(STR) = empty_unibyte_string; \
else XSTRING (STR)->size_byte = -1; } while (0)
+/* Mark STR as a multibyte string. Assure that STR contains only
+ ASCII characters in advance. */
+#define STRING_SET_MULTIBYTE(STR) \
+ do { if (EQ (STR, empty_unibyte_string)) \
+ (STR) = empty_multibyte_string; \
+ else XSTRING (STR)->size_byte = XSTRING (STR)->size; } while (0)
+
/* Get text properties. */
#define STRING_INTERVALS(STR) (XSTRING (STR)->intervals + 0)