mirror of
https://github.com/nlohmann/json.git
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SamareshSingh
62f3b41b30
* fix: treat single-element brace-init as copy/move
When passing a json value using brace initialization with a single element
(e.g., `json j{someObj}` or `foo({someJson})`), C++ always prefers the
initializer_list constructor over the copy/move constructor. This caused
the value to be unexpectedly wrapped in a single-element array.
This bug was previously compiler-dependent (GCC wrapped, Clang did not),
but Clang 20 started matching GCC behavior, making it a universal issue.
Fix: In the initializer_list constructor, when type deduction is enabled
and the list has exactly one element, copy/move it directly instead of
creating a single-element array.
Before:
json obj = {{"key", 1}};
json j{obj}; // -> [{"key":1}] (wrong: array)
foo({obj}); // -> [{"key":1}] (wrong: array)
After:
json j{obj}; // -> {"key":1} (correct: copy)
foo({obj}); // -> {"key":1} (correct: copy)
To explicitly create a single-element array, use json::array({value}).
Fixes the issue #5074
Signed-off-by: Samaresh Kumar Singh <ssam3003@gmail.com>
* fix: regenerate amalgamated single_include/nlohmann/json.hpp
- Add missing comment from include/nlohmann/json.hpp explaining the
single-element brace-init fix (issue #5074)
- Fix extra 4-space indentation in embedded json_fwd.hpp section
Regenerated by running: make amalgamate
Signed-off-by: Samaresh Kumar Singh <ssam3003@gmail.com>
* Revert brace-init semantics change and fix amalgamation
The single-element brace-init change was a breaking change that cannot be accepted upstream. Reverted all related source, test, and doc changes, then regenerated single_include with correct indentation to pass the amalgamation CI check.
Signed-off-by: Samaresh Kumar Singh <ssam3003@gmail.com>
* Fix: add JSON_BRACE_INIT_COPY_SEMANTICS opt-in macro for issue #5074
Single-element brace initialization wrapping in an array cannot be fixed without breaking existing code. Added JSON_BRACE_INIT_COPY_SEMANTICS as an opt-in macro (default 0) so users can enable copy/move semantics for single-element brace init without affecting anyone relying on the current behavior.
Signed-off-by: Samaresh Kumar Singh <ssam3003@gmail.com>
* docs: add dedicated macro page and CI test target for JSON_BRACE_INIT_COPY_SEMANTICS
Signed-off-by: Samaresh Kumar Singh <ssam3003@gmail.com>
* fix: remove compiler-dependent assertions from #5074 regression test
Signed-off-by: Samaresh Kumar Singh <ssam3003@gmail.com>
* fix: use defined() guard for JSON_BRACE_INIT_COPY_SEMANTICS to satisfy -Wundef
Signed-off-by: Samaresh Kumar Singh <ssam3003@gmail.com>
* docs: fix section name in json_brace_init_copy_semantics.md to pass style check
Signed-off-by: Samaresh Kumar Singh <ssam3003@gmail.com>
* docs: move Default definition section before Notes to fix style check order
Signed-off-by: Samaresh Kumar Singh <ssam3003@gmail.com>
---------
Signed-off-by: Samaresh Kumar Singh <ssam3003@gmail.com>
49 lines
1.3 KiB
C++
49 lines
1.3 KiB
C++
// __ _____ _____ _____
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// __| | __| | | | JSON for Modern C++
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// | | |__ | | | | | | version 3.12.0
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// |_____|_____|_____|_|___| https://github.com/nlohmann/json
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//
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// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
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// SPDX-License-Identifier: MIT
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#pragma once
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// restore clang diagnostic settings
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#if defined(__clang__)
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#pragma clang diagnostic pop
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#endif
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// clean up
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#undef JSON_ASSERT
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#undef JSON_INTERNAL_CATCH
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#undef JSON_THROW
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#undef JSON_PRIVATE_UNLESS_TESTED
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#undef NLOHMANN_BASIC_JSON_TPL_DECLARATION
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#undef NLOHMANN_BASIC_JSON_TPL
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#undef JSON_EXPLICIT
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#undef NLOHMANN_CAN_CALL_STD_FUNC_IMPL
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#undef JSON_INLINE_VARIABLE
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#undef JSON_NO_UNIQUE_ADDRESS
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#undef JSON_DISABLE_ENUM_SERIALIZATION
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#undef JSON_USE_GLOBAL_UDLS
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#undef JSON_BRACE_INIT_COPY_SEMANTICS
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#ifndef JSON_TEST_KEEP_MACROS
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#undef JSON_CATCH
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#undef JSON_TRY
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#undef JSON_HAS_CPP_11
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#undef JSON_HAS_CPP_14
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#undef JSON_HAS_CPP_17
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#undef JSON_HAS_CPP_20
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#undef JSON_HAS_CPP_23
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#undef JSON_HAS_CPP_26
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#undef JSON_HAS_FILESYSTEM
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#undef JSON_HAS_EXPERIMENTAL_FILESYSTEM
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#undef JSON_HAS_THREE_WAY_COMPARISON
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#undef JSON_HAS_RANGES
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#undef JSON_HAS_STATIC_RTTI
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#undef JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON
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#endif
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#include <nlohmann/thirdparty/hedley/hedley_undef.hpp>
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