C++(11)：static_pointer_cast/dynamic_pointer_cast

C++11引入了static_pointer_cast用于在编译期做向下转型（从基类向派生类转型），但是不做类型安全检查。同时引入了dynamic_pointer_cast，用于在运行期做类型安全检查的向下转型。

#include <iostream> #include <memory> struct FileBase { virtual ~FileBase() = default; virtual const char* kind() const { return "FileBase"; } }; struct TextFile : FileBase { const char* kind() const override { return "TextFile"; } void write_line() const { std::cout << "TextFile::write_line() called" << '\n'; } }; struct BinaryFile : FileBase { const char* kind() const override { return "BinaryFile"; } void dump_bytes() const { std::cout << "BinaryFile::dump_bytes() called" << '\n'; } }; void print_owner_count(const char* name, const std::shared_ptr<FileBase>& ptr) { std: