cvs commit: src/lib/msun/i387 fenv.c fenv.h

[Warner Losh]

From: Maxim Sobolev <sobomax at portaone.com>
Subject: Re: cvs commit: src/lib/msun/i387 fenv.c fenv.h
Date: Fri, 18 Mar 2005 11:05:19 +0200

> Scott Long wrote:
> > Maxim Sobolev wrote:
> > 
> >> Warner Losh wrote:
> >>
> >>> From: Maxim Sobolev <sobomax at portaone.com>
> >>> Subject: Re: cvs commit: src/lib/msun/i387 fenv.c fenv.h
> >>> Date: Fri, 18 Mar 2005 09:44:25 +0200
> >>>
> >>>
> >>>> David Schultz wrote:
> >>>>
> >>>>> On Thu, Mar 17, 2005, Warner Losh wrote:
> >>>>>
> >>>>>
> >>>>>>> You had better bump the version number for libm before 6.0 rolls
> >>>>>>> around!!  I've just found a 3rd party binary-only package that
> >>>>>>> supports 'FreeBSD 5.x' but is linked against libm.so.2.  Ugh.  We
> >>>>>>> need to bury that mistake and NOT make it again.
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>> 6.0 already has /lib/libm.so.3
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>> So does 5.3.  I think Scott's point is that if we're going to bump
> >>>>> it for 6.X at all, we had better do it soon or risk running into
> >>>>> the same mess we had before.  I agree with that, although at
> >>>>> present I don't know of a compelling reason to do the bump the
> >>>>> libm version number at all.
> >>>>
> >>>>
> >>>>
> >>>> Haven't several functions been removed from -CURRENT version of libm 
> >>>> recently? IMHO this provides sufficient reason for version bump. 
> >>>> Actually I think it makes sense to bump all libraries automatically 
> >>>> when -CURRENT goes one major number up. There is just no much sense 
> >>>> in preserving partial compatibility.
> >>>
> >>>
> >>>
> >>>
> >>> One of the problems with an overly agressive bumping is that if you
> >>> bump, you have to bump *EVERYTHING* that depends on the library to get
> >>> true compatbility, even the ports (and have different majors build
> >>> based on using libc.so.5 vs libc.so.6, a real pita).  When I looked
> >>> into the major abi issues we had a while ago, I came to this
> >>> conclusion.  I also came to the conclusion that we'd be better off
> >>> keeping compatibility and *NEVER* bumping a fundamental library's
> >>> major number to avoid these problems.  Alas, no one listens to me, and
> >>> they make incompatible changes (like removing functions), so we're
> >>> stuck in the false belief that major numbers are going to save us.[*]
> >>
> >>
> >>
> >> What's the problem with ports? I think one who want to run older ports 
> >> on newer system can install compatXX package, no?
> >>
> >> -Maxim
> > 
> > 
> > No, I think that what he's worried about is that you have port foo that
> > generates a library called libfoo.so.1, and that library is linked
> > against libm.so.2.  You then have port bar that generates a binary
> > linked against libfoo.so.1 and libm.so.2.  Now lets say that libm.so.2
> > gets bumped to libm.so.3, and you also rebuild port bar.  Now bar is
> > linked to libfoo.so.1 and libm.so.3, but libfoo.so.1 is still linked
> > against libm.so.2; mass panic ensues and the universe is driven into 
> > chaos and death.
> 
> I see, but this is non-issue, since actually the only sensible approach 
> when going from release x.y to release x+1.y is to rebuild all 
> third-party packages, at least ones that install shared libraries. The 
> reason for that is simple - libc is linked into virtually every package, 
> while I can't remember a single major release when version number for 
> libc has not been bumped.

It is an issue for people that have binaries releases they don't have
source for.  We claim to have binary compatibiltiy, when in fact we
don't really.  It mostly works most of the time.

People do complain when this doesn't work.  I've spent a lot of time
in the past tracking down why programs randomly core dumped after
upgrading one minor part of the system, and this was a leading cause
after we changed the size of FILE.  It caused me a lot of pain.

Warner