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Deprecation warning for operator== when using ordered_json when building with clang #5288

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#5289
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Deprecation warning for operator== when using ordered_json when building with clang#5288
#5289
Labels
confirmedkind: bugsolution: proposed fixa fix for the issue has been proposed and waits for confirmation
Milestone
Release 3.13.0

Description

@Jezza2
Jezza2
opened on Jul 22, 2026

Description

When building with clangd and using ordered_json, calling .at(ordered_json::json_pointer{}) produces a deprecation warning for operator==(std::string, std::string). No warning is displayed with GCC.

Reproduction steps

Build the below code sample using clang.

Expected vs. actual results

Either the .at() overload for ordered_json::json_pointer should be marked deprecated, or there should be no deprecation warning shown. Behaviour should also be consistent across compilers.

Minimal code example

#include "json/json.hpp"

using json = nlohmann::ordered_json;

int main()
{
    const json j = R"({"hi":"nlohmann"})"_json;
    j.at(json::json_pointer{"/hi"});
}

Error messages

In file included from /workspaces/scmessage-refactor/test.cpp:1:
In file included from /workspaces/scmessage-refactor/thirdparty/json/json.hpp:23:
In file included from /usr/lib/gcc/x86_64-linux-gnu/14/../../../../include/c++/14/functional:49:
/usr/lib/gcc/x86_64-linux-gnu/14/../../../../include/c++/14/bits/stl_function.h:497:43: warning: 'operator==' is deprecated: Since 3.11.2; use operator==(json_pointer, json_pointer) [-Wdeprecated-declarations]
  497 |         noexcept(noexcept(std::forward<_Tp>(__t) == std::forward<_Up>(__u)))
      |                                                  ^
/workspaces/scmessage-refactor/thirdparty/json/json.hpp:4108:10: note: in instantiation of exception specification for 'operator()<std::basic_string<char>, nlohmann::json_pointer<std::basic_string<char>>>' requested here
 4108 | decltype(std::declval<Compare>()(std::declval<A>(), std::declval<B>())),
      |          ^
/workspaces/scmessage-refactor/thirdparty/json/json.hpp:4120:31: note: during template argument deduction for class template partial specialization 'is_comparable<Compare, A, B, void_t<decltype(std::declval<Compare>()(std::declval<A>(), std::declval<B>())), decltype(std::declval<Compare>()(std::declval<B>(), std::declval<A>()))>>' [with Compare = std::equal_to<void>, A = std::basic_string<char>, B = nlohmann::json_pointer<std::basic_string<char>>]
 4120 |                               is_comparable<Comparator, ObjectKeyType, KeyTypeCVRef>::value
      |                               ^
/workspaces/scmessage-refactor/thirdparty/json/json.hpp:4120:31: note: in instantiation of template class 'nlohmann::detail::is_comparable<std::equal_to<void>, std::basic_string<char>, nlohmann::json_pointer<std::basic_string<char>>>' requested here
/workspaces/scmessage-refactor/thirdparty/json/json.hpp:4138:5: note: in instantiation of template type alias 'is_usable_as_key_type' requested here
 4138 |     is_usable_as_key_type<typename BasicJsonType::object_comparator_t,
      |     ^
/workspaces/scmessage-refactor/thirdparty/json/json.hpp:22044:26: note: in instantiation of template type alias 'is_usable_as_basic_json_key_type' requested here
 22044 |                  detail::is_usable_as_basic_json_key_type<basic_json_t, KeyType>::value, int> = 0>
       |                          ^
/workspaces/scmessage-refactor/thirdparty/json/json.hpp:22045:15: note: while substituting prior template arguments into non-type template parameter [with KeyType = json::json_pointer]
 22045 |     reference at(KeyType && key)
       |               ^~~~~~~~~~~~~~~~~~
 22046 |     {
       |     ~
 22047 |         // at only works for objects
       |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 22048 |         if (JSON_HEDLEY_UNLIKELY(!is_object()))
       |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 22049 |         {
       |         ~
 22050 |             JSON_THROW(type_error::create(304, detail::concat("cannot use at() with ", type_name()), this));
       |             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 22051 |         }
       |         ~
 22052 | 
 22053 |         auto it = m_data.m_value.object->find(std::forward<KeyType>(key));
       |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 22054 |         if (it == m_data.m_value.object->end())
       |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 22055 |         {
       |         ~
 22056 |             JSON_THROW(out_of_range::create(403, detail::concat("key '", string_t(std::forward<KeyType>(key)), "' not found"), this));
       |             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 22057 |         }
       |         ~
 22058 |         return set_parent(it->second);
       |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 22059 |     }
       |     ~
/workspaces/scmessage-refactor/test.cpp:8:7: note: while substituting deduced template arguments into function template 'at' [with KeyType = json::json_pointer, $1 = (no value)]
    8 |     j.at(json::json_pointer{"/hi"});
      |       ^
/workspaces/scmessage-refactor/thirdparty/json/json.hpp:15453:13: note: 'operator==' has been explicitly marked deprecated here
 15453 | inline bool operator==(const StringType& lhs,
       |             ^
In file included from /workspaces/scmessage-refactor/test.cpp:1:
In file included from /workspaces/scmessage-refactor/thirdparty/json/json.hpp:23:
In file included from /usr/lib/gcc/x86_64-linux-gnu/14/../../../../include/c++/14/functional:49:
/usr/lib/gcc/x86_64-linux-gnu/14/../../../../include/c++/14/bits/stl_function.h:497:43: warning: 'operator==<std::basic_string<char>, std::basic_string<char>>' is deprecated: Since 3.11.2; use operator==(json_pointer, json_pointer) [-Wdeprecated-declarations]
  497 |         noexcept(noexcept(std::forward<_Tp>(__t) == std::forward<_Up>(__u)))
      |                                                  ^
/workspaces/scmessage-refactor/thirdparty/json/json.hpp:15452:1: note: 'operator==<std::basic_string<char>, std::basic_string<char>>' has been explicitly marked deprecated here
 15452 | JSON_HEDLEY_DEPRECATED_FOR(3.11.2, operator==(json_pointer, json_pointer))
       | ^
/workspaces/scmessage-refactor/thirdparty/json/json.hpp:1376:75: note: expanded from macro 'JSON_HEDLEY_DEPRECATED_FOR'
 1376 |     #define JSON_HEDLEY_DEPRECATED_FOR(since, replacement) __attribute__((__deprecated__("Since " #since "; use " #replacement)))
      |                                                                           ^
In file included from /workspaces/scmessage-refactor/test.cpp:1:
In file included from /workspaces/scmessage-refactor/thirdparty/json/json.hpp:23:
In file included from /usr/lib/gcc/x86_64-linux-gnu/14/../../../../include/c++/14/functional:49:
/usr/lib/gcc/x86_64-linux-gnu/14/../../../../include/c++/14/bits/stl_function.h:497:43: warning: 'operator==' is deprecated: Since 3.11.2; use operator==(json_pointer, json_pointer) [-Wdeprecated-declarations]
  497 |         noexcept(noexcept(std::forward<_Tp>(__t) == std::forward<_Up>(__u)))
      |                                                  ^
/workspaces/scmessage-refactor/thirdparty/json/json.hpp:4109:10: note: in instantiation of exception specification for 'operator()<nlohmann::json_pointer<std::basic_string<char>>, std::basic_string<char>>' requested here
 4109 | decltype(std::declval<Compare>()(std::declval<B>(), std::declval<A>()))
      |          ^
/workspaces/scmessage-refactor/thirdparty/json/json.hpp:4120:31: note: during template argument deduction for class template partial specialization 'is_comparable<Compare, A, B, void_t<decltype(std::declval<Compare>()(std::declval<A>(), std::declval<B>())), decltype(std::declval<Compare>()(std::declval<B>(), std::declval<A>()))>>' [with Compare = std::equal_to<void>, A = std::basic_string<char>, B = nlohmann::json_pointer<std::basic_string<char>>]
 4120 |                               is_comparable<Comparator, ObjectKeyType, KeyTypeCVRef>::value
      |                               ^
/workspaces/scmessage-refactor/thirdparty/json/json.hpp:4120:31: note: in instantiation of template class 'nlohmann::detail::is_comparable<std::equal_to<void>, std::basic_string<char>, nlohmann::json_pointer<std::basic_string<char>>>' requested here
/workspaces/scmessage-refactor/thirdparty/json/json.hpp:4138:5: note: in instantiation of template type alias 'is_usable_as_key_type' requested here
 4138 |     is_usable_as_key_type<typename BasicJsonType::object_comparator_t,
      |     ^
/workspaces/scmessage-refactor/thirdparty/json/json.hpp:22044:26: note: in instantiation of template type alias 'is_usable_as_basic_json_key_type' requested here
 22044 |                  detail::is_usable_as_basic_json_key_type<basic_json_t, KeyType>::value, int> = 0>
       |                          ^
/workspaces/scmessage-refactor/thirdparty/json/json.hpp:22045:15: note: while substituting prior template arguments into non-type template parameter [with KeyType = json::json_pointer]
 22045 |     reference at(KeyType && key)
       |               ^~~~~~~~~~~~~~~~~~
 22046 |     {
       |     ~
 22047 |         // at only works for objects
       |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 22048 |         if (JSON_HEDLEY_UNLIKELY(!is_object()))
       |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 22049 |         {
       |         ~
 22050 |             JSON_THROW(type_error::create(304, detail::concat("cannot use at() with ", type_name()), this));
       |             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 22051 |         }
       |         ~
 22052 | 
 22053 |         auto it = m_data.m_value.object->find(std::forward<KeyType>(key));
       |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 22054 |         if (it == m_data.m_value.object->end())
       |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 22055 |         {
       |         ~
 22056 |             JSON_THROW(out_of_range::create(403, detail::concat("key '", string_t(std::forward<KeyType>(key)), "' not found"), this));
       |             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 22057 |         }
       |         ~
 22058 |         return set_parent(it->second);
       |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 22059 |     }
       |     ~
/workspaces/scmessage-refactor/test.cpp:8:7: note: while substituting deduced template arguments into function template 'at' [with KeyType = json::json_pointer, $1 = (no value)]
    8 |     j.at(json::json_pointer{"/hi"});
      |       ^
/workspaces/scmessage-refactor/thirdparty/json/json.hpp:15444:13: note: 'operator==' has been explicitly marked deprecated here
 15444 | inline bool operator==(const json_pointer<RefStringTypeLhs>& lhs,
       |             ^
In file included from /workspaces/scmessage-refactor/test.cpp:1:
In file included from /workspaces/scmessage-refactor/thirdparty/json/json.hpp:23:
In file included from /usr/lib/gcc/x86_64-linux-gnu/14/../../../../include/c++/14/functional:49:
/usr/lib/gcc/x86_64-linux-gnu/14/../../../../include/c++/14/bits/stl_function.h:497:43: warning: 'operator==<std::basic_string<char>, std::basic_string<char>>' is deprecated: Since 3.11.2; use operator==(json_pointer, json_pointer) [-Wdeprecated-declarations]
  497 |         noexcept(noexcept(std::forward<_Tp>(__t) == std::forward<_Up>(__u)))
      |                                                  ^
/workspaces/scmessage-refactor/thirdparty/json/json.hpp:15443:1: note: 'operator==<std::basic_string<char>, std::basic_string<char>>' has been explicitly marked deprecated here
 15443 | JSON_HEDLEY_DEPRECATED_FOR(3.11.2, operator==(json_pointer, json_pointer))
       | ^
/workspaces/scmessage-refactor/thirdparty/json/json.hpp:1376:75: note: expanded from macro 'JSON_HEDLEY_DEPRECATED_FOR'
 1376 |     #define JSON_HEDLEY_DEPRECATED_FOR(since, replacement) __attribute__((__deprecated__("Since " #since "; use " #replacement)))
      |                                                                           ^
4 warnings generated.

Compiler and operating system

Debian 13, Clang 19.1.7, GCC 14.2.0

Library version

3.12.0

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