cs & io: fix 'any line reading mode and buffer boundary

Closes #3434

pkgs/racket-test-core/tests/racket/port.rktl

@@ -1100,6 +1100,44 @@
   (check-srcloc #f 3 #f)
   (check-srcloc 1 3 29))
 
+;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Regression test for interaction of `read-line`, "\r\n", and
+;; input buffering
+
+(let ()
+  (define f1 (make-temporary-file "line-feed1~a.txt"))
+  (define f2 (make-temporary-file "line-feed2~a.txt"))
+
+  (define p1 (open-output-file f1 #:exists 'truncate))
+  (define p2 (open-output-file f2 #:exists 'truncate))
+
+  (define (write-prefix p)
+    (for ([i 1364])
+      (write-bytes #"x\r\n" p)))
+
+  (write-prefix p1)
+  (write-prefix p2)
+  (write-bytes #"\r\ny\r\ny\r\n" p1)
+  (write-bytes #"y\r\ny\r\ny\r\n" p2)
+
+  (close-output-port p1)
+  (close-output-port p2)
+
+  (define (count f)
+    (call-with-input-file f
+                          (lambda (in)
+                            (let loop ()
+                              (define v (read-line in 'any))
+                              (if (eof-object? v)
+                                  0
+                                  (add1 (loop)))))))
+
+  (test 1367 count f1)
+  (test 1367 count f2)
+
+  (delete-file f1)
+  (delete-file f2))
+
 ;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
 (report-errs)

racket/src/io/port/read-and-peek.rkt

@@ -323,6 +323,13 @@
                   (eqv? (bytes-ref bstr (fx+ i 1)) (char->integer #\linefeed)))
              (finish i (fx+ i 2))]
             [cr?
-             (finish i (fx+ i 1))]
+             (cond
+               [(and crlf?
+                     ((fx+ i 1) . fx= . end))
+                ;; needs more input to decide
+                (end-atomic)
+                #f]
+               [else
+                (finish i (fx+ i 1))])]
             [else (loop (fx+ i 1))])]
          [else (loop (fx+ i 1))])])))