Always return a simple-string from OCTETS-TO-STRING

UCS and UTF external formats were returning the adjustable array
directly, which wasn't necessarily a disaster in itself but was also
not conforming with the type declaration of OCTETS-TO-STRING, so could
have led to problems in downstream code.

NEWS

@@ -40,6 +40,9 @@ changes in the external-format-line-endings branch:
   * bug fix: converting from octets using the UCS-2, UCS-4 and UTF-32 external
     formats no longer reads past the end of an octet array with a non-integral
     number of two- or four-byte units.
+  * bug fix: converting from octets using the UCS-2, UCS-4, UTF-16 or UTF-32
+    external formats now returns a simple string, as required by the type
+    declaration of OCTETS-TO-STRING.
   * bug fix: providing an invalid external format argument to OPEN or
     WITH-OPEN-FILE (or the internal MAKE-FD-STREAM) no longer leaks a file
     descriptor.

src/code/external-formats/enc-ucs.lisp

@@ -220,7 +220,7 @@
                            (dotimes (i (length instead))
                              (vector-push-extend (char instead i) string))))
                      (incf pos bytes)))
-          string))
+          (copy-seq string)))
       (defun ,name-be (array astart aend replacement)
         (declare (optimize speed #.*safety-0*)
                  (type ,type array)
@@ -243,7 +243,7 @@
                            (dotimes (i (length instead))
                              (vector-push-extend (char instead i) string))))
                      (incf pos bytes)))
-          string)))))
+          (copy-seq string))))))
 
 (instantiate-octets-definition define-ucs-2->string)
 
@@ -416,7 +416,7 @@
                          (string (dotimes (i (length thing))
                                    (vector-push-extend (char thing i) string)))))
                      (incf pos bytes)))
-          string))
+          (copy-seq string)))
       (defun ,name-be (array astart aend replacement)
         (declare (optimize speed #.*safety-0*)
                  (type ,type array)
@@ -438,7 +438,7 @@
                          (string (dotimes (i (length thing))
                                    (vector-push-extend (char thing i) string)))))
                      (incf pos bytes)))
-          string)))))
+          (copy-seq string))))))
 
 (instantiate-octets-definition define-ucs-4->string)
 

src/code/external-formats/enc-utf.lisp

@@ -231,7 +231,7 @@
                        (t (dotimes (i (length invalid))
                             (vector-push-extend (char invalid i) string))))
                      (incf pos bytes)))
-          string))
+          (copy-seq string)))
       (defun ,name-be (array astart aend replacement)
         (declare (optimize speed #.*safety-0*)
                  (type ,type array)
@@ -251,7 +251,7 @@
                        (t (dotimes (i (length invalid))
                             (vector-push-extend (char invalid i) string))))
                      (incf pos bytes)))
-          string)))))
+          (copy-seq string))))))
 
 (instantiate-octets-definition define-utf-16->string)
 
@@ -479,7 +479,7 @@
                          (string (dotimes (i (length thing))
                                    (vector-push-extend (char thing i) string)))))
                      (incf pos bytes)))
-          string))
+          (copy-seq string)))
       (defun ,name-be (array astart aend replacement)
         (declare (optimize speed #.*safety-0*)
                  (type ,type array)
@@ -501,7 +501,7 @@
                          (string (dotimes (i (length thing))
                                    (vector-push-extend (char thing i) string)))))
                      (incf pos bytes)))
-          string)))))
+          (copy-seq string))))))
 
 (instantiate-octets-definition define-utf-32->string)