Fwd: FYI: svn commit: r258283 - in head: . include lib lib/libc lib/libc/iconv lib/libc_nonshared

FYI, for folks not following commit messages..

There is a potential new-binaries-on-old-systems gotcha here.

If you compile an iconv-using program on a system *after* this commit and
try to run the binary on an *old* pre-commit system, you will get undefined
symbols.

Going forwards is fine - a buildworld on an established system is safe.
Old binaries run on new systems.

Most folks would never hit this, except perhaps:
* you build a bunch of iconv-using binaries in /usr/local, then revert your
/usr/src to and old rev and buildworld.
* you try and copy/install binary packages build on a new system onto an
old system.

New binaries on old systems generally isn't supported.  Particularly so on
-current.

---------- Forwarded message ----------
From: Peter Wemm <peter_at_freebsd.org>
Date: Sun, Nov 17, 2013 at 2:52 PM
Subject: svn commit: r258283 - in head: . include lib lib/libc
lib/libc/iconv lib/libc_nonshared
To: src-committers_at_freebsd.org, svn-src-all_at_freebsd.org,
svn-src-head_at_freebsd.org


Author: peter
Date: Sun Nov 17 22:52:17 2013
New Revision: 258283
URL: http://svnweb.freebsd.org/changeset/base/258283

Log:
  Attempt to move the POSIX iconv* symbols out of runtime linker space.
  FreeBSD systems usually implemented this as a third party module and
  our implementation hasn't played as nicely with the old way as it could
  have.

  To that end:
  * Rename the iconv* symbols in libc.so.7 to have a __bsd_ prefix.
  * Provide .symver compatability with existing 10.x+ binaries that
    referenced the iconv symbols. All existing binaries should work.
  * Like on Linux/glibc systems, add a libc_nonshared.a to the ldscript
    at /usr/lib/libc.so.
  * Move the "iconv*" wrapper symbols to libc_nonshared.a

  This should solve the runtime ambiguity about which symbols resolve
  to where.  If you compile against the iconv in libc, your runtime
  dependencies will be unambiguous.

  Old 9.x libraries and binaries will always resolve against their
  libiconv.so.3 like they did on 9.x.  They won't resolve against libc.

  Old 10.x binaries will be satisified by the .symver helpers.

  This should allow ports to selectively compile against the libiconv
  port if needed and it should behave without ambiguity now.



-- 
Peter Wemm - peter_at_wemm.org; peter_at_FreeBSD.org; peter_at_yahoo-inc.com; KI6FJV