關(guān)鍵是熟悉內(nèi)存分布
#include <iostream>
using namespace std;
class A{
private:
?? int i;
public:
?void printa()
?{
??printf("%d\n",i);
?}
};
class B{
private:
?A a;
};
int main()
{
? B b;
? A* aa=(A*)&b;
? int* ii=(int*)aa;
? *ii=100;
? aa->printa();
? return 0;
}
100
媽的!太變態(tài)!!
#include <iostream>
using namespace std;
class A{
private:
?? int i;
public:
?void printa()
?{
??printf("%d",i);
?}
};
class B{
private:
?int j1;
?A a;
?int j2;
public:
?void printb()
?{
??? printf("%d\n",j1);
?}
};
int main()
{
? B b;
? int *jj=(int*)&b;
? *jj=100;
? b.printb();
? return 0;
}
得到100
#include <iostream>
using namespace std;
class A{
private:
?? int i;
public:
?void printa()
?{
??printf("%d\n",i);
?}
};
class B{
private:
?A a;
?int j;
public:
?void printb()
?{
??? printf("%d\n",j);
?}
};
int main()
{
? B b;
? A* aa=(A*)&b;
? int* ii=(int*)aa;
? *ii=100;
? aa->printa();
?
? int*jj=(int*)aa+1;//為什么是1呢?我用sizeof(A)是錯的
? *jj=200;
? b.printb();
? return 0;
}
100
200
#include <iostream>
using namespace std;
class A{
private:
?? int i;
public:
?void printa()
?{
??printf("%d\n",i);
?}
};
class B{
private:
?A a;
?int j;
public:
?void printb()
?{
??? printf("%d\n",j);
?}
};
int main()
{
? B b;
? A* aa=(A*)&b;
? int* ii=(int*)aa;
? *ii=100;
? aa->printa();
?
? int*jj=(int*)aa+1;
? *jj=200;
? b.printb();
? char *jj2=(char*)&b+sizeof(A);//這樣才能用sizeof(A)
? *jj2=300;//這里解完地址后,用的是char,最大255,300超出了范圍.只取有效的部分,就是44
? b.printb();
? int *jj3=(int*)jj2;
? *jj3=400;
? b.printb();
? return 0;
}
100
200
44
400