adjust ffi/unsafe/com to use ffi/unsafe/string-list

The one-off `_ptr-to-string/utf-16` can be `_string-list/utf-16`.

racket/collects/ffi/unsafe/com.rkt

@@ -4,6 +4,7 @@
          ffi/winapi
          ffi/unsafe/atomic
          ffi/unsafe/custodian
+         ffi/unsafe/string-list
          ffi/file
          racket/date
          racket/runtime-path
@@ -333,7 +334,7 @@
    [GetTypeInfo (_hmfun _UINT _LCID (p : (_ptr o _pointer))
                         -> GetTypeInfo (cast p _pointer _ITypeInfo-pointer))
                 #:release-with-function Release]
-   [GetIDsOfNames (_hmfun _REFIID _ptr-to-string/utf-16
+   [GetIDsOfNames (_hmfun _REFIID _string-list/utf-16
                           (_UINT = 1) _LCID
                           (p : (_ptr o _DISPID))
                           -> GetIDsOfNames
@@ -1937,7 +1938,7 @@
 
 (define (find-memid who obj name)
   (define-values (r memid)
-    (GetIDsOfNames (com-object-get-dispatch obj) IID_NULL name LOCALE_SYSTEM_DEFAULT))
+    (GetIDsOfNames (com-object-get-dispatch obj) IID_NULL (list name) LOCALE_SYSTEM_DEFAULT))
   (cond
    [(zero? r) memid]
    [(= r DISP_E_UNKNOWNNAME) (error who "unknown method name: ~e" name)]

racket/collects/ffi/unsafe/private/win32.rkt

@@ -371,29 +371,12 @@
            2
            1))))
 
-(define (string->pointer s [alloc SysAllocStringLen])
+(define (string->pointer s)
   (let ([v (malloc _gcpointer)])
     (ptr-set! v _string/utf-16 s)
     (let ([p (ptr-ref v _gcpointer)])
       (let ([len (utf-16-length s)])
-        (alloc p len)))))
-
-;; Like (_ptr i _string/utf-16), but as a single atomic (and immobile
-;; and GCable) object, so it can be passed to a function in CS:
-(define _ptr-to-string/utf-16
-  (make-ctype _gcpointer
-              (lambda (s)
-                (string->pointer
-                 s
-                 (lambda (p len)
-                   (define slen (+ len 2)) ; add terminator
-                   (define p2 (malloc 'atomic-interior
-                                      (+ slen (ctype-sizeof _pointer))))
-                   (memcpy p2 (ctype-sizeof _pointer) p slen)
-                   (ptr-set! p2 _pointer 0 p)
-                   p2)))
-              (lambda (p)
-                (cast p _pointer _string/utf-16))))
+        (SysAllocStringLen p len)))))
 
 (define _SAFEARRAY-pointer (_cpointer 'SAFEARRAY))