PR 10979

	* common.cc (Sort_commons::operator()): Stabilize sort when both
	entries are NULL.
	(Symbol_table::do_allocate_commons_list): When allocating common
	symbols, skip a symbol which is no longer common.
	* symtab.h (Symbol::is_common): Test whether the symbol comes from
	an object before checking its type.
	* testsuite/common_test_2.c: New file.
	* testsuite/common_test_3.c: New file.
	* testsuite/Makefile.am (check_PROGRAMS): Add common_test_2.
	(common_test_2_SOURCES, common_test_2_DEPENDENCIES): Define.
	(common_test_2_LDFLAGS, common_test_2_LDADD): Define.
	(common_test_2_pic.o, common_test_2.so): New targets.
	(common_test_3_pic.o, common_test_3.so): New targets.
	* testsuite/Makefile.in: Rebuild.

1 files changed, 21 insertions, 1 deletions

diff --git a/gold/common.cc b/gold/common.cc
index c4ff047d47a..885933807c6 100644
--- a/gold/common.cc
+++ b/gold/common.cc
@@ -91,7 +91,16 @@ bool
 Sort_commons<size>::operator()(const Symbol* pa, const Symbol* pb) const
 {
   if (pa == NULL)
-    return false;
+    {
+      if (pb == NULL)
+	{
+	  // Stabilize sort.  The order really doesn't matter, because
+	  // these entries will be discarded, but we want to return
+	  // the same result every time we compare pa and pb.
+	  return pa < pb;
+	}
+      return false;
+    }
   if (pb == NULL)
     return true;
 
@@ -312,6 +321,17 @@ Symbol_table::do_allocate_commons_list(
       Symbol* sym = *p;
       if (sym == NULL)
 	break;
+
+      // Because we followed forwarding symbols above, but we didn't
+      // do it reliably before adding symbols to the list, it is
+      // possible for us to have the same symbol on the list twice.
+      // This can happen in the horrible case where a program defines
+      // a common symbol with the same name as a versioned libc
+      // symbol.  That will show up here as a symbol which has already
+      // been allocated and is therefore no longer a common symbol.
+      if (!sym->is_common())
+	continue;
+
       Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym);
 
       // Record the symbol in the map file now, before we change its