libstdc++: Allow std::condition_variable waits to be cancelled [PR103382]
std::condition_variable::wait(unique_lock<mutex>&) is incorrectly marked noexcept, which means that the __forced_unwind exception used by NPTL cancellation will terminate the process. It should allow exceptions to pass through, so that a thread can be cleanly cancelled when waiting on a condition variable. The new behaviour is exported as a new version of the symbol, to avoid an ABI break for existing code linked to the non-throwing definition of the function. Code linked against older releases will have a reference to the @GLIBCXX_3.4.11 version, andcode compiled against the new libstdc++ will get a reference to the @@GLIBCXX_3.4.30 version. libstdc++-v3/ChangeLog: PR libstdc++/103382 * config/abi/pre/gnu.ver (GLIBCXX_3.4.11): Do not export old symbol if .symver renaming is supported. (GLIBCXX_3.4.30): Export new symbol if .symver renaming is supported. * doc/xml/manual/evolution.xml: Document change. * doc/html/manual/api.html: Regenerate. * include/bits/std_mutex.h (__condvar::wait, __condvar::wait_until): Remove noexcept. * include/std/condition_variable (condition_variable::wait): Likewise. * src/c++11/condition_variable.cc (condition_variable::wait): Likewise. * src/c++11/compatibility-condvar.cc (__nothrow_wait_cv::wait): Define nothrow wrapper around std::condition_variable::wait and export the old symbol as an alias to it. * testsuite/30_threads/condition_variable/members/103382.cc: New test.
This commit is contained in:
Jonathan Wakely
parent
db5fa0837e
commit
9e18a25331
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@ -1285,7 +1285,6 @@ GLIBCXX_3.4.11 {
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# condition_variable
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_ZNSt18condition_variable10notify_allEv;
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_ZNSt18condition_variable10notify_oneEv;
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_ZNSt18condition_variable4waitERSt11unique_lockISt5mutexE;
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_ZNSt18condition_variableC1Ev;
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_ZNSt18condition_variableC2Ev;
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_ZNSt18condition_variableD1Ev;
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@ -1295,6 +1294,12 @@ GLIBCXX_3.4.11 {
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_ZNSt22condition_variable_anyD1Ev;
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_ZNSt22condition_variable_anyD2Ev;
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#ifndef HAVE_SYMVER_SYMBOL_RENAMING_RUNTIME_SUPPORT
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# The original definition of this symbol gets versioned as @GLIBCXX_3.4.11
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# if ".symver" is supported, or as @@GLIBCXX_3.4.11 otherwise.
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_ZNSt18condition_variable4waitERSt11unique_lockISt5mutexE;
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#endif
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# thread
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_ZNSt6thread4joinEv;
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_ZNSt6thread6detachEv;
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@ -2401,6 +2406,11 @@ GLIBCXX_3.4.30 {
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_ZSt21__glibcxx_assert_fail*;
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#ifdef HAVE_SYMVER_SYMBOL_RENAMING_RUNTIME_SUPPORT
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# The new definition of this symbol gets versioned as @@GLIBCXX_3.4.30
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_ZNSt18condition_variable4waitERSt11unique_lockISt5mutexE;
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#endif
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} GLIBCXX_3.4.29;
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# Symbols in the support library (libsupc++) have their own tag.
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@ -450,4 +450,9 @@ options for <code class="option">--enable-libstdcxx-allocator</code> were remove
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For the <code class="literal">new</code> option, <code class="classname">std::allocator</code>
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no longer derives from <code class="classname">__gnu_cxx::new_allocator</code>;
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they both derive from <code class="classname">std::__new_allocator</code> instead.
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</p><p>
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<code class="function">std::condition_variable::wait</code> changed to be
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<code class="code">noexcept(false)</code> to allow thread cancellation exceptions to
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be thrown from <code class="function">pthread_cond_wait</code> without aborting
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the process.
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</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="abi.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="appendix_porting.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="backwards.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">ABI Policy and Guidelines </td><td width="20%" align="center"><a accesskey="h" href="../index.html">Home</a></td><td width="40%" align="right" valign="top"> Backwards Compatibility</td></tr></table></div></body></html>
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@ -1041,6 +1041,13 @@ no longer derives from <classname>__gnu_cxx::new_allocator</classname>;
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they both derive from <classname>std::__new_allocator</classname> instead.
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</para>
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<para>
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<function>std::condition_variable::wait</function> changed to be
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<code>noexcept(false)</code> to allow thread cancellation exceptions to
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be thrown from <function>pthread_cond_wait</function> without aborting
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the process.
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</para>
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</section>
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</section>
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@ -149,7 +149,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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// Expects: Calling thread has locked __m.
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void
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wait(mutex& __m) noexcept
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wait(mutex& __m)
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{
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int __e __attribute__((__unused__))
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= __gthread_cond_wait(&_M_cond, __m.native_handle());
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@ -157,14 +157,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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}
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void
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wait_until(mutex& __m, timespec& __abs_time) noexcept
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wait_until(mutex& __m, timespec& __abs_time)
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{
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__gthread_cond_timedwait(&_M_cond, __m.native_handle(), &__abs_time);
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}
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#ifdef _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT
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void
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wait_until(mutex& __m, clockid_t __clock, timespec& __abs_time) noexcept
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wait_until(mutex& __m, clockid_t __clock, timespec& __abs_time)
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{
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pthread_cond_clockwait(&_M_cond, __m.native_handle(), __clock,
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&__abs_time);
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@ -92,7 +92,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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notify_all() noexcept;
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void
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wait(unique_lock<mutex>& __lock) noexcept;
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wait(unique_lock<mutex>& __lock);
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template<typename _Predicate>
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void
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@ -54,4 +54,35 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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_GLIBCXX_END_NAMESPACE_VERSION
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} // namespace std
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#if ! _GLIBCXX_INLINE_VERSION
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// XXX GLIBCXX_ABI Deprecated
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// gcc-12.1
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// std::condition_variable::wait changed to noexcept(false)
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#if defined(_GLIBCXX_SYMVER_GNU) && defined(_GLIBCXX_SHARED) \
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&& defined(_GLIBCXX_HAVE_AS_SYMVER_DIRECTIVE) \
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&& defined(_GLIBCXX_HAVE_SYMVER_SYMBOL_RENAMING_RUNTIME_SUPPORT)
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namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
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{
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struct __nothrow_wait_cv : std::condition_variable
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{
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void wait(std::unique_lock<std::mutex>&) noexcept;
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};
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__attribute__((used))
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void
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__nothrow_wait_cv::wait(std::unique_lock<std::mutex>& lock) noexcept
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{
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this->condition_variable::wait(lock);
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}
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} // namespace __gnu_cxx
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// Export a noexcept wrapper around std::condition_variable::wait
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// with the original @GLIBCXX_3.4.11 symbol version.
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asm(
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".symver _ZN9__gnu_cxx17__nothrow_wait_cv4waitERSt11unique_lockISt5mutexE,"
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"_ZNSt18condition_variable4waitERSt11unique_lockISt5mutexE@GLIBCXX_3.4.11"
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);
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#endif
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#endif
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#endif // _GLIBCXX_HAS_GTHREADS && _GLIBCXX_USE_C99_STDINT_TR1
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@ -36,7 +36,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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condition_variable::~condition_variable() noexcept = default;
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void
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condition_variable::wait(unique_lock<mutex>& __lock) noexcept
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condition_variable::wait(unique_lock<mutex>& __lock)
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{
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_M_cond.wait(*__lock.mutex());
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}
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@ -0,0 +1,66 @@
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// { dg-options "-pthread" }
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// { dg-do run { target { *-*-linux* *-*-gnu* } } }
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// { dg-require-effective-target c++11 }
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// { dg-require-effective-target pthread }
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// { dg-require-gthreads "" }
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#include <condition_variable>
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#include <chrono>
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#include <mutex>
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#include <thread>
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// PR libstdc++/103382
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template<typename F>
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void
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test_cancel(F wait)
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{
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std::mutex m;
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std::condition_variable cv;
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bool waiting = false;
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std::thread t([&] {
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std::unique_lock<std::mutex> lock(m);
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waiting = true;
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wait(cv, lock); // __forced_unwind exception should not terminate process.
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});
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// Ensure the condition variable is waiting before we cancel.
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// This shouldn't be necessary because pthread_mutex_lock is not
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// a cancellation point, but no harm in making sure we test what
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// we intend to test: that cancel during a wait doesn't abort.
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while (true)
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{
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std::unique_lock<std::mutex> lock(m);
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if (waiting)
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break;
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}
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pthread_cancel(t.native_handle());
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t.join();
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}
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int main()
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{
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test_cancel(
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[](std::condition_variable& cv, std::unique_lock<std::mutex>& l) {
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cv.wait(l);
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});
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test_cancel(
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[](std::condition_variable& cv, std::unique_lock<std::mutex>& l) {
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cv.wait(l, []{ return false; });
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});
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using mins = std::chrono::minutes;
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test_cancel(
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[](std::condition_variable& cv, std::unique_lock<std::mutex>& l) {
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cv.wait_for(l, mins(1));
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});
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test_cancel(
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[](std::condition_variable& cv, std::unique_lock<std::mutex>& l) {
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cv.wait_until(l, std::chrono::system_clock::now() + mins(1));
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});
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}
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