+#ifdef ENABLE_TRACING
+extern volatile int cp_line[];
+extern volatile char *cp_file[];
+extern volatile int cp_index;
+extern void cp_trace(void);
+
+#define cp() { cp_line[cp_index] = __LINE__; cp_file[cp_index] = __FILE__; cp_index++; cp_index %= 16; }
+#define ecp() { fprintf(stderr, "Explicit checkpoint in %s line %d\n", __FILE__, __LINE__); }
+#else
+#define cp()
+#define ecp()
+#define cp_trace()
+#endif