Question

使用msvc2017编译器并升级1.65.1，下面的代码无法编译。

#include <boost/optional.hpp>

boost::optional<double>
foo()
{
    return boost::optional<double>(4.0);
}

int
main(void)
{
    boost::optional<double> result;
    result = foo();
}

生成的错误是：

C:/boost/optional/optional.hpp(954): error C2248: 'boost::optional_detail::optional_base<T>::optional_base': cannot access protected member declared in class 'boost::optional_detail::optional_base<T>'
        with
        [
            T=double
        ]
C:/boost/optional/optional.hpp(157): note: see declaration of 'boost::optional_detail::optional_base<T>::optional_base'
        with
        [
            T=double
        ]
C:/boost/optional/optional.hpp(771): note: see declaration of 'boost::optional_detail::optional_base<T>'
        with
        [
            T=double
        ]
C:/boost/optional/optional.hpp(954): note: while checking that elided copy-constructor 'boost::optional_detail::optional_base<T>::optional_base(const boost::optional_detail::optional_base<T> &)' is callable
        with
        [
            T=double
        ]
C:/boost/optional/optional.hpp(157): note: see declaration of 'boost::optional_detail::optional_base<T>::optional_base'
        with
        [
            T=double
        ]
C:/boost/optional/optional.hpp(954): note: when converting from 'boost::optional_detail::optional_base<T>' to 'boost::optional_detail::optional_base<T> &&'
        with
        [
            T=double
        ]
C:/boost/optional/optional.hpp(953): note: while compiling class template member function 'boost::optional<double> &boost::optional<double>::operator =(boost::optional<double> &&) noexcept'
main.cpp(13): note: see reference to function template instantiation 'boost::optional<double> &boost::optional<double>::operator =(boost::optional<double> &&) noexcept' being compiled
main.cpp(5): note: see reference to class template instantiation 'boost::optional<double>' being compiled

其他编译器不会出现此问题（我测试了clang和gcc）。所以这对我来说似乎是一个Microsoft编译器错误？

boost :: msvc的可选赋值

0 个答案: