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<condition_variable>: Fixes bad timeout in wait_until with unsigned rep #3761

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merged 3 commits into from
Jun 15, 2023
Merged

<condition_variable>: Fixes bad timeout in wait_until with unsigned rep #3761

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5048e7a
Fixes bad timeout in wait_until with unsigned rep
MattStephanson Jun 11, 2023
43ae3f4
test fix/code review feedback
MattStephanson Jun 11, 2023
22bca57
more PR feedback
MattStephanson Jun 13, 2023
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5 changes: 4 additions & 1 deletion stl/inc/condition_variable
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Original file line number Diff line number Diff line change
Expand Up @@ -95,7 +95,10 @@ public:
#if _HAS_CXX20
static_assert(chrono::is_clock_v<_Clock>, "Clock type required");
#endif // _HAS_CXX20
return wait_for(_Lck, _Abs_time - _Clock::now());
using _CommonDuration = common_type_t<_Duration, typename _Clock::duration>;
const auto _Now = _Clock::now();
const _CommonDuration _Rel_time = (_Abs_time <= _Now) ? _CommonDuration::zero() : _Abs_time - _Now;
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return wait_for(_Lck, _Rel_time);
}

template <class _Lock, class _Clock, class _Duration, class _Predicate>
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35 changes: 31 additions & 4 deletions tests/std/tests/GH_000685_condition_variable_any/test.cpp
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Expand Up @@ -7,8 +7,10 @@
#include <chrono>
#include <condition_variable>
#include <mutex>
#include <type_traits>

using namespace std;
using namespace std::chrono;

namespace {
class my_mutex { // user-defined mutex type
Expand All @@ -31,8 +33,8 @@ namespace {
int num_lock = 0;
};

const chrono::nanoseconds interval{20};
const chrono::nanoseconds zero_dur{0};
const nanoseconds interval{20};
const nanoseconds zero_dur{0};

void test_condition_variable_any() { // test wait functions of condition variables
condition_variable_any cnd;
Expand All @@ -46,15 +48,40 @@ namespace {
cnd.wait_for(mtx, interval);
assert(mtx.num_locks() == 3);

cnd.wait_until(mtx, chrono::steady_clock::now());
cnd.wait_until(mtx, steady_clock::now());
assert(mtx.num_locks() == 4);

cnd.wait_until(mtx, chrono::steady_clock::now() + interval);
cnd.wait_until(mtx, steady_clock::now() + interval);
assert(mtx.num_locks() == 5);
}
}

void test_condition_variable_any_already_timed_out() {
using unsigned_duration = duration<make_unsigned_t<system_clock::rep>, system_clock::period>;
const auto right_now = time_point_cast<unsigned_duration>(system_clock::now());
const auto yesterday = right_now - hours{24};
assert(yesterday - right_now > system_clock::duration::zero()); // unsigned overflow

my_mutex m;
condition_variable_any cond;
unique_lock<my_mutex> guard(m);

const auto status = cond.wait_until(m, yesterday);
assert(status == cv_status::timeout);
assert(m.num_locks() == 2);

assert(cond.wait_until(m, yesterday, []() { return false; }) == false);
assert(m.num_locks() == 3);

#if _HAS_CXX20
stop_token token;
assert(cond.wait_until(m, token, yesterday, []() { return false; }) == false);
assert(m.num_locks() == 4);
#endif // _HAS_CXX20
}
} // unnamed namespace

int main() {
test_condition_variable_any();
test_condition_variable_any_already_timed_out();
}