[英]Creating a 2D array in the shared memory
I want to create a program to store data in a 2D array. 我想创建一个程序以2D数组存储数据。 This 2D array should be created in the shared memory. 此2D数组应在共享内存中创建。
#include <stdio.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
key_t key;
int shmBuf1id;
int *buf1Ptr;
main(int argc, int *argv[])
{
createBuf1();
}
createBuf1()
{
key = ftok(".",'b');
shmBuf1id = shmget(key,sizeof(int[9][9]),IPC_CREAT|0666);
if(shmBuf1id == -1 )
{
perror("shmget");
exit(1);
}
else
{
printf("Creating new Sahred memory sement\n");
buf1Ptr[3] = shmat(shmBuf1id,0,0);
if(buf1Ptr == -1 )
{
perror("shmat");
exit(1);
}
}
}
But when I run this program it gives a segmentation fault(Core dumped) error. 但是,当我运行该程序时,它给出了分段错误(Core dumped)错误。 Have I created the 2D array in the shared memory correctly? 我是否在共享内存中正确创建了2D数组?
First, int *buf1Ptr
is a pointer to int. 首先, int *buf1Ptr
是指向int的指针。 In your case you want a pointer to a 2-dimensional array of integers, so you should declare it as: 在您的情况下,您需要一个指向二维整数数组的指针,因此应将其声明为:
int (*buf1Ptr)[9];
Then you need to initialize the pointer itself: 然后,您需要初始化指针本身:
buf1Ptr = shmat(shmBuf1id,0,0);
Now you can access your array through buf1Ptr (ie. buf1Ptr[0][0] = 1
). 现在,您可以通过buf1Ptr访问数组(即buf1Ptr[0][0] = 1
)。 Here's a complete working version of your program: 这是您程序的完整工作版本:
#include <stdlib.h>
#include <stdio.h>
#include <sys/ipc.h>
#include <sys/shm.h>
key_t key;
int shmBuf1id;
int (*buf1Ptr)[9];
void
createBuf1()
{
key = ftok(".",'b');
shmBuf1id = shmget(key,sizeof(int[9][9]),IPC_CREAT|0666);
if(shmBuf1id == -1 )
{
perror("shmget");
exit(1);
}
else
{
printf("Creating new Sahred memory sement\n");
buf1Ptr = shmat(shmBuf1id,0,0);
if(buf1Ptr == (void*) -1 )
{
perror("shmat");
exit(1);
}
}
}
int
main(int argc, int *argv[])
{
createBuf1();
return 0;
}
you forgot allocate memory: 您忘记分配内存:
#include <stdio.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
key_t key;
int shmBuf1id;
int *buf1Ptr;
int main(int argc, char *argv[])
{
createBuf1();
}
createBuf1()
{
key = ftok(".",'b');
shmBuf1id = shmget(key,sizeof(int[9][9]),IPC_CREAT|0666);
if(shmBuf1id == -1 )
{
perror("shmget");
exit(1);
}
else
{
printf("Creating new Sahred memory sement\n");
int buf1Ptr[4];
buf1Ptr[3] = shmat(shmBuf1id,0,0);
if(buf1Ptr == -1 )
{
perror("shmat");
exit(1);
}
}
}
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