re PR libstdc++/54388 (std::array.at() const results in undefined behaviour)

	PR libstdc++/54388
	* include/std/array (array::at() const): Ensure lvalue result.
	* testsuite/23_containers/array/element_access/54388.cc: New.
	* testsuite/23_containers/array/tuple_interface/get_neg.cc: Adjust
	dg-error line numbers.
	* testsuite/23_containers/array/tuple_interface/tuple_element_neg.cc:
	Likewise.

From-SVN: r191114

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 34a9d76db1da0ffb3b343456905389ee764089eb..fd47591c8bb6955264b7fc756ad7294fa39ebb2f 100644 (file)
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,13 @@
+2012-09-08  Jonathan Wakely  <jwakely.gcc@gmail.com>
+
+       PR libstdc++/54388
+       * include/std/array (array::at() const): Ensure lvalue result.
+       * testsuite/23_containers/array/element_access/54388.cc: New.
+       * testsuite/23_containers/array/tuple_interface/get_neg.cc: Adjust
+       dg-error line numbers.
+       * testsuite/23_containers/array/tuple_interface/tuple_element_neg.cc:
+       Likewise.
+
 2012-09-09  Ulrich Drepper  <drepper@gmail.com>
            Dominique d'Humieres  <dominiq@lps.ens.fr>
            Jack Howarth  <howarth@bromo.med.uc.edu>

diff --git a/libstdc++-v3/include/std/array b/libstdc++-v3/include/std/array
index 58263ce418a2cc098b92ec7588827bc861faa290..4ee21998b01476fec4bc110815f9292ab3239225 100644 (file)
--- a/libstdc++-v3/include/std/array
+++ b/libstdc++-v3/include/std/array
@@ -164,22 +164,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
        return _M_instance[__n];
       }
 
-#ifdef __EXCEPTIONS
       constexpr const_reference
       at(size_type __n) const
       {
-       return __n < _Nm ? 
-              _M_instance[__n] : throw out_of_range(__N("array::at"));
+       // Result of conditional expression must be an lvalue so use
+       // boolean ? lvalue : (throw-expr, lvalue)
+       return __n < _Nm ? _M_instance[__n]
+         : (std::__throw_out_of_range(__N("array::at")), _M_instance[0]);
       }
-#else
-      const_reference
-      at(size_type __n) const
-      {
-       if (__n >= _Nm)
-         std::__throw_out_of_range(__N("array::at"));
-       return _M_instance[__n];
-      }
-#endif
 
       reference 
       front()

diff --git a/libstdc++-v3/testsuite/23_containers/array/element_access/54388.cc b/libstdc++-v3/testsuite/23_containers/array/element_access/54388.cc
new file mode 100644 (file)
index 0000000..a69a5ed
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/array/element_access/54388.cc
@@ -0,0 +1,42 @@
+// { dg-options "-std=gnu++0x" }
+//
+// Copyright (C) 2012 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+//
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#include <array>
+#include <testsuite_hooks.h>
+
+struct A
+{
+  bool valid = true;
+  ~A() { valid = false; }
+};
+
+void
+test01()
+{
+  bool test __attribute__((unused)) = true;
+
+  const std::array<A, 1> a;
+  const A& aa = a.at(0);
+  VERIFY(aa.valid);
+}
+
+int main()
+{
+  test01();
+}

diff --git a/libstdc++-v3/testsuite/23_containers/array/tuple_interface/get_neg.cc b/libstdc++-v3/testsuite/23_containers/array/tuple_interface/get_neg.cc
index ecc25bf83878e634ad2c00667dcb92dd15e0ec9c..2fc443edad6b0321015c97d478d8902d7584073b 100644 (file)
--- a/libstdc++-v3/testsuite/23_containers/array/tuple_interface/get_neg.cc
+++ b/libstdc++-v3/testsuite/23_containers/array/tuple_interface/get_neg.cc
@@ -29,4 +29,4 @@ int n3 = std::get<1>(ca);
 
 // { dg-error "static assertion failed" "" { target *-*-* } 275 }
 // { dg-error "static assertion failed" "" { target *-*-* } 283 }
-// { dg-error "static assertion failed" "" { target *-*-* } 291 }
+// { dg-error "static assertion failed" "" { target *-*-* } 267 }

diff --git a/libstdc++-v3/testsuite/23_containers/array/tuple_interface/tuple_element_neg.cc b/libstdc++-v3/testsuite/23_containers/array/tuple_interface/tuple_element_neg.cc
index 72638138106a8c5bdcbdfff7053e85de676f9be0..97938ba669a742cc5d9c95988cb9696ade913cd0 100644 (file)
--- a/libstdc++-v3/testsuite/23_containers/array/tuple_interface/tuple_element_neg.cc
+++ b/libstdc++-v3/testsuite/23_containers/array/tuple_interface/tuple_element_neg.cc
@@ -22,4 +22,4 @@
 
 typedef std::tuple_element<1, std::array<int, 1>>::type type;
 
-// { dg-error "static assertion failed" "" { target *-*-* } 267 }
+// { dg-error "static assertion failed" "" { target *-*-* } 259 }