From: Erik Faye-Lund <kusmabite@googlemail.com>
Date: Fri, 15 Jan 2010 23:08:28 GMT
Subject: Re: [PATCH v2 13/14] daemon: use select() instead of poll()
Message-ID: <40aa078e1001151508j208fa50boc5565a3be6bef893@mail.gmail.com>
In-Reply-To: <201001152349.06418.j6t@kdbg.org>

On Fri, Jan 15, 2010 at 11:49 PM, Johannes Sixt <j6t@kdbg.org> wrote:
> On Freitag, 15. Januar 2010, Erik Faye-Lund wrote:
>> +#undef FD_SET
>> +#define FD_SET(fd, set) do { \
>> +     ((fd_set*)(set))->fd_array[((fd_set *)(set))->fd_count++] =
>> _get_osfhandle(fd); \ +       } while(0)
>> +#undef FD_ISSET
>> +#define FD_ISSET(fd, set) __WSAFDIsSet(_get_osfhandle(fd), (fd_set
>> *)(set)) +
>
> I'm worried about the internals that you have to use here. Isn't it possible
> save the original macro text and use it in the new definition, like (this is
> for exposition only):
>
> #define ORIG_FD_SET(fd, set) FD_SET(fd, set)
> #undef FD_SET
> #define FD_SET(fd, set) ORIG_FD_SET(_get_osfhandle(fd), set)
>

Redefining it is indeed fishy - I guess I should also have noted that
I even stripped the code down slightly (compared to the original).

I'm no preprocessor wizard, but I'll give it a stab.

> Another approach would be to extend the poll emulation such that it uses
> select if all FDs to wait for are sockets, and I think this would be the case
> in this application.
>

The problem with that is differentiating between pipes and sockets.
GetFileType() returns FILE_TYPE_PIPE for sockets (ugh). I did find
some code in gnulib that used WSAEnumNetworkEvents() to differentiate
between them, but I find this quite hacky.

-- 
Erik "kusma" Faye-Lund