On Sun, Jun 08, 2008 at 01:24:31AM -0700, Matt Tolton <[EMAIL PROTECTED]> wrote:
> In getting libev running on windows, I think I may have found a bug in
> the select_modify() function in ev_select.c.
What you actually found is yet another bug on that horribly broken
platform.
Well spotted (none of my programs aggressively re-use fds :)
> an array for its fd set, and it doesn't check to see if the fd is
> already in the set when you do an FD_SET.
Right, because FD_SET is guarenteed to not to add an fd twice even as per
msdn docs - of course, the implementation is broken as always.
Since microsoft will unliekly bother to fix their pile of bugs, libev has to
yield again.
> kept returning EBADF, but libev couldn't find the bad fd. I imagine
> that most fd sets use bitvectors or something so this isn't a problem
> (not that I know much about this stuff).
Well, the point of having those macros is to not have to know about how they
are implemented - the berkeley sockets interface guarantees that FD_SET only
adds the fd once to the set (after all, thats a set), and microsoft claims
to follow this.
So the problem is not how its implemented, but the fatc that it is simply
broken - the whole point of having FD_SET was to not have that bug in the
first place. *sigh*.
> I made the following
> modification to select_modify (sorry it's not in diff format...I'm
> sure you can see where it goes):
Indeed, for such small patches, it's ok (you could have formatted it
better, though...)
I will try to add somrething like that that only punishes windows to libev.
Thanks a lot for catching this and analysing the situation!
> It seems that something like this should be added to the real libev
> source. You could also, of course, use the FD_ISSET macro. This
> would probably be more foolproof, but I'm guessing it would be slower
> (not that we'll get much performance out of windows using select()
> anyway).
oev <-> nev changes should catch 100% of the transitions for each fd,
except after a fork, which doesn't matter as this is not an operation
windows supports in a sensible way.
--
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