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Date: Fri, 02 Jun 2006 17:29:33 +0200
From: Lionel Perrin <perrin@domain.hid>
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Subject: [Xenomai-help] shm_open, ftruncate
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To: xenomai@xenomai.org

Hi,

I got some problems with shared memory.
I started from the shm_open example from opengroup.org.
When I compile it as non real time tasks, it works properly. But since I 
tried to compile it with
gcc $(xeno-config --posix-cflags) shm_open.c $(xeno-config 
--posix-ldflags) -o xeno_shm_open,
i get an EINVAL error from ftruncate that i can fix.

Does shm under xenomai require particular things ?

Thanks for your help...

Lionel

#include <unistd.h>
#include <sys/mman.h>
...


#define MAX_LEN 10000
struct region {        /* Defines "structure" of shared memory */
    int len;
    char buf[MAX_LEN];
};
struct region *rptr;
int fd;


/* Create shared memory object and set its size */


fd = shm_open("/myregion", O_CREAT | O_RDWR, S_IRUSR | S_IWUSR);
if (fd == -1)
    /* Handle error */;


if (ftruncate(fd, sizeof(struct region)) == -1)
    /* Handle error */;


/* Map shared memory object */


rptr = mmap(NULL, sizeof(struct region),
       PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
if (rptr == MAP_FAILED)
    /* Handle error */;


/* Now we can refer to mapped region using fields of rptr;
   for example, rptr->len */