Don't override definition a shared object by one in a later shared object.

In PR 16979, a reference to malloc is being resolved to an unversioned
reference in libmalloc.so. When linked with --as-needed, however, the
dynamic table does not list libmalloc.so as a DT_NEEDED library.

If we have a reference to an unversioned symbol in a shared object,
and we later see a versioned definition in another shared object, we
were overriding the first definition with the second in the process of
defining the default version. As a result, we no longer think that the
first shared object was actually needed to resolve any symbols, and we
don't list it as a DT_NEEDED library.

This patch fixes the problem by treating the two definitions as separate
symbols, so the second definition does not override the first.

2016-03-30  Cary Coutant  <ccoutant@gmail.com>

gold/
	PR gold/16979
	* symtab.cc (Symbol_table::define_default_version): Check for case
	where symbols are both in different shared objects.

1 files changed, 7 insertions, 0 deletions

diff --git a/gold/symtab.cc b/gold/symtab.cc
index fd75aff..a7edbb1 100644
--- a/gold/symtab.cc
+++ b/gold/symtab.cc
@@ -865,6 +865,9 @@ Symbol_table::define_default_version(Sized_symbol<size>* sym,
       // other is defined in a shared object, then they are different
       // symbols.
 
+      // If the two symbols are from different shared objects,
+      // they are different symbols.
+
       // Otherwise, we just resolve the symbols as though they were
       // the same.
 
@@ -876,6 +879,10 @@ Symbol_table::define_default_version(Sized_symbol<size>* sym,
       else if (pdef->second->visibility() != elfcpp::STV_DEFAULT
 	       && sym->is_from_dynobj())
 	;
+      else if (pdef->second->is_from_dynobj()
+	       && sym->is_from_dynobj()
+	       && pdef->second->object() != sym->object())
+        ;
       else
 	{
 	  const Sized_symbol<size>* symdef;