From: Beman Dawes (bdawes_at_[hidden])
Date: 2001-06-27 09:20:26
At 09:27 AM 6/27/2001, Peter Dimov wrote:
>From: "Beman Dawes" <bdawes_at_[hidden]>
>
>> >Why not use something like
>> >
>> >namespace thread
>> >{
>> > class id; // or 'desc', if you like
>> >
>> > id create(...);
>> >
>> >// etc
>> >};
>>
>> Yes, that sort of low-level interface is the fallback if we can't work
>out
>> a "spirit of C++" interface.
>>
>> While I'm really pressing to see if it is possilbe to develop a high
>level
>> interface, I'm not opposed to making the lower level interface public,
>just
>> as the C++ standard supports both <cstdio> and <iostream>.
>
>But this low-level, non-C++-spirited interface is nearly equivalent to
the
>class-based one that Bill posted; that was my point. The user never deals
>with 'thread' instances anyway; the thread class is a "glorified
>namespace",
>as Bill correctly noted. The user creates, and manipulates, only
>thread_desc
>instances - this corresponds to thread::id above.
>
>FWIW, I actually like procedural interfaces, when they fit. There is
>nothing
>inherently low-level about them. thread::id may implement the
>handle/refcounted body idiom under the hood, or it may be a Win32 HANDLE.
>In
>a way, this interface is higher level, because it hides more of the
>implementation.
>
>The important difference between thread::id and FILE* is that a FILE* may
>leak. A thread::id can never leak. It has proper value semantics, so the
>'thread reference' it contains will be released upon its destruction; and
>the thread will terminate itself when it's done.
>
>thread::id is, using a file based analogy, a FILE* wrapper with the
>appropriate copy/destroy semantics.
I'm not disagreeing with any of the above, but I'm worried about the
negative consequences of providing only that procedural interface.
* Many programmers will roll their own thread class, wrapping the
procedural functions, and we will end up with a proliferation of
incompatible classes, many of which fail under stress because they didn't
to the wrapping correctly.
* Endless hours will be wasted explaining over-and-over again why there
isn't a "real C++" thread class in the library. Part of the reason (the
other was the name) this discussion started was the lack a convincing
sounding rationale for the lack of a real threads class.
* Some programmers won't bother to wrap, and won't bother to ask for
rationale. They will just reject the library out-of-hand because of the
lack of a "spirt of C++" thread class. That may well include the standards
committee.
I see the possibility of those negative consequences as so high that I'm
willing to put quite a lot of effort in helping Bill, Greg, and other
boosters find a good, workable thread object interface.
--Beman