re PR c++/68782 (bad reference member formed with constexpr)

	PR c++/68782

gcc/
	* tree.c (recompute_constructor_flags): Split out from
	build_constructor.
	(verify_constructor_flags): New.
	* tree.h: Declare them.
gcc/cp/
	* constexpr.c (cxx_eval_bare_aggregate): Update TREE_CONSTANT
	and TREE_SIDE_EFFECTS.
	(cxx_eval_constant_expression) [CONSTRUCTOR]: Call
	verify_constructor_flags.

From-SVN: r232847

1 files changed, 44 insertions, 12 deletions

diff --git a/gcc/tree.c b/gcc/tree.c
index 9c67bea..fa7646b 100644
--- a/gcc/tree.c
+++ b/gcc/tree.c
@@ -1790,34 +1790,66 @@ build_vector_from_val (tree vectype, tree sc)
     }
 }
 
-/* Return a new CONSTRUCTOR node whose type is TYPE and whose values
-   are in the vec pointed to by VALS.  */
-tree
-build_constructor (tree type, vec<constructor_elt, va_gc> *vals)
+/* Something has messed with the elements of CONSTRUCTOR C after it was built;
+   calculate TREE_CONSTANT and TREE_SIDE_EFFECTS.  */
+
+void
+recompute_constructor_flags (tree c)
 {
-  tree c = make_node (CONSTRUCTOR);
   unsigned int i;
-  constructor_elt *elt;
+  tree val;
   bool constant_p = true;
   bool side_effects_p = false;
+  vec<constructor_elt, va_gc> *vals = CONSTRUCTOR_ELTS (c);
 
-  TREE_TYPE (c) = type;
-  CONSTRUCTOR_ELTS (c) = vals;
-
-  FOR_EACH_VEC_SAFE_ELT (vals, i, elt)
+  FOR_EACH_CONSTRUCTOR_VALUE (vals, i, val)
     {
       /* Mostly ctors will have elts that don't have side-effects, so
 	 the usual case is to scan all the elements.  Hence a single
 	 loop for both const and side effects, rather than one loop
 	 each (with early outs).  */
-      if (!TREE_CONSTANT (elt->value))
+      if (!TREE_CONSTANT (val))
 	constant_p = false;
-      if (TREE_SIDE_EFFECTS (elt->value))
+      if (TREE_SIDE_EFFECTS (val))
 	side_effects_p = true;
     }
 
   TREE_SIDE_EFFECTS (c) = side_effects_p;
   TREE_CONSTANT (c) = constant_p;
+}
+
+/* Make sure that TREE_CONSTANT and TREE_SIDE_EFFECTS are correct for
+   CONSTRUCTOR C.  */
+
+void
+verify_constructor_flags (tree c)
+{
+  unsigned int i;
+  tree val;
+  bool constant_p = TREE_CONSTANT (c);
+  bool side_effects_p = TREE_SIDE_EFFECTS (c);
+  vec<constructor_elt, va_gc> *vals = CONSTRUCTOR_ELTS (c);
+
+  FOR_EACH_CONSTRUCTOR_VALUE (vals, i, val)
+    {
+      if (constant_p && !TREE_CONSTANT (val))
+	internal_error ("non-constant element in constant CONSTRUCTOR");
+      if (!side_effects_p && TREE_SIDE_EFFECTS (val))
+	internal_error ("side-effects element in no-side-effects CONSTRUCTOR");
+    }
+}
+
+/* Return a new CONSTRUCTOR node whose type is TYPE and whose values
+   are in the vec pointed to by VALS.  */
+tree
+build_constructor (tree type, vec<constructor_elt, va_gc> *vals)
+{
+  tree c = make_node (CONSTRUCTOR);
+
+  TREE_TYPE (c) = type;
+  CONSTRUCTOR_ELTS (c) = vals;
+
+  recompute_constructor_flags (c);
 
   return c;
 }