问题

以下代码不会在C11(也不是C14)中编译.我了解编译器的错误输出,但为什么标准不允许？

@H_403_4@//main.cpp #include <vector> int main(void) { double a = 3.0; double b = 3.0; //It works with mere pointers const double* ptrToConst = &a; /***/ double* ptrToObj = &a; // ptrToObj = ptrToConst; //Illegal : that's understandable… ptrToConst = ptrToObj; //Works //But the same doesn't work with vectors to pointers std::vector<const double*> ptrsToConst = {&a,&b}; std::vector</***/ double*> ptrsToObj = {&a,&b}; // ptrsToObj = ptrsToConst; //Illegal : that's understandable ptrsToConst = ptrsToObj; //Illegal : but why?! }

错误来自ptrsToConst = ptrsToObj.实际上,似乎不可能复制指针的向量std :: vector< T *>变成一个向量指向常量的std :: vector< const T *>.请注意,在这两种情况下,指针本身不是常量.

为什么这个行为是非法的？
最优雅的工作是什么？

更多细节

如果我通过调用clang –std = c 11 main.cpp进行编译,则会显示以下错误消息：

@H_403_4@main.cpp:19:17: error: no viable overloaded '=' ptrsToConst = ptrsToObj; //Illegal : but why?! ~~~~~~~~~~~ ^ ~~~~~~~~~ /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0/../../../../include/c++/5.4.0/bits/stl_vector.h:436:7: note: candidate function not viable: no known conversion from 'vector<double *,allocator<double *>>' to 'const vector<const double *,allocator<const double *>>' for 1st argument operator=(const vector& __x); ^ /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0/../../../../include/c++/5.4.0/bits/stl_vector.h:448:7: note: candidate function not viable: no known conversion from 'vector<double *,allocator<double *>>' to 'vector<const double *,allocator<const double *>>' for 1st argument operator=(vector&& __x) noexcept(_Alloc_traits::_S_nothrow_move()) ^ /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0/../../../../include/c++/5.4.0/bits/stl_vector.h:470:7: note: candidate function not viable: no known conversion from 'std::vector<double *>' to 'initializer_list<value_type>' (aka 'initializer_list<const double *>') for 1st argument operator=(initializer_list<value_type> __l) ^ 1 error generated.

与gcc(g)一样尝试产生类似的错误消息.

显然,实现向量的方式不允许我正在尝试执行的操作.但是对于正确性来说,这是一个安全的操作呢？