Re: Threads - When?

From:
"James Kanze" <james.kanze@gmail.com>
Newsgroups:
comp.lang.c++.moderated
Date:
31 Dec 2006 15:18:20 -0500
Message-ID:
<1167581214.214360.61990@h40g2000cwb.googlegroups.com>
Le Chaud Lapin wrote:

Joe Seigh wrote:

Unfortunately, they seem to be concentrating on low level design
right now, specifically the memory model. The problem is they
don't know how to do high level specification so they're creating
a low level specification and will do the higher level constructs
in the form of a meta implementation.


What do you mean here? Are they concocting new low-level C++
primitives that presume the existence of hardware instructions to
support those new primitives?


No. They're defining what it means to access memory from more
than one thread at a time. Until this is done, any
multithreaded program in C++ works either by chance (which is
probably the case of most multithreaded programs), or because it
is based on additional guarantees given by the
implementation---there are "intuitive" mappings for much of the
Posix C model to C++, for example, even if they do leave a
number of C++ issues unanswered. (Note that on the platform I
most frequently program on, Sun CC and g++ use incompatible
mappings, which means that a program which is correct with
regards to threading for Sun CC may not be with g++, and vice
versa.)

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