[gcc r17-2856] libstdc++: Implement LWG 4301 changes to condition_variable{_any}
Patrick Palka
ppalka@gcc.gnu.org
Fri Jul 31 18:13:51 GMT 2026
https://gcc.gnu.org/g:0a4e2861d9ed69eac1e1c69b84fd61d9e1925ff2
commit r17-2856-g0a4e2861d9ed69eac1e1c69b84fd61d9e1925ff2
Author: Patrick Palka <ppalka@redhat.com>
Date: Fri Jul 31 14:11:38 2026 -0400
libstdc++: Implement LWG 4301 changes to condition_variable{_any}
* include/std/condition_variable (condition_variable::wait_until):
Take timeout parameter by value as per LWG 4301.
(condition_variable::wait_for): Likewise.
(condition_variable::__wait_until_impl): Likewise.
(condition_variable_any::wait_until): Likewise.
(condition_variable_any::wait_for): Likewise.
Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com>
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
Diff:
---
libstdc++-v3/include/std/condition_variable | 34 +++++++++++++++++------------
1 file changed, 20 insertions(+), 14 deletions(-)
diff --git a/libstdc++-v3/include/std/condition_variable b/libstdc++-v3/include/std/condition_variable
index ce995ed57779..b5831cdd8714 100644
--- a/libstdc++-v3/include/std/condition_variable
+++ b/libstdc++-v3/include/std/condition_variable
@@ -107,24 +107,27 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
wait(__lock);
}
+ // _GLIBCXX_RESOLVE_LIB_DEFECTS
+ // 4301. condition_variable{_any}::wait_{for, until} should take timeout by value
+
#ifdef _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT
template<typename _Duration>
cv_status
wait_until(unique_lock<mutex>& __lock,
- const chrono::time_point<steady_clock, _Duration>& __atime)
+ chrono::time_point<steady_clock, _Duration> __atime)
{ return __wait_until_impl(__lock, __atime); }
#endif
template<typename _Duration>
cv_status
wait_until(unique_lock<mutex>& __lock,
- const chrono::time_point<system_clock, _Duration>& __atime)
+ chrono::time_point<system_clock, _Duration> __atime)
{ return __wait_until_impl(__lock, __atime); }
template<typename _Clock, typename _Duration>
cv_status
wait_until(unique_lock<mutex>& __lock,
- const chrono::time_point<_Clock, _Duration>& __atime)
+ chrono::time_point<_Clock, _Duration> __atime)
{
#if __cplusplus > 201703L
static_assert(chrono::is_clock_v<_Clock>);
@@ -149,7 +152,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _Clock, typename _Duration, typename _Predicate>
bool
wait_until(unique_lock<mutex>& __lock,
- const chrono::time_point<_Clock, _Duration>& __atime,
+ chrono::time_point<_Clock, _Duration> __atime,
_Predicate __p)
{
while (!__p())
@@ -161,7 +164,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _Rep, typename _Period>
cv_status
wait_for(unique_lock<mutex>& __lock,
- const chrono::duration<_Rep, _Period>& __rtime)
+ chrono::duration<_Rep, _Period> __rtime)
{
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 3504. condition_variable::wait_for is overspecified
@@ -174,7 +177,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _Rep, typename _Period, typename _Predicate>
bool
wait_for(unique_lock<mutex>& __lock,
- const chrono::duration<_Rep, _Period>& __rtime,
+ chrono::duration<_Rep, _Period> __rtime,
_Predicate __p)
{
using __dur = typename steady_clock::duration;
@@ -193,7 +196,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _Dur>
cv_status
__wait_until_impl(unique_lock<mutex>& __lock,
- const chrono::time_point<steady_clock, _Dur>& __atime)
+ chrono::time_point<steady_clock, _Dur> __atime)
{
__gthread_time_t __ts = chrono::__to_timeout_gthread_time_t(__atime);
_M_cond.wait_until(*__lock.mutex(), CLOCK_MONOTONIC, __ts);
@@ -206,7 +209,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _Dur>
cv_status
__wait_until_impl(unique_lock<mutex>& __lock,
- const chrono::time_point<system_clock, _Dur>& __atime)
+ chrono::time_point<system_clock, _Dur> __atime)
{
__gthread_time_t __ts = chrono::__to_timeout_gthread_time_t(__atime);
_M_cond.wait_until(*__lock.mutex(), __ts);
@@ -312,10 +315,13 @@ _GLIBCXX_BEGIN_INLINE_ABI_NAMESPACE(_V2)
wait(__lock);
}
+ // _GLIBCXX_RESOLVE_LIB_DEFECTS
+ // 4301. condition_variable{_any}::wait_{for, until} should take timeout by value
+
template<typename _Lock, typename _Clock, typename _Duration>
cv_status
wait_until(_Lock& __lock,
- const chrono::time_point<_Clock, _Duration>& __atime)
+ chrono::time_point<_Clock, _Duration> __atime)
{
shared_ptr<mutex> __mutex = _M_mutex;
unique_lock<mutex> __my_lock(*__mutex);
@@ -330,7 +336,7 @@ _GLIBCXX_BEGIN_INLINE_ABI_NAMESPACE(_V2)
typename _Duration, typename _Predicate>
bool
wait_until(_Lock& __lock,
- const chrono::time_point<_Clock, _Duration>& __atime,
+ chrono::time_point<_Clock, _Duration> __atime,
_Predicate __p)
{
while (!__p())
@@ -341,14 +347,14 @@ _GLIBCXX_BEGIN_INLINE_ABI_NAMESPACE(_V2)
template<typename _Lock, typename _Rep, typename _Period>
cv_status
- wait_for(_Lock& __lock, const chrono::duration<_Rep, _Period>& __rtime)
+ wait_for(_Lock& __lock, chrono::duration<_Rep, _Period> __rtime)
{ return wait_until(__lock, __clock_t::now() + __rtime); }
template<typename _Lock, typename _Rep,
typename _Period, typename _Predicate>
bool
wait_for(_Lock& __lock,
- const chrono::duration<_Rep, _Period>& __rtime, _Predicate __p)
+ chrono::duration<_Rep, _Period> __rtime, _Predicate __p)
{ return wait_until(__lock, __clock_t::now() + __rtime, std::move(__p)); }
#ifdef __glibcxx_jthread
@@ -383,7 +389,7 @@ _GLIBCXX_BEGIN_INLINE_ABI_NAMESPACE(_V2)
template <class _Lock, class _Clock, class _Duration, class _Predicate>
bool wait_until(_Lock& __lock,
stop_token __stoken,
- const chrono::time_point<_Clock, _Duration>& __abs_time,
+ chrono::time_point<_Clock, _Duration> __abs_time,
_Predicate __p)
{
if (__stoken.stop_requested())
@@ -418,7 +424,7 @@ _GLIBCXX_BEGIN_INLINE_ABI_NAMESPACE(_V2)
template <class _Lock, class _Rep, class _Period, class _Predicate>
bool wait_for(_Lock& __lock,
stop_token __stoken,
- const chrono::duration<_Rep, _Period>& __rel_time,
+ chrono::duration<_Rep, _Period> __rel_time,
_Predicate __p)
{
auto __abst = std::chrono::steady_clock::now() + __rel_time;
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