svn commit: r255219 - in head: contrib/tcpdump lib/libc lib/libc/capability lib/libc/include lib/libc/sys lib/libprocstat sbin/dhclient sbin/hastd sys/amd64/linux32 sys/bsm sys/cddl/compat/opensola...

[Konstantin Belousov]

On Thu, Jan 02, 2014 at 11:23:55AM -0800, Alfred Perlstein wrote:
> 
> On 1/2/14, 11:14 AM, John-Mark Gurney wrote:
> > Konstantin Belousov wrote this message on Thu, Jan 02, 2014 at 15:13 +0200:
> >>>> Afaik you could just remove the "spare" and steal 2 or 4 entries from
> >>>> _kf_ispare until it is sorted.
> >>> Yes, this would work for current cap_rights_t structure, at least for
> >>> i386 and amd64, but would only allow to expand the structure by one
> >>> uint64_t in the future (which might or might not be enough). The
> >>> cap_rights_t structure is designed to be expanded to 5 uint64_ts without
> >>> breaking ABI. I don't want to stuck with current cap_rights_t that is
> >>> designed to expand, but cannot be, because kinfo_file wasn't modified at
> >>> the start of a major branch.
> >> The ABI stability is not limited to the single branch.  It must be
> >> preserved across whole project lifetime.
> > Umm. when did this policy change happen?  I thought ABI compatibility
> > was limited to major releases of FreeBSD?  How are you suppose to do
> > any work if you can't break ABI ever?
> >
> > I did a quick search for "freebsd policy abi breakage" and found some
> > mailing list posts about this, but no authoritative statement...
> >
> > Of course the problem is that when we move to
> > (ASN.1/libnv/ctf/YAML/JSON/XML/etc) we will break ABI compatibility too,
> > or introduce tons of compatibility code that will rot...
> >
> I agree, however there is a very easy way to fix it for the time being.  
> Let's not be binary about it "well it's going to have to break, so let's 
> break it!" when such an easy way to not break it exists.  It should be 
> "let's see if there's a non-intrusive way of not breaking it" and the 
> answer to that seems to be "yes".

If parts of ABI is broken, then why spend efforts trying to keep other
parts stable ?  You already have random set of binaries broken, sometimes
in subtle way.  Then, making other interfaces stable is just a waste.

ABI stability is a yes/no proposition, you cannot have it partly done.
Personally, I do not want to spend a time on hobbyist system.

BTW, to point out obvious thing, Linux has almost perfect ABI stability
and forward compatibility.  It is pity to see that our people do not
understand the importance and benefits of it.
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