C++ 智能指针动态内存简单测试
代码示例,主要来自《C++ Primer》,动态内存相关那章内容。
#include <iostream>
#include <memory>
#include <string>
namespace
{
// 未初始化的智能指针,默认保存的空指针
void def_null_sp_test();
// 不是唯一用户,复制一份新的考拷贝。
void sp_unique_copy_test();
// weak_ptr 测试
void wp_test();
// 智能指针和动态数组
void smartPtr_arr_test();
// allocator 类测试
void allocator_test();
}
int main()
{
using namespace std;
cout << "/*********def_null_sp_test()*********/" << endl;
def_null_sp_test();
cout << "/*********def_null_sp_test()*********/" << endl << endl;
cout << "/*********sp_unique_copy_test()*********/" << endl;
sp_unique_copy_test();
cout << "/*********sp_unique_copy_test()*********/" << endl << endl;
cout << "/*********wp_test()*********/" << endl;
wp_test();
cout << "/*********wp_test()*********/" << endl << endl;
cout << "/*********smartPtr_arr_test()*********/" << endl;
smartPtr_arr_test();
cout << "/*********smartPtr_arr_test()*********/" << endl << endl;
cout << "/*********allocator_test()*********/" << endl;
allocator_test();
cout << "/*********allocator_test()*********/" << endl << endl;
return 0;
}
namespace
{
void def_null_sp_test()
{
using namespace std;
shared_ptr<string> p1;
//cout << *p1 << endl; // p1 默认保存的是空指针
if (!p1)
{
p1.reset(new string("hi, I'am jack."));
}
cout << *p1 << endl;
*p1 = "";
if (p1 && p1->empty())
{
*p1 = "hello world!";
}
cout << *p1 << endl;
}
void sp_unique_copy_test()
{
using namespace std;
shared_ptr<string> p1(new string("hello world!"));
shared_ptr<string> p2 = p1;
shared_ptr<string> p3 = p2;
cout << "p1 对象的引用次数,use_count = " << p1.use_count() << endl;
cout << "p3 = " << *p3 << endl;
if (!p3.unique())
{
p3.reset(new string(*p3));
}
*p3 += " good morning.";
cout << "p3 新内容是:" << *p3 << endl;
cout << "p1 对象的引用次数,use_count = " << p1.use_count() << endl;
cout << "p1 的内容是:" << *p1 << endl;
}
void wp_test()
{
using namespace std;
auto sp = make_shared<int>(100);
weak_ptr<int> wp(sp);
cout << "sp 的引用次数 use_count = " << sp.use_count() << endl;;
auto ret = wp.lock();
if (!ret)
{
cout << "对象已经被释放!" << endl;
}
else
{
cout << "sp 的引用次数 use_count = " << sp.use_count() << endl;
}
}
void smartPtr_arr_test()
{
using namespace std;
unique_ptr<int[]> up_arr(new int[10]); // 释放时自己会调用 delete[], 人肉经常会忘记[]
for (size_t i = 0; i != 10; ++i)
{// 赋值
up_arr[i] = i * 10;
}
for (size_t i = 0; i != 10; ++i)
{// 显示
cout << "up_arr[i] = " << up_arr[i] << " ";
}
cout << endl;
// 如果用 shared_ptr 管理动态数组,需要自定义删除器,记得带[]
shared_ptr<int> sp_arr(new int[10], [](int* p) {delete[] p; });
// 遍历只能这样
for (size_t i = 0; i != 10; ++i)
{
*(sp_arr.get() + i) = i * 10;
}
for (size_t i = 0; i != 10; ++i)
{
cout << "sp_arr[i] = " << *(sp_arr.get() + i) << " ";
}
cout << endl;
}
void allocator_test()
{
using namespace std;
const size_t ALLOC_SIZE = 3;
allocator<string> allco_strs;
auto const p = allco_strs.allocate(ALLOC_SIZE); // 分配n个未初始化的string
auto q = p;
allco_strs.construct(q++); // 空字符串
allco_strs.construct(q++, 5, 'c');
allco_strs.construct(q++, "hello world");
cout << *p << endl;
cout << "allocator 遍历:" << endl;
while (q != p)
{
auto temp = --q;
cout << *temp << endl;
allco_strs.destroy(temp); // 析构
}
allco_strs.deallocate(p, ALLOC_SIZE); // 释放,归还系统
}
}
输出:
/*********def_null_sp_test()*********/
hi, I'am jack.
hello world!
/*********def_null_sp_test()*********/
/*********sp_unique_copy_test()*********/
p1 对象的引用次数,use_count = 3
p3 = hello world!
p3 新内容是:hello world! good morning.
p1 对象的引用次数,use_count = 2
p1 的内容是:hello world!
/*********sp_unique_copy_test()*********/
/*********wp_test()*********/
sp 的引用次数 use_count = 1
sp 的引用次数 use_count = 2
/*********wp_test()*********/
/*********smartPtr_arr_test()*********/
up_arr[i] = 0 up_arr[i] = 10 up_arr[i] = 20 up_arr[i] = 30 up_arr[i] = 40 up_arr[i] = 50 up_arr[i] = 60 up_arr[i] = 70 up_arr[i] = 80 up_arr[i] = 90
sp_arr[i] = 0 sp_arr[i] = 10 sp_arr[i] = 20 sp_arr[i] = 30 sp_arr[i] = 40 sp_arr[i] = 50 sp_arr[i] = 60 sp_arr[i] = 70 sp_arr[i] = 80 sp_arr[i] = 90
/*********smartPtr_arr_test()*********/
/*********allocator_test()*********/
allocator 遍历:
hello world
ccccc
/*********allocator_test()*********/
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