re PR libstdc++/49060 (use of deleted memory in __gnu_cxx::hashtable::erase)

	PR libstdc++/49060
	* include/backward/hashtable.h (hashtable::erase): Don't crash if
	erasing first and another element with a reference to the other
	element.
	* testsuite/backward/hash_set/49060.cc: New.

From-SVN: r174240

libstdc++-v3/ChangeLog

+2011-05-25  Ian Lance Taylor  <iant@google.com>
+
+	PR libstdc++/49060
+	* include/backward/hashtable.h (hashtable::erase): Don't crash if
+	erasing first and another element with a reference to the other
+	element.
+	* testsuite/backward/hash_set/49060.cc: New.
+
 2011-05-25  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	* include/bits/random.h (random_device::min, max): Specify constexpr.

libstdc++-v3/include/backward/hashtable.h

@@ -898,13 +898,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 		  __next = __cur->_M_next;
 		}
 	    }
-	  if (_M_equals(_M_get_key(__first->_M_val), __key))
-	    {
-	      _M_buckets[__n] = __first->_M_next;
-	      _M_delete_node(__first);
-	      ++__erased;
-	      --_M_num_elements;
-	    }
+	  bool __delete_first = _M_equals(_M_get_key(__first->_M_val), __key);
 	  if (__saved_slot)
 	    {
 	      __next = __saved_slot->_M_next;
@@ -913,6 +907,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	      ++__erased;
 	      --_M_num_elements;
 	    }
+	  if (__delete_first)
+	    {
+	      _M_buckets[__n] = __first->_M_next;
+	      _M_delete_node(__first);
+	      ++__erased;
+	      --_M_num_elements;
+	    }
 	}
       return __erased;
     }

libstdc++-v3/testsuite/backward/hash_set/49060.cc

+// { dg-options "-Wno-deprecated" }
+
+#include <backward/hashtable.h>
+#include <utility>
+
+struct modulo2_hash
+{
+  size_t operator()(int const key) const
+  {
+    return key % 2;
+  }
+};
+
+struct modulo2_eq
+{
+  bool operator()(int const left, int const right) const
+  {
+    return left % 2 == right % 2;
+  }
+};
+
+int main()
+{
+  typedef std::_Select1st<std::pair<int const, int> > extract_type;
+  typedef
+    __gnu_cxx::hashtable<std::pair<int const, int>, int, modulo2_hash,
+			 extract_type, modulo2_eq, std::allocator<int> >
+      table_type;
+  table_type table(4, modulo2_hash(), modulo2_eq(), extract_type(),
+		   std::allocator<int>());
+
+  table.insert_equal(std::make_pair(2, 1));
+  table_type::iterator it(table.insert_equal(std::make_pair(4, 2)));
+  table.erase(it->first);
+}