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[libcxx][libc] Hand in Hand PoC with from_chars
Implements std::from_chars for float and double. The implementation uses LLVM-libc to do the real parsing. Since this is the first time libc++ uses LLVM-libc there is a bit of additional infrastructure code. The patch is based on the [RFC] Project Hand In Hand (LLVM-libc/libc++ code sharing) https://discourse.llvm.org/t/rfc-project-hand-in-hand-llvm-libc-libc-code-sharing/77701
1 parent 2c93598 commit 967de3d

36 files changed

+2365
-21
lines changed

‎libc/shared/fp_bits.h

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//===-- Floating point number utils -----------------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_LIBC_SHARED_FP_BITS_H
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#define LLVM_LIBC_SHARED_FP_BITS_H
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#include "src/__support/FPUtil/FPBits.h"
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namespace LIBC_NAMESPACE_DECL {
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namespace shared {
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using fputil::FPBits;
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} // namespace shared
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} // namespace LIBC_NAMESPACE_DECL
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#endif // LLVM_LIBC_SHARED_FP_BITS_H

‎libc/shared/str_to_float.h

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//===-- String to float conversion utils ------------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_LIBC_SHARED_STR_TO_FLOAT_H
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#define LLVM_LIBC_SHARED_STR_TO_FLOAT_H
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12+
#include "src/__support/str_to_float.h"
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namespace LIBC_NAMESPACE_DECL {
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namespace shared {
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using internal::ExpandedFloat;
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using internal::FloatConvertReturn;
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using internal::RoundDirection;
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using internal::binary_exp_to_float;
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using internal::decimal_exp_to_float;
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} // namespace shared
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} // namespace LIBC_NAMESPACE_DECL
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#endif // LLVM_LIBC_SHARED_STR_TO_FLOAT_H

‎libc/shared/str_to_integer.h

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//===-- String to int conversion utils --------------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_LIBC_SHARED_STR_TO_INTEGER_H
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#define LLVM_LIBC_SHARED_STR_TO_INTEGER_H
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#include "src/__support/str_to_integer.h"
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namespace LIBC_NAMESPACE_DECL {
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namespace shared {
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using LIBC_NAMESPACE::StrToNumResult;
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using internal::strtointeger;
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} // namespace shared
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} // namespace LIBC_NAMESPACE_DECL
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#endif // LLVM_LIBC_SHARED_STR_TO_INTEGER_H

‎libc/src/__support/FPUtil/FPBits.h

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//
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//===----------------------------------------------------------------------===//
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// -----------------------------------------------------------------------------
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// **** WARNING ****
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// This file is shared with libc++. You should also be careful when adding
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// dependencies to this file, since it needs to build for all libc++ targets.
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// -----------------------------------------------------------------------------
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#ifndef LLVM_LIBC_SRC___SUPPORT_FPUTIL_FPBITS_H
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#define LLVM_LIBC_SRC___SUPPORT_FPUTIL_FPBITS_H
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static_assert(cpp::always_false<UnqualT>, "Unsupported type");
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}
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// -----------------------------------------------------------------------------
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// **** WARNING ****
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// This interface is shared with libc++, if you change this interface you need
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// to update it in both libc and libc++. You should also be careful when adding
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// dependencies to this file, since it needs to build for all libc++ targets.
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// -----------------------------------------------------------------------------
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// A generic class to manipulate C++ floating point formats.
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// It derives its functionality to FPRepImpl above.
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template <typename T>

‎libc/src/__support/high_precision_decimal.h

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//
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//===----------------------------------------------------------------------===//
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// -----------------------------------------------------------------------------
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// **** WARNING ****
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// This file is shared with libc++. You should also be careful when adding
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// dependencies to this file, since it needs to build for all libc++ targets.
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// -----------------------------------------------------------------------------
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#ifndef LLVM_LIBC_SRC___SUPPORT_HIGH_PRECISION_DECIMAL_H
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#define LLVM_LIBC_SRC___SUPPORT_HIGH_PRECISION_DECIMAL_H
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char const *power_of_five;
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};
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// -----------------------------------------------------------------------------
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// **** WARNING ****
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// This interface is shared with libc++, if you change this interface you need
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// to update it in both libc and libc++.
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// -----------------------------------------------------------------------------
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// This is used in both this file and in the main str_to_float.h.
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// TODO: Figure out where to put this.
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enum class RoundDirection { Up, Down, Nearest };

‎libc/src/__support/str_to_float.h

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//
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//===----------------------------------------------------------------------===//
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// -----------------------------------------------------------------------------
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// **** WARNING ****
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// This file is shared with libc++. You should also be careful when adding
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// dependencies to this file, since it needs to build for all libc++ targets.
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// -----------------------------------------------------------------------------
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#ifndef LLVM_LIBC_SRC___SUPPORT_STR_TO_FLOAT_H
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#define LLVM_LIBC_SRC___SUPPORT_STR_TO_FLOAT_H
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namespace LIBC_NAMESPACE_DECL {
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namespace internal {
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// -----------------------------------------------------------------------------
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// **** WARNING ****
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// This interface is shared with libc++, if you change this interface you need
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// to update it in both libc and libc++.
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// -----------------------------------------------------------------------------
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template <class T> struct ExpandedFloat {
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typename fputil::FPBits<T>::StorageType mantissa;
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int32_t exponent;
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};
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// -----------------------------------------------------------------------------
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// **** WARNING ****
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// This interface is shared with libc++, if you change this interface you need
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// to update it in both libc and libc++.
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// -----------------------------------------------------------------------------
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template <class T> struct FloatConvertReturn {
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ExpandedFloat<T> num = {0, 0};
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int error = 0;
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return -(309 + 15 + 20);
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}
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// -----------------------------------------------------------------------------
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// **** WARNING ****
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// This interface is shared with libc++, if you change this interface you need
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// to update it in both libc and libc++.
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// -----------------------------------------------------------------------------
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// Takes a mantissa and base 10 exponent and converts it into its closest
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// floating point type T equivalient. First we try the Eisel-Lemire algorithm,
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// then if that fails then we fall back to a more accurate algorithm for
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return output;
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}
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// -----------------------------------------------------------------------------
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// **** WARNING ****
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// This interface is shared with libc++, if you change this interface you need
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// to update it in both libc and libc++.
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// -----------------------------------------------------------------------------
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// Takes a mantissa and base 2 exponent and converts it into its closest
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// floating point type T equivalient. Since the exponent is already in the right
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// form, this is mostly just shifting and rounding. This is used for hexadecimal

‎libc/src/__support/str_to_integer.h

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//
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//===----------------------------------------------------------------------===//
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// -----------------------------------------------------------------------------
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// **** WARNING ****
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// This file is shared with libc++. You should also be careful when adding
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// dependencies to this file, since it needs to build for all libc++ targets.
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// -----------------------------------------------------------------------------
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#ifndef LLVM_LIBC_SRC___SUPPORT_STR_TO_INTEGER_H
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#define LLVM_LIBC_SRC___SUPPORT_STR_TO_INTEGER_H
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return 10;
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}
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// -----------------------------------------------------------------------------
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// **** WARNING ****
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// This interface is shared with libc++, if you change this interface you need
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// to update it in both libc and libc++.
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// -----------------------------------------------------------------------------
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// Takes a pointer to a string and the base to convert to. This function is used
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// as the backend for all of the string to int functions.
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template <class T>

‎libc/src/__support/str_to_num_result.h

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//
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//===----------------------------------------------------------------------===//
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// -----------------------------------------------------------------------------
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// **** WARNING ****
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// This file is shared with libc++. You should also be careful when adding
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// dependencies to this file, since it needs to build for all libc++ targets.
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// -----------------------------------------------------------------------------
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#ifndef LLVM_LIBC_SRC___SUPPORT_STR_TO_NUM_RESULT_H
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#define LLVM_LIBC_SRC___SUPPORT_STR_TO_NUM_RESULT_H
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namespace LIBC_NAMESPACE_DECL {
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// -----------------------------------------------------------------------------
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// **** WARNING ****
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// This interface is shared with libc++, if you change this interface you need
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// to update it in both libc and libc++.
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// -----------------------------------------------------------------------------
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template <typename T> struct StrToNumResult {
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T value;
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int error;

‎libcxx/docs/Status/Cxx17Papers.csv

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"`P0394R4 <https://wg21.link/P0394R4>`__","Hotel Parallelifornia: terminate() for Parallel Algorithms Exception Handling","2016-06 (Oulu)","|Complete|","17.0",""
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"","","","","",""
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"`P0003R5 <https://wg21.link/P0003R5>`__","Removing Deprecated Exception Specifications from C++17","2016-11 (Issaquah)","|Complete|","5.0",""
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"`P0067R5 <https://wg21.link/P0067R5>`__","Elementary string conversions, revision 5","2016-11 (Issaquah)","|Partial|","","``std::(to|from)_chars`` for integrals has been available since version 7.0. ``std::to_chars`` for ``float`` and ``double`` since version 14.0 ``std::to_chars`` for ``long double`` uses the implementation for ``double``."
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"`P0067R5 <https://wg21.link/P0067R5>`__","Elementary string conversions, revision 5","2016-11 (Issaquah)","|Partial|","","``std::(to|from)_chars`` for integrals has been available since version 7.0. ``std::to_chars`` for ``float`` and ``double`` since version 14.0 ``std::to_chars`` for ``long double`` uses the implementation for ``double``. ``std::from_chars`` for ``float`` and ``double`` since version 20.0."
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"`P0403R1 <https://wg21.link/P0403R1>`__","Literal suffixes for ``basic_string_view``\ ","2016-11 (Issaquah)","|Complete|","4.0",""
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"`P0414R2 <https://wg21.link/P0414R2>`__","Merging shared_ptr changes from Library Fundamentals to C++17","2016-11 (Issaquah)","|Complete|","11.0",""
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"`P0418R2 <https://wg21.link/P0418R2>`__","Fail or succeed: there is no atomic lattice","2016-11 (Issaquah)","","",""

‎libcxx/docs/Status/Cxx2cIssues.csv

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"","","","","",""
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"`LWG3343 <https://wg21.link/LWG3343>`__","Ordering of calls to ``unlock()`` and ``notify_all()`` in Effects element of ``notify_all_at_thread_exit()`` should be reversed","Not Adopted Yet","|Complete|","16.0",""
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"`LWG4139 <https://wg21.link/LWG4139>`__","§[time.zone.leap] recursive constraint in <=>","Not Adopted Yet","|Complete|","20.0",""
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"`LWG3456 <https://wg21.link/LWG3456>`__","Pattern used by std::from_chars is underspecified (option B)",,"Not Yet Adopted","|Complete|","20.0",""
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"","","","","",""

‎libcxx/include/CMakeLists.txt

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__bit/rotate.h
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__bit_reference
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__charconv/chars_format.h
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__charconv/from_chars_floating_point.h
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__charconv/from_chars_integral.h
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__charconv/from_chars_result.h
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__charconv/tables.h

‎libcxx/include/__charconv/from_chars_floating_point.h

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// -*- C++ -*-
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//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
6+
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7+
//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP___CHARCONV_FROM_CHARS_FLOATING_POINT_H
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#define _LIBCPP___CHARCONV_FROM_CHARS_FLOATING_POINT_H
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#include <__assert>
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#include <__charconv/chars_format.h>
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#include <__charconv/from_chars_result.h>
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#include <__config>
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#include <__system_error/errc.h>
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#include <cstddef>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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# pragma GCC system_header
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#endif
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_LIBCPP_PUSH_MACROS
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#include <__undef_macros>
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_LIBCPP_BEGIN_NAMESPACE_STD
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#if _LIBCPP_STD_VER >= 17
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template <class _Fp>
32+
struct __from_chars_result {
33+
_Fp __value;
34+
ptrdiff_t __n;
35+
errc __ec;
36+
};
37+
38+
template <class _Fp>
39+
_LIBCPP_EXPORTED_FROM_ABI __from_chars_result<_Fp> __from_chars_floating_point(
40+
[[clang::noescape]] const char* __first, [[clang::noescape]] const char* __last, chars_format __fmt);
41+
42+
extern template __from_chars_result<float> __from_chars_floating_point(
43+
[[clang::noescape]] const char* __first, [[clang::noescape]] const char* __last, chars_format __fmt);
44+
45+
extern template __from_chars_result<double> __from_chars_floating_point(
46+
[[clang::noescape]] const char* __first, [[clang::noescape]] const char* __last, chars_format __fmt);
47+
48+
template <class _Fp>
49+
_LIBCPP_HIDE_FROM_ABI from_chars_result
50+
__from_chars(const char* __first, const char* __last, _Fp& __value, chars_format __fmt) {
51+
__from_chars_result<_Fp> __r = std::__from_chars_floating_point<_Fp>(__first, __last, __fmt);
52+
if (__r.__ec != errc::invalid_argument)
53+
__value = __r.__value;
54+
return {__first + __r.__n, __r.__ec};
55+
}
56+
57+
_LIBCPP_AVAILABILITY_FROM_CHARS_FLOATING_POINT _LIBCPP_HIDE_FROM_ABI inline from_chars_result
58+
from_chars(const char* __first, const char* __last, float& __value, chars_format __fmt = chars_format::general) {
59+
return std::__from_chars<float>(__first, __last, __value, __fmt);
60+
}
61+
62+
_LIBCPP_AVAILABILITY_FROM_CHARS_FLOATING_POINT _LIBCPP_HIDE_FROM_ABI inline from_chars_result
63+
from_chars(const char* __first, const char* __last, double& __value, chars_format __fmt = chars_format::general) {
64+
return std::__from_chars<double>(__first, __last, __value, __fmt);
65+
}
66+
67+
#endif // _LIBCPP_STD_VER >= 17
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_LIBCPP_END_NAMESPACE_STD
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_LIBCPP_POP_MACROS
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73+
#endif // _LIBCPP___CHARCONV_FROM_CHARS_FLOATING_POINT_H

‎libcxx/include/__configuration/availability.h

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// in all versions of the library are available.
8888
#if defined(_LIBCPP_HAS_NO_VENDOR_AVAILABILITY_ANNOTATIONS)
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90+
# define _LIBCPP_INTRODUCED_IN_LLVM_20 1
91+
# define _LIBCPP_INTRODUCED_IN_LLVM_20_ATTRIBUTE /* nothing */
92+
9093
# define _LIBCPP_INTRODUCED_IN_LLVM_19 1
9194
# define _LIBCPP_INTRODUCED_IN_LLVM_19_ATTRIBUTE /* nothing */
9295

@@ -132,6 +135,11 @@
132135

133136
// clang-format off
134137

138+
// LLVM 20
139+
// TODO: Fill this in
140+
# define _LIBCPP_INTRODUCED_IN_LLVM_20 0
141+
# define _LIBCPP_INTRODUCED_IN_LLVM_20_ATTRIBUTE __attribute__((unavailable))
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// LLVM 19
136144
// TODO: Fill this in
137145
# define _LIBCPP_INTRODUCED_IN_LLVM_19 0
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409417
#define _LIBCPP_AVAILABILITY_HAS_BAD_EXPECTED_ACCESS_KEY_FUNCTION _LIBCPP_INTRODUCED_IN_LLVM_19
410418
#define _LIBCPP_AVAILABILITY_BAD_EXPECTED_ACCESS_KEY_FUNCTION _LIBCPP_INTRODUCED_IN_LLVM_19_ATTRIBUTE
411419

420+
// This controls the availability of floating-point std::from_chars functions.
421+
// These overloads were added later than the integer overloads.
422+
#define _LIBCPP_AVAILABILITY_HAS_FROM_CHARS_FLOATING_POINT _LIBCPP_INTRODUCED_IN_LLVM_20
423+
#define _LIBCPP_AVAILABILITY_FROM_CHARS_FLOATING_POINT _LIBCPP_INTRODUCED_IN_LLVM_20_ATTRIBUTE
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// Define availability attributes that depend on _LIBCPP_HAS_EXCEPTIONS.
413426
// Those are defined in terms of the availability attributes above, and
414427
// should not be vendor-specific.

‎libcxx/include/charconv

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6565
constexpr from_chars_result from_chars(const char* first, const char* last,
6666
see below& value, int base = 10); // constexpr since C++23
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68+
from_chars_result from_chars(const char* first, const char* last,
69+
float& value, chars_format fmt);
70+
71+
from_chars_result from_chars(const char* first, const char* last,
72+
double& value, chars_format fmt);
73+
6874
} // namespace std
6975
7076
*/
@@ -73,6 +79,7 @@ namespace std {
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7480
#if _LIBCPP_STD_VER >= 17
7581
# include <__charconv/chars_format.h>
82+
# include <__charconv/from_chars_floating_point.h>
7683
# include <__charconv/from_chars_integral.h>
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# include <__charconv/from_chars_result.h>
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# include <__charconv/tables.h>

‎libcxx/include/module.modulemap

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899899
module charconv {
900900
module chars_format { header "__charconv/chars_format.h" }
901+
module from_chars_floating_point { header "__charconv/from_chars_floating_point.h" }
901902
module from_chars_integral { header "__charconv/from_chars_integral.h" }
902903
module from_chars_result { header "__charconv/from_chars_result.h" }
903904
module tables { header "__charconv/tables.h" }

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