什么是野指针？（What is a wild pointer?）

未被初始化的变量称为野指针（wild pointer）。顾名思义，我们不知道这个指针指向内存中的什么地址，使用不当程序会产生各种各样的问题。

理解下面的例子：

int main()
{
    int *p;  // wild pointer, some unknown memory location is pointed
 
    *p = 12; // Some unknown memory location is being changed
 
    // This should never be done.
}

要注意的是，如果指针指向已知的变量就不是野指针。下面的代码中指针p在指向变量a之前一直是野指针。

int main()
{
    int  *p; // wild pointer, some unknown memory is pointed
    int a = 10;
 
    p = &a;  // p is not a wild pointer now, since we know where p is pointing
 
    *p = 12; // This is fine. Value of a is changed
}

如果我们需要指向一个没有变量名的值，我们应该给这个值分配内存，将这个值放在分配的内存中。

int main()
{
    //malloc returns NULL if no free memory was found
    int *p = malloc(sizeof(int));
 
    //now we should check if memory was allocated or not
    if(p != NULL)
    {
        *p = 12; // This is fine (because malloc doesn't return NULL)
    }
    else
    {
        printf("MEMORY LIMIT REACHED");
    }
}