On 03/05/21 09:43 -0700, Thomas Rodgers wrote:
From: Thomas Rodgers <rodg...@twrodgers.com>
This should also be backported to gcc-11
The additional _M_laundered data member changes the object layout.
That isn't safe for the branch. Would it be possible to smuggle that
flag in the least significant bit of the _M_addr member, which is
always aligned to more than one byte? Just on the gcc-11 branch, not
for trunk.
libstdc++/ChangeLog:
* include/bits/atomic_wait.h (__waiter::_M_do_wait_v): loop
until observe value change.
(__waiter_base::_M_laundered): New member.
(__watier_base::_M_notify): Check _M_laundered to determine
whether to wake one or all.
(__detail::__atomic_compare): Do not implicitly convert
result of __buildtin_memcpmp to bool,
Typos, and the description doesn't seem accurate (it wasn't implicitly
converting it to bool, there was always an explicit comparison, but
now it's == rather than !=).
(__waiter_base::_S_do_spin_v): Adjust predicate.
* testsuite/29_atomics/atomic/wait_notify/100334.cc: New
test.
OK for trunk with a fixed changelog, but we need a different patch for
the branch.
