Re: [boost] [thread library rework] Ready to start

From: David Abrahams (dave_at_[hidden])
Date: 2005-08-29 19:54:33

Ion Gaztañaga <igaztanaga_at_[hidden]> writes:

>> They were wrong to do so, most especially for templates, which are
>> hugely useful in embedded programming.
>
> I agree with you in templates, if you take care with code bloating.

Bah.  Templates can just as easily reduce code bloat.
http://groups.google.com/group/comp.lang.c++.moderated/msg/82674634c2a6b3a0
http://groups.google.com/group/comp.lang.c++.moderated/msg/2efe6b65b0e51a4f

>> In my opinion, that would be a huge mistake.  EC++ was created as a
>> "language subset" without the consent or cooperation of the C++
>> committee.  Crippling C++ library interfaces simply in order to
>> maintain compatibility with it is the wrong thing to do, again IMO.
>
> Well, I'm not talking about EC++  but embedded world in general. In my 
> work I program for embedded systems everyday in C and C++ and threading, 
> in my opinion, is a very basic building block for embedded systems, so 
> if we want to put C++ in those systems just like we can do with C (you 
> don't pay for what you don't use) we should have a way to launch a 
> thread in a standard way in limited systems.

I agree.

> Exception system has a size overhead (well, that depends, but if you
> have 512KB-1MB of RAM...) and in most systems RTTI and exceptions
                                       ^
                                       embedded
> are disabled to save space. 

I wonder how much space gets spent on error handling without
exceptions, and I wonder if the error handling is correct.

> Exceptions are also not recommended in real-time systems, and you
> can use threads and mutexes. As an example, in iostreams, you can
> activate or not exceptions.

I know.

> Not that I think we must limit C++ because of EC++, but that we
> should think that a very important C++ market (growing nowadays)
> will be embedded/realtime systems, replacing many C applications,
> because productivity in C++ is higher and you can get nearly C
> performance. 

IMO it is crucial to engage compiler developers for embedded systems
in optimizing their runtimes for those environments.
http://groups.google.com/group/comp.lang.c++.moderated/msg/d37971376bfd7e09?dmode=source

However I agree as a practical matter there should be an obvious way
to implementat Boost.Threads that works on a system with exceptions
disabled.

> And again IMO, threads are too basic. I would never say
> this for regular expressions, serialization, or any other
> library. If we can't do anything about that, that's ok, but why not
> try? I agree that it is hard to get, but that's the beauty of C++,
> you can put it everywhere, from tiny devices to mainframes. And I
> think that Kevlin's approach can be safely used in embedded systems
> if we see that it's easy to get a subset of the full standard, using
> the same programming style (for example, futures).
>
> It's not that I love EC++ (I don't follow its guidelines, because I
> use templates in some embedded systems), it's that I see a practical
> need to take in care those aspects. If C can have it, C++ can. I'm
> not saying I would sacrifice C++ for embedded world, but it is
> better to take in care aspects so that we can spread C++ further.

Agreed.
-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com