[gcc(refs/users/guojiufu/heads/guojiufu-branch)] libstdc++: allow string_view insertion to work with <iosfwd> (PR 94051)

[Jiu Fu Guo]

https://gcc.gnu.org/g:6a7052832a4791047b0ff4f18dcbb55c93a7336c

commit 6a7052832a4791047b0ff4f18dcbb55c93a7336c
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Thu Mar 5 16:46:28 2020 +0000

    libstdc++: allow string_view insertion to work with <iosfwd> (PR 94051)
    
    I don't think this is actually required to compile, because using
    operator<< without a definition of the ostream doesn't seem valid to me.
    But it's easy to make it work.
    
            PR libstdc++/94051
            * include/std/string_view: Include <bits/ostream_insert.h>.
            * testsuite/21_strings/basic_string_view/inserters/94051.cc: New test.

Diff:
---
 libstdc++-v3/ChangeLog                             |  6 +++++
 libstdc++-v3/include/std/string_view               |  1 +
 .../basic_string_view/inserters/94051.cc           | 28 ++++++++++++++++++++++
 3 files changed, 35 insertions(+)

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index df3b040abca..fd4d502badd 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,9 @@
+2020-03-05  Jonathan Wakely  <jwakely@redhat.com>
+
+	PR libstdc++/94051
+	* include/std/string_view: Include <bits/ostream_insert.h>.
+	* testsuite/21_strings/basic_string_view/inserters/94051.cc: New test.
+
 2020-03-04  Jonathan Wakely  <jwakely@redhat.com>
 
 	* include/bits/cpp_type_traits.h (__memcpyable): Fix comment.
diff --git a/libstdc++-v3/include/std/string_view b/libstdc++-v3/include/std/string_view
index ea5d547e006..99a81bb04fa 100644
--- a/libstdc++-v3/include/std/string_view
+++ b/libstdc++-v3/include/std/string_view
@@ -42,6 +42,7 @@
 #include <bits/functional_hash.h>
 #include <bits/int_limits.h>
 #include <bits/range_access.h>
+#include <bits/ostream_insert.h>
 
 namespace std _GLIBCXX_VISIBILITY(default)
 {
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/inserters/94051.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/inserters/94051.cc
new file mode 100644
index 00000000000..326669133d7
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/inserters/94051.cc
@@ -0,0 +1,28 @@
+// Copyright (C) 2020 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++17 } }
+
+#include <iosfwd>
+#include <string_view>
+
+void
+test01(std::ostream& os, std::string_view sv)
+{
+  os << sv;
+}