diff --git a/bin/main.c b/bin/main.c
index 63eef93..b393242 100644
--- a/bin/main.c
+++ b/bin/main.c
@@ -512,6 +512,8 @@ static int on_fed_cnode_in_interactive_mode (hcl_t* hcl, hcl_cnode_t* obj)
 
 	if (!xtn->feed.ongoing)
 	{
+		/* the first expression in the current user input line.
+		 * arrange to clear byte-codes before compiling the expression. */
 		flags = HCL_COMPILE_CLEAR_CODE | HCL_COMPILE_CLEAR_FNBLK;
 		xtn->feed.ongoing = 1;
 	}
@@ -525,8 +527,13 @@ static int on_fed_cnode_in_interactive_mode (hcl_t* hcl, hcl_cnode_t* obj)
 	else
 	{
 		hcl_oow_t i;
+
 		for (i = xtn->feed.pos; i < xtn->feed.len; i++)
 		{
+			/* this loop is kind of weird. it is to check the current feed buffer is left with
+			 * spaces only and to execute the compiled bytecodes so far if the check is true.
+			 * the check is performed because a single line of the user input can have multiple
+			 * expressions joined with a semicolon or contains trailing spaces. */
 			if (!hcl_is_bch_space(xtn->feed.buf[i])) break;
 		}
 
diff --git a/lib/hcl.h b/lib/hcl.h
index 8e6fe94..2210e0d 100644
--- a/lib/hcl.h
+++ b/lib/hcl.h
@@ -2404,7 +2404,7 @@ HCL_EXPORT int hcl_addliteraltocode (
 );
 
 /**
- * The hcl_brewcode() initializes the structure pointed to by \a code.partially or entirely.
+ * The hcl_brewcode() initializes the structure pointed to by \a code partially or entirely.
  * The part already initialized is not destroyed and/or reinitialized.
  */
 HCL_EXPORT int hcl_brewcode (
@@ -2413,7 +2413,7 @@ HCL_EXPORT int hcl_brewcode (
 );
 
 /**
- * The hcl_purgecode() function cleans up the data held in memory
+ * The hcl_purgecode() function cleans up the data held in code space memory
  * pointed to by \a code.
  */
 HCL_EXPORT void hcl_purgecode (
diff --git a/lib/obj.c b/lib/obj.c
index 5933b70..baaee31 100644
--- a/lib/obj.c
+++ b/lib/obj.c
@@ -24,7 +24,6 @@
 
 #include "hcl-prv.h"
 
-
 #if defined(HCL_PROFILE_VM)
 #include <sys/time.h>
 #include <sys/resource.h> /* getrusage */
@@ -339,13 +338,19 @@ hcl_oop_t hcl_makebytestring (hcl_t* hcl, const hcl_ooch_t* ptr, hcl_oow_t len,
 	hcl_oow_t i;
 	hcl_oob_t v;
 
-	b = alloc_numeric_array(hcl, HCL_BRAND_BYTE_ARRAY, HCL_NULL, len, HCL_OBJ_TYPE_BYTE, HCL_SIZEOF(hcl_oob_t), 1, ngc);
-	if (HCL_UNLIKELY(!b)) return HCL_NULL;
-
-	for (i = 0; i < len; i++)
+	b = (hcl_oop_byte_t)alloc_numeric_array(hcl, HCL_BRAND_BYTE_ARRAY, HCL_NULL, len, HCL_OBJ_TYPE_BYTE, HCL_SIZEOF(hcl_oob_t), 1, ngc);
+	if (HCL_UNLIKELY(!b))
 	{
-		v = ptr[i] & 0xFF;
-		HCL_OBJ_SET_BYTE_VAL(b, i, v);
+		const hcl_ooch_t* orgmsg = hcl_backuperrmsg(hcl);
+		hcl_seterrbfmt (hcl, HCL_ERRNUM(hcl), "unable to make bytestring - %js", orgmsg);
+	}
+	else
+	{
+		for (i = 0; i < len; i++)
+		{
+			v = ptr[i] & 0xFF;
+			HCL_OBJ_SET_BYTE_VAL(b, i, v);
+		}
 	}
 
 	return (hcl_oop_t)b;
@@ -353,8 +358,15 @@ hcl_oop_t hcl_makebytestring (hcl_t* hcl, const hcl_ooch_t* ptr, hcl_oow_t len,
 
 hcl_oop_t hcl_makestring (hcl_t* hcl, const hcl_ooch_t* ptr, hcl_oow_t len, int ngc)
 {
-	/*return hcl_alloccharobj(hcl, HCL_BRAND_STRING, ptr, len);*/
-	return alloc_numeric_array(hcl, HCL_BRAND_STRING, ptr, len, HCL_OBJ_TYPE_CHAR, HCL_SIZEOF(hcl_ooch_t), 1, ngc);
+	hcl_oop_char_t c;
+	/*c = hcl_alloccharobj(hcl, HCL_BRAND_STRING, ptr, len);*/
+	c = (hcl_oop_char_t)alloc_numeric_array(hcl, HCL_BRAND_STRING, ptr, len, HCL_OBJ_TYPE_CHAR, HCL_SIZEOF(hcl_ooch_t), 1, ngc);
+	if (HCL_UNLIKELY(!c))
+	{
+		const hcl_ooch_t* orgmsg = hcl_backuperrmsg(hcl);
+		hcl_seterrbfmt (hcl, HCL_ERRNUM(hcl), "unable to make string - %js", orgmsg);
+	}
+	return (hcl_oop_t)c;
 }
 
 hcl_oop_t hcl_makefpdec (hcl_t* hcl, hcl_oop_t value, hcl_ooi_t scale)
@@ -375,7 +387,12 @@ hcl_oop_t hcl_makefpdec (hcl_t* hcl, hcl_oop_t value, hcl_ooi_t scale)
 	f = (hcl_oop_fpdec_t)hcl_allocoopobj(hcl, HCL_BRAND_FPDEC, HCL_FPDEC_NAMED_INSTVARS);
 	hcl_popvolat (hcl);
 
-	if (HCL_UNLIKELY(!f)) return HCL_NULL;
+	if (HCL_UNLIKELY(!f))
+	{
+		const hcl_ooch_t* orgmsg = hcl_backuperrmsg(hcl);
+		hcl_seterrbfmt (hcl, HCL_ERRNUM(hcl), "unable to make fpdec - %js", orgmsg);
+		return HCL_NULL;
+	}
 
 	f->value = value;
 	f->scale = HCL_SMOOI_TO_OOP(scale);
@@ -392,7 +409,12 @@ hcl_oop_t hcl_makeclass (hcl_t* hcl, hcl_oop_t superclass, hcl_ooi_t nivars, hcl
 	hcl_pushvolat (hcl, &cvars_str);
 	c = (hcl_oop_class_t)hcl_allocoopobj(hcl, HCL_BRAND_CLASS, HCL_CLASS_NAMED_INSTVARS + ncvars);
 	hcl_popvolats (hcl, 3);
-	if (HCL_UNLIKELY(!c)) return HCL_NULL;
+	if (HCL_UNLIKELY(!c))
+	{
+		const hcl_ooch_t* orgmsg = hcl_backuperrmsg(hcl);
+		hcl_seterrbfmt (hcl, HCL_ERRNUM(hcl), "unable to make class - %js", orgmsg);
+		return HCL_NULL;
+	}
 
 	c->superclass = superclass;
 	c->nivars = HCL_SMOOI_TO_OOP(nivars);
diff --git a/lib/xchg.c b/lib/xchg.c
index fd86d68..c6d1721 100644
--- a/lib/xchg.c
+++ b/lib/xchg.c
@@ -604,6 +604,8 @@ int hcl_unmarshalcodefrommem (hcl_t* hcl, hcl_code_t* code, const hcl_ptl_t* src
 
 int hcl_brewcode (hcl_t* hcl, hcl_code_t* code)
 {
+	/* create space to hold byte code and debug information */
+
 	if (!code->bc.ptr)
 	{
 		code->bc.ptr = (hcl_oob_t*)hcl_allocmem(hcl, HCL_SIZEOF(*code->bc.ptr) * HCL_BC_BUFFER_INIT); /* TODO: set a proper intial size */