Merge pull request #206 from CYP12138/master

编译器优化sizeof,private继承访问权限更改

basic_content/sizeof/README.md

@@ -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
      */

basic_content/sizeof/geninhe.cpp

@@ -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
 
     /**

practical_exercises/10_day_practice/day5/继承访问权限/readme.md

@@ -1,14 +1,30 @@
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+
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+
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+
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+
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@@ -16,6 +32,14 @@
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+
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+
+protected          ->                  protected
+
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+
 
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