cout << (void *) test 什么意思?

[mr_moran]

#include <new>
using namespace std;
int main()
{
char total[512];
char* pd1 = new (total) char[2];
char* pd2 = new (total) char[2];
cout << "The address of total is " << &total << endl
<< "The address of pd1 is " << &pd1 << endl
<< "The address of pd2 is " << &pd2 << endl;

cout << "The other address of total is " << (void *) total << endl
<< "The other address of pd1 is " << (void *) pd1 << endl
<< "The other address of pd2 is " << (void *) pd2 << endl;
cin.get();
}

两个cout 显示的结果不相同,不明白void * 究竟是什么意思.

[yeahspyme]

cout << "The address of total is " << &total << endl
<< "The address of pd1 is " << &pd1 << endl
<< "The address of pd2 is " << &pd2 << endl;
// 这象是在输出指针的指针

cout << "The other address of total is " << (void *) total << endl
<< "The other address of pd1 is " << (void *) pd1 << endl
<< "The other address of pd2 is " << (void *) pd2 << endl;
// 因为<<对于char*(char[])是作为C字符串看待的，为了输出total指针的内容，用了类型转换而已

[mr_moran]

cout << "The other address of total is " << (void *) total << endl
<< "The other address of pd1 is " << (void *) pd1 << endl
<< "The other address of pd2 is " << (void *) pd2 << endl;

那么为什么这条cout 语句输出的结果都是一样的呢?都是相同的内存地址.
这不是我的意图啊.

我在total的512里面各划分了两个字节分配给pd1 和 pd2 .
pd1 和 pd2的内存地址应该相差2啊. 而且pd1的内存地址,不也应该等于total的首地址么?
可是,编译的结果却不是这样的啊。.

[fangrk]

char* pd1 = new (total) char[2];
char* pd2 = new (total) char[2];

这属于"定位new"，pd1/pd2是在total的位置上的，都等于total

[tatbaby]

#include <iostream>
#include <new>
using namespace std;
那是因为你用错了！！！！！！！！！！
int main()
{
char total[512];
char* pd1 = new (total) char[2];
char* pd2 = new (total) char[2];
cout << "The address of total is " << &total << endl
<< "The address of pd1 is " << &pd1 << endl
<< "The address of pd2 is " << &pd2 << endl;

cout << "The other address of total is " << (void *) &total << endl ///&
<< "The other address of pd1 is " << (void *) &pd1 << endl ///&
<< "The other address of pd2 is " << (void *) &pd2 << endl;///&
cin.get();
}

注意，多了3个取地址&

[tatbaby]

char* pd1 = new (total) char[2];
char* pd2 = new (total+2) char[2]; //是否应该加2，否则同一个地址上new两次？？
cout << "The address of total is " <<(void *) total << endl
<< "The address of pd1 is " <<(void*) pd1 << endl //这才是输出pd1分配到的空间的地址写法
<< "The address of pd2 is " <<(void*) pd2 << endl;

[mr_moran]

char* pd2 = new (total+2) char[2]; //这句的意思是不是说,以total为首地址,再开辟一个2bit的空间?

[mr_moran]

错了,是以total为首地址,开辟一块2bit的空间,
然后,再以total+2为首地址,开辟另一块2bit的空间?

[wf520pb]

恩

[mr_moran]

哦,那我明白了,感谢大家.
结帖,送分~!