mirror of
https://github.com/microsoft/GSL
synced 2026-08-26 04:23:04 -04:00
08687fb42a
* Fix floating-to-integral narrow undefined behavior * Format narrow conversion changes * Suppress float-equal warning in narrow_cast
100 lines
3.4 KiB
C++
100 lines
3.4 KiB
C++
///////////////////////////////////////////////////////////////////////////////
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//
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// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
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//
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// This code is licensed under the MIT License (MIT).
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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// THE SOFTWARE.
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//
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///////////////////////////////////////////////////////////////////////////////
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#ifndef GSL_NARROW_H
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#define GSL_NARROW_H
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#include "./assert" // for GSL_SUPPRESS
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#include "./util" // for narrow_cast
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#include <exception> // for std::exception
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namespace gsl
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{
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namespace details
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{
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template <class T, class U>
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constexpr bool static_cast_is_defined(U u, /*is_floating_point_to_integral=*/std::true_type)
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{
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if (std::is_same<typename std::remove_cv<T>::type, bool>::value) { return true; }
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U upper_bound{1};
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for (int i = 0; i < std::numeric_limits<T>::digits; i++)
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{
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upper_bound *= std::numeric_limits<T>::radix;
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}
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if (u >= U{}) { return u < upper_bound; }
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if (!std::is_signed<T>::value) { return u > U{-1}; }
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return u + upper_bound > U{-1};
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}
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template <class T, class U>
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constexpr bool static_cast_is_defined(U, /*is_floating_point_to_integral=*/std::false_type)
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{
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return true;
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}
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} // namespace details
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struct narrowing_error : public std::exception
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{
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const char* what() const noexcept override { return "narrowing_error"; }
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};
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// narrow() : a checked version of narrow_cast() that throws if the cast changed the value
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template <class T, class U, typename std::enable_if<std::is_arithmetic<T>::value>::type* = nullptr>
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GSL_SUPPRESS(type.1) constexpr T narrow(U u)
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{
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constexpr const bool is_different_signedness =
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(std::is_signed<T>::value != std::is_signed<U>::value);
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using is_floating_point_to_integral =
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std::integral_constant<bool,
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std::is_integral<T>::value && std::is_floating_point<U>::value>;
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if (!details::static_cast_is_defined<T, U>(u, is_floating_point_to_integral{}))
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{
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throw narrowing_error{};
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}
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GSL_SUPPRESS(es.103) // don't overflow
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GSL_SUPPRESS(es.104) // don't underflow
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const T t = narrow_cast<T>(u);
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#if defined(__clang__) || defined(__GNUC__)
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#pragma GCC diagnostic push
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#pragma GCC diagnostic ignored "-Wfloat-equal"
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#endif
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// Note: NaN will always throw, since NaN != NaN
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if (static_cast<U>(t) != u || (is_different_signedness && ((t < T{}) != (u < U{}))))
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{
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throw narrowing_error{};
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}
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#if defined(__clang__) || defined(__GNUC__)
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#pragma GCC diagnostic pop
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#endif
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return t;
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}
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template <class T, class U, typename std::enable_if<!std::is_arithmetic<T>::value>::type* = nullptr>
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GSL_SUPPRESS(type.1) constexpr T narrow(U u)
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{
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const T t = narrow_cast<T>(u);
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if (static_cast<U>(t) != u) { throw narrowing_error{}; }
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return t;
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}
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} // namespace gsl
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#endif // GSL_NARROW_H
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