C Memory Management

malloc

1
2
3
4
5
6

// with the help of a typecast and sizeof 
ptr = (int *) malloc(n * sizeof(int));
/* check if malloc was successful */
if (ptr == NULL) {
    /* handle error */
}

1
2
3

ptr = (int *) realloc(ptr, (n+1) * sizeof(int));

free(ptr); // realloc(ptr, 0)

不要踩坑！

An array name is not a variable. – K&R

when call &arr , just get the address of the first element of the array

Linked List Example

1
2
3
4
5
6
7
8
9

struct node {
    char *data;
    struct node *next;
};
typedef struct node *List; // 定义 List 为 struct node 的指针类型

List create_empty_list() {
    return NULL;
}

Memory Locations

分配内存的方式

三个存储池

栈的映像图 LIFO

Memory Management

stack, static memory are easy to handle, but heap is a bit more complicated…

Implementing malloc and free

When Memory Goes Bad

• 不要轻易的访问栈区指针 / 地址

• 忘记realloc会移动数据

• 移动指针但是胡乱free or double free 🤯

Valgrind?

• Valgrind is a tool for detecting memory errors in C and C++ programs.