On Fri, 11 Feb 2022 at 17:40, Thomas Rodgers via Libstdc++ <libstd...@gcc.gnu.org> wrote: > > <recording this here for future reference> > PR102994 "atomics: std::atomic<ptr>::wait is not marked const" raises the > issue that the current libstdc++ implementation marks the notify members > const, the implementation strategy used by libstdc++, as well as libc++ > and the Microsoft STL, do not require the atomic to be mutable (it is hard > to conceive of a desirable implementation approach that would require it). > The original paper proposing the wait/notify functionality for atomics > (p1185) also had these members marked const for the first three revisions, > but that was changed without explanation in r3 and subsequent revisions of > the paper. > > After raising the issue to the authors of p1185 and the author of the > libc++ implementation, the consensus seems to be "meh, it's harmless" so > there seems little appetite for an LWG issue to revisit the subject. > > This patch changes the libstdc++ implementation to be in agreement with > the standard by removing const from those notify_one/notify_all members. > > libstdc++-v3/ChangeLog:
Might as well add a "PR libstdc++/102994" here to the bug gets updated automatically. OK for trunk with that change. > * include/bits/atomic_base.h (atomic_flag::notify_one, > notify_all): Remove const qualification. > (__atomic_base::notify_one, notify_all): Likewise. > * include/std/atomic (atomic<bool>::notify_one, notify_all): > Likewise. > (atomic::notify_one, notify_all): Likewise. > (atomic<T*>::notify_one, notify_all): Likewise. > (atomic_notify_one, atomic_notify_all): Likewise. > * testsuite/29_atomics/atomic/wait_notify/102994.cc: Adjust test > to account for change in notify_one/notify_all signature. > > Tested x86_64-pc-linux-gnu.
