-cstrings are used as parameters to and from functions. An implementation, such as CMUCL,
-may not convert these to a foreign type for efficiency sake. Thus, it is not
-possible to "allocate" a cstring. In contrast, foreign strings
-always need to have memory for them.
+
+cstrings are used as parameters to and from functions. An
+implementation, such as CMUCL and Lispworks, a cstring may not be a
+foreign type but rather the Lisp string itself while on other
+platforms a cstring is a newly allocated foreign vector for storing
+characters. Thus, it is not possible to portably
+<emphasis>allocate</emphasis> a cstring.
+</para>
+<para>
+In contrast, foreign strings
+are always a foreign vector of characters which have a memory
+allocated to hold them. Because of this, if you need to allocate memory to
+hold the return value of a string, use a foreign string and not a cstring.