使用 std::addressof 时出现 GCC 7 编译错误

Question

我观察到一些奇怪的行为，我无法完全解释自己。 代码如下所示：

#include <memory>
#include <vector>
#include <algorithm>
int main(){
std::vector<double> t1(10, 5.0);
std::vector<double*> t2(10);
std::transform(t1.begin(), t1.end(), t2.begin(), std::addressof<double>);
//std::transform(t1.begin(), t1.end(), t2.begin(), [](double& a){return &a;});
}

这是一个可以玩 https://godbolt.org/g/YcNdbf 的版本 问题是这段代码使用 gcc4.9-6.3 编译得很好，但在 gcc 7.1 下失败了。叮当也不喜欢。

(编辑(来自gcc 7.1的错误消息：

<source>: In function 'int main()':
8 : <source>:8:76: error: no matching function for call to 'transform(std::vector<double>::iterator, std::vector<double>::iterator, std::vector<double*>::iterator, <unresolved overloaded function type>)'
std::transform(t1.begin(), t1.end(), t2.begin(), std::addressof<double>);
      ^
In file included from /opt/compiler-explorer/gcc-7.1.0/include/c++/7.1.0/algorithm:62:0,
from <source>:3:
/opt/compiler-explorer/gcc-7.1.0/include/c++/7.1.0/bits/stl_algo.h:4281:5: note: candidate: template<class _IIter, class _OIter, class _UnaryOperation> _OIter std::transform(_IIter, _IIter, _OIter, _UnaryOperation)
transform(_InputIterator __first, _InputIterator __last,
^~~~~~~~~
/opt/compiler-explorer/gcc-7.1.0/include/c++/7.1.0/bits/stl_algo.h:4281:5: note:   template argument deduction/substitution failed:
8 : <source>:8:76: note:   could not resolve address from overloaded function 'addressof<double>'
std::transform(t1.begin(), t1.end(), t2.begin(), std::addressof<double>);
      ^
In file included from /opt/compiler-explorer/gcc-7.1.0/include/c++/7.1.0/algorithm:62:0,
from <source>:3:
/opt/compiler-explorer/gcc-7.1.0/include/c++/7.1.0/bits/stl_algo.h:4318:5: note: candidate: template<class _IIter1, class _IIter2, class _OIter, class _BinaryOperation> _OIter std::transform(_IIter1, _IIter1, _IIter2, _OIter, _BinaryOperation)
transform(_InputIterator1 __first1, _InputIterator1 __last1,
^~~~~~~~~
/opt/compiler-explorer/gcc-7.1.0/include/c++/7.1.0/bits/stl_algo.h:4318:5: note:   template argument deduction/substitution failed:
8 : <source>:8:76: note:   could not resolve address from overloaded function 'addressof<double>'
std::transform(t1.begin(), t1.end(), t2.begin(), std::addressof<double>);
      ^
Compiler exited with result code 1

但是，我不太清楚为什么它不起作用。

提前感谢任何试图帮助:)的人

Answer 1

为了避免意外获取临时人员的地址，图书馆获得了第二个(已删除(签名addressof：

template <class T> constexpr T* addressof(T& r) noexcept;
template <class T> const T* addressof(const T&& elem) = delete;

见 http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-defects.html#2598

所以现在编译器不知道你的代码是否应该与已删除的函数匹配......