[C++ PATCH] class member ordering

https://gcc.gnu.org/ml/gcc-patches/2017-09/msg01426.html
	* name-lookup.c (member_name_cmp): Use DECL_UID for final
	ordering.

From-SVN: r253048

gcc/cp/ChangeLog

+2017-09-20  Nathan Sidwell  <nathan@acm.org>
+
+	* name-lookup.c (member_name_cmp): Use DECL_UID for final
+	ordering.
+
 2017-09-20  Jakub Jelinek  <jakub@redhat.com>
 
 	P0409R2 - allow lambda capture [=, this]

gcc/cp/name-lookup.c

@@ -1434,29 +1434,38 @@ member_name_cmp (const void *a_p, const void *b_p)
     b = OVL_FUNCTION (b);
 
   /* We're in STAT_HACK or USING_DECL territory (or possibly error-land). */
-  if (TREE_CODE (a) == TREE_CODE (b))
-    /* We can get two TYPE_DECLs or two USING_DECLs.  Place in source
-       order.  */
-    return DECL_SOURCE_LOCATION (a) < DECL_SOURCE_LOCATION (b) ? -1 : +1;
-
-  /* If one of them is a TYPE_DECL, it loses.  */
-  if (TREE_CODE (a) == TYPE_DECL)
-    return +1;
-  else if (TREE_CODE (b) == TYPE_DECL)
-    return -1;
-
-  /* If one of them is a USING_DECL, it loses.  */
-  if (TREE_CODE (a) == USING_DECL)
-    return +1;
-  else if (TREE_CODE (b) == USING_DECL)
-    return -1;
-
-  /* There are no other cases, as duplicate detection should have
-     kicked in earlier.  However, some erroneous cases get though.
-     Order by source location.  We should really prevent this
-     happening.  */
-  gcc_assert (errorcount);
-  return DECL_SOURCE_LOCATION (a) < DECL_SOURCE_LOCATION (b) ? -1 : +1;
+  if (TREE_CODE (a) != TREE_CODE (b))
+    {
+      /* If one of them is a TYPE_DECL, it loses.  */
+      if (TREE_CODE (a) == TYPE_DECL)
+	return +1;
+      else if (TREE_CODE (b) == TYPE_DECL)
+	return -1;
+
+      /* If one of them is a USING_DECL, it loses.  */
+      if (TREE_CODE (a) == USING_DECL)
+	return +1;
+      else if (TREE_CODE (b) == USING_DECL)
+	return -1;
+
+      /* There are no other cases with different kinds of decls, as
+	 duplicate detection should have kicked in earlier.  However,
+	 some erroneous cases get though. */
+      gcc_assert (errorcount);
+    }
+  
+  /* Using source location would be the best thing here, but we can
+     get identically-located decls in the following circumstances:
+
+     1) duplicate artificial type-decls for the same type.
+
+     2) pack expansions of using-decls.
+
+     We should not be doing #1, but in either case it doesn't matter
+     how we order these.  Use UID as a proxy for source ordering, so
+     that identically-located decls still have a well-defined stable
+     ordering.  */
+  return DECL_UID (a) < DECL_UID (b) ? -1 : +1;
 }
 
 static struct {