Re: corebase runloop integration

[Luboš Doležel]

On Tue, 4 Feb 2014 08:45:32 +0000, David Chisnall wrote:
> On 3 Feb 2014, at 23:14, Luboš Doležel <address@hidden> wrote:
>
> > I looked into it again:
> >
> > "Methods defined in categories can replace methods defined in the 
> > class
> > proper, but they cannot reliably replace methods defined in other
> > categories."
> >
> > I suppose this could be good enough after all. I wouldn't expect any
> > other NSRunLoop overrides around.
>
> The problem is that if someone else provides a category in a shared
> library, there is no guarantee whether yours or theirs will be loaded
> first, and it depends entirely on link / load order so may not be
> stable.
>
> However, I'm not sure I understand why this is an issue for
> CFRunLoop.  The CFRunLoop is roughly analogous to GSRunLoopCtx, and 
> so
> the right way of doing this would be to rename GSRunLoopCtx to
> CFRunLoop, clean up its APIs, and make it public.  There are multiple
> implementations of this currently, and it would also be nice to have
> one that used libdispatch at the core so that we could use
> libdispatch's main queue as the main thread and so on.

I'm afraid The only thing that CFRunLoop and GSRunLoopCtx have in 
common is that there is some kind of loop.

The way I understand CFRunLoop, it doesn't actually poll for a set of 
fds, CFRunLoopSources version 0 do this on their own in a separate 
thread (or a libdispatch queue). CFRunLoopSources version 1 are used for 
Mach ports only - CFRunLoop polls these, but I don't think we can swap a 
Mach port for an fd.

You're right, libdispatch would be great for this. But what I fear is 
that as soon as I start working in that direction, someone will come and 
either start complaining about a libdispatch dependency or Clang 
requirement once I dare to use a block. And the last thing I would do is 
to write one worse implementation for GCC and one nice implementation 
for Clang.

So one thing we should be clear about is whether we approve of CoreBase 
being a project where we strive for nice modern implementations *or* 
whether we still cringe to legacy compilers and the 
provide-fallback-for-every-dependency strategy.

--
Luboš Doležel