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From: Beman Dawes (bdawes_at_[hidden])
Date: 2001-08-03 14:31:10

At 12:26 PM 8/3/2001, John Max Skaller wrote:
>williamkempf_at_[hidden] wrote:
>> Yes, and with valid reason. C++ is not C. Some things that make
>> sense in a C API are either difficult to live with in C++, or even
>> result in conflicts with the language design.
> I support Bill's approach. I'd like to remind people
>that we're actually talking about defining a threading library
>that works for a yet to be determined extension of the C++
>abstract machine. The relationship with Windows and POSIX
>threading should be that those models can be used to implement
>the C++ model. Conversely, the C++ model must provide at least
>minimal support for real threading requirements as both
>Windows and POSIX models do.
>> Firstly, it's not a mix of two APIs. Everything here is designed
>> from the ground up. Usage patterns and known problems/strengths for
>> all (not both, other libraries than POSIX and Win32 have been
>> considered, including from other languages) have been paid attention
>> to, but none of them are the basis for Boost.Threads.
> I think this approach is the only feasible one.
>Designing a new threading model is necessary. Obviously,
>existing models should be used as input data in making
>the design decisions, but it seems to me Bill is doing that.
> The purpose of the library (and abstract machine extensions)
>isn't to do POSIX or Windows threading, but to introduce concurrency
>into C++. Since concurrent execution is _intrinsically_ bound up
>with language semantics -- it is after all a fundamental concept
>to have concurrent threads of control -- I'd like to think those
>with expertise will help Bill in his effort.
> In particular, we need a library to see what changes
>are needed to the core language to make concurrency work: Beman
>has already outlined a synchronisation model in his paper.
>The key issue involves sharing data: if a thread writes to
>some shared memory, how can another thread read that data?

Yes, what Butenhof in "Programming with POSIX Threads" (highly recommended
reading) calls "Memory visibility between threads" will have to be a key
part of the core language specification. This is definitely going to need
help from John and other core language experts.


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