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Re: shmget() returns xx if current user is not a administrator
- From: Corinna Vinschen <corinna-cygwin at cygwin dot com>
- To: cygwin at cygwin dot com
- Date: Fri, 12 Oct 2007 11:30:46 +0200
- Subject: Re: shmget() returns xx if current user is not a administrator
- References: <470F39C7.email@example.com>
- Reply-to: cygwin at cygwin dot com
On Oct 12 11:09, patrick ficheux wrote:
> In SANE (scanner project), the backend for snapscan failed to call shmget()
> with error EACCES (Permission denied) if the current user isn't
> When I'am logged as windows administrator, shmget() is called successfully
> In both case, the env. variable CYGWIN exists and this value is
> cygserver is installed and runs
> Is it possible to call shmget() without administrator's privileges ?
> In this case, what kind of privileges a user must have ? and how to set
> those privileges ?
> extract from snapscan backend
> #ifndef SHM_R
> #define SHM_R 0
> #ifndef SHM_W
> #define SHM_W 0
This is the problem. SHM_R and SHM_W are not defined on Cygwin.
These flags are not defined by POSIX and relying on them as above is
non-portable. As a result, you create a shared mem region with
permission bits set to 000.
> int shm_id = shmget (IPC_PRIVATE, shm_size, IPC_CREAT | SHM_R | SHM_W);
Try something like
int shm_id = shmget (IPC_PRIVATE, shm_size, IPC_CREAT | S_IRWXU);
Corinna Vinschen Please, send mails regarding Cygwin to
Cygwin Project Co-Leader cygwin AT cygwin DOT com
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