CPP: Add a test of common mistakes using locking and similar classes.

cpp/ql/test/examples/BadLocking/UnintendedDeclaration.cpp

@@ -0,0 +1,93 @@
+
+class Mutex
+{
+public:
+	Mutex();
+	~Mutex();
+
+	void lock();
+	void unlock();
+
+private:
+	// ...
+};
+
+template<class T>
+class Lock
+{
+public:
+	Lock() : m(0)
+	{
+	}
+
+	Lock(T &_m) : m(&_m)
+	{
+		m->lock();
+	}
+
+	~Lock()
+	{
+		m->unlock();
+	}
+
+private:
+	T *m;
+};
+
+Mutex myMutex;
+
+void test1()
+{
+	Lock<Mutex> myLock(myMutex); // GOOD (creates `myLock` on `myMutex`)
+
+	// ...
+}
+
+void test2()
+{
+	Lock<Mutex> myLock(); // BAD (interpreted as a function declaration, this does nothing)
+
+	// ...
+}
+
+void test3()
+{
+	Lock<Mutex> myLock; // GOOD (creates an uninitialized variable called `myLock`, probably intended)
+
+	// ...
+}
+
+void test4()
+{
+	Lock<Mutex>(myMutex); // BAD (creates an uninitialized variable called `myMutex`, probably not intended)
+
+	// ...
+}
+
+void test5()
+{
+	Lock<Mutex> myLock(Mutex); // BAD (interpreted as a function declaration, this does nothing)
+
+	// ...
+}
+
+class MyTestClass
+{
+public:
+	void test6()
+	{
+		Lock<Mutex> myLock(memberMutex); // GOOD (creates `myLock` on `memberMutex`)
+
+		// ...
+	}
+
+	void test7()
+	{
+		Lock<Mutex>(memberMutex); // BAD (creates an uninitialized variable called `memberMutex`, probably not intended) [NOT DETECTED]
+
+		// ...
+	}
+
+private:
+	Mutex memberMutex;
+};