默认情况下，lambda中捕获的变量 ptr 是const，即 ptr 的类型为 const std :: shared_ptr< int> .

The captured variable ptr in a lambda is by default const, i.e. the type of ptr is const std::shared_ptr<int>.

std :: move 无法移出const对象，因此创建了副本.

std::move cannot move out const objects, so a copy is created instead.

如果您确实要移动它，则必须允许 ptr 是可变的:

If you really want to move it, the ptr must be allowed to be mutable:

auto lambda = [ptr]() mutable {
//                    ^~~~~~~