Fix binary output on files created by mkstemp!

Some operating systems require a O_BINARY flag.

* libguile/filesys.c (scm_i_mkstemp): Don't mask out O_BINARY flag
* test-suite/tests/posix.test ("binary mode honored"): new test

libguile/filesys.c

@@ -1513,9 +1513,9 @@ SCM_DEFINE (scm_i_mkstemp, "mkstemp!", 1, 1, 0,
       /* mkostemp(2) only defines O_APPEND, O_SYNC, and O_CLOEXEC to be
          useful, as O_RDWR|O_CREAT|O_EXCL are implicitly added.  It also
          notes that other flags may error on some systems, which turns
-         out to be the case.  Of those flags, O_APPEND is the only one
+         out to be the case.  Of those flags, O_APPEND and O_BINARY are
-         of interest anyway, so limit to that flag.  */
+         the only ones of interest anyway, so limit to those flags.  */
-      open_flags &= O_APPEND;
+      open_flags &= O_APPEND | O_BINARY;
       mode_bits = scm_i_mode_bits (mode);
     }
 

test-suite/tests/posix.test

@@ -76,7 +76,22 @@
            (result   (not (string=? str template))))
       (close-port port)
       (delete-file str)
-      result)))
+      result))
+
+  (pass-if "binary mode honored"
+    (let* ((template "T-XXXXXX")
+           (str      (string-copy template))
+           (outport  (mkstemp! str "wb")))
+      (display "\n" outport)
+      (close-port outport)
+      (let* ((inport (open-input-file str #:binary #t))
+             (char1  (read-char inport))
+             (char2  (read-char inport))
+             (result (and (char=? char1 #\newline)
+                          (eof-object? char2))))
+        (close-port inport)
+        (delete-file str)
+        result))))
 
 ;;
 ;; putenv