Re: snap-2004-11-03 breakage

[Alexander Terekhov <TEREKHOV at de dot ibm dot com>]

> But how does ec_thread_getpid() portably determine if the thread
> exists or not?

Define "exists" first. If you mean "tryjoin", see 
<http://www.terekhov.de/mythread.c> illustration.

> Every function that takes a thread ID argument has the same problem
> as pthread_kill() if pointers are used.

Yes, but it's an application bug.

regards,
alexander.



Sent by:        pthreads-win32-owner@sources.redhat.com
To:     pthreads-win32 <pthreads-win32@sources.redhat.com>
cc:      
Subject:        Re: snap-2004-11-03 breakage


Alexander Terekhov wrote:

>>Code like (from Ettercap)
>>  pthread_t pid = ec_thread_getpid("golem");
>>  if (pid != 0)
>>    ec_thread_destroy(pid);
>> 
>>
>
>Code it like
>
>  pthread_t tid;
>  if (ec_thread_getpid("golem",&tid)
>    ec_thread_destroy(tid);
>
> 
>
But how does ec_thread_getpid() portably determine if the thread
exists or not?

>Don't rely on idiotic pthread_kill() "testing". The standard 
>doesn't preclude the use of pointers for thread IDs (e.g. 
>inside pthread_t structure).
>
Oops. I should have recognised that because ...

>Pointers become indeterminate and
>trigger undefined behavior for any nonassignment access once 
>the reference storage gets freed. Conforming implementations 
>are allowed to reclaim/free that referenced storage when 
>detached thread is terminated or joinable thread is terminated 
>and joined. Use of "retired" pthread_t values (e.g. as 
>pthread_kill() argument) after that moment will trigger 
>undefined behavior. 
>
> 
>
... that's exactly why pthread_t was changed in pthreads-win32.

Every function that takes a thread ID argument has the same problem
as pthread_kill() if pointers are used.

Ross

>regards,
>alexander.
>
> 
>