错误显示C ++中的访问冲突

Question

struct root
{
    struct Qgroup
    {
        struct Qpost
        {
            struct Qcomment
            {
                struct Qcomment *next;
                int likes;
                int address;
            } QComment[100];
            int likes;
            int comments;
            int address;
        } QPost[100];
        int address;
        int posts;
        int users;
    }QGroup[8];
}*Root = (struct root *)malloc(sizeof(struct root *));

Getting the Access Violation Error at the following line.

for(int i=0;i<5;i++)
Root->QGroup[i].address = i*128+1024*1024;

Please help me out of this? I tried both static allocation and dynamic allocation, but both failed in reading the data given in above loop. This error is from the starting of the execution after main()

Answer 1

Your problen is the memory allocation:

malloc(sizeof(struct root *));

You allocate memory for a pointer, which is only 4 or 8 bytes on most modern systems.

I don't really see a need to use a pointer here in the first place.

Answer 2

Root = malloc(sizeof(struct root *));

This has to correct as follows:

Root = (struct root *)malloc(sizeof(struct root ));

No need to cast to struct root * since malloc returns a void pointer and you can assign it to any other type in C. But in case of C++ you need to cast as you did.

In case of C++ it is always better to use new and delete instead malloc and free . So you can simply the usage as follows:

 Root = new root ;