
+    SECTION("100000-deep nested object")
+    {
+        std::size_t allocations_before = 0;
+        {
+            failing_json j = make_deep_nest<failing_json>(100000, true);
+            allocations_before = failing_allocator_allocations;
+            fail_next_allocation = true;
+        }
+
+        CHECK(fail_next_allocation);
+        fail_next_allocation = false;
+        CHECK(failing_allocator_allocations == allocations_before);
+    }
+
+    SECTION("100000-deep nested ordered_json")
+    {
+        std::size_t allocations_before = 0;
+        {
+            failing_ordered_json j = make_deep_nest<failing_ordered_json>(100000, true);
+            allocations_before = failing_allocator_allocations;
+            fail_next_allocation = true;
+        }
+
+        CHECK(fail_next_allocation);
+        fail_next_allocation = false;
+        CHECK(failing_allocator_allocations == allocations_before);
+    }
+
+    SECTION("wide and deep: 1000 arrays of 1000 elements, each a small nested object")
+    {
+        std::size_t allocations_before = 0;
+        {
+            failing_json wide = failing_json::array();
+            for (std::size_t i = 0; i < 1000; ++i)
+            {
+                failing_json inner = failing_json::array();
+                for (std::size_t k = 0; k < 1000; ++k)
+                {
+                    inner.push_back(failing_json::object({{"a", 1}, {"b", failing_json::array({1, 2, 3})}}));
+                }
+                wide.push_back(std::move(inner));
+            }
+
+            allocations_before = failing_allocator_allocations;
+            fail_next_allocation = true;
+        }
+
+        CHECK(fail_next_allocation);
+        fail_next_allocation = false;
+        CHECK(failing_allocator_allocations == allocations_before);
+    }
+}
+#endif
+
 DOCTEST_CLANG_SUPPRESS_WARNING_POP
@@ -8,14 +8,6 @@

 #include "doctest_compatibility.h"

-// capture whether JSON_DELETE_DEPRECATED_FUNCTIONS was enabled on the command
-// line *before* including json.hpp, since the library #undefs it once the header
-// has been fully processed (see include/nlohmann/detail/macro_unscope.hpp); the
-// tests of deprecated functions are skipped if these functions are deleted
-#if defined(JSON_DELETE_DEPRECATED_FUNCTIONS) && (JSON_DELETE_DEPRECATED_FUNCTIONS == 1)
-    #define JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
-#endif
-
 #include <nlohmann/json.hpp>
 using nlohmann::json;

@@ -56,7 +48,6 @@ TEST_CASE("serialization")
        }
    }

-#ifndef JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
    SECTION("operator>>")
    {
        SECTION("no given width")
@@ -88,7 +79,6 @@ TEST_CASE("serialization")
                  "[\n\t\"foo\",\n\t1,\n\t2,\n\t3,\n\tfalse,\n\t{\n\t\t\"one\": 1\n\t}\n]");
        }
    }
-#endif

    SECTION("dump")
    {
@@ -8,14 +8,6 @@

 #include "doctest_compatibility.h"

-// capture whether JSON_DELETE_DEPRECATED_FUNCTIONS was enabled on the command
-// line *before* including json.hpp, since the library #undefs it once the header
-// has been fully processed (see include/nlohmann/detail/macro_unscope.hpp); the
-// tests of deprecated functions are skipped if these functions are deleted
-#if defined(JSON_DELETE_DEPRECATED_FUNCTIONS) && (JSON_DELETE_DEPRECATED_FUNCTIONS == 1)
-    #define JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
-#endif
-
 #include <nlohmann/json.hpp>
 using nlohmann::json;

@@ -2220,10 +2212,8 @@ TEST_CASE("UBJSON input that cannot be read is discarded by every overload")
    CHECK_THROWS_AS(_ = json::from_ubjson(input.begin(), input.end()), json::parse_error&);
    CHECK(json::from_ubjson(input, true, false).is_discarded());
    CHECK(json::from_ubjson(input.begin(), input.end(), true, false).is_discarded());
-#ifndef JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
    CHECK(json::from_ubjson(input.data(), input.size(), true, false).is_discarded());
    CHECK(json::from_ubjson({input.data(), input.size()}, true, false).is_discarded());
-#endif
 }

 TEST_CASE("UBJSON SAX parsing stops at every event")
@@ -2971,14 +2961,12 @@ TEST_CASE("UBJSON roundtrips" * doctest::skip())
                CHECK(j1 == j2);
            }

-#ifndef JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
            {
                INFO_WITH_TEMP(filename + ": uint8_t* and size");
                json j2;
                CHECK_NOTHROW(j2 = json::from_ubjson({packed.data(), packed.size()}));
                CHECK(j1 == j2);
            }
-#endif

            {
                INFO_WITH_TEMP(filename + ": output to output adapters");
Author	SHA1	Message	Date
Niels LohmannandMichael Sam	77fccaf0e7	Test that destroy() performs no allocation, even under memory pressure Update the #4842 regression test: it used to check that destroying a nested array/object made at least one allocation through the provided allocator (the old flattening stack). Now that destroy() does not allocate at all, assert the opposite: zero allocations, deallocations only. Rework the #5135 regression test to use a dedicated failing/counting allocator instead of overriding the process-wide ::operator new and ::operator delete, which affected every allocation in the whole unit-regression2 binary rather than just the values under test. Keep the original small repro as one case, and add deep (100000 levels) and wide-and-deep nested array/object/ordered_json cases, all destroyed while every further allocation is made to fail: the destructor must complete without allocating, without throwing, and without leaking. Co-authored-by: Michael Sam <9461037+michaelsam94@users.noreply.github.com> Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-10-04 22:22:17 +02:00
Niels LohmannandMichael Sam	d0278f8983	Make json_value::destroy() non-recursive and allocation-free destroy() used to flatten a nested array/object into a heap-allocated std::vector to avoid recursing per nesting level. That vector could itself throw bad_alloc under memory pressure, and since it now used the basic_json's own allocator (#4842), a failing allocator supplied by the caller made this more likely, not less. An exception thrown from inside ~basic_json(), which is noexcept, terminates the program (#5135). Replace the vector-based stack with a pointer-reversal walk that visits the tree without recursing per level and without allocating anything: cur is the array/object currently being emptied, prev is its parent (or null at the top). A parent's last child slot doubles as storage for that parent's own parent link while we are below it, so no extra memory is needed. A child is only ever removed once it is a scalar or an empty array/object, which neither allocates nor recurses more than one level deep. take() moves m_data between these locals directly, bypassing set_parents()/assert_invariant() (the former is O(#children) per call under JSON_DIAGNOSTICS, which would make the walk quadratic otherwise). This also removes the std::vector<basic_json, allocator_type> stack added by #4842, so the extra allocations it introduced disappear along with it. Co-authored-by: Michael Sam <9461037+michaelsam94@users.noreply.github.com> Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-10-04 22:22:06 +02:00
Michael Sam	ae43e8ded4	Fix allocation failure during JSON destruction Signed-off-by: Michael Sam <michaelsam94@users.noreply.github.com> Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-10-04 18:11:25 +02:00
Niels Lohmann	5185181552	Test that the destructor uses the provided allocator Adds a regression test for #4842: destroying a nested array or object must allocate its temporary stack through the basic_json allocator, not std::allocator. Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-10-04 18:00:22 +02:00
Vesko Karaganev	13d555538b	Use the provided allocator in destroy() (#4842 ) Uses the provided allocator to allocate the stack used to avoid recursion in the destroy() implementation used by ~basic_json. Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-10-04 18:00:21 +02:00