Re: [boost] Re: boost.threads

From: Alexander Terekhov (terekhov_at_[hidden])
Date: 2001-08-07 07:27:21

> I've reformulated the description:
>
> Unless otherwise specified, each thread shares all aspects of its
execution
> environment with other threads in the program. Shared aspects of the
> execution environment include, but are not limited to, the following:
>
> ·  Static storage duration (static, extern) objects [3.7.1].
>
> ·  Dynamic storage duration (heap) memory [3.7.3]. Thus each memory
> allocation will return a unique addresses, regardless of the thread
making
> the allocation request.
>
> ·  Automatic storage duration (stack) objects [3.7.2] accessed via
pointer
> or reference from another thread.
>
> ·  Resources provided by the operating system. For example, files.
>
> ·  The program itself. In other words, each thread is executing some
> function of the same program, not a totally different program.
>
> Each thread has its own:
>
> ·  Registers and current execution sequence (program counter) [1.9/5].
>
> ·  Automatic storage duration (stack) objects [3.7.2].
>
>  >but it occurs to me that on a multi-processor, the constraint
>  >would allow CPU local memory to be used for the stack, which
>  >could be a significant optimisation.
>
> Since that would disallow inter-thread pointers or references to stack
> objects, I don't think it would allow a conforming thread implementation.

and a lot of existing C/C++ code would become broken if auto
storage would become non-GLOBAL/thread non-shareable. however,
IMHO it would be really great if the new thread-aware C++ would
introduce two new "standard" storage types/durations:

thread local/specific static storage duration memory/objects - that
is basically what MS VC __declspec(thread) does.

thread local/specific dynamic storage duration memory/objects - that
is basically what pthread_get/setspecific (or javas ThreadLocal) does.

regards,
alexander.