ConcurrentQueue is currently used only by two classes and a test, but
modifying concurrent_queue.h requires recompiling 30 source files. None
of the member functions is so lightweight as to make it worth inlining.
An alternative to `@note ConcurrentQueue is unable to execute jobs if
@p threadCount == 0.` is `assert(threadCount != 0);`. But this would
force classes that contain a ConcurrentQueue data member to always start
a thread, even if they detect at runtime that they are never going to
enqueue a job.
Add Job type alias to avoid repeating the type.
Use default member initializers instead of the member initializer list
to make it clear [to the reader of the header] that no data member is
left uninitialized.
Place common Qt Test qmake code into tests/qt_test.pri.
Build tests as part of top-level YACReader project unless no_tests
CONFIG option is set. This way the tests are built by default during
development. Packagers can skip building tests by running
`qmake "CONFIG+=no_tests"`.
Both ConcurrentQueueTest::singleUserThread() and
ConcurrentQueueTest::multipleUserThreads() pass. Evidently
ConcurrentQueue::enqueue() can be safely called from multiple threads on
the same ConcurrentQueue object with no additional synchronization. Once
each thread enqueues all its jobs, one thread can safely call waitAll().
