Mark mutex locking and unlocking functions with noexcept

Unlocking a mutex can never throw an exception. That doesn't make
sense and our code should make sure it can't happen. Right now,
provided that the system-level functions don't throw, we don't either.

Locking a mutex cannot throw on Linux because we use futexes
directly. A non-recursive mutex is just a futex, whereas a recursive
mutex uses a mutex (a futex) to manage a lock count.

However, on other platforms, due to the freelist, there can be memory
allocation, which means it might throw std::bad_alloc. Not because of
the freelist itself (that uses malloc and will just crash if malloc
fails) but because of Q_GLOBAL_STATIC. In 5.1, the global static will
be noexcept provided the type's constructor is so too (it is, in this
case).

Change-Id: I4c562383f48de1be7827b9afb512d73eaf0792d5
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/corelib/thread/qmutex_win.cpp b/src/corelib/thread/qmutex_win.cpp
index 1fdf97b0d0..0e06c6a26e 100644
--- a/src/corelib/thread/qmutex_win.cpp
+++ b/src/corelib/thread/qmutex_win.cpp
@@ -61,7 +61,7 @@ bool QMutexPrivate::wait(int timeout)
     return (WaitForSingleObject(event, timeout < 0 ? INFINITE : timeout) ==  WAIT_OBJECT_0);
 }
 
-void QMutexPrivate::wakeUp()
+void QMutexPrivate::wakeUp() Q_DECL_NOTHROW
 { SetEvent(event); }
 
 QT_END_NAMESPACE