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From:	patl AT cag DOT lcs DOT mit DOT edu (Patrick J. LoPresti)
To:	cygwin AT sourceware DOT cygnus DOT com
Subject:	Observations on select.cc (19990922 snapshot)
Date:	24 Sep 1999 16:40:20 -0400
Message-ID:	<s5gvh909h6z.fsf@egghead.curl.com>
Lines:	24

Just some observations from reading the code and playing with strace.
Pull up select.cc and follow along.

The peek_pipe() function frequently gets called on the input side of a
pipe.  That causes the call to PeekNamedPipe() to fail with a
permission error (Win32 only lets you peek at the output side), which
is kind of annoying.  Perhaps peek_pipe() could check read_selected
before doing the PeekNamedPipe?

Also, there currently seem to be only clunky attempts to enforce the
invariant that the bits set in the fd_sets when select() returns are
subsets of the bits which were passed in.  (I'm not even certain this
is always true.)  Wouldn't it make sense for the set_bits() function
to enforce this invariant by checking {read,write,except}_selected
before setting the corresponding bit?  Then many of the read_selected
tests around the file could be removed.

By the way, I am not asking anyone else to do this work (unless they
want to).  I just want to confirm with the developers that these are
reasonable things to do before I bother...

Thanks!

 - Pat

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