mirror of
https://github.com/nlohmann/json.git
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Jonas Greitemann
85839d7408
`std::from_chars` is locale-independent and thus avoids the TOCTOU issue #5198 when it's available. This commit introduces a `from_chars` utility in the `detail` namespace which merely wraps `std::from_chars` if it is available and emulates its API and behavior using the `strto*` family of functions when it is not. As of this commit, the `strto*`-based fallback is still locale-dependent and only matches `std::from_chars` when the "C" locale is used. Availability of `std::from_chars` for floating point numbers is varied. For instance, as of libc++ 22, `std::from_chars` for `long double` isn't supported and, consequently, the feature-test macro `__cpp_lib_to_chars` is not set, while the overloads for `float` and `double` are available. To avoid complicating matters further, the feature-test macro is taken as the authoritative indicator for (full) `std::from_chars` support and the fallback is used otherwise. If `std::from_chars` is available, our wrapper additionally tweaks its output in the case of floating-point out-of-range results. The behavior in this case is poorly (under-)specified and existing implementations do not agree. The wrapper's tweaks are intended to ensure consistent behavior across all toolchains in this edge case. In practice, this should only take effect when parsing out-of-range floats on libstdc++. The unit tests for the `from_chars` helper are intentionally compiled in both C++11 and C++17 modes. This ensures that the test expectations align with the actual behavior we're trying to model. The tests are not aiming to cover all of floating-point parsing comprehensively, as `std::from_chars` is specified to behave mostly the same as `strto*` and instead focuses on the edge cases where the two differ: - leading whitespace is not tolerated - `+` sign is not allowed (outside of the exponent) - out-parameter is left unchanged in case of `invalid_argument` and integral `result_out_of_range` errors Signed-off-by: Jonas Greitemann <jgreitemann@gmail.com>
51 lines
1.4 KiB
C++
51 lines
1.4 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_FROM_CHARS
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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_STD_FORMAT
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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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