[PATCH] PR libstdc++/81221 fix namespace qualification for parallel mode

[Jonathan Wakely]

std::sample needs to call _GLIBCXX_STD_A::__sample instead of
std::__sample, so that it works when Parallel Mode is active.

        PR libstdc++/81221
        * include/bits/stl_algo.h (sample): Qualify with _GLIBCXX_STD_A not
        std.
        * testsuite/25_algorithms/sample/81221.cc: New.

Tested powerpc64le-linux, committed to trunk, and will commit to the
gcc-7-branch shortly.



commit e55a8a53c38e9c914d0f12e7a4fd98e6790ad68e
Author: Jonathan Wakely <jwak...@redhat.com>
Date:   Tue Jun 27 13:46:43 2017 +0100

    PR libstdc++/81221 fix namespace qualification for parallel mode
    
        PR libstdc++/81221
        * include/bits/stl_algo.h (sample): Qualify with _GLIBCXX_STD_A not
        std.
        * testsuite/25_algorithms/sample/81221.cc: New.

diff --git a/libstdc++-v3/include/bits/stl_algo.h 
b/libstdc++-v3/include/bits/stl_algo.h
index 246193f..fbebfdb 100644
--- a/libstdc++-v3/include/bits/stl_algo.h
+++ b/libstdc++-v3/include/bits/stl_algo.h
@@ -5831,8 +5831,9 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
                    "sample size must be an integer type");
 
       typename iterator_traits<_PopulationIterator>::difference_type __d = __n;
-      return std::__sample(__first, __last, __pop_cat{}, __out, __samp_cat{},
-                          __d, std::forward<_UniformRandomBitGenerator>(__g));
+      return _GLIBCXX_STD_A::
+       __sample(__first, __last, __pop_cat{}, __out, __samp_cat{}, __d,
+                std::forward<_UniformRandomBitGenerator>(__g));
     }
 #endif // C++17
 #endif // C++14
diff --git a/libstdc++-v3/testsuite/25_algorithms/sample/81221.cc 
b/libstdc++-v3/testsuite/25_algorithms/sample/81221.cc
new file mode 100644
index 0000000..e6dd5e0
--- /dev/null
+++ b/libstdc++-v3/testsuite/25_algorithms/sample/81221.cc
@@ -0,0 +1,23 @@
+// Copyright (C) 2017 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/>.
+
+// { dg-options "-std=gnu++17" }
+// { dg-do compile { target c++1z } }
+
+#undef _GLIBCXX_PARALLEL
+#define _GLIBCXX_PARALLEL 1
+#include <algorithm>