小编use*_*107的帖子

我遇到了一些我不理解 malloc 的行为。

例如，为结构分配内存工作得很好，即：

typedef struct my_struct {
        char buffer[4096];
        struct my_struct *next;
} MY_STRUCT;

...

MY_STRUCT *ptr = (MY_STRUCT *)malloc(sizeof(struct my_struct));
        printf("malloc() gave us %lu bytes\n", sizeof(*ptr));
        printf("My structure's first member is %lu in length\n", sizeof(ptr->buffer));
        free(ptr);

...

退货

malloc() gave us 4104 bytes
My structure's first member is 4096 in length

……正如预期的那样。现在，当我尝试为字符串动态分配缓冲区时：

int bufsize = 4096;
char *buffer = (char *)malloc(sizeof(char)*bufsize);
printf("bufsize: %d\n", bufsize);
printf("Allocated buffer size: %lu\n", sizeof(*buffer));
free(buffer);

...返回

bufsize: 4096
Allocated buffer size: 8

现在，我可以硬编码 …