Add project files.

source/tests/UndefinedSymbolFixture/src/Fixture.cpp

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+/* A genuine ODR violation, kept deliberately: a non-inline static
+ * class member that is declared but never given an out-of-class
+ * definition. This compiles cleanly and links cleanly into a shared
+ * library -- a shared library is allowed to keep undefined symbols by
+ * default -- and only fails once something actually calls
+ * trigger_undefined_symbol() below, ODR-using counter for the first
+ * time. See source/HotReload/README.md's "hot_reload_last_error()"
+ * section for the full story; HotReloadTests/Main.cpp loads this
+ * fixture specifically to confirm hot_reload_last_error() reports
+ * something useful for exactly this case, rather than leaving it a
+ * silent "load failed" black box.
+ */
+class HasUndefinedStaticMember
+{
+public:
+	static int useIt()
+	{
+		return counter;
+	}
+
+private:
+	static int counter; // declared, deliberately never defined anywhere
+};
+
+extern "C" int trigger_undefined_symbol()
+{
+	return HasUndefinedStaticMember::useIt();
+}