static变量初始化

1.在C++中，全局static变量和class的static成员变量在main函数之前初始化，main函数之后销毁

2. 函数内部的局部static变量在该函数第一次被调用时初始化，在main函数之后销毁

3.对于static数据即使是函数内部的对象则存放在全局数据区，全局数据区的数据并不会因为函数的退出就将空间释放。

#include <iostream>

using namespace std;

struct Date

{

	Data(){cout<<"create"<<endl;}

	~Data(){cout<<"destroy"<<endl;}

};

static Data g_sData;

int main()

{

	cout << "main start" << endl;

	cout << "main end" << endl;

	return 0;

}

output:

create
main begin
main end
destroy

#include <iostream>

using namespace std;

struct Date

{

Data(){cout<<"create"<<endl;}

~Data(){cout<<"destroy"<<endl;}

};

class Test

{

	static Data m_sData;

};

Data Test::m_sData;

int main()

{

cout << "main start" << endl;

cout << "main end" << endl;

return 0;

}

output:

create
main begin
main end
destroy

#include <iostream>

using namespace std;

struct Date

{

Data(){cout<<"create"<<endl;}

~Data(){cout<<"destroy"<<endl;}

};

void test()

{

	static Data sData;

}

int main()

{

cout << "main start" << endl;

cout << "first time call test" << endl;

test();

cout << "second time call test" << endl;

test();

cout << "main end" << endl;

return 0;

}

main begin
first
create
second
main end
destroy

在看一个比较BT的题目。

在系统中只能调用一次函数

void caller()
{
	cout<<"first call\n";
}

void FirstCall()
{
	static int d = (caller(),1);
}

int main()
{
	FirstCall();
	FirstCall();
}