問(wèn)題描述

假設(shè)我有一個(gè)類，其中有一個(gè)靜態(tài)成員，但我沒(méi)有創(chuàng)建任何該類型的對(duì)象.靜態(tài)變量會(huì)占用內(nèi)存嗎?如果它會(huì)被占用，把它放在一個(gè)班級(jí)里有什么意義?

Say I have a class and I have a static member in it, but I don't create any objects of that type. Will the memory be occupied for the static variable? If it would be occupied, what is the point of putting it in a class?

推薦答案

沒(méi)有

靜態(tài)成員不屬于類的實(shí)例.它們甚至不會(huì)增加 1 位實(shí)例和類大小！

static members don't belong to the instances of class. they don't increase instances and class size even by 1 bit!

struct A
{
    int i;
    static int j;
};
struct B
{
    int i;
};
std::cout << (sizeof(A) == sizeof(B)) << std::endl;

輸出:

1

即A和B的大小完全一樣.靜態(tài)成員更像是通過(guò) A::j 訪問(wèn)的全局對(duì)象.

That is, size of A and B is exactly same. static members are more like global objects accessed through A::j.

在 ideone 上查看演示:http://www.ideone.com/YeYxe

See demonstration at ideone : http://www.ideone.com/YeYxe

$9.4.2/1 來(lái)自 C++ 標(biāo)準(zhǔn) (2003)，

$9.4.2/1 from the C++ Standard (2003),

靜態(tài)數(shù)據(jù)成員不屬于一個(gè)類的子對(duì)象.有只有一個(gè)靜態(tài)數(shù)據(jù)成員的副本由所有對(duì)象共享類.

$9.4.2/3 和 7 來(lái)自標(biāo)準(zhǔn)，

$9.4.2/3 and 7 from the Standard,

一旦靜態(tài)數(shù)據(jù)成員被定義，即使沒(méi)有對(duì)象它也存在已經(jīng)創(chuàng)建了它的類.

靜態(tài)數(shù)據(jù)成員被初始化并完全像非本地一樣銷毀對(duì)象 (3.6.2, 3.6.3).

正如我所說(shuō)，靜態(tài)成員更像是全局對(duì)象！

As I said, static members are more like global objects!

這篇關(guān)于如果沒(méi)有創(chuàng)建該類的對(duì)象，該類的靜態(tài)成員是否會(huì)占用內(nèi)存?的文章就介紹到這了，希望我們推薦的答案對(duì)大家有所幫助，也希望大家多多支持html5模板網(wǎng)！