John Baldwin wrote:
On Thursday 25 October 2007 07:04:08 pm Scott Long wrote:
Robert Watson wrote:
On Thu, 25 Oct 2007, Andrey Chernov wrote:
On Thu, Oct 25, 2007 at 12:05:40PM -0700, LI Xin wrote:
Well, I think the problem is not exposing a new symbol by itself, but
__mb_sb_limit is being used in _ctype.h, in a form of __inline
functions. Therefore, the change will break new binaries running on
older systems.
Yes. Only vice versa compatibility supported.
I think the issue here is that the change occurred very quickly after
the branch, and when users wanted to 'change gears' back to RELENG_7
from HEAD once it was created immediately ran into the problem. It
seems like a useful piece of post-branch advice to developers in the
future will be, "Please don't do things that make switching branches --
back or forward -- for the first few weeks after the branch is
created". In general, I don't think we care about forward
compatibility, but we are currently getting lots of reports because this
is one of those few times where a lot of moving backward happens.
We do care about forward compatibility within STABLE branches, as Ken
and I have discussed in side threads. But yes, forward compat between
major branches is merely desired; i.e. changes will happen, and
hopefully not for gratuitous reasons.
If we care about forward compatiblity then we can't add new features to
RELENG_X branches. For example, MFCing MSI to 6.x broke forward compat since
a 6.3 module might call the MSI methods thus can't be used on a 6.2 kernel.
AFAIK, we have _never_ promised anything wrt forward compat, only backwards
ABI compat. I can agree with Robert above that during a transition time such
as now it's really handy to be able to switch easily between branches, but I
didn't think it was ever a concern otherwise. If we are going to change the
policy for that then there's a whole bunch of crap I need to go back out of
6.x to restore compat. :-/
You're right that nothing can be promised, but you're ignoring what Ken
and I are saying about having a justification for changes. Yes, MSI
added a feature that wasn't present in previous releases. But it's
something that is optional and can be easily ifdef'd in source. The
ctype ABI change isn't like that at all; it's mandatory and it can't be
worked around. We also asked that even justifiable changes be evaluated
to see if there was any work-around to avoid breakage. Several have
already been suggested for the ctype change.
Scott
_______________________________________________
[email protected] mailing list
http://lists.freebsd.org/mailman/listinfo/cvs-all
To unsubscribe, send any mail to "[EMAIL PROTECTED]"
