Add note about usage of STRINGLIB_EMPTY.

diff --git a/Objects/stringlib/README.txt b/Objects/stringlib/README.txt
index c884ec3c2fdd14def063659baf5bb38bc2301eb3..ab506d60f94bbaa49dc8770ad4c78dbc4a42c855 100644 (file)
--- a/Objects/stringlib/README.txt
+++ b/Objects/stringlib/README.txt
@@ -13,7 +13,8 @@ STRINGLIB_CHAR
 
 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 @@ STRINGLIB_CHAR* STRINGLIB_STR(PyObject*)
 
 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