PR c++/87109 - wrong ctor with maybe-rvalue semantics.

	* call.c (build_user_type_conversion_1): Refine the maybe-rvalue
	check to only return if we're converting the return value to a base
	class.

	* g++.dg/cpp0x/ref-qual19.C: Adjust the expected results.
	* g++.dg/cpp0x/ref-qual20.C: New test.

From-SVN: r264452

gcc/cp/ChangeLog

+2018-09-20  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/87109 - wrong ctor with maybe-rvalue semantics.
+	* call.c (build_user_type_conversion_1): Refine the maybe-rvalue
+	check to only return if we're converting the return value to a base
+	class.
+
 2018-09-20  Allan Sandfeld Jensen  <allan.jensen@qt.io>
 
 	* g++spec.c (lang_specific_driver): Handle -r like -nostdlib.

gcc/cp/call.c

@@ -4034,10 +4034,12 @@ build_user_type_conversion_1 (tree totype, tree expr, int flags,
     conv->bad_p = true;
 
   /* We're performing the maybe-rvalue overload resolution and
-     a conversion function is in play.  This isn't going to work
-     because we would not end up with a suitable constructor.  */
+     a conversion function is in play.  Reject converting the return
+     value of the conversion function to a base class.  */
   if ((flags & LOOKUP_PREFER_RVALUE) && !DECL_CONSTRUCTOR_P (cand->fn))
-    return NULL;
+    for (conversion *t = cand->second_conv; t; t = next_conversion (t))
+      if (t->kind == ck_base)
+	return NULL;
 
   /* Remember that this was a list-initialization.  */
   if (flags & LOOKUP_NO_NARROWING)

gcc/testsuite/ChangeLog

+2018-09-20  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/87109 - wrong ctor with maybe-rvalue semantics.
+	* g++.dg/cpp0x/ref-qual19.C: Adjust the expected results.
+	* g++.dg/cpp0x/ref-qual20.C: New test.
+
 2018-09-20  Allan Sandfeld Jensen  <allan.jensen@qt.io>
 
 	* g++.dg/ipa/pr64059.C: Removed now redundant -nostdlib.

gcc/testsuite/g++.dg/cpp0x/ref-qual19.C

@@ -85,13 +85,13 @@ int
 main ()
 {
   C c1 = f (A());
-  if (c1.i != 1)
+  if (c1.i != 2)
     __builtin_abort ();
   C c2 = f2 (A());
   if (c2.i != 2)
     __builtin_abort ();
   C c3 = f3 ();
-  if (c3.i != 1)
+  if (c3.i != 2)
     __builtin_abort ();
   C c4 = f4 ();
   if (c4.i != 2)
@@ -100,13 +100,13 @@ main ()
   if (c5.i != 2)
     __builtin_abort ();
   D c6 = f6 (B());
-  if (c6.i != 3)
+  if (c6.i != 4)
     __builtin_abort ();
   D c7 = f7 (B());
   if (c7.i != 4)
     __builtin_abort ();
   D c8 = f8 ();
-  if (c8.i != 3)
+  if (c8.i != 4)
     __builtin_abort ();
   D c9 = f9 ();
   if (c9.i != 4)

gcc/testsuite/g++.dg/cpp0x/ref-qual20.C

+// PR c++/87109
+// { dg-do run { target c++11 } }
+
+#include <utility>
+
+struct Y {
+  int y;
+  Y(int y_) : y(y_) { }
+};
+struct X : public Y {
+  int x;
+  X(int x_, int y_) : x(x_), Y(y_) { }
+};
+
+struct A {
+  operator X() & { return { 0, 2 }; }
+  operator X() && { return { 0, -1 }; }
+};
+
+Y
+f (A a)
+{
+  return a;
+}
+
+Y
+f2 (A a)
+{
+  return std::move (a);
+}
+
+Y
+f3 ()
+{
+  A a;
+  return a;
+}
+
+Y
+f4 ()
+{
+  A a;
+  return std::move (a);
+}
+
+Y
+f5 ()
+{
+  return A();
+}
+
+int
+main ()
+{
+  Y y1 = f (A());
+  if (y1.y != 2)
+    __builtin_abort ();
+  Y y2 = f2 (A());
+  if (y2.y != -1)
+    __builtin_abort ();
+  Y y3 = f3 ();
+  if (y3.y != 2)
+    __builtin_abort ();
+  Y y4 = f4 ();
+  if (y4.y != -1)
+    __builtin_abort ();
+  Y y5 = f5 ();
+  if (y5.y != -1)
+    __builtin_abort ();
+}