c++ - 删除数组指针

Question

所以，

我遇到了一个我无法弄清楚的错误(除非我的理解不正确)。

我有以下代码:

    int doubleSize=size*2;
    int *newArr = new int[doubleSize];
    for(int i=0; i<size; i ++) {
        newArr[i]=jon[i];
    }
    size*=2;

    display(newArr);
    jon=newArr;
    display(jon);
    delete[] newArr;
    display(jon);

在第一次和第二次通话后，我得到了我想要/期望的结果。在第三次显示调用中，0 和 1 索引是内存地址，索引中的其余值与前 2 次调用匹配。可能是什么原因造成的？

我还有另一个跟进问题，使用我现有的代码，删除 jon[] 不会导致“旧”jon[] 留在内存中吗？

谢谢!

Answer 1

你有未定义的行为，所以任何事情都有可能发生。

int *newArr = new int[size*2];
// now newArr is a pointer to a memory area
jon=newArr;
// now jon is a pointer to the same area, whatever jon pointed to before is leaked
delete[] newArr;
// now the memory area no longer exists
display(jon);
// using jon is now illegal, it has the address of a deleted memory area

可能正确的解决方案是:

int *newArr = new int[doubleSize]; // allocate a new area
for( int i=0; i<size; ++i ) {       // fill it in
    newArr[i] = jon[i];
}
delete [] jon; // get rid of the old area we don't need anymore
jon = newArr;  // now jon is linked to our brand new data in a brand new area