_SD_BEGIN_DECLARATIONS;
-const char *sd_utf8_is_valid(const char *s);
-const char *sd_ascii_is_valid(const char *s);
+_sd_pure_ const char *sd_utf8_is_valid(const char *s);
+_sd_pure_ const char *sd_ascii_is_valid(const char *s);
_SD_END_DECLARATIONS;