From: Jonathan Wakely <jwakely@redhat.com>
To: libstdc++@gcc.gnu.org, gcc-patches@gcc.gnu.org
Subject: [committed] libstdc++: Fix std::move_only_function for incomplete parameter types
Date: Fri, 21 Oct 2022 10:51:19 +0100 [thread overview]
Message-ID: <20221021095119.473425-1-jwakely@redhat.com> (raw)
Tested powerpc64le-linux. Pushed to trunk.
-- >8 --
The std::move_only_function::__param_t alias template attempts to
optimize argument passing for the invoker, by passing by rvalue
reference for types that are non-trivial or large. However, the
precondition for is_trivally_copyable makes it unsuitable for using
here, and can cause ODR violations. Just use is_scalar instead, and pass
all class types (even small, trivial ones) by value.
libstdc++-v3/ChangeLog:
* include/bits/mofunc_impl.h (move_only_function::__param_t):
Use __is_scalar instead of is_trivially_copyable.
* testsuite/20_util/move_only_function/call.cc: Check parameters
involving incomplete types.
---
libstdc++-v3/include/bits/mofunc_impl.h | 5 +----
.../testsuite/20_util/move_only_function/call.cc | 11 +++++++++++
2 files changed, 12 insertions(+), 4 deletions(-)
diff --git a/libstdc++-v3/include/bits/mofunc_impl.h b/libstdc++-v3/include/bits/mofunc_impl.h
index 405c4054642..47e1e506306 100644
--- a/libstdc++-v3/include/bits/mofunc_impl.h
+++ b/libstdc++-v3/include/bits/mofunc_impl.h
@@ -205,10 +205,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
private:
template<typename _Tp>
- using __param_t
- = __conditional_t<is_trivially_copyable_v<_Tp>
- && sizeof(_Tp) <= sizeof(long),
- _Tp, _Tp&&>;
+ using __param_t = __conditional_t<is_scalar_v<_Tp>, _Tp, _Tp&&>;
using _Invoker = _Res (*)(_Mofunc_base _GLIBCXX_MOF_CV*,
__param_t<_ArgTypes>...) noexcept(_Noex);
diff --git a/libstdc++-v3/testsuite/20_util/move_only_function/call.cc b/libstdc++-v3/testsuite/20_util/move_only_function/call.cc
index 68aa20568eb..3e159836412 100644
--- a/libstdc++-v3/testsuite/20_util/move_only_function/call.cc
+++ b/libstdc++-v3/testsuite/20_util/move_only_function/call.cc
@@ -191,10 +191,21 @@ test04()
VERIFY( std::move(std::as_const(f5))() == 3 );
}
+struct Incomplete;
+
+void
+test_params()
+{
+ std::move_only_function<void(Incomplete)> f1;
+ std::move_only_function<void(Incomplete&)> f2;
+ std::move_only_function<void(Incomplete&&)> f3;
+}
+
int main()
{
test01();
test02();
test03();
test04();
+ test_params();
}
--
2.37.3
reply other threads:[~2022-10-21 9:51 UTC|newest]
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