Question

我们有一起使用共同记忆的C份申请。第一项申请增加了信息,第二项总是从共享记忆中读取。

struct messagestruct {
 unsigned int sessionid;
 uint8_t message[16]; //unsigned 8bit int
}__attribute__ ((__packed__));

我们需要举行3次会议(供3名用户使用)。定义的共有记忆体

#define SHARED_SIZE ( 3 *  sizeof(messagestruct)) + sizeof(int)

我们获得共同记忆

int sesskey = ftok("/path/to/a/file", "B");
int shmemoryid = shmget(sesskey, SHARED_SIZE, 0666 | IPC_CREAT);

在复制用于共享记忆的建筑时,对流星报告错误(无效书写尺寸1)

void *shmaddr = shmat(shmemoryid, NULL, 0);
int *sessnum;
struct messagestruct *msgstruct;
sessnum = (int *)shmaddr;
msgstruct = (struct messagestruct*)((void*) shmaddr + sizeof(int));   
memcpy(shmaddr, currentsessionsstruct, SHARED_SIZE); //-->valgrind error invalid write size 1

thanks for any helpful info.

Answer 1

memcpy(shmaddr, currentsessionsstruct, SHARED_SIZE);

You are copying 3 * sizeof(messagestruct) + sizeof(int). I believe you want to copy only sizeof(currentsessionstruct).

友情链接