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编译器优化sizeof,private继承访问权限更改

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CYP12138
2022-03-16 18:05:59 +08:00
parent 696b01a42c
commit c0d76f164d
3 changed files with 57 additions and 10 deletions
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21
basic_content/sizeof/README.md
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@@ -93,7 +93,7 @@ int main()
/**
* @file geninhe.cpp
* @brief 1.普通单继承,继承就是基类+派生类自身的大小(注意字节对齐)
* 注意：类的数据成员按其声明顺序加入内存，与访问权限无关，只看声明顺序。
* 注意：类的数据成员按其声明顺序加入内存，无访问权限无关，只看声明顺序。
* 2.虚单继承，派生类继承基类vptr
* @author 光城
* @version v1
@@ -117,7 +117,14 @@ class A
* int b
* short a
* long b
* 根据字节对齐4+4=8+8+8=24
* 根据字节对齐4+4+8+8=24
*
* 或编译器优化
* char a
* short a
* int b
* long b
* 根据字节对齐2+2+4+8=16
*/
class B:A
{
@@ -125,24 +132,30 @@ class B:A
short a;
long b;
};
/**
* 把A的成员拆开看，char为1，int为4，所以是1+（3）+4+1+（3）=12，（）为字节补齐
*/
class C
{
A a;
char c;
};
class A1
{
virtual void fun(){}
};
class C1:public A1
class C1:public A
{
};
int main()
{
cout<<sizeof(A)<<endl; // 8
cout<<sizeof(B)<<endl; // 24
cout<<sizeof(B)<<endl; // 16 或 24
cout<<sizeof(C)<<endl; // 12
/**
* @brief 对于虚单函数继承，派生类也继承了基类的vptr，所以是8字节
*/

14
basic_content/sizeof/geninhe.cpp
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@@ -25,7 +25,14 @@ class A
* int b
* short a
* long b
* 根据字节对齐4+4=8+8+8=24
* 根据字节对齐4+4+8+8=24
*
* 或编译器优化
* char a
* short a
* int b
* long b
* 根据字节对齐2+2+4+8=16
*/
class B:A
{
@@ -33,6 +40,9 @@ class B:A
short a;
long b;
};
/**
* 把A的成员拆开看，char为1，int为4，所以是1+（3）+4+1+（3）=12，（）为字节补齐
*/
class C
{
A a;
@@ -51,7 +61,7 @@ class C1:public A
int main()
{
cout<<sizeof(A)<<endl; // 8
cout<<sizeof(B)<<endl; // 24
cout<<sizeof(B)<<endl; // 16
cout<<sizeof(C)<<endl; // 12
/**

32
practical_exercises/10_day_practice/day5/继承访问权限/readme.md
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@@ -1,14 +1,30 @@
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public -> private
protected -> private
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@@ -16,6 +32,14 @@
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