我正在观察一些我自己无法完全解释的奇怪行为。 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;});
}
这是一个可以玩的版本 https://godbolt.org/g/YcNdbf 问题是此代码使用 gcc4.9-6.3 编译良好，但在 gcc 7.1 下失败。 Clang 也不喜欢它。
(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，我不太明白为什么它不起作用。
提前感谢任何试图提供帮助的人:)
最佳答案
为了避免意外获取临时地址，库已经为 addressof 获得了第二个(已删除的)签名:
template <class T> constexpr T* addressof(T& r) noexcept;
template <class T> const T* addressof(const T&& elem) = delete;
参见 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匹配被删除的函数......
关于c++ - 使用 std::addressof 时出现 GCC 7 编译错误，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/45670453/