The constructor for an immediately-owned unique_lock initializes the
ownership flag to false and then calls the checked lock() modifier, which
sets the flag to true. The constructor then sets it to true again. The
destructor similarly calls the checked unlock() modifier after already
testing ownership.
Match the implementation pattern used by shared_lock: construct the object
directly in its final ownership state, call the mutex operations directly
during construction and destruction, and remove unlock()'s redundant mutex
pointer check after ownership has been established. This avoids duplicated
checks and exception paths without changing observable behavior.
No new test is needed because the change has no observable behavior. The
existing tests cover construction, destruction, explicit unlocking, and
condition_variable_any waits.
Tested on x86_64-pc-linux-gnu with no regressions.
libstdc++-v3/ChangeLog:
* include/bits/unique_lock.h (unique_lock::unique_lock): Construct
directly in the owned state and call the mutex directly.
(unique_lock::~unique_lock): Unlock the mutex directly.
(unique_lock::unlock): Remove redundant mutex pointer check.
Assisted-by: OpenAI Codex
---
libstdc++-v3/include/bits/unique_lock.h | 16 +++++-----------
1 file changed, 5 insertions(+), 11 deletions(-)
diff --git a/libstdc++-v3/include/bits/unique_lock.h
b/libstdc++-v3/include/bits/unique_lock.h
index 51596ef31..162be4b62 100644
--- a/libstdc++-v3/include/bits/unique_lock.h
+++ b/libstdc++-v3/include/bits/unique_lock.h
@@ -70,11 +70,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
[[__nodiscard__]]
explicit unique_lock(mutex_type& __m)
- : _M_device(std::__addressof(__m)), _M_owns(false)
- {
- lock();
- _M_owns = true;
- }
+ : _M_device(std::__addressof(__m)), _M_owns(true)
+ { __m.lock(); }
unique_lock(mutex_type& __m, defer_lock_t) noexcept
: _M_device(std::__addressof(__m)), _M_owns(false)
@@ -111,7 +108,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
~unique_lock()
{
if (_M_owns)
- unlock();
+ _M_device->unlock();
}
unique_lock(const unique_lock&) = delete;
@@ -198,11 +195,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{
if (!_M_owns)
__throw_system_error(int(errc::operation_not_permitted));
- else if (_M_device)
- {
- _M_device->unlock();
- _M_owns = false;
- }
+ _M_device->unlock();
+ _M_owns = false;
}
void
--
2.43.0
