Re: [Mingw-w64-public] Fwd: [patch] Reimplement GNU threads library on native Windows

[Jonathan Wakely <jwakely at redhat dot com>]

On 02/07/19 12:15 +0200, Jacek Caban wrote:
> On 02/07/2019 12:12, Jacek Caban wrote:
> > On 02/07/2019 11:57, Liu Hao wrote:
> >
> > > 在 2019/7/2 下午5:19, Eric Botcazou 写道:
> > > > > It seems inappropriate to use handles as thread identifiers 
> > > > > (as handles
> > > > > imply resource ownership and are not unique identifiers); 
> > > > > thread IDs (as
> > > > > `DWORD` or `unsigned long`) would be a better alternative.
> > > > This was considered but ultimately rejected, as you can do 
> > > > nothing with a
> > > > thread Id, i.e. you need a handle for everything.  But the 
> > > > __gthread_equal
> > > > routine does compare the Ids and not the handles.
> > > The `OpenThread()` function can obtain a handle by thread ID. It returns
> > > a real handle that has to be closed when it is out of use. Using the
> > > pseudo handle returned by `GetCurrentThread()` may be more efficient if
> > > the target thread ID is equal to `GetCurrentThreadId()`.
> >
> >
> > The problem with thread id is that it's not valid nor guaranteed to 
> > be identical after the thread is terminated. A handle needs to be 
> > used for that.
>
>
> I meant unique, not identical.

The C++ standard says:

"The library may reuse the value of a thread::id of a terminated
thread that can no longer be joined."

So that's not a reason to use a handle.