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Implement LWG-3343 Ordering of calls to unlock() and notify_all() in Effects element of notify_all_at_thread_exit() should be reversed #5912

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Merged
Stephan T. Lavavej (StephanTLavavej) merged 4 commits into from
Dec 8, 2025
Merged

Implement LWG-3343 Ordering of calls to unlock() and notify_all() in Effects element of notify_all_at_thread_exit() should be reversed #5912

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9ac653b
Swap mutex unlock and condition_variable notify_all at thread exit.
vmichal Nov 26, 2025
24fda93
Don't skip libcpp test std/thread/thread.condition/notify_all_at_thre…
vmichal Nov 26, 2025
8465ac0
Merge branch 'main' into reverse-effects-of-notify_all_at_thread_exit
StephanTLavavej Dec 6, 2025
f058a91
YOU SHALL PASS!
StephanTLavavej Dec 6, 2025
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2 changes: 1 addition & 1 deletion stl/src/xnotify.cpp
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Expand Up @@ -93,8 +93,8 @@ _CRTIMP2_PURE void __cdecl _Cnd_do_broadcast_at_thread_exit() noexcept {
if (block->data[i].res) {
*block->data[i].res = 1;
}
_Mtx_unlock(block->data[i].mtx);
_Cnd_broadcast(block->data[i].cnd);
_Mtx_unlock(block->data[i].mtx);
block->data[i].mtx = nullptr;
--block->num_used;
}
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5 changes: 0 additions & 5 deletions tests/libcxx/expected_results.txt
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Expand Up @@ -626,11 +626,6 @@ std/thread/futures/futures.task/futures.task.members/make_ready_at_thread_exit.p
# LWG-3120 Unclear behavior of monotonic_buffer_resource::release()
std/utilities/utility/mem.res/mem.res.monotonic.buffer/mem.res.monotonic.buffer.mem/release_reset_initial_status.pass.cpp FAIL

# LWG-3343 "Ordering of calls to unlock() and notify_all() in Effects element of notify_all_at_thread_exit() should be reversed" (Open)
# libc++ speculatively implements LWG-3343. If we wanted to do the same thing,
# we'd need to reverse the order of the _Mtx_unlock() and _Cnd_broadcast() calls in xnotify.cpp.
std/thread/thread.condition/notify_all_at_thread_exit_lwg3343.pass.cpp SKIPPED


# *** C1XX COMPILER BUGS ***
# DevCom-1436243 VSO-1335743 constexpr new initialized array
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