From 8cf428bfd3ca967b3d135e311d3e391998a39335 Mon Sep 17 00:00:00 2001 From: Jonathan Wakely Date: Thu, 26 Aug 2021 13:13:27 +0100 Subject: [PATCH] libstdc++: Add static assertions for std::function requirements Add static assertions to std::function, so that more user-friendly diagnostics are given when trying to store a non-copyable target object. These preconditions were added as "Mandates:" by LWG 2447, but I'm committing them separately from implementing that, to allow just this change to be backported more easily. Signed-off-by: Jonathan Wakely libstdc++-v3/ChangeLog: * include/bits/std_function.h (function::function(F)): Add static assertions to check constructibility requirements. --- libstdc++-v3/include/bits/std_function.h | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/libstdc++-v3/include/bits/std_function.h b/libstdc++-v3/include/bits/std_function.h index fb86ff1c5f84..e081cd81ef48 100644 --- a/libstdc++-v3/include/bits/std_function.h +++ b/libstdc++-v3/include/bits/std_function.h @@ -422,6 +422,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION function(_Functor __f) : _Function_base() { + static_assert(is_copy_constructible<_Functor>::value, + "std::function target must be copy-constructible"); + static_assert(is_constructible<_Functor, _Functor>::value, + "std::function target must be constructible from the " + "constructor argument"); + using _My_handler = _Function_handler<_Res(_ArgTypes...), _Functor>; if (_My_handler::_M_not_empty_function(__f)) -- 2.47.2