More testing for std::pair layout change

	* testsuite/20_util/pair/87822.cc: Test deeper nesting.

From-SVN: r265680

libstdc++-v3/ChangeLog

 2018-10-31  Jonathan Wakely  <jwakely@redhat.com>
 
+	* testsuite/20_util/pair/87822.cc: Test deeper nesting.
+
 	PR libstdc++/87822
 	* include/bits/stl_pair.h (__pair_base): Change to class template.
 	(pair): Make base class type depend on template parameters.

libstdc++-v3/testsuite/20_util/pair/87822.cc

@@ -26,6 +26,7 @@ test01()
   static_assert(sizeof(p) == (3 * sizeof(int)), "PR libstdc++/87822");
 #endif
   VERIFY( (void*)&p == (void*)&p.first );
+  VERIFY( (void*)&p == (void*)&p.first.first );
 }
 
 struct empty { };
@@ -40,8 +41,24 @@ test02()
   VERIFY( (void*)&p == (void*)&p.first );
 }
 
+void
+test03()
+{
+  typedef std::pair<int, int> int_pair;
+  typedef std::pair<int_pair, int_pair> int_pair_pair;
+  std::pair<int_pair_pair, int_pair_pair> p;
+#if __cplusplus >= 201103L
+  static_assert(sizeof(int_pair_pair) == (2 * sizeof(int_pair)), "nested");
+  static_assert(sizeof(p) == (2 * sizeof(int_pair_pair)), "nested again");
+#endif
+  VERIFY( (void*)&p == (void*)&p.first );
+  VERIFY( (void*)&p == (void*)&p.first.first );
+  VERIFY( (void*)&p == (void*)&p.first.first.first );
+}
+
 int main()
 {
   test01();
   test02();
+  test03();
 }