cygwin 1.3.10 semctl fails, but does not set errno
Michael Potter
pottmi@lidp.com
Mon Jun 3 09:25:00 GMT 2002
#include <stdio.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/ipc.h>
#include <sys/shm.h>
/* ----------------------------------------------------------------
** This program demostrates that semctl returns -1 (an error) but
** does not set errno (or at least sets it to 0).
**
** Compile this test program like this:
** gcc -o semctltest semctltest.c -lcygipc
**
** The problem is demostrated when you get this output:
** -> ./shmctltest
** shmctl failed with 0
**
** If you get:
** -> ./shmctltest
** shmget failed with 17
** Then you need to use ipcrm to remove the shared memory.
*/
int main(int argc, char *argv[])
{
int shmid;
int SaveErrno;
struct shmid_ds shmid_ds;
if ((shmid = shmget(508, 1024*1024, 0666|IPC_CREAT|IPC_EXCL)) == -1)
{
SaveErrno = errno;
printf("shmget failed with %d\n", SaveErrno);
exit(1);
}
shmid_ds.shm_perm.uid = getuid();
shmid_ds.shm_perm.gid = getgid();
shmid_ds.shm_perm.mode = 0666;
if (shmctl(shmid, IPC_SET, &shmid_ds) == -1)
{
SaveErrno = errno;
printf("shmctl failed with %d\n", SaveErrno);
exit(1);
}
exit(0);
}
--
Michael Potter
LIDP Consulting Inc.
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