Re: [Qemu-devel] [RFC PATCH 0/2] port network layer onto glib

[Paolo Bonzini <pbonzini@redhat.com>]

Il 19/03/2013 11:12, Peter Maydell ha scritto:
> On 19 March 2013 09:30, Markus Armbruster <armbru@redhat.com> wrote:
>> Coroutines are a perfectly pedestrian control flow construct.
> 
> In some languages, sure. Not in C, and we're writing C.
> 
>> Coroutines fit about as well with C as threads, namely not really.
> 
> Threads are supported by the language runtime provided on all
> the systems we support, which is why they are reasonably usable.
> When you've persuaded glibc, MacOSX libc and Windows to implement
> coroutines please come back and let me know :-)

Windows supports them (it calls them fibers) and glibc does on many
architectures (all but ARM, basically).

Paolo

>> If portable coroutines in C really was an intractable problem, the
>> solution could not be "no more coroutines, please", only "no coroutines,
>> period".  As long as we have to pay the price for coroutines anyway, I
>> can't see why we should deny ourselves the benefits.
> 
> I'd like to see coroutines gone completely. The first step is not
> to let them get used more than they are already.
> 
>> C programs have been doing coroutines since forever, using either hand
>> coded assembly language stack switching, sigaltstack() trickery,
>> ucontext(), w32 fibers, or some coroutine library built on top of these.
> 
> ...and there's a wide range of really nasty options because none
> of them are actually decent solutions to the problem.
> 
> -- PMM
>