re PR c++/67813 ([C++14] copy-initialization of object with pointer member fails…

re PR c++/67813 ([C++14] copy-initialization of object with pointer member fails in constexpr function)

	PR c++/67813
	* constexpr.c (cxx_eval_store_expression): Always use *valp if
	set.

From-SVN: r229270

gcc/cp/ChangeLog

+2015-10-23  Jason Merrill  <jason@redhat.com>
+
+	PR c++/67813
+	* constexpr.c (cxx_eval_store_expression): Always use *valp if
+	set.
+
 2015-10-22  Jason Merrill  <jason@redhat.com>
 
 	* call.c (add_template_conv_candidate): Pass DEDUCE_CALL.

gcc/cp/constexpr.c

@@ -2802,10 +2802,13 @@ cxx_eval_store_expression (const constexpr_ctx *ctx, tree t,
     {
       /* Create a new CONSTRUCTOR in case evaluation of the initializer
 	 wants to modify it.  */
-      new_ctx.ctor = build_constructor (type, NULL);
       if (*valp == NULL_TREE)
-	*valp = new_ctx.ctor;
+	{
+	  *valp = new_ctx.ctor = build_constructor (type, NULL);
 	  CONSTRUCTOR_NO_IMPLICIT_ZERO (new_ctx.ctor) = no_zero_init;
+	}
+      else
+	new_ctx.ctor = *valp;
       new_ctx.object = target;
     }
 

gcc/testsuite/g++.dg/cpp1y/constexpr-copy1.C

+// PR c++/67813
+// { dg-do compile { target c++14 } }
+
+struct Ptr {
+  int* p;
+
+  constexpr Ptr(int* p) noexcept : p{p} {}
+  constexpr int& operator*() const {
+    return *p;
+  }
+};
+
+constexpr int f(int& i) {
+  //Ptr first{&i}; // Works.
+  Ptr first = &i;  // Error
+  return *first;
+}
+
+constexpr int g() {
+  int i = 42;
+  return f(i);
+}
+
+#define SA(X) static_assert((X), #X)
+SA(g() == 42);