这个程序有什么问题?
#include <memory> #include <vector> int main() { std::vector<std::unique_ptr<int>> vec; int x(1); std::unique_ptr<int> ptr2x(&x); vec.push_back(ptr2x); //This tiny command has a vicious error. return 0; }
错误:
In file included from c:\mingw\bin\../lib/gcc/mingw32/4.5.0/include/c++/mingw32/bits/c++allocator.h:34:0, from c:\mingw\bin\../lib/gcc/mingw32/4.5.0/include/c++/bits/allocator.h:48, from c:\mingw\bin\../lib/gcc/mingw32/4.5.0/include/c++/memory:64, from main.cpp:6: c:\mingw\bin\../lib/gcc/mingw32/4.5.0/include/c++/bits/unique_ptr.h: In member function 'void __gnu_cxx::new_allocator<_Tp>::construct(_Tp*, const _Tp&) [with _Tp = std::unique_ptr<int>, _Tp* = std::unique_ptr<int>*]': c:\mingw\bin\../lib/gcc/mingw32/4.5.0/include/c++/bits/stl_vector.h:745:6: instantiated from 'void std::vector<_Tp, _Alloc>::push_back(const value_type&) [with _Tp = std::unique_ptr<int>, _Alloc = std::allocator<std::unique_ptr<int> >, value_type = std::unique_ptr<int>]' main.cpp:16:21: instantiated from here c:\mingw\bin\../lib/gcc/mingw32/4.5.0/include/c++/bits/unique_ptr.h:207:7: error: deleted function 'std::unique_ptr<_Tp, _Tp_Deleter>::unique_ptr(const std::unique_ptr<_Tp, _Tp_Deleter>&) [with _Tp = int, _Tp_Deleter = std::default_delete<int>, std::unique_ptr<_Tp, _Tp_Deleter> = std::unique_ptr<int>]' c:\mingw\bin\../lib/gcc/mingw32/4.5.0/include/c++/ext/new_allocator.h:105:9: error: used here In file included from c:\mingw\bin\../lib/gcc/mingw32/4.5.0/include/c++/vector:69:0, from main.cpp:7: c:\mingw\bin\../lib/gcc/mingw32/4.5.0/include/c++/bits/unique_ptr.h: In member function 'void std::vector<_Tp, _Alloc>::_M_insert_aux(std::vector<_Tp, _Alloc>::iterator, _Args&& ...) [with _Args = {const std::unique_ptr<int>&}, _Tp = std::unique_ptr<int>, _Alloc = std::allocator<std::unique_ptr<int> >, std::vector<_Tp, _Alloc>::iterator = __gnu_cxx::__normal_iterator<std::unique_ptr<int>*, std::vector<std::unique_ptr<int> > >, typename std::vector<_Tp, _Alloc>::_Base::_Tp_alloc_type::pointer = std::unique_ptr<int>*]': c:\mingw\bin\../lib/gcc/mingw32/4.5.0/include/c++/bits/stl_vector.h:749:4: instantiated from 'void std::vector<_Tp, _Alloc>::push_back(const value_type&) [with _Tp = std::unique_ptr<int>, _Alloc = std::allocator<std::unique_ptr<int> >, value_type = std::unique_ptr<int>]' main.cpp:16:21: instantiated from here c:\mingw\bin\../lib/gcc/mingw32/4.5.0/include/c++/bits/unique_ptr.h:207:7: error: deleted function 'std::unique_ptr<_Tp, _Tp_Deleter>::unique_ptr(const std::unique_ptr<_Tp, _Tp_Deleter>&) [with _Tp = int, _Tp_Deleter = std::default_delete<int>, std::unique_ptr<_Tp, _Tp_Deleter> = std::unique_ptr<int>]' c:\mingw\bin\../lib/gcc/mingw32/4.5.0/include/c++/bits/vector.tcc:314:4: error: used here
您需要移动unique_ptr:
unique_ptr
vec.push_back(std::move(ptr2x));
unique_ptr保证单个unique_ptr容器拥有持有的指针的所有权。这意味着您不能复制 a unique_ptr(因为两个unique_ptrs 将拥有所有权),因此您只能移动它。
但是请注意,您当前的使用unique_ptr不正确。您不能使用它来管理指向局部变量的指针。局部变量的生命周期是自动管理的:局部变量在块结束时被销毁(例如,在这种情况下,当函数返回时)。您需要动态分配对象:
std::unique_ptr<int> ptr(new int(1));
在 C++14 中,我们有一个更好的方法来做到这一点:
make_unique<int>(5);