Add note about usage of STRINGLIB_EMPTY.
diff --git a/Objects/stringlib/README.txt b/Objects/stringlib/README.txt
index c884ec3..ab506d6 100644
--- a/Objects/stringlib/README.txt
+++ b/Objects/stringlib/README.txt
@@ -13,7 +13,8 @@
STRINGLIB_EMPTY
- a PyObject representing the empty string
+ a PyObject representing the empty string, only to be used if
+ STRINGLIB_MUTABLE is 0
Py_ssize_t STRINGLIB_LEN(PyObject*)
@@ -31,9 +32,9 @@
int STRINGLIB_CHECK_EXACT(PyObject *)
- returns true if the object is an instance of our type, not a subclass.
+ returns true if the object is an instance of our type, not a subclass
STRINGLIB_MUTABLE
- Must be 0 or 1 to tell the cpp macros in stringlib code if the object
- being operated on is mutable or not.
+ must be 0 or 1 to tell the cpp macros in stringlib code if the object
+ being operated on is mutable or not