diff --git a/bin/main.c b/bin/main.c
index 687760c..cac769a 100644
--- a/bin/main.c
+++ b/bin/main.c
@@ -1164,7 +1164,7 @@ hcl_logufmt (hcl, HCL_LOG_WARN, fmt, ustr, 0x6789);
 #if 0
 // TODO: change the option name
 // in the INTERACTIVE mode, the compiler generates MAKE_FUNCTION for lambda functions.
-// in the non-INTERACTIVE mode, the compiler generates MAKE_CONTEXT for lambda functions.
+// in the non-INTERACTIVE mode, the compiler generates MAKE_BLOCK for lambda functions.
 {
 	hcl_bitmask_t trait;
 	hcl_getoption (hcl, HCL_TRAIT, &trait);
diff --git a/lib/comp2.c b/lib/comp2.c
index 5a02a55..e6ed05c 100644
--- a/lib/comp2.c
+++ b/lib/comp2.c
@@ -3108,7 +3108,7 @@ int hcl_compile2 (hcl_t* hcl, hcl_cnode_t* obj)
 	 * translated to base context objects instead.
 	 * 
 	 * In the INTERACTIVE mode, the literal frame base plays a key role.
-	 * hcl_compile() is called for the top-level expression andthe literal
+	 * hcl_compile() is called for the top-level expression and the literal
 	 * frame base can be 0. The means it is ok for a top-level code to 
 	 * reference part of the literal frame reserved for a lambda function.
 	 *
diff --git a/lib/exec.c b/lib/exec.c
index 33574ee..2c08656 100644
--- a/lib/exec.c
+++ b/lib/exec.c
@@ -1807,10 +1807,10 @@ static int __activate_function (hcl_t* hcl, hcl_oop_function_t rcv_func, hcl_ooi
 	hcl_ooi_t local_ntmprs, i;
 
 	/*
-	 * (defun sum (x)
-	 *     (if (< x 2) 1
-	 *      else (+ x (sum (- x 1)))))
-	 * (printf ">>>> %d\n" (sum 10))
+	  (defun sum (x)
+	      (if (< x 2) 1
+	       else (+ x (sum (- x 1)))))
+	  (printf ">>>> %d\n" (sum 10))
 	 */
 
 	/* the receiver must be a function */
@@ -3645,6 +3645,7 @@ hcl_oop_t hcl_execute (hcl_t* hcl)
 	#endif
 	}
 
+	/* create a virtual function object that hold the bytes codes generated */
 	func = make_function(hcl, hcl->code.lit.len, hcl->code.bc.ptr, hcl->code.bc.len);
 	if (HCL_UNLIKELY(!func)) return HCL_NULL;
 
diff --git a/lib/hcl.h b/lib/hcl.h
index 31a3bff..a5fbd45 100644
--- a/lib/hcl.h
+++ b/lib/hcl.h
@@ -532,7 +532,7 @@ struct hcl_fpdec_t
 #define HCL_FUNCTION_GET_CODE_BYTE(m) HCL_OBJ_GET_TRAILER_BYTE(m)
 #define HCL_FUNCTION_GET_CODE_SIZE(m) HCL_OBJ_GET_TRAILER_SIZE(m)
 
-#define HCL_FUNCTION_NAMED_INSTVARS 3   /* this excludes literal frames and byte codes */
+#define HCL_FUNCTION_NAMED_INSTVARS 4   /* this excludes literal frames and byte codes */
 typedef struct hcl_function_t hcl_function_t;
 typedef struct hcl_function_t* hcl_oop_function_t;
 
@@ -552,6 +552,8 @@ struct hcl_function_t
 	hcl_oop_t nargs;  /* smooi. number of arguments */
 	hcl_oop_context_t home; /* home context. nil for the initial function */
 
+	hcl_oop_t dbgi_file_offset;
+
 	/* == variable indexed part == */
 	hcl_oop_t literal_frame[1]; /* it stores literals. it may not exist */
 
@@ -838,7 +840,6 @@ enum hcl_dbgi_type_t
 	HCL_DBGI_TYPE_CODE_FILE    = 0,
 	HCL_DBGI_TYPE_CODE_CLASS   = 1,
 	HCL_DBGI_TYPE_CODE_TEXT    = 2,
-	/* TODO: interface? etc? */
 	HCL_DBGI_TYPE_CODE_METHOD  = 3, /* method instruction location information */
 
 	/* low 8 bits */