From 8520132bc362d5f915eb1cb20038492e37b3cf88 Mon Sep 17 00:00:00 2001
From: Jonathan Wakely <jwakely@redhat.com>
Date: Fri, 24 Feb 2023 13:03:49 +0000
Subject: [PATCH] libstdc++: Constrain net::executor constructors
The TS says the arguments to these constructors shall meet the Executor
requirements, so it's undefined if they don't. Constraining on a subset
of those requirements won't affect valid cases, but prevents the
majority of invalid cases from trying to instantiate the constructor.
This prevents the non-explicit executor(Executor) constructor being a
candidate anywhere that a net::executor could be constructed e.g.
comparing ip::tcp::v4() == ip::udp::v4() would try to convert both
operands to executor using that constructor, then compare then using
operator==(const executor&, const executor&).
libstdc++-v3/ChangeLog:
* include/experimental/executor (executor): Constrain template
constructors.
---
libstdc++-v3/include/experimental/executor | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/libstdc++-v3/include/experimental/executor b/libstdc++-v3/include/experimental/executor
index cd75d99ddb3b..1dae8925916d 100644
--- a/libstdc++-v3/include/experimental/executor
+++ b/libstdc++-v3/include/experimental/executor
@@ -1012,6 +1012,9 @@ inline namespace v1
class executor
{
+ template<typename _Executor>
+ using _Context_t = decltype(std::declval<_Executor&>().context());
+
public:
// construct / copy / destroy:
@@ -1021,12 +1024,14 @@ inline namespace v1
executor(const executor&) noexcept = default;
executor(executor&&) noexcept = default;
- template<typename _Executor>
+ template<typename _Executor,
+ typename = _Require<is_lvalue_reference<_Context_t<_Executor>>>>
executor(_Executor __e)
: _M_target(make_shared<_Tgt1<_Executor>>(std::move(__e)))
{ }
- template<typename _Executor, typename _ProtoAlloc>
+ template<typename _Executor, typename _ProtoAlloc,
+ typename = _Require<is_lvalue_reference<_Context_t<_Executor>>>>
executor(allocator_arg_t, const _ProtoAlloc& __a, _Executor __e)
: _M_target(allocate_shared<_Tgt2<_Executor, _ProtoAlloc>>(__a,
std::move(__e), __a))
--
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