sem_open really strange behavior

[Andrew Haley]

On 06/22/2010 02:16 PM, Sergio Sobarzo wrote:
>
> I'm writing an application using semaphores. Here is a simple code
> recreating the problem:
> 
> ***********************************************
> #include <sys/types.h>
> #include <stdio.h>
> #include <semaphore.h>
> #include <sys/types.h>
> #include <sys/stat.h>
> #include <fcntl.h>
> #include <stdlib.h>
> 
> int main()
> {
>   int ok;
> //key_t t;
> char *shm,*s;
> sem_t *mutex;
> 
>   mutex = sem_open("/vik",O_CREAT|O_EXCL);
>   if(mutex == SEM_FAILED)
>     {
>       perror("unable to create semaphore");
>       sem_unlink("vik");
>       exit(-1);
>     }
> 
>   sem_close(mutex);
>   sem_unlink("vik");
>   exit(0);
> }
> ************************************************
> 
> This, is going to generate "unable to create semaphore: Invalid
> argument" no matter how many times I execute it. It is compiled with
> "gcc sem.c -lrt"
> 
> However, once I uncomment the key_t line, everything works fine. What
> should be wrong? I'm stuck on this little thing for hours.

I'm sure this isn't a gcc problem.  Maybe a bug in the library, or something?
Hard to say.

Andrew.