From b88e5f9107f5fc7f74fc644c26db4751f85ccddc Mon Sep 17 00:00:00 2001
From: Niels Lohmann <mail@nlohmann.me>
Date: Mon, 28 Sep 2026 21:26:39 +0200
Subject: [PATCH] Keep the behavior-changing configuration readable after
 json.hpp

json.hpp undefines JSON_STRICT_NUL_HANDLING and
JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON at its end. Code that builds on
the library after it, such as the planned json_view.hpp, reads them from
detail::abi_config instead. The constants live in the ABI namespace, which
already encodes both settings, so they always match the basic_json in use.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---
 BUILD.bazel                            |  1 +
 include/nlohmann/detail/abi_config.hpp | 34 +++++++++++++++++++++++
 include/nlohmann/json.hpp              |  1 +
 single_include/nlohmann/json.hpp       | 37 ++++++++++++++++++++++++++
 4 files changed, 73 insertions(+)
 create mode 100644 include/nlohmann/detail/abi_config.hpp

diff --git a/BUILD.bazel b/BUILD.bazel
index 03f73fa92..61ed0c753 100644
--- a/BUILD.bazel
+++ b/BUILD.bazel
@@ -20,6 +20,7 @@ cc_library(
     hdrs = [
         "include/nlohmann/adl_serializer.hpp",
         "include/nlohmann/byte_container_with_subtype.hpp",
+        "include/nlohmann/detail/abi_config.hpp",
         "include/nlohmann/detail/abi_macros.hpp",
         "include/nlohmann/detail/bit_ops.hpp",
         "include/nlohmann/detail/conversions/from_json.hpp",
diff --git a/include/nlohmann/detail/abi_config.hpp b/include/nlohmann/detail/abi_config.hpp
new file mode 100644
index 000000000..0e99c81ad
--- /dev/null
+++ b/include/nlohmann/detail/abi_config.hpp
@@ -0,0 +1,34 @@
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  JSON for Modern C++
+// |  |  |__   |  |  | | | |  version 3.12.0
+// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
+//
+// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
+// SPDX-License-Identifier: MIT
+
+#pragma once
+
+#include <nlohmann/detail/abi_macros.hpp>
+
+NLOHMANN_JSON_NAMESPACE_BEGIN
+namespace detail
+{
+
+/*!
+@brief the configuration macros that change the library's behavior
+
+json.hpp undefines these macros at its end (see macro_unscope.hpp), so code
+that builds on the library after it (json_view.hpp) reads them here. Like the
+macros, they are part of the ABI namespace, so they always match the
+basic_json they are used with.
+*/
+struct abi_config
+{
+    /// JSON_STRICT_NUL_HANDLING: a null byte is an error, not the end of input
+    static constexpr bool strict_nul_handling = JSON_STRICT_NUL_HANDLING != 0;
+    /// JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON
+    static constexpr bool legacy_discarded_value_comparison = JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON != 0;
+};
+
+}  // namespace detail
+NLOHMANN_JSON_NAMESPACE_END
diff --git a/include/nlohmann/json.hpp b/include/nlohmann/json.hpp
index 78c4e4f62..e72b02c8d 100644
--- a/include/nlohmann/json.hpp
+++ b/include/nlohmann/json.hpp
@@ -45,6 +45,7 @@
 
 #include <nlohmann/adl_serializer.hpp>
 #include <nlohmann/byte_container_with_subtype.hpp>
+#include <nlohmann/detail/abi_config.hpp>
 #include <nlohmann/detail/conversions/from_json.hpp>
 #include <nlohmann/detail/conversions/to_json.hpp>
 #include <nlohmann/detail/exceptions.hpp>
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index 3974f6add..6d58cfbb8 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -7236,6 +7236,43 @@ class byte_container_with_subtype : public BinaryType
 
 NLOHMANN_JSON_NAMESPACE_END
 
+// #include <nlohmann/detail/abi_config.hpp>
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  JSON for Modern C++
+// |  |  |__   |  |  | | | |  version 3.12.0
+// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
+//
+// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
+// SPDX-License-Identifier: MIT
+
+
+
+// #include <nlohmann/detail/abi_macros.hpp>
+
+
+NLOHMANN_JSON_NAMESPACE_BEGIN
+namespace detail
+{
+
+/*!
+@brief the configuration macros that change the library's behavior
+
+json.hpp undefines these macros at its end (see macro_unscope.hpp), so code
+that builds on the library after it (json_view.hpp) reads them here. Like the
+macros, they are part of the ABI namespace, so they always match the
+basic_json they are used with.
+*/
+struct abi_config
+{
+    /// JSON_STRICT_NUL_HANDLING: a null byte is an error, not the end of input
+    static constexpr bool strict_nul_handling = JSON_STRICT_NUL_HANDLING != 0;
+    /// JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON
+    static constexpr bool legacy_discarded_value_comparison = JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON != 0;
+};
+
+}  // namespace detail
+NLOHMANN_JSON_NAMESPACE_END
+
 // #include <nlohmann/detail/conversions/from_json.hpp>
 
 // #include <nlohmann/detail/conversions/to_json.hpp>