diff --git a/moo/lib/comp.c b/moo/lib/comp.c
index 852e446..fceb011 100644
--- a/moo/lib/comp.c
+++ b/moo/lib/comp.c
@@ -2352,7 +2352,7 @@ retry:
 	return 0;
 }
 
-static void clear_io_names (moo_t* moo)
+void moo_clearcionames (moo_t* moo)
 {
 	moo_iolink_t* cur;
 
@@ -7026,7 +7026,13 @@ static int add_compiled_method (moo_t* moo)
 		if (moo_addmethodtodbgi(moo, file_offset, cc->dbgi_class_offset, cc->mth.name.ptr, cc->mth.code.locptr, cc->mth.code.len, &method_offset) <= -1)
 		{
 			/* TODO: warning. no debug information about this method will be available */
+			method_offset = 0;
 		}
+		else if (method_offset > MOO_SMOOI_MAX)
+		{
+			method_offset = 90;
+		}
+		/* TODO mth->code_sline = MOO_SMOOI_TO_OOP(method_offset); */
 	}
 
 	/*TODO: preserve source??? mth->text = cc->mth.text
@@ -9681,7 +9687,7 @@ static void fini_compiler (moo_t* moo)
 	/* called before the moo object is closed */
 	if (moo->c)
 	{
-		clear_io_names (moo);
+		moo_clearcionames (moo);
 
 		if (moo->c->tok.name.ptr) moo_freemem (moo, moo->c->tok.name.ptr);
 		if (moo->c->balit.ptr) moo_freemem (moo, moo->c->balit.ptr);
@@ -9731,7 +9737,7 @@ static MOO_INLINE int _compile (moo_t* moo, moo_ioimpl_t io)
 	 * I clear such names before i begin this function. i don't clear it
 	 * at the end of this function because i may be referenced as an error
 	 * location */
-	clear_io_names (moo);
+	moo_clearcionames (moo);
 
 	/* reset pragma flags */
 	moo->c->pragma_flags = 0;
diff --git a/moo/lib/exec.c b/moo/lib/exec.c
index 63d7d2e..452b8f4 100644
--- a/moo/lib/exec.c
+++ b/moo/lib/exec.c
@@ -2218,14 +2218,15 @@ static moo_pfrc_t pf_context_find_exception_handler (moo_t* moo, moo_mod_t* mod,
 /* ------------------------------------------------------------------ */
 static moo_pfrc_t pf_method_get_source_file (moo_t* moo, moo_mod_t* mod, moo_ooi_t nargs)
 {
+	moo_oop_method_t rcv;
 	moo_oop_t retv = moo->_nil;
 
+/* TODO: return something else lighter-weight than a string? */
+	rcv = (moo_oop_method_t)MOO_STACK_GETRCV(moo, nargs);
+	MOO_PF_CHECK_RCV (moo, MOO_CLASSOF(moo, rcv) == moo->_method);
+
 	if (moo->dbgi)
 	{
-		moo_oop_method_t rcv;
-
-/* TODO: return something else lighter-weight than a string? */
-		rcv = (moo_oop_method_t)MOO_STACK_GETRCV(moo, nargs);
 		if (MOO_OOP_IS_SMOOI(rcv->source_file) && MOO_OOP_TO_SMOOI(rcv->source_file) > 0)
 		{
 			moo_dbgi_file_t* di;
@@ -2246,6 +2247,38 @@ static moo_pfrc_t pf_method_get_source_file (moo_t* moo, moo_mod_t* mod, moo_ooi
 	return MOO_PF_SUCCESS;
 }
 
+static moo_pfrc_t pf_method_get_code_source_line (moo_t* moo, moo_mod_t* mod, moo_ooi_t nargs)
+{
+	/* get source line of the given instruction pointer */
+	moo_oop_method_t rcv;
+
+	rcv = (moo_oop_method_t)MOO_STACK_GETRCV(moo, nargs);
+	MOO_PF_CHECK_RCV (moo, MOO_CLASSOF(moo, rcv) == moo->_method);
+
+	if (moo->dbgi && MOO_OOP_IS_SMOOI(rcv->source_line))
+	{
+		moo_oop_t ip;
+		moo_ooi_t source_line, ipv;
+
+		ip = MOO_STACK_GETARG(moo, nargs, 0);
+		MOO_PF_CHECK_ARGS (moo, nargs, MOO_OOP_IS_SMOOI(ip));
+
+		source_line = MOO_OOP_TO_SMOOI(rcv->source_line);
+		ipv = MOO_OOP_TO_SMOOI(ip);
+#if 0
+		if (MOO_OOP_IS_SMOOI(rcv->code_sline))
+		{
+			moo_dbgi_method_t* di;
+
+			di = (moo_dbgi_method_t*)&((moo_uint8_t*)moo->dbgi)[MOO_OOP_TO_SMOOI(rcv->code_sline)];
+			/* ... TODO .. */
+		}
+#endif
+	}
+
+	return MOO_PF_SUCCESS;
+}
+
 /* ------------------------------------------------------------------ */
 
 static moo_pfrc_t __block_value (moo_t* moo, moo_oop_context_t rcv_blkctx, moo_ooi_t nargs, moo_ooi_t num_first_arg_elems, moo_oop_context_t* pblkctx)
diff --git a/moo/lib/moo-prv.h b/moo/lib/moo-prv.h
index 5f3fbf1..91ae0a4 100644
--- a/moo/lib/moo-prv.h
+++ b/moo/lib/moo-prv.h
@@ -1679,6 +1679,7 @@ int moo_addmethodtodbgi (moo_t* moo, moo_oow_t file_offset, moo_oow_t class_offs
 /* ========================================================================= */
 #if defined(MOO_INCLUDE_COMPILER)
 const moo_ooch_t* moo_addcioname (moo_t* moo, const moo_oocs_t* name);
+void moo_clearcionames (moo_t* moo);
 #endif
 
 #if defined(__cplusplus)
diff --git a/moo/lib/moo.h b/moo/lib/moo.h
index 8df9563..96ec7c4 100644
--- a/moo/lib/moo.h
+++ b/moo/lib/moo.h
@@ -586,8 +586,9 @@ struct moo_method_t
 #endif
 
 	moo_oop_t       source_text; /* source text. String if available. nil if not */
-	moo_oop_t       source_file; /* SmallInteger. source file path that contains the definition of this method. offset from moo->dbgi. 0 for the main stream. */
-	moo_oop_t       source_line; /* SmallInteger. line of the source file where the method definition begins. valid only if source_file is not nil */
+	moo_oop_t       source_file; /* SmallInteger. source file path that contains the definition of this method. offset from moo->dbgi. 0 if unavailable */
+	moo_oop_t       source_line; /* SmallInteger. line of the source file where the method definition begins. valid only if source_file is greater than 0 */
+	//moo_oop_t       code_line; /* SmallInteger */
 
 	/* == variable indexed part == */
 	moo_oop_t       literal_frame[1]; /* it stores literals */