https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84532
Bug ID: 84532
Summary: [7/8 Regression] std::thread::__make_invoker
prematurely unwraps reference_wrappers
Product: gcc
Version: 8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: rs2740 at gmail dot com
Target Milestone: ---
std::thread::__make_invoker uses make_tuple, which unwraps reference_wrappers,
so instead of passing a DECAY_COPY'd reference_wrapper<T> rvalue to __invoke,
it (incorrectly) passes a T lvalue instead.
This means that we accept invalid code like
int i = 0;
std::thread t([](auto&){}, std::ref(i));
It's not too hard to come up with code that changes meaning and valid code that
gets rejected either.
This is a 7/8 regression: previously the now-removed __bind_simple was used,
which correctly just does a simple decay.
