re PR c++/57901 (Cannot call-by-value such that class has non-trivial (constexpr) move constructor)

	PR c++/57901
	* semantics.c (build_data_member_initialization, constexpr_fn_retval):
	Use break_out_target_exprs instead of unshare_expr.

From-SVN: r201338

gcc/cp/ChangeLog

+2013-07-29  Jason Merrill  <jason@redhat.com>
+
+	PR c++/57901
+	* semantics.c (build_data_member_initialization, constexpr_fn_retval):
+	Use break_out_target_exprs instead of unshare_expr.
+
 2013-07-29  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	PR c++/57948

gcc/cp/semantics.c

@@ -6016,7 +6016,7 @@ build_data_member_initialization (tree t, vec<constructor_elt, va_gc> **vec)
       || TREE_CODE (t) == MODIFY_EXPR)
     {
       member = TREE_OPERAND (t, 0);
-      init = unshare_expr (TREE_OPERAND (t, 1));
+      init = break_out_target_exprs (TREE_OPERAND (t, 1));
     }
   else if (TREE_CODE (t) == CALL_EXPR)
     {
@@ -6024,7 +6024,7 @@ build_data_member_initialization (tree t, vec<constructor_elt, va_gc> **vec)
       /* We don't use build_cplus_new here because it complains about
 	 abstract bases.  Leaving the call unwrapped means that it has the
 	 wrong type, but cxx_eval_constant_expression doesn't care.  */
-      init = unshare_expr (t);
+      init = break_out_target_exprs (t);
     }
   else if (TREE_CODE (t) == DECL_EXPR)
     /* Declaring a temporary, don't add it to the CONSTRUCTOR.  */
@@ -6261,7 +6261,7 @@ constexpr_fn_retval (tree body)
       }
 
     case RETURN_EXPR:
-      return unshare_expr (TREE_OPERAND (body, 0));
+      return break_out_target_exprs (TREE_OPERAND (body, 0));
 
     case DECL_EXPR:
       if (TREE_CODE (DECL_EXPR_DECL (body)) == USING_DECL)

gcc/testsuite/g++.dg/cpp0x/constexpr-value4.C

+// PR c++/57901
+// { dg-require-effective-target c++11 }
+
+struct Z {
+    Z()         = default;
+    Z(Z const&) = default;
+    constexpr Z(Z&&) {} /* non-trivial (constexpr) move ctor */
+};
+
+template<typename T>
+constexpr int fn0(T v) { return 0; }
+template<typename T>
+constexpr int fn (T v) { return fn0(v); }
+
+constexpr auto t0 = fn0(Z()); // OK!
+constexpr auto t  = fn (Z()); // error! (GCC 4.8.1)