Learning C++ pointer runs into core dump with following code, I really don't why?

Question

#include <stdlib.h>
int main(){
    int *array = new int[2];
    array[0] = 1;
    array[1] = 2;
    int ** dp = NULL;
    *dp = array;
    return 0;
}    

when I run it ,Segmentation fault (core dumped). g++ version is

Reading specs from /usr/lib/gcc/x86_64-redhat-linux/3.4.5/specs Configured with: ../configure --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info --enable-shared --enable-threads=posix --disable-checking --with-system-zlib --enable-__cxa_atexit --disable-libunwind-exceptions --enable-java-awt=gtk --host=x86_64-redhat-linux Thread model: posix gcc version 3.4.5 20051201 (Red Hat 3.4.5-2)

Answer 1

Change the following statements

int ** dp = new int *;

*dp = array;

Or even you could write one statement instead of the two above

int ** dp = new int *( array );

Also do not forget to free the allocated memory

delete dp;
delete []array;

As for your code then you are trying to dereference a null pointer.

Take into account that C header <stdlib.h> in C++ is named like <cstdlib>. And this header is not used in your program. So you may remove it.

The program could look like

#include <iostream>

int main() 
{
    int *array = new int[2] { 1, 2 };
    int ** dp = new int *( array );

    std::cout << ( *dp )[0] << '\t' << ( *dp )[1] << std::endl;

    delete dp;
    delete []array;

    return 0;
}

The output is

1   2

Answer 2

This line

*dp = array;

does not do what you intend. 'dp' is a pointer to a pointer and its initial value is zero (NULL). So you are trying to tell the system to place the address of 'array' to memory location 0 which is illegal. To make it work first you need to allocate a number of int *

dp = new int*[5];  // for example...
dp[0] = array;

This will assign the first pointer to your array