Switch to clang and improve cpprt

src/kernel/cpprt.cpp

@@ -1,3 +1,37 @@
+#include "kutil/assert.h"
+
+using __exit_func = void (*)(void *);
+
 extern "C" {
-	void __cxa_pure_virtual() { while(1); }
+	void *__dso_handle __attribute__ ((__weak__));
+	int __cxa_atexit(__exit_func, void *, void *);
+	void __cxa_pure_virtual();
+}
+
+
+struct __exit_func_entry
+{
+	__exit_func func;
+	void *obj;
+	void *dso;
+};
+
+static int __num_exit_funcs = 0;
+static const int __max_exit_funcs = 64;
+__exit_func_entry __exit_funcs[__max_exit_funcs];
+
+int
+__cxa_atexit(__exit_func f, void *o, void *dso)
+{
+	int i = __num_exit_funcs++;
+	if (i >= __max_exit_funcs) return -1;
+	__exit_funcs[i].func = f;
+	__exit_funcs[i].obj = o;
+	__exit_funcs[i].dso = dso;
+	return 0;
+}
+
+void __cxa_pure_virtual()
+{
+	kassert(0, "Pure virtual function call");
 }