Date: Tue, 28 Aug 2007 11:44:43 -0400 From: John Baldwin <jhb@freebsd.org> To: Daniel Eischen <deischen@freebsd.org> Cc: src-committers@freebsd.org, peterjeremy@optushome.com.au, yar@comp.chem.msu.su, alfred@freebsd.org, cvs-all@freebsd.org, cvs-src@freebsd.org, "M. Warner Losh" <imp@bsdimp.com> Subject: Re: cvs commit: src/lib/libc/gen fts-compat.c fts-compat.h Message-ID: <200708281144.45019.jhb@freebsd.org> In-Reply-To: <Pine.GSO.4.64.0708280017490.1357@sea.ntplx.net> References: <Pine.GSO.4.64.0708271757570.28508@sea.ntplx.net> <20070827.204618.-1350500405.imp@bsdimp.com> <Pine.GSO.4.64.0708280017490.1357@sea.ntplx.net>
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On Tuesday 28 August 2007 12:31:32 am Daniel Eischen wrote: > On Mon, 27 Aug 2007, M. Warner Losh wrote: > > > In message: <Pine.GSO.4.64.0708272127371.28508@sea.ntplx.net> > > Daniel Eischen <deischen@freebsd.org> writes: > > : I think you're a little confused here. CURRENT users did NOT have > > : to rebuild ports when fts(3) or stdio(3) ABIs changed. They > > : would only have to rebuild if one of these ABIs changed _more > > : than once between releases_. That hasn't ever happened to my > > : knowledge in the past, and it really shouldn't happen as long > > : as things are tested and reviewed properly. > > > > One of the reasons that it hasn't happened before is that we forced > > people who tried to make, or proposed making, such changes to make > > them in a compatible sort of way. We have all kinds of ugliness in > > and around FILE to try, alas in vain, to be compatible. One of the > > reasons people would like to see symbol versioning is to make it > > easier to change the size of different structures because we have > > stood on our heads in the past to not change sizes. > > > > I'm concerned that the empirical evidence from the past might not be a > > good thing to base our future plans upon. We knew we had sucky tools > > to deal with binary incompatibility in the past, so we stood on our > > heads to not make too many binary incompatible changes. With that > > limitation gone, I think the likelihood is large we will see multiple > > ABI changes between major releases on something. Especially since it > > happens when structures change size and there are many functions that > > take pointers to multiple structures... > > The emphasis should be on trying to get things right, tested, and > reviewed the first time ;-) But also to keep compat shims to a > minimum too. It may be easier to create different versions and > keep compatibility, but the SV'd libraries are going to grow with > compat shims if we don't try to reduce ABI changes like we've > done in the past. I think we need an ABI review board monitored > by -standards ;-) > > If you are really concerned about it (I'm not!), then you can > always add another version in between releases, or just bump > the version every time you break an ABI in -current. I'm not > advocating this because I don't think it's necessary. I don't > think you need to have both private and public versions in > -current, just use 1.x and bump x for every ABI change. -current > will always have all versions 1.0 - 1.x, and prior branches > will have some of them. Whenever -current is branched, both > the branch and -current will once again have all versions > until the ABI in -current changes again. See, I'd like to minimize the number of symbols in RELENG_x branches to actually be the symbols used only in prior RELENG_x branches as a way to cap the bloat some. Things don't get always get done right in -HEAD on the first try, but the FBSD-current thing gives us a strategy to allow HEAD to be fluid to eventually get things right while not bloating RELENG_x branches with unneeded compat shims. -- John Baldwin
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