[gcc r13-6087] libstdc++: Implement <experimental/synchronized_value> (P0290)
Jonathan Wakely
redi@gcc.gnu.org
Thu Feb 16 14:40:08 GMT 2023
https://gcc.gnu.org/g:b85c77e19ad9c40231c4050e6ad373b30de7b2b9
commit r13-6087-gb85c77e19ad9c40231c4050e6ad373b30de7b2b9
Author: Jonathan Wakely <jwakely@redhat.com>
Date: Wed Feb 15 15:07:15 2023 +0000
libstdc++: Implement <experimental/synchronized_value> (P0290)
This was approved for the Concurrency TS v2 in Issaquah.
Although the TS is based on C++20, this enables the new header for C++17
as well. This will make it available to more users, and I hope that will
get more feedback on the feature.
libstdc++-v3/ChangeLog:
* include/Makefile.am: Add new header.
* include/Makefile.in: Regenerate.
* include/experimental/synchronized_value: New file.
* testsuite/experimental/synchronized_value.cc: New test.
Diff:
---
libstdc++-v3/include/Makefile.am | 1 +
libstdc++-v3/include/Makefile.in | 1 +
.../include/experimental/synchronized_value | 100 +++++++++++++++++++++
.../testsuite/experimental/synchronized_value.cc | 42 +++++++++
4 files changed, 144 insertions(+)
diff --git a/libstdc++-v3/include/Makefile.am b/libstdc++-v3/include/Makefile.am
index 5b501272830..a880e8ee227 100644
--- a/libstdc++-v3/include/Makefile.am
+++ b/libstdc++-v3/include/Makefile.am
@@ -798,6 +798,7 @@ experimental_headers = \
${experimental_srcdir}/source_location \
${experimental_srcdir}/string \
${experimental_srcdir}/string_view \
+ ${experimental_srcdir}/synchronized_value \
${experimental_srcdir}/system_error \
${experimental_srcdir}/timer \
${experimental_srcdir}/tuple \
diff --git a/libstdc++-v3/include/Makefile.in b/libstdc++-v3/include/Makefile.in
index 36e35e13806..0ff875b280b 100644
--- a/libstdc++-v3/include/Makefile.in
+++ b/libstdc++-v3/include/Makefile.in
@@ -1144,6 +1144,7 @@ experimental_headers = \
${experimental_srcdir}/source_location \
${experimental_srcdir}/string \
${experimental_srcdir}/string_view \
+ ${experimental_srcdir}/synchronized_value \
${experimental_srcdir}/system_error \
${experimental_srcdir}/timer \
${experimental_srcdir}/tuple \
diff --git a/libstdc++-v3/include/experimental/synchronized_value b/libstdc++-v3/include/experimental/synchronized_value
new file mode 100644
index 00000000000..9a91da912ca
--- /dev/null
+++ b/libstdc++-v3/include/experimental/synchronized_value
@@ -0,0 +1,100 @@
+// <experimental/synchronized_value> -*- C++ -*-
+
+// Copyright The GNU Toolchain Authors.
+//
+// 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.
+
+// Under Section 7 of GPL version 3, you are granted additional
+// permissions described in the GCC Runtime Library Exception, version
+// 3.1, as published by the Free Software Foundation.
+
+// You should have received a copy of the GNU General Public License and
+// a copy of the GCC Runtime Library Exception along with this program;
+// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
+// <http://www.gnu.org/licenses/>.
+
+/** @file include/experimental/synchronized_value
+ * This is a TS C++ Library header.
+ * @ingroup libfund-ts
+ */
+
+#ifndef _GLIBCXX_EXPERIMENTAL_SYNCVAL
+#define _GLIBCXX_EXPERIMENTAL_SYNCVAL 1
+
+#pragma GCC system_header
+
+#include <bits/requires_hosted.h> // for std::mutex
+
+#if __cplusplus >= 201703L
+#include <mutex>
+#include <bits/invoke.h>
+
+namespace std _GLIBCXX_VISIBILITY(default)
+{
+_GLIBCXX_BEGIN_NAMESPACE_VERSION
+namespace experimental::inline concurrency_v2
+{
+#define __cpp_lib_concurrency_v2_synchronized_value 202302
+
+ template<typename _Tp>
+ class synchronized_value
+ {
+ // TODO: Use partial specialization after PR c++/71954 is fixed.
+ template<typename... _Args>
+ static inline constexpr bool __is_self
+ = sizeof...(_Args) == 1
+ && (is_same_v<__remove_cvref_t<_Args>, synchronized_value> && ...);
+
+#if ! __cpp_concepts
+ template<typename... _Args>
+ using __not_self = bool_constant<!__is_self<_Args...>>;
+#endif
+
+ public:
+ synchronized_value(const synchronized_value&) = delete;
+ synchronized_value& operator=(const synchronized_value&) = delete;
+
+#if __cpp_concepts
+ template<typename... _Args>
+ requires (!__is_self<_Args...>) && is_constructible_v<_Tp, _Args...>
+#else
+ template<typename... _Args, typename = _Require<__not_self<_Args...>>,
+ typename = _Require<is_constructible<_Tp, _Args...>>>
+#endif
+ synchronized_value(_Args&&... __args)
+ noexcept(is_nothrow_constructible_v<_Tp, _Args...>)
+ : _M_val(std::forward<_Args>(__args)...)
+ { }
+
+ template<typename _Fn, typename _Up, typename ... _Types>
+ friend invoke_result_t<_Fn, _Up&, _Types&...>
+ apply(_Fn&&, synchronized_value<_Up>&, synchronized_value<_Types>&...);
+
+ private:
+ mutex _M_mut;
+ _Tp _M_val;
+ };
+
+ template<typename _Fn, typename _Tp, typename... _Types>
+ inline invoke_result_t<_Fn, _Tp&, _Types&...>
+ apply(_Fn&& __f, synchronized_value<_Tp>& __val,
+ synchronized_value<_Types>&... __vals)
+ {
+ scoped_lock __l(__val._M_mut, __vals._M_mut...);
+ return std::__invoke(std::forward<_Fn>(__f), __val._M_val,
+ __vals._M_val...);
+ }
+} // namespace experimental::concurrency_v2
+_GLIBCXX_END_NAMESPACE_VERSION
+} // namespace std
+#endif // C++20
+#endif // _GLIBCXX_EXPERIMENTAL_SYNCVAL
diff --git a/libstdc++-v3/testsuite/experimental/synchronized_value.cc b/libstdc++-v3/testsuite/experimental/synchronized_value.cc
new file mode 100644
index 00000000000..8e8134699a2
--- /dev/null
+++ b/libstdc++-v3/testsuite/experimental/synchronized_value.cc
@@ -0,0 +1,42 @@
+// { dg-do run { target c++17 } }
+
+#include <experimental/synchronized_value>
+#include <testsuite_hooks.h>
+#include <string>
+
+using std::experimental::synchronized_value;
+
+synchronized_value<std::string> s;
+
+std::string read_value(){
+ return apply([](auto& x){return x;},s);
+}
+
+void set_value(std::string const& new_val){
+ apply([&](auto& x){ x = new_val; }, s);
+}
+
+void
+test_single()
+{
+ set_value("new value");
+ VERIFY( read_value() == "new value" );
+}
+
+void
+test_multi()
+{
+ synchronized_value<int> a(1), b(2), c(3);
+ int sum = apply([](auto&... ints) { return (ints++ + ...); }, a, b, c);
+ VERIFY( sum == 6 );
+ auto get = [](int& i) { return i; };
+ VERIFY( apply(get, a) == 2 );
+ VERIFY( apply(get, b) == 3 );
+ VERIFY( apply(get, c) == 4 );
+}
+
+int main()
+{
+ test_single();
+ test_multi();
+}
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