From 1f53367fb5f16985e82c39f56368b956292cf86c Mon Sep 17 00:00:00 2001 From: Jonathan Wakely Date: Wed, 22 Jul 2020 20:10:38 +0100 Subject: [PATCH] libstdc++: Add static assertions to futures and promises [LWG 3458] LWG recently decided it should be ill-formed to instantiate std::future and std::shared_future for types that can't be returned from a function. This adds static assertions to enforce it (std::future already failed, but this makes the error more understandable). LWG 3466 extends that to std::promise. The actual constraint is that t.~T() is well-formed for the primary template, but rejecting arrays and functions as done for futures matches that condition. libstdc++-v3/ChangeLog: * include/std/future (future, shared_future, promise): Add static assertions to the primary template to reject array and function types. * testsuite/30_threads/future/requirements/lwg3458.cc: New test. * testsuite/30_threads/promise/requirements/lwg3466.cc: New test. * testsuite/30_threads/shared_future/requirements/lwg3458.cc: New test. --- libstdc++-v3/include/std/future | 15 ++++++++ .../30_threads/future/requirements/lwg3458.cc | 34 +++++++++++++++++++ .../promise/requirements/lwg3466.cc | 34 +++++++++++++++++++ .../shared_future/requirements/lwg3458.cc | 32 +++++++++++++++++ 4 files changed, 115 insertions(+) create mode 100644 libstdc++-v3/testsuite/30_threads/future/requirements/lwg3458.cc create mode 100644 libstdc++-v3/testsuite/30_threads/promise/requirements/lwg3466.cc create mode 100644 libstdc++-v3/testsuite/30_threads/shared_future/requirements/lwg3458.cc diff --git a/libstdc++-v3/include/std/future b/libstdc++-v3/include/std/future index 6eef6864f4d..bdf4a75d694 100644 --- a/libstdc++-v3/include/std/future +++ b/libstdc++-v3/include/std/future @@ -763,6 +763,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION template class future : public __basic_future<_Res> { + // _GLIBCXX_RESOLVE_LIB_DEFECTS + // 3458. Is shared_future intended to work with arrays or function types? + static_assert(!is_array<_Res>{}, "result type is not an array"); + static_assert(!is_function<_Res>{}, "result type is not a function"); + friend class promise<_Res>; template friend class packaged_task; template @@ -893,6 +898,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION template class shared_future : public __basic_future<_Res> { + // _GLIBCXX_RESOLVE_LIB_DEFECTS + // 3458. Is shared_future intended to work with arrays or function types? + static_assert(!is_array<_Res>{}, "result type is not an array"); + static_assert(!is_function<_Res>{}, "result type is not a function"); + typedef __basic_future<_Res> _Base_type; public: @@ -1045,6 +1055,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION template class promise { + // _GLIBCXX_RESOLVE_LIB_DEFECTS + // 3466: Specify the requirements for promise/future/[...] consistently + static_assert(!is_array<_Res>{}, "result type is not an array"); + static_assert(!is_function<_Res>{}, "result type is not a function"); + typedef __future_base::_State_base _State; typedef __future_base::_Result<_Res> _Res_type; typedef __future_base::_Ptr<_Res_type> _Ptr_type; diff --git a/libstdc++-v3/testsuite/30_threads/future/requirements/lwg3458.cc b/libstdc++-v3/testsuite/30_threads/future/requirements/lwg3458.cc new file mode 100644 index 00000000000..2bc206c9450 --- /dev/null +++ b/libstdc++-v3/testsuite/30_threads/future/requirements/lwg3458.cc @@ -0,0 +1,34 @@ +// 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 +// . + +// { dg-do compile { target c++11 } } + +// LWG 3458 +// Is shared_future intended to work with arrays or function types? + +#include + +std::future good; +std::future good2; + +std::future bad; // { dg-error "here" } +// { dg-error "result type is not an array" "" { target *-*-* } 0 } +// { dg-prune-output "function returning an array" } + +std::future bad2; // { dg-error "here" } +// { dg-error "result type is not a function" "" { target *-*-* } 0 } +// { dg-prune-output "function returning a function" } diff --git a/libstdc++-v3/testsuite/30_threads/promise/requirements/lwg3466.cc b/libstdc++-v3/testsuite/30_threads/promise/requirements/lwg3466.cc new file mode 100644 index 00000000000..124c86c0392 --- /dev/null +++ b/libstdc++-v3/testsuite/30_threads/promise/requirements/lwg3466.cc @@ -0,0 +1,34 @@ +// 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 +// . + +// { dg-do compile { target c++11 } } + +// LWG 3466 +// Specify the requirements for promise/future/shared_future consistently + +#include + +std::promise good; +std::promise good2; + +std::promise bad; // { dg-error "here" } +// { dg-error "result type is not an array" "" { target *-*-* } 0 } +// { dg-prune-output {request for member '~int \[1\]'} } + +std::promise bad2; // { dg-error "here" } +// { dg-error "result type is not a function" "" { target *-*-* } 0 } +// { dg-prune-output {'sizeof \(int\(\)\)'} } diff --git a/libstdc++-v3/testsuite/30_threads/shared_future/requirements/lwg3458.cc b/libstdc++-v3/testsuite/30_threads/shared_future/requirements/lwg3458.cc new file mode 100644 index 00000000000..df5bfd2b976 --- /dev/null +++ b/libstdc++-v3/testsuite/30_threads/shared_future/requirements/lwg3458.cc @@ -0,0 +1,32 @@ +// 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 +// . + +// { dg-do compile { target c++11 } } + +// LWG 3458 +// Is shared_future intended to work with arrays or function types? + +#include + +std::shared_future good; +std::shared_future good2; + +std::shared_future bad; // { dg-error "here" } +// { dg-error "result type is not an array" "" { target *-*-* } 0 } + +std::shared_future bad2; // { dg-error "here" } +// { dg-error "result type is not a function" "" { target *-*-* } 0 } -- 2.30.2