Hi, ----- Original Message ----- From: "Anthony Williams" <anthony.ajw@gmail.com> To: <boost@lists.boost.org> Sent: Wednesday, May 28, 2008 12:47 PM Subject: Re: [boost] [thread] Are thread ids unique during an applicationslife time?
Johan Torp <johan.torp@gmail.com> writes:
Peter Dimov-5 wrote:
IIRC, windows thread ids can be re-used. That is, if you stop a thread X and later start a thread Y they might get the same thread id. Is this the case with boost.thread? What about the standard? It states:
"An object of type thread::id provides a unique identifier for each thread of execution and a single distinct value for all thread objects that do not represent a thread of execution ([thread.threads.class]). Each thread of execution has a thread::id that is not equal to the thread::id of other threads of execution and that is not equal to the thread::id of std::thread objects that do not represent threads of execution."
http://www.open-std.org/JTC1/SC22/WG21/docs/lwg-active.html#783
I also expect re-use will mean users have to re-implement "unique_thread_id" and some really difficult-to-fix bugs for people who do not think about it. OTOH, I see some value in that std::thread::id are the same as window's thread ids when you're debugging and post-mortem debugging.
Since issue #783 is marked as ready, does it mean it is closed and the proposed text has been added to the standard? I was hoping re-use would be disallowed :/
No, it means it will be voted on at the June meeting.
If the thread::id can not be reused an exception should be thown when no more ids are available. The current proposal states that a thread::id of a terminated thread that can no longer be joined is reusable, i.e. immediatlly and even if there are other ids never used available I'm working on a Locally Unique Identifier library (that work for intergral types) having the following feautures: A released id can be either: a - never reused, or b - recoverable A recoverable id can be reused A - even if there are other ids which have never been used B - only if there are no more ids which have never been used The recoverable id could be reused 1 - Immediatlly, or 2- only - after a frozen period - if there is not an older free id (fifo), i.e. first recovered first reusable The current Boost.Thread thread::id proposal corresponds to the policy b+A+1, but the thread::id is not an intergral type, so I'm not sure the above can be applied to the thread::id type. The question is which are the policies having a sens for a thread::id without implying a given representation for the thread::id type and allowing an efficient implementation? If there are several possibilities, the next questions is, should this choice be provided to the user through a given inteface? globally? per thread? or, should this choice be let to the library implementors? Any thoughts? Best regards Vicente