Re: C++ fluency

From:

James Kanze <james.kanze@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Fri, 8 May 2009 03:13:46 -0700 (PDT)

Message-ID:

<3cddebc1-65d8-4ea8-9879-226d0c5d9779@n8g2000vbb.googlegroups.com>

On May 8, 12:05 pm, Ian Collins <ian-n...@hotmail.com> wrote:

James Kanze wrote:

On May 7, 10:26 pm, Ian Collins <ian-n...@hotmail.com> wrote:

James Kanze wrote:

(I've vaguely heard of systems for small, embedded
processors, where you could control the timing of external
events, but I've never actually seen one. And of course,
you have absolutely no control over when Windows or Unix
does a context switch.)

(And I'd simply love it if someone could prove me wrong
about the above.)

I don't know about windows, but most if not all Unix
variants have a real-time scheduling class.

Which does what? (And where do you get it? None of the
Unix variants I know have any classes---their interface is
pure C.)

What do scheduling classes have to do with C?

I understood "class" as the C++ keyword. What do you mean by
it? (I can't find any use of the word in the Posix
documentation.)

At least on Solaris a real time thread will not be time-sliced
or prempted by anything other than a higher priority real time
thread. So they are ideal for simulating RTOS behaviour.

Different Unix can (and often will) support different scheduling
policies. I don't quite see how this affects testability; the
question is what happens when thread A interrupts thread B at
any given instant (say because thread A has a higher priority
than thread B).

For a simple example of the sort of thing I'm talking about, see
g++ bug 21334 (which I found by code review, not by testing).

--
James Kanze (GABI Software) email:james.kanze@gmail.com
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