Replace CL_REQUIRE/CL_PROVIDE(cl_no_ring) with portable code.

The order of initialization of non-local objects in different compilation units
is not specified in C++. Hence special care should be taken to avoid static
initialization order fiasco. CLN solved the problem with some evil (GCC
specific, and even GCC-version-specific) hack. Replace it with a technique
similar to one used in STL to initialize std::cout and friends.

include/cln/ring.h

@@ -381,7 +381,15 @@ public:
 
 extern const cl_ring cl_no_ring;
 extern cl_class cl_class_no_ring;
-CL_REQUIRE(cl_no_ring)
+
+class cl_no_ring_init_helper
+{
+	static int count;
+public:
+	cl_no_ring_init_helper();
+	~cl_no_ring_init_helper();
+};
+static cl_no_ring_init_helper cl_no_ring_init_helper_instance;
 
 inline cl_ring::cl_ring ()
 	: cl_rcpointer (as_cl_private_thing(cl_no_ring)) {}

src/base/ring/cl_no_ring.cc

@@ -3,8 +3,6 @@
 // General includes.
 #include "cl_sysdep.h"
 
-CL_PROVIDE(cl_no_ring)
-
 // Specification.
 #include "cln/ring.h"
 
@@ -152,14 +150,32 @@ static void cl_no_ring_dprint (cl_heap* pointer)
 	fprint(cl_debugout, "(cl_ring) cl_no_ring");
 }
 
-cl_class cl_class_no_ring = {
-	cl_no_ring_destructor,
-	0,
-	cl_no_ring_dprint
-};
+cl_class cl_class_no_ring;
+
+static cl_heap_no_ring* cl_heap_no_ring_instance;
+// const cl_ring cl_no_ring = cl_ring (new cl_heap_no_ring());
+const cl_ring cl_no_ring = cl_no_ring;
+
+
+int cl_no_ring_init_helper::count = 0;
+
+cl_no_ring_init_helper::cl_no_ring_init_helper()
+{
+	if (count++ == 0) {
+		cl_class_no_ring.destruct = cl_no_ring_destructor;
+		cl_class_no_ring.flags = 0;
+		cl_class_no_ring.dprint = cl_no_ring_dprint;
+
+		cl_heap_no_ring_instance = new cl_heap_no_ring();
+		new((void*)&cl_no_ring) cl_ring(cl_heap_no_ring_instance);
+	}
+}
 
-const cl_ring cl_no_ring = cl_ring (new cl_heap_no_ring());
+cl_no_ring_init_helper::~cl_no_ring_init_helper()
+{
+	if (--count == 0)
+		delete cl_heap_no_ring_instance;
+}
 
 }  // namespace cln
 
-CL_PROVIDE_END(cl_no_ring)