1 #include <bits/stdc++.h> 2 using namespace std; 3 typedef long long LL; 4 const int N=1e5+10; 5 const int INF=0x3f3f3f3f; 6 int cas=1,T; 7 struct node{ 8 int *p; 9 ~node() 10 { 11 cout<<"~node() "; 12 if(p) delete p; 13 } 14 }; 15 int main() 16 { 17 void * a=new float(3.0); 18 printf("%d %d ",*((int*)a),(int)(*(float*)a)); 19 delete a; 20 printf("%d %d ",*((int*)a),(int)(*(float*)a)); 21 a=new long long(3); 22 printf("%d %d ",*((int*)a),(int)(*(long long*)a)); 23 delete a; 24 printf("%d %d ",*((int*)a),(int)(*(long long*)a)); 25 node *b=new node; 26 b->p=new int(4); 27 int *c=b->p; 28 a=b; 29 delete a; 30 printf("p:%p ",((node*)a)->p); 31 printf("%d ",*c); 32 return 0;
1 请按 ENTER 或其它命令继续 2 test.cpp: In function ‘int main()’: 3 test.cpp:19:9: warning: deleting ‘void*’ is undefined [-Wdelete-incomplete] 4 delete a; 5 ^ 6 test.cpp:23:9: warning: deleting ‘void*’ is undefined [-Wdelete-incomplete] 7 delete a; 8 ^ 9 test.cpp:29:9: warning: deleting ‘void*’ is undefined [-Wdelete-incomplete] 10 delete a; 11 ^ 12 13 请按 ENTER 或其它命令继续 14 1077936128 3 15 0 0 16 3 3 17 0 0 18 p:(nil) 19 4 20 21 请按 ENTER 或其它命令继续
void *a 原来的类型是float型，存的值是3.0,然后*((int*)a)直接强制将指针类型转成int*之后输出的值不是3,但(int)(*((float*)a))将a转成float*之后再将值转成(int)输出的值就是3了，说明void*指针强制转换后还是会读到原来的二进制，没有进行指针所指向的值的转换
delete a之后两个值都为0说明delete void能成功delete void*成功,后面的结构体没有输出~node()说明没有调用自定义类型的~node()函数，只是将该指针指向的内存free调，也说明系统会记住一个指针所指向的内存的大小
后面的long long结果不变说明void*强制转换时如果大小不一样采用尾截法取指向的内存