[binutils-gdb] Don't override definition a shared object by one in a later shared object.

[Cary Coutant]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=b60ecbc6ddeaf7af8f2515841b58035f0d4d2db7

commit b60ecbc6ddeaf7af8f2515841b58035f0d4d2db7
Author: Cary Coutant <ccoutant@gmail.com>
Date:   Wed Mar 30 19:14:16 2016 -0700

    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.

Diff:
---
 gold/ChangeLog | 6 ++++++
 gold/symtab.cc | 7 +++++++
 2 files changed, 13 insertions(+)

diff --git a/gold/ChangeLog b/gold/ChangeLog
index e03536b..bce42df 100644
--- a/gold/ChangeLog
+++ b/gold/ChangeLog
@@ -1,3 +1,9 @@
+2016-03-30  Cary Coutant  <ccoutant@gmail.com>
+
+	PR gold/16979
+	* symtab.cc (Symbol_table::define_default_version): Check for case
+	where symbols are both in different shared objects.
+
 2016-03-27  Cary Coutant  <ccoutant@gmail.com>
 
 	PR gold/16111
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;