On Sat, May 27, 2006 at 04:36:05PM +0900, YAMAMOTO Takashi wrote:
> 
> and they make _EVENTHANDLER_INVOKE even bigger...
> 

Not by a whole lot, the mask function adds a couple more terms to an
if conditional, run once adds a simple if statement.  Not large
changes.

> do you mean that doshutdownhooks can be called again and again?
> i don't think it happens in normal path.
> 

I agree, I don't think it happens in the normal path but _someone_
felt the need to carefully remove the list entries when the shutdown
hooks were run and add a comment saying this was done to ensure the
hooks were only run once in the orignal code I replaced.  I do not
feel qualified to overrule that decision.

> in the case of mountroothook, i doubt it should have been
> implemented as a hook in the first place.
> 

Again, I don't know why it was there but someone put a gating around
whether or not the hook function would be run.  I chose to build in
functionality to perform the same.

> 
> i personally don't think it's so bad to use an xxx_args structure argument.
> 

ok, I was going down this line of thinking too when I first proposed
the generic hooking interface.  If we do this there are two
alternatives:

1) we do the same sort of macro tricks so the hook functions get
passed the correctly typed xxx_args pointer.
2) we just cast to and from void * and hope that the arg structure we
are getting is what we expected.

1 is, I think, about as complex as what eventhandler currently uses
but should error during compile. 2 is fast and loose and will cause
some "interesting" effects at run time if the function is not passed
the correct structure.

> 
> a big downside is _EVENTHANDLER_INVOKE itself,
> which is a big and complex macro.
> 

It is, there is no arguing with that.  We do have other macros which
are of about the same complexity - see queue.h for examples.

As it stands, the eventhandler interface I have proposed is
compatable with the FreeBSD version.  It may be a small thing but it
would be nice if we can have a common interface.

-- 
Brett Lymn