代码之家 › 专栏 › 技术社区 › Andrej

shmctl在C中抛出“无法分配内存”

shared-memory c

Andrej · 技术社区 · 7 年前

我有这个代码:

#define SHMSIZE 8388606
int main()
{
    int shmid;
    void *shmPtr;
    char *shm;
    if ((shmid = shmget(IPC_PRIVATE, sizeof(char) * SHMSIZE , IPC_CREAT |        0666)) < 0) {
        perror("shmget");
        exit(1);
    }

    if ((shmPtr = shmat(shmid, NULL, 0)) == (char *) -1) {
       perror("shmat");
       exit(1);
    }
    shm = (char *)shmPtr;
    strncpy(shm, "0\n", 2);

    struct shmid_ds  shmid_ds;
    int rtrn = shmctl(shmid, SHM_LOCK, &shmid_ds);
    if(rtrn < 0) {
        perror("shmctl");
        exit(1);
    }
    else {
        printf("Nailed it\n" );
    }
    return 0;
}

运行它,我得到了错误:

这段代码如何通过shmget()调用成功运行?我错过重要的东西了吗?

1 回复 | 直到 7 年前

Kanji Viroja 7 年前

阅读本文,它可能会帮助您解决问题:

   The caller can prevent or allow swapping of a shared memory segment
   with the following cmd values:

   SHM_LOCK (Linux-specific)
             Prevent swapping of the shared memory segment.  The caller
             must fault in any pages that are required to be present
             after locking is enabled.  If a segment has been locked,
             then the (nonstandard) SHM_LOCKED flag of the shm_perm.mode
             field in the associated data structure retrieved by
             IPC_STAT will be set.

   SHM_UNLOCK (Linux-specific)
             Unlock the segment, allowing it to be swapped out.

   In kernels before 2.6.10, only a privileged process could employ
   SHM_LOCK and SHM_UNLOCK.  Since kernel 2.6.10, an unprivileged
   process can employ these operations if its effective UID matches the
   owner or creator UID of the segment, and (for SHM_LOCK) the amount of
   memory to be locked falls within the RLIMIT_MEMLOCK resource limit
   (see setrlimit(2)).

试试这个:

int rtrn=shmctl(shmid、IPC_STAT和shmid_ds);

推荐文章

Community wiki · C中有哪些耗时的操作?

1 年前

Tintenfisch · 传递参数:array与C和C中的*&array和&array[0]之间的差异++

1 年前

daryldxn · Windows筛选平台计算通过TCP连接发送的字节和接收的字节

1 年前

Mike Balts · 它们将被打印多少次,为什么?我知道:“阿尔法”一次,“贝塔”两次,“欧米茄”两次但我不知道为什么

1 年前

Mohammed Eid · 数据类型“char”是否可以被视为数据类型“int”?

1 年前

Community wiki · 将所有处理器电源都投入到任务中

1 年前

Community wiki · 在C&数据结构中实现不同数据结构的聪明方法,应该更频繁地使用

1 年前

Community wiki · C++为C添加了什么?[已关闭]

1 年前

Abhinav Kumar · 如何将#define的数据类型设置为长双精度?

1 年前

Community wiki · 打印1到1000,不带循环或条件

1 年前