Merge from trunk revision 89be17a1b231ade643f28fbe616d53377e069da8.

1 files changed, 29 insertions, 8 deletions

diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
index 0c2498a..8a5dd06 100644
--- a/gcc/cp/constexpr.c
+++ b/gcc/cp/constexpr.c
@@ -2787,12 +2787,34 @@ cxx_eval_call_expression (const constexpr_ctx *ctx, tree t,
 					&jump_target);
 
 	  if (DECL_CONSTRUCTOR_P (fun))
-	    /* This can be null for a subobject constructor call, in
-	       which case what we care about is the initialization
-	       side-effects rather than the value.  We could get at the
-	       value by evaluating *this, but we don't bother; there's
-	       no need to put such a call in the hash table.  */
-	    result = lval ? ctx->object : ctx->ctor;
+	    {
+	      /* This can be null for a subobject constructor call, in
+		 which case what we care about is the initialization
+		 side-effects rather than the value.  We could get at the
+		 value by evaluating *this, but we don't bother; there's
+		 no need to put such a call in the hash table.  */
+	      result = lval ? ctx->object : ctx->ctor;
+
+	      /* If we've just evaluated a subobject constructor call for an
+		 empty union member, it might not have produced a side effect
+		 that actually activated the union member.  So produce such a
+		 side effect now to ensure the union appears initialized.  */
+	      if (!result && new_obj
+		  && TREE_CODE (new_obj) == COMPONENT_REF
+		  && TREE_CODE (TREE_TYPE
+				(TREE_OPERAND (new_obj, 0))) == UNION_TYPE
+		  && is_really_empty_class (TREE_TYPE (new_obj),
+					    /*ignore_vptr*/false))
+		{
+		  tree activate = build2 (MODIFY_EXPR, TREE_TYPE (new_obj),
+					  new_obj,
+					  build_constructor (TREE_TYPE (new_obj),
+							     NULL));
+		  cxx_eval_constant_expression (ctx, activate, lval,
+						non_constant_p, overflow_p);
+		  ggc_free (activate);
+		}
+	    }
 	  else if (VOID_TYPE_P (TREE_TYPE (res)))
 	    result = void_node;
 	  else
@@ -7480,8 +7502,7 @@ cxx_eval_outermost_constant_expr (tree t, bool allow_non_constant,
 
   /* Remember the original location if that wouldn't need a wrapper.  */
   if (location_t loc = EXPR_LOCATION (t))
-    if (CAN_HAVE_LOCATION_P (r))
-      SET_EXPR_LOCATION (r, loc);
+    protected_set_expr_location (r, loc);
 
   return r;
 }