When converting from a coarse duration with a very large value, the
existing code scales that up to chrono::seconds which overflows the
chrono::seconds::rep type. For example, sleep_for(chrono::hours::max())
tries to calculate LLONG_MAX * 3600, which overflows to -3600 and so the
sleep returns immediately.
The solution in this commit is inspired by this_thread::sleep_for in
libc++ which compares the duration argument to
chrono::duration<long double>(nanoseconds::max()) and limits the
duration to nanoseconds::max(). Because we split the duration into
seconds and nanoseconds, we can use seconds::max() as our upper limit.
We might need to limit further if seconds::max() doesn't fit in the
type used for sleeping, which is one of std::time_t, unsigned int, or
chrono::milliseconds.
To fix this everywhere that uses timeouts, new functions are introduced
for converting from a chrono::duration or chrono::time_point to a
timespec (or __gthread_time_t which is just a timespec on Linux). These
functions provide one central place where we can avoid overflow and also
handle negative timeouts (as these produce errors when passed to OS
functions that do not accept absolute times before the epoch). All
negative durations are converted to zero, and negative time_points are
converted to the epoch.
libstdc++-v3/ChangeLog:
PR libstdc++/113327
PR libstdc++/116586
PR libstdc++/119258
PR libstdc++/58931
* include/bits/chrono.h (__to_timeout_timespec): New overloaded
function templates for converting chrono types to timespec.
(__to_timeout_gthread_time_t): New function template for
converting time_point to __gthread_time_t.
* include/bits/this_thread_sleep.h (sleep_for): Use
__to_timeout_timespec.
(__sleep_for): Remove namespace-scope declaration.
* include/std/condition_variable: Likewise.
* include/std/mutex: Likewise.
* include/std/shared_mutex: Likewise.
* src/c++11/thread.cc (limit): New helper function.
(__sleep_for): Use limit to prevent overflow when converting
chrono::seconds to time_t, unsigned, or chrono::milliseconds.
* src/c++20/atomic.cc: Use __to_timeout_timespec and
__to_timeout_gthread_time_t for timeouts.
* testsuite/30_threads/this_thread/113327.cc: New test.
Reviewed-by: Mike Crowe <[email protected]>
---
v2: followed Mike's suggestion to rename the functions from
__to_timespec and __to_gthread_time_t to __to_timeout_timespec and
__to_timeout_gthread_time_t.
Tested x86_64-linux.
libstdc++-v3/include/bits/chrono.h | 95 +++++++++++++++++++
libstdc++-v3/include/bits/this_thread_sleep.h | 20 ++--
libstdc++-v3/include/std/condition_variable | 20 +---
libstdc++-v3/include/std/mutex | 18 +---
libstdc++-v3/include/std/shared_mutex | 39 +-------
libstdc++-v3/src/c++11/thread.cc | 32 ++++++-
libstdc++-v3/src/c++20/atomic.cc | 18 +---
.../30_threads/this_thread/113327.cc | 29 ++++++
8 files changed, 172 insertions(+), 99 deletions(-)
create mode 100644 libstdc++-v3/testsuite/30_threads/this_thread/113327.cc
diff --git a/libstdc++-v3/include/bits/chrono.h
b/libstdc++-v3/include/bits/chrono.h
index 8de8e756c714..c20b68140192 100644
--- a/libstdc++-v3/include/bits/chrono.h
+++ b/libstdc++-v3/include/bits/chrono.h
@@ -50,6 +50,9 @@
#include <bits/version.h>
+// TODO move __to_gthread_time_t to a better place
+#include <bits/gthr.h> // for __gthread_time_t
+
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
@@ -1515,6 +1518,98 @@ _GLIBCXX_END_INLINE_ABI_NAMESPACE(_V2)
} // namespace filesystem
#endif // C++17 && HOSTED
+#if defined _GLIBCXX_USE_NANOSLEEP || defined _GLIBCXX_USE_CLOCK_REALTIME \
+ || defined _GLIBCXX_HAS_GTHREADS
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wc++17-extensions"
+namespace chrono
+{
+/// @cond undocumented
+
+ // Convert a chrono::duration to a relative time represented as timespec
+ // (e.g. for use with nanosleep).
+ template<typename _Rep, typename _Period>
+ [[__nodiscard__]] _GLIBCXX14_CONSTEXPR inline
+ struct ::timespec
+ __to_timeout_timespec(const duration<_Rep, _Period>& __d)
+ {
+ struct ::timespec __ts{};
+
+ if (__d < __d.zero()) // Negative timeouts don't make sense.
+ return __ts;
+
+ if constexpr (__or_<ratio_greater<_Period, ratio<1>>,
+ treat_as_floating_point<_Rep>>::value)
+ {
+ // Converting from e.g. chrono::hours::max() to chrono::seconds
+ // would evaluate LLONG_MAX * 3600 which would overflow.
+ // Limit to chrono::seconds::max().
+ chrono::duration<double> __fmax(chrono::seconds::max());
+ if (__d > __fmax) [[__unlikely__]]
+ return chrono::__to_timeout_timespec(chrono::seconds::max());
+ }
+
+ auto __s = chrono::duration_cast<chrono::seconds>(__d);
+
+ if constexpr (is_integral<time_t>::value) // POSIX.1-2001 allows floating
+ {
+ // Also limit to time_t maximum (only relevant for 32-bit time_t).
+ constexpr auto __tmax = numeric_limits<time_t>::max();
+ if (__s.count() > __tmax) [[__unlikely__]]
+ {
+ __ts.tv_sec = __tmax;
+ return __ts;
+ }
+ }
+
+ auto __ns = chrono::duration_cast<chrono::nanoseconds>(__d - __s);
+
+ if constexpr (treat_as_floating_point<_Rep>::value)
+ if (__ns.count() > 999999999) [[__unlikely__]]
+ __ns = chrono::nanoseconds(999999999);
+
+ __ts.tv_sec = static_cast<time_t>(__s.count());
+ __ts.tv_nsec = static_cast<long>(__ns.count());
+ return __ts;
+ }
+
+ // Convert a chrono::time_point to an absolute time represented as timespec.
+ // All times before the epoch get converted to the epoch, so this assumes
+ // that we only use it for clocks where that's true.
+ // It should be safe to use this for system_clock and steady_clock.
+ template<typename _Clock, typename _Dur>
+ [[__nodiscard__]] _GLIBCXX14_CONSTEXPR inline
+ struct ::timespec
+ __to_timeout_timespec(const time_point<_Clock, _Dur>& __t)
+ {
+ return chrono::__to_timeout_timespec(__t.time_since_epoch());
+ }
+
+#ifdef _GLIBCXX_HAS_GTHREADS
+ // Convert a time_point to an absolute time represented as __gthread_time_t
+ // (which is typically just a typedef for struct timespec).
+ template<typename _Clock, typename _Dur>
+ [[__nodiscard__]] _GLIBCXX14_CONSTEXPR inline
+ __gthread_time_t
+ __to_timeout_gthread_time_t(const time_point<_Clock, _Dur>& __t)
+ {
+ auto __ts = chrono::__to_timeout_timespec(__t.time_since_epoch());
+ if constexpr (is_same<::timespec, __gthread_time_t>::value)
+ return __ts;
+ else if constexpr (is_convertible<::timespec, __gthread_time_t>::value)
+ return __ts;
+ else if constexpr (is_scalar<__gthread_time_t>::value)
+ return static_cast<__gthread_time_t>(__ts.tv_sec);
+ else // Assume this works:
+ return __gthread_time_t{ __ts.tv_sec, __ts.tv_nsec };
+ }
+#endif // HAS_GTHREADS
+
+/// @endcond
+} // namespace chrono
+#pragma GCC diagnostic pop
+#endif // USE_NANOSLEEP || USE_CLOCK_REALTIME || HAS_GTHREADS
+
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std
diff --git a/libstdc++-v3/include/bits/this_thread_sleep.h
b/libstdc++-v3/include/bits/this_thread_sleep.h
index 57f89f858952..01f25dda2af0 100644
--- a/libstdc++-v3/include/bits/this_thread_sleep.h
+++ b/libstdc++-v3/include/bits/this_thread_sleep.h
@@ -36,6 +36,7 @@
#if __cplusplus >= 201103L
#include <bits/chrono.h> // std::chrono::*
+#include <ext/numeric_traits.h> // __int_traits
#ifdef _GLIBCXX_USE_NANOSLEEP
# include <cerrno> // errno, EINTR
@@ -59,11 +60,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{
#ifndef _GLIBCXX_NO_SLEEP
-#ifndef _GLIBCXX_USE_NANOSLEEP
- void
- __sleep_for(chrono::seconds, chrono::nanoseconds);
-#endif
-
/// this_thread::sleep_for
template<typename _Rep, typename _Period>
inline void
@@ -71,18 +67,16 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{
if (__rtime <= __rtime.zero())
return;
- auto __s = chrono::duration_cast<chrono::seconds>(__rtime);
- auto __ns = chrono::duration_cast<chrono::nanoseconds>(__rtime - __s);
+
+ struct timespec __ts = chrono::__to_timeout_timespec(__rtime);
#ifdef _GLIBCXX_USE_NANOSLEEP
- struct ::timespec __ts =
- {
- static_cast<std::time_t>(__s.count()),
- static_cast<long>(__ns.count())
- };
while (::nanosleep(&__ts, &__ts) == -1 && errno == EINTR)
{ }
#else
- __sleep_for(__s, __ns);
+ using chrono::seconds;
+ using chrono::nanoseconds;
+ void __sleep_for(seconds __s, nanoseconds __ns);
+ __sleep_for(seconds(__ts.tv_sec), nanoseconds(__ts.tv_nsec));
#endif
}
diff --git a/libstdc++-v3/include/std/condition_variable
b/libstdc++-v3/include/std/condition_variable
index 3525ff35ba31..dcf0b9235cf3 100644
--- a/libstdc++-v3/include/std/condition_variable
+++ b/libstdc++-v3/include/std/condition_variable
@@ -193,15 +193,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
__wait_until_impl(unique_lock<mutex>& __lock,
const chrono::time_point<steady_clock, _Dur>& __atime)
{
- auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
- auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
-
- __gthread_time_t __ts =
- {
- static_cast<std::time_t>(__s.time_since_epoch().count()),
- static_cast<long>(__ns.count())
- };
-
+ __gthread_time_t __ts = chrono::__to_timeout_gthread_time_t(__atime);
_M_cond.wait_until(*__lock.mutex(), CLOCK_MONOTONIC, __ts);
return (steady_clock::now() < __atime
@@ -214,15 +206,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
__wait_until_impl(unique_lock<mutex>& __lock,
const chrono::time_point<system_clock, _Dur>& __atime)
{
- auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
- auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
-
- __gthread_time_t __ts =
- {
- static_cast<std::time_t>(__s.time_since_epoch().count()),
- static_cast<long>(__ns.count())
- };
-
+ __gthread_time_t __ts = chrono::__to_timeout_gthread_time_t(__atime);
_M_cond.wait_until(*__lock.mutex(), __ts);
return (system_clock::now() < __atime
diff --git a/libstdc++-v3/include/std/mutex b/libstdc++-v3/include/std/mutex
index 631c38069d4a..d4fc4c646488 100644
--- a/libstdc++-v3/include/std/mutex
+++ b/libstdc++-v3/include/std/mutex
@@ -179,14 +179,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_M_try_lock_until(const chrono::time_point<chrono::system_clock,
_Duration>& __atime)
{
- auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
- auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
-
- __gthread_time_t __ts = {
- static_cast<std::time_t>(__s.time_since_epoch().count()),
- static_cast<long>(__ns.count())
- };
-
+ __gthread_time_t __ts = chrono::__to_timeout_gthread_time_t(__atime);
return static_cast<_Derived*>(this)->_M_timedlock(__ts);
}
@@ -196,14 +189,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_M_try_lock_until(const chrono::time_point<chrono::steady_clock,
_Duration>& __atime)
{
- auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
- auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
-
- __gthread_time_t __ts = {
- static_cast<std::time_t>(__s.time_since_epoch().count()),
- static_cast<long>(__ns.count())
- };
-
+ __gthread_time_t __ts = chrono::__to_timeout_gthread_time_t(__atime);
return static_cast<_Derived*>(this)->_M_clocklock(CLOCK_MONOTONIC,
__ts);
}
diff --git a/libstdc++-v3/include/std/shared_mutex
b/libstdc++-v3/include/std/shared_mutex
index 94c8532399d9..a267ad7c4f66 100644
--- a/libstdc++-v3/include/std/shared_mutex
+++ b/libstdc++-v3/include/std/shared_mutex
@@ -520,15 +520,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
try_lock_until(const chrono::time_point<chrono::system_clock,
_Duration>& __atime)
{
- auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
- auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
-
- __gthread_time_t __ts =
- {
- static_cast<std::time_t>(__s.time_since_epoch().count()),
- static_cast<long>(__ns.count())
- };
-
+ struct timespec __ts = chrono::__to_timeout_timespec(__atime);
int __ret = __glibcxx_rwlock_timedwrlock(&_M_rwlock, &__ts);
// On self-deadlock, we just fail to acquire the lock. Technically,
// the program violated the precondition.
@@ -546,15 +538,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
try_lock_until(const chrono::time_point<chrono::steady_clock,
_Duration>& __atime)
{
- auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
- auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
-
- __gthread_time_t __ts =
- {
- static_cast<std::time_t>(__s.time_since_epoch().count()),
- static_cast<long>(__ns.count())
- };
-
+ struct timespec __ts = chrono::__to_timeout_timespec(__atime);
int __ret = pthread_rwlock_clockwrlock(&_M_rwlock, CLOCK_MONOTONIC,
&__ts);
// On self-deadlock, we just fail to acquire the lock. Technically,
@@ -596,14 +580,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
try_lock_shared_until(const chrono::time_point<chrono::system_clock,
_Duration>& __atime)
{
- auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
- auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
-
- __gthread_time_t __ts =
- {
- static_cast<std::time_t>(__s.time_since_epoch().count()),
- static_cast<long>(__ns.count())
- };
+ struct timespec __ts = chrono::__to_timeout_timespec(__atime);
int __ret;
// Unlike for lock(), we are not allowed to throw an exception so if
@@ -636,15 +613,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
try_lock_shared_until(const chrono::time_point<chrono::steady_clock,
_Duration>& __atime)
{
- auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
- auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
-
- __gthread_time_t __ts =
- {
- static_cast<std::time_t>(__s.time_since_epoch().count()),
- static_cast<long>(__ns.count())
- };
-
+ struct timespec __ts = chrono::__to_timeout_timespec(__atime);
int __ret = pthread_rwlock_clockrdlock(&_M_rwlock, CLOCK_MONOTONIC,
&__ts);
// On self-deadlock, we just fail to acquire the lock. Technically,
diff --git a/libstdc++-v3/src/c++11/thread.cc b/libstdc++-v3/src/c++11/thread.cc
index 6c2ec2978f88..0768a99d6741 100644
--- a/libstdc++-v3/src/c++11/thread.cc
+++ b/libstdc++-v3/src/c++11/thread.cc
@@ -231,10 +231,30 @@ namespace std _GLIBCXX_VISIBILITY(default)
_GLIBCXX_BEGIN_NAMESPACE_VERSION
namespace this_thread
{
+namespace
+{
+ // returns min(s, Dur::max())
+ template<typename Dur>
+ inline chrono::seconds
+ limit(chrono::seconds s)
+ {
+ static_assert(ratio_equal<typename Dur::period, ratio<1>>::value,
+ "period must be seconds to avoid potential overflow");
+
+ if (s > Dur::max()) [[__unlikely__]]
+ s = chrono::duration_cast<chrono::seconds>(Dur::max());
+ return s;
+ }
+}
+
void
__sleep_for(chrono::seconds __s, chrono::nanoseconds __ns)
{
#ifdef _GLIBCXX_USE_NANOSLEEP
+#pragma GCC diagnostic ignored "-Wc++17-extensions"
+ if constexpr (is_integral<time_t>::value) // POSIX.1-2001 allows floating
+ __s = limit<chrono::duration<time_t>>(__s);
+
struct ::timespec __ts =
{
static_cast<std::time_t>(__s.count()),
@@ -246,6 +266,8 @@ namespace this_thread
const auto target = chrono::steady_clock::now() + __s + __ns;
while (true)
{
+ __s = limit<chrono::duration<unsigned>>(__s);
+
unsigned secs = __s.count();
if (__ns.count() > 0)
{
@@ -271,11 +293,19 @@ namespace this_thread
break;
__s = chrono::duration_cast<chrono::seconds>(target - now);
__ns = chrono::duration_cast<chrono::nanoseconds>(target - (now + __s));
- }
+ }
#elif defined(_GLIBCXX_USE_WIN32_SLEEP)
+ // Can't use limit<chrono::milliseconds>(__s) here because it would
+ // multiply __s by 1000 which could overflow.
+ auto max_ms = chrono::milliseconds::max() / 1000;
+ auto max_ms_in_s = chrono::duration_cast<chrono::seconds>(max_ms);
+ if (__s > max_ms_in_s)
+ __s = max_ms_in_s;
+
unsigned long ms = __ns.count() / 1000000;
if (__ns.count() > 0 && ms == 0)
ms = 1;
+
::Sleep(chrono::milliseconds(__s).count() + ms);
#endif
}
diff --git a/libstdc++-v3/src/c++20/atomic.cc b/libstdc++-v3/src/c++20/atomic.cc
index 4120e1a0817f..7978809cd223 100644
--- a/libstdc++-v3/src/c++20/atomic.cc
+++ b/libstdc++-v3/src/c++20/atomic.cc
@@ -350,14 +350,7 @@ __platform_wait_until(const __platform_wait_t* __addr,
__platform_wait_t __old,
const __wait_clock_t::time_point& __atime) noexcept
{
- auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
- auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
-
- struct timespec __rt =
- {
- static_cast<std::time_t>(__s.time_since_epoch().count()),
- static_cast<long>(__ns.count())
- };
+ struct timespec __rt = chrono::__to_timeout_timespec(__atime);
if (syscall (SYS_futex, __addr,
static_cast<int>(__futex_wait_flags::__wait_bitset_private),
@@ -378,14 +371,7 @@ bool
__cond_wait_until(__condvar& __cv, mutex& __mx,
const __wait_clock_t::time_point& __atime)
{
- auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
- auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
-
- __gthread_time_t __ts =
- {
- static_cast<std::time_t>(__s.time_since_epoch().count()),
- static_cast<long>(__ns.count())
- };
+ __gthread_time_t __ts = chrono::__to_timeout_gthread_time_t(__atime);
#ifdef _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT
if constexpr (is_same_v<chrono::steady_clock, __wait_clock_t>)
diff --git a/libstdc++-v3/testsuite/30_threads/this_thread/113327.cc
b/libstdc++-v3/testsuite/30_threads/this_thread/113327.cc
new file mode 100644
index 000000000000..2daa2b0e46e2
--- /dev/null
+++ b/libstdc++-v3/testsuite/30_threads/this_thread/113327.cc
@@ -0,0 +1,29 @@
+// { dg-do run { target c++11 } }
+// { dg-additional-options "-pthread" { target pthread } }
+// { dg-require-gthreads "" }
+
+// PR libstdc++/113327
+// std::sleep_for(std::chrono::hours::max()) returns immediately
+
+#include <thread>
+#include <chrono>
+#include <cstdlib>
+#include <csignal>
+
+int main()
+{
+ std::thread sleepy([] {
+ // Rather than overflowing to a negative value, the timeout should be
+ // truncated to seconds::max() and so sleep for 292 billion years.
+ std::this_thread::sleep_for(std::chrono::minutes::max());
+ // This should not happen:
+ throw 1;
+ });
+ // Give the new thread a chance to start sleeping:
+ std::this_thread::yield();
+ std::this_thread::sleep_for(std::chrono::seconds(2));
+ // If we get here without the other thread throwing an exception
+ // then it should be sleeping peacefully, so the test passed.
+ // pthread_kill(sleepy.native_handle(), SIGINT);
+ std::_Exit(0);
+}
--
2.51.0
