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Date: Mon, 1 Jun 2009 17:48:07 +0200
From: cpghost <cpghost@cordula.ws>
To: Vlad Galu <dudu@dudu.ro>
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Cc: freebsd-stable@freebsd.org
Subject: Re: Unnamed POSIX shared semaphores
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On Mon, Jun 01, 2009 at 06:33:42PM +0300, Vlad Galu wrote:
> Hello,
> 
> According to sem_init(3), we can't have shared unnamed semaphores.
> However, the following code snippet seems to work just  fine:
> 
> -- cut here --
>         sem_t semaphore;
>         if (sem_init(&semaphore, 1, 10) < 0)
>                 std::cout << "Couldn't init semaphore: " <<
> strerror(errno) << std::endl;
>         if (sem_wait(&semaphore) < 0)
>                 std::cout << "Couldn't decrement semaphore: " <<
> strerror(errno) << std::endl;
>         int val;
>         sem_getvalue(&semaphore, &val);
>         std::cout << "Value is " << val << std::endl;
> -- and here --
> 
> Is this a case where sem_init() silently reports success, or should be
> the man page get an update?

You may want to read the comments in /usr/src/lib/libc/gen/sem.c
regarding sem_init().

But yes, the man page is somewhat unclear and I'm not sure the last
paragraph is still totally accurate.

> Thanks,
> Vlad

-cpghost.

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