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From: Ross Johnson <>
To: pthreads-win32 <>
Subject: Re: snap-2004-11-03 breakage
Date: Wed, 03 Nov 2004 14:33:00 -0000	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <0b0b01c4c1a7$8a2fe3b0$>


I definitely don't want to break applications unnecessarily and 
particularly applications that have been ported to several different 
POSIX systems, but on the other hand POSIX thread IDs are not required 
to be scalar. See the rationale from the definition of pthread_equal() 
in the Single Unix Specification version 3, which says:


    Implementations may choose to define a thread ID as a structure.
    This allows additional flexibility and robustness over using an
    *int*. For example, a thread ID could include a sequence number that
    allows detection of "dangling IDs" (copies of a thread ID that has
    been detached). Since the C language does not support comparison on
    structure types, the /pthread_equal/() function is provided to
    compare thread IDs.

I don't think this is new to SUS or SUS version 3 either.

Nor (given the above) does the value 0 (zero) for a thread ID have any 
special meaning in the standard, although it obviously does as the value 
returned by ec_thread_getpid() in ettercap. If you want to test if a 
thread exists given it's thread ID, use:

    if (pthread_kill(pid, 0) == 0)  /* or (... != ESRCH) */

That should be portable to all POSIX implementations.

I'm not dismissing your problem, but in this case I think it would be 
better to fix the application.


Gisle Vanem wrote:

> snap-2004-11-03 breaks a lot of applications by the way 'pthread_t' is 
> defined:
> typedef struct {
>    void * p;                   /* Pointer to actual object */
>    unsigned int x;             /* Extra information - reuse count etc */
> } ptw32_handle_t;
> typedef ptw32_handle_t pthread_t;
> Code like (from Ettercap)
>  pthread_t pid = ec_thread_getpid("golem");
>  if (pid != 0)
>    ec_thread_destroy(pid);
> no longer works; you cannot compare a struct against 0.
> I'm not sure you really meant to do that or if the typedef should be
> typedef ptw32_handle_t *pthread_t;
> --gv

  parent reply	other threads:[~2004-11-03 14:33 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2004-11-03 13:18 Gisle Vanem
2004-11-03 14:28 ` Robert Kindred
2004-11-03 16:18   ` Ross Johnson
2004-11-03 16:30     ` Peter Slacik
2004-11-04 18:06     ` Robert Kindred
2004-11-03 14:33 ` Ross Johnson [this message]
     [not found] ` <>
2004-11-03 15:02   ` Gisle Vanem
2004-11-03 15:38     ` Ross Johnson
2004-11-03 15:32 ` Alexander Terekhov
2004-11-03 16:19   ` Ross Johnson
2004-11-03 16:32     ` Alexander Terekhov
2004-11-03 16:15 Bossom, John

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