C编程内存子分配器的循环列表

Question

我正在尝试构建一个内存子分配器。我的代码有一些错误，它告诉我:

free_list_ptr->next = &firstByte;
free_list_ptr->prev = &firstByte;

我收到 gcc 错误警告 warning: assignment from incompatible pointer type

//primitive variable of byte as char, always positive.
typedef unsigned char byte;
static byte *memory = NULL;

struct header;

typedef struct _header {
    int signiture;
    int size;
    struct header* next;
    struct header* prev;
} header;


static header *free_list_ptr;


void allocator_init(u_int32_t size){

    memory = (byte*) malloc(size);

    //initialize free_list_ptr;
    free_list_ptr = (header*) memory;

        header* firstByte = (header*) memory;

    free_list_ptr->size = size;

    //error here: warning: assignment from incompatible pointer type
    free_list_ptr->prev = &firstByte;
    free_list_ptr->next = &firstByte;
}

Answer 1

这很可能是错误的:

struct header;               // forward declare "struct header"

typedef struct _header {
    int signiture;
    int size;
    struct header* next;     // refer to the forward declared "struct header"
    struct header* prev;
} header;                    // declare type-alias "header"

改为做

typedef struct header header; // forward declaration of both

struct header {
    int signiture;
    int size;
    header* next;
    header* prev;
};

在 C 中，struct header 和 typedefed header 位于两个不同的 namespace 中。您转发声明的 struct header 但您从未定义它。

此外，以 _ 开头的标识符通常保留用于内部，因此您不应该将它们用于您自己的东西。