sairate
4108f6c42d
- 新增现代 C++ 教程的 Preface 章节，包括英文和中文版本 - 添加 C++ Primer 练习代码 - 新增 Learn C++ 教程的 C++ 开发简介章节 - 添加头文件解析文档 - 更新 mkdocs.yml，包含新教程的目录结构 - 修改项目设置，使用 Python 3.10环境
53 lines
1.8 KiB
C++
53 lines
1.8 KiB
C++
//
|
|
// 5.1.shared.ptr.cpp
|
|
// chapter 05 start pointers and memory management
|
|
// modern c++ tutorial
|
|
//
|
|
// created by changkun at changkun.de
|
|
// https://github.com/changkun/modern-cpp-tutorial
|
|
//
|
|
|
|
#include <iostream>
|
|
#include <memory>
|
|
|
|
void foo(std::shared_ptr<int> i)
|
|
{
|
|
(*i)++;
|
|
}
|
|
|
|
int main()
|
|
{
|
|
// auto pointer = new int(10); // illegal, no direct assignment
|
|
// std::shared_ptr construction
|
|
auto pointer = std::make_shared<int>(10);
|
|
auto pointer2 = pointer; // reference count + 1
|
|
auto pointer3 = pointer; // reference count + 1
|
|
|
|
|
|
foo(pointer);
|
|
std::cout << *pointer << std::endl; // 11
|
|
int *p = pointer.get(); // does not increase reference count
|
|
|
|
std::cout << "pointer.use_count() = " << pointer.use_count() << std::endl;
|
|
std::cout << "pointer2.use_count() = " << pointer2.use_count() << std::endl;
|
|
std::cout << "pointer3.use_count() = " << pointer3.use_count() << std::endl;
|
|
|
|
pointer2.reset();
|
|
std::cout << "reset pointer2:" << std::endl;
|
|
std::cout << "pointer.use_count() = " << pointer.use_count() << std::endl;
|
|
std::cout << "pointer2.use_count() = " << pointer2.use_count() << std::endl;
|
|
std::cout << "pointer3.use_count() = " << pointer3.use_count() << std::endl;
|
|
|
|
pointer3.reset();
|
|
std::cout << "reset pointer3:" << std::endl;
|
|
std::cout << "pointer.use_count() = " << pointer.use_count() << std::endl;
|
|
std::cout << "pointer2.use_count() = " << pointer2.use_count() << std::endl;
|
|
std::cout << "pointer3.use_count() = " << pointer3.use_count() << std::endl;
|
|
// std::cout << *pointer << std::endl; // reference count equals 0, illegal access
|
|
|
|
|
|
// Before leaving the scope, the pointer is destructed and
|
|
// the reference count is reduced to 0
|
|
return 0;
|
|
}
|