标签：c c11 initializer-list unique-ptr
参见英文答案 > initializer_list and move semantics 6个
我想知道为什么initializer_list不能与unique_ptr一起使用：
std::vector<std::unique_ptr<int>> vptr = {std::make_unique<int>(1), std::make_unique<int>(2)};
不编译.
然而：
std::vector<std::unique_ptr<int>> vptr(2);
vptr[0] =std::make_unique<int>(1);
vptr[1] =std::make_unique<int>(2);
编译.
和
std::vector<int*>vint={new int{1},new int{2}};
要么
std::vector<std::shared_ptr<int>> vptr= {std::make_shared<int>(1), std::make_shared<int>(2)};
编译.
unique_ptr变体在clang中给出了此错误消息：
In file included from main.cpp:2:
In file included from /usr/local/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.9.0/../../../../include/c++/4.9.0/vector:62:
/usr/local/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.9.0/../../../../include/c++/4.9.0/bits/stl_construct.h:75:38: error: call to deleted constructor of 'std::unique_ptr<int, std::default_delete<int> >'
{ ::new(static_cast<void*>(__p)) _T1(std::forward<_Args>(__args)...); }
^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/local/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.9.0/../../../../include/c++/4.9.0/bits/stl_uninitialized.h:75:8: note: in instantiation of function template specialization 'std::_Construct<std::unique_ptr<int, std::default_delete<int> >, const std::unique_ptr<int, std::default_delete<int> > &>' requested here
std::_Construct(std::__addressof(*__cur), *__first);
^
/usr/local/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.9.0/../../../../include/c++/4.9.0/bits/stl_uninitialized.h:125:2: note: in instantiation of function template specialization 'std::__uninitialized_copy<false>::__uninit_copy<const std::unique_ptr<int, std::default_delete<int> > *, std::unique_ptr<int, std::default_delete<int> > *>' requested here
__uninit_copy(__first, __last, __result);
^
/usr/local/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.9.0/../../../../include/c++/4.9.0/bits/stl_uninitialized.h:278:19: note: in instantiation of function template specialization 'std::uninitialized_copy<const std::unique_ptr<int, std::default_delete<int> > *, std::unique_ptr<int, std::default_delete<int> > *>' requested here
{ return std::uninitialized_copy(__first, __last, __result); }
^
/usr/local/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.9.0/../../../../include/c++/4.9.0/bits/stl_vector.h:1284:11: note: in instantiation of function template specialization 'std::__uninitialized_copy_a<const std::unique_ptr<int, std::default_delete<int> > *, std::unique_ptr<int, std::default_delete<int> > *, std::unique_ptr<int, std::default_delete<int> > >' requested here
std::__uninitialized_copy_a(__first, __last,
^
/usr/local/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.9.0/../../../../include/c++/4.9.0/bits/stl_vector.h:377:2: note: in instantiation of function template specialization 'std::vector<std::unique_ptr<int, std::default_delete<int> >, std::allocator<std::unique_ptr<int, std::default_delete<int> > > >::_M_range_initialize<const std::unique_ptr<int, std::default_delete<int> > *>' requested here
_M_range_initialize(__l.begin(), __l.end(),
^
main.cpp:10:42: note: in instantiation of member function 'std::vector<std::unique_ptr<int, std::default_delete<int> >, std::allocator<std::unique_ptr<int, std::default_delete<int> > > >::vector' requested here
std::vector<std::unique_ptr<int>> vptr = {std::make_unique<int>(1), std::make_unique<int>(2)};
^
/usr/local/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.9.0/../../../../include/c++/4.9.0/bits/unique_ptr.h:356:7: note: 'unique_ptr' has been explicitly marked deleted here
unique_ptr(const unique_ptr&) = delete;
^
1 error generated.
解决方法:
向量< T>的构造函数.采用initializer_list< T>将元素从初始化列表复制到向量中.当您处理不可复制的类型时,这不起作用：unique_ptr< T>的设计.防止制作副本.它允许移动,这就是赋值工作的原因：make_unique返回一个rvalue,编译器知道它可以安全移动.
你需要某种构造函数采用initializer_list< T&&>,但C没有这样的构造函数(事实上,正如dyp指出的那样,类型initializer_list< T&&>>甚至功能).
标签：c,c11,initializer-list,unique-ptr 来源： https://codeday.me/bug/20190830/1767945.html
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