[Bug tree-optimization/52188] New: [4.7 regression] IPA-CP change broke libstdc++ symbol versioning on Solaris

["ro at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52188

             Bug #: 52188
           Summary: [4.7 regression] IPA-CP change broke libstdc++ symbol
                    versioning on Solaris
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: ro@gcc.gnu.org
                CC: jamborm@gcc.gnu.org, paolo.carlini@oracle.com
              Host: *-*-solaris2*
            Target: *-*-solaris2.*
             Build: *-*-solaris2.*


As already discussed to some length in

  http://gcc.gnu.org/ml/gcc-patches/2012-01/msg01163.html

the following patch

2011-07-18  Martin Jambor  <mjambor@suse.cz>

        * ipa-prop.h: Include alloc-pool.h, all sorts of updates to general
        comments.
        (ipcp_values_pool): Declare.
        (ipcp_sources_pool): Likewise.
[...]

caused libstdc++.so symbol versioning to be broken on Solaris.  Before the
patch,
when compiling locale-const.cc only contains references and definitions of

_ZNSt19istreambuf_iteratorIcSt11char_traitsIcEEppEv.constprop.36

After the patch, the same source has references to

_ZNSt19istreambuf_iteratorIcSt11char_traitsIcEEppEv

The latter is matched by the linker map and exported at version GLIBCXX_3.4.15,
which is effectively closed with the release of gcc 4.6 where the symbol wasn't
present.

To avoid breaking symbol versioning on Solaris, the question is what to do
here:
we obviously cannot export it at 3.4.15, but could instead export it at
3.4.17 *on Solaris* instead.  Before going that route, I need to make certain
that this isn't just a code generation accident and the symbol can vanish again
later: the exported interface of a shared object *must not* depend on the 
vagaries of code generation changes.

Martin?