thread/spinlock: assert the lock isn't held at destruction

thread/spinlock.cpp

@@ -21,16 +21,28 @@ spinlock::spinlock ():
 { ; }
 
 
+//-----------------------------------------------------------------------------
+spinlock::~spinlock ()
+{
+    CHECK (!held);
+}
+
+
 //-----------------------------------------------------------------------------
 spinlock::spinlock (spinlock &&rhs) noexcept:
     held (rhs.held.load ())
-{ ; }
+{
+    rhs.held = false;
+}
 
 
 //-----------------------------------------------------------------------------
 spinlock& spinlock::operator= (spinlock &&rhs) noexcept
 {
+    CHECK (!held);
+
     held = rhs.held.load ();
+    rhs.held = false;
     return *this;
 }
 

thread/spinlock.hpp

@@ -24,6 +24,8 @@ namespace cruft::thread {
     class spinlock {
     public:
         spinlock ();
+        ~spinlock ();
+
         spinlock (spinlock &&) noexcept;
         spinlock& operator= (spinlock &&) noexcept;