On Thu, 8 May 2008 01:55:32 -0400 (EDT) Daniel Eischen <[EMAIL PROTECTED]> wrote:
> On Wed, 7 May 2008, Jason Evans wrote: > > > Alexander Kabaev wrote: > >> kan 2008-05-07 15:39:34 UTC > >> > >> FreeBSD src repository > >> > >> Modified files: > >> lib/libc Versions.def Log: > >> Keep versions on a dependency chain to exclude even remote > >> possiblity of private version ever getting index 2. > > > > Why is this the right thing to do? Clearly FBSDprivate_1.0 should > > never be incremented, but it does not make sense to me to have it > > depend on any other version. In the absence of a compelling > > argument, I am of the opinion that Dan Eischen made a good change. > > Did you discuss this issue with him? > > I think it has more to do with how rtld works, though I don't > know the details. You can see that kan made this same exact > change in rev 1.3 of Versions.def. So in actuality, I backed > kan's change out thinking that I had originally committed it > that way. > -- > DE rtld magically expects version with verndx 2 to be the oldest version applied to the shared library. It uses this to resolve symbols for old unversioned binaries that happen to run against the versioned library. Having FBSDPrivate to be a root of its own depenency tree can potentionally cause linker to assign it version #2 instead of FBSD_1.0, breaking old binaries. Keeping all versions in a dependency chain rooted at FBSD_1.0 is a simple way to avoid the breakage. In general, 'dependency' in version strings is useless and people should read too much into it. Nor should they apply their object-oriented language concepts while looking at what version inherits from what other version. > > FYI, before I commited this change, I looked at how glibc did it. > Their private namespace does not inherit from the GLIBC public > namespace. But perhaps they have other ways of preventing > exactly what kan is trying to avoid. > You looked at sources, I guess, not what gets generated after they run their AWK script on it. $ readelf -V /compat/linux/lib/libc-2.3.6.so ... Version definition section '.gnu.version_d' contains 18 entries: Addr: 0x0000000000011b40 Offset: 0x011b40 Link: 4 (.dynstr) 000000: Rev: 1 Flags: BASE Index: 1 Cnt: 1 Name: libc.so.6 0x001c: Rev: 1 Flags: none Index: 2 Cnt: 1 Name: GLIBC_2.0 0x0038: Rev: 1 Flags: none Index: 3 Cnt: 2 Name: GLIBC_2.1 0x0054: Parent 1: GLIBC_2.0 ... 0x0230: Rev: 1 Flags: none Index: 17 Cnt: 2 Name: GLIBC_PRIVATE 0x024c: Parent 1: GLIBC_2.3.4 -- Alexander Kabaev
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