diff --git a/src/nbdebug.h b/src/nbdebug.h
new file mode 100644
index 0000000..46b2c08
--- /dev/null
+++ b/src/nbdebug.h
@@ -0,0 +1,81 @@
+/* vi:set ts=8 sts=8 sw=8:
+ *
+ * VIM - Vi IMproved	by Bram Moolenaar
+ *			Visual Workshop integration by Gordon Prieur
+ *
+ * Do ":help uganda"  in Vim to read copying and usage conditions.
+ * Do ":help credits" in Vim to see a list of people who contributed.
+ */
+
+
+#ifndef NBDEBUG_H
+#define NBDEBUG_H
+
+#ifdef NBDEBUG
+
+#ifndef ASSERT
+#define ASSERT(c) \
+    if (!(c)) { \
+	fprintf(stderr, "Assertion failed: line %d, file %s\n", \
+		__LINE__, __FILE__); \
+	fflush(stderr); \
+	abort(); \
+    }
+#endif
+
+#define nbdebug(a) nbdbg##a
+
+#define NB_TRACE		0x00000001
+#define NB_TRACE_VERBOSE	0x00000002
+#define NB_TRACE_COLONCMD	0x00000004
+#define NB_DEBUG_ALL		0xffffffff
+
+#define NBDLEVEL(flags)		(nb_debug != NULL && (nb_dlevel & (flags)))
+
+#define NBDEBUG_TRACE	1
+//#define NBDEBUG_SENSE	2
+
+typedef enum {
+		WT_ENV = 1,		/* look for env var if set */
+		WT_WAIT,		/* look for ~/.gvimwait if set */
+		WT_STOP			/* look for ~/.gvimstop if set */
+} WtWait;
+
+
+void		 nbdbg(char *, ...);
+void		 nbtrace(char *, ...);
+
+void nbdebug_wait __ARGS((u_int wait_flags, char *wait_var, u_int wait_secs));
+void nbdebug_log_init __ARGS((char *log_var, char *level_var));
+
+extern FILE	*nb_debug;
+extern u_int	 nb_dlevel;		/* nb_debug verbosity level */
+
+# else		/* not NBDEBUG */
+
+#ifndef ASSERT
+# define ASSERT(c)
+#endif
+
+/*
+ * The following 2 stubs are needed because a macro cannot be used because of
+ * the variable number of arguments.
+ */
+
+void
+nbdbg(
+	char		*fmt,
+	...)
+{
+}
+
+
+void
+nbtrace(
+	char		*fmt,
+	...)
+{
+}
+
+#endif /* NBDEBUG */
+#endif /* NBDEBUG_H */