[rfc] Return old cleanup when doing a restore_cleanups()

[Kevin Buettner]

On Aug 13,  3:28pm, Andrew Cagney wrote:

> The attached patch tweeks the restore_cleanups() family of functions so 
> that the old cleanup is returned.
> 
> In theory, that returned cleanup should be NULL (since the cleanup chain 
> will have been drained just prior to the restore_cleanups() call).  In 
> reality, I'm not too sure.  I'd like to find out what the old chain was 
> so I can add an assert to certain callers (e.g. catch_errors()).
> 
> I guess the alternative is to just stick the assert in 
> restore_cleanups() and see what breaks.
> 
> Thoughts?  Preference?

At the moment, the only caller of restore_cleanups() is
catch_errors(), so the assert could just as easily go in
restore_cleanups() without causing any more breakage than placing the
assert in catch_errors().

If all (future) callers of restore_cleanups are supposed to drain the
cleanup chain first, then I think the assert belongs in
restore_cleanups().  If you think there might be a good reason to
violate this rule, then the assert belongs in the caller.  Personally,
I'd rather see the assert go in restore_cleanups() until someone can
demonstrate a good reason for not draining the cleanup chain.

Kevin