From 9887669ab0c797f0fa5c133c5901679908ceb1ea Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Tue, 4 Oct 2016 10:09:48 -0600
Subject: [PATCH] fix single-argument `write-byte` and `write-char`

Repairs a mistake in 8e7792d8

Closes PR 15363
---
 pkgs/racket-test-core/tests/racket/file.rktl | 14 ++++++++++++++
 racket/src/racket/src/portfun.c              |  2 ++
 2 files changed, 16 insertions(+)

diff --git a/pkgs/racket-test-core/tests/racket/file.rktl b/pkgs/racket-test-core/tests/racket/file.rktl
index c9f7ca6c70..f65203d79a 100644
--- a/pkgs/racket-test-core/tests/racket/file.rktl
+++ b/pkgs/racket-test-core/tests/racket/file.rktl
@@ -1849,6 +1849,20 @@
            resolve-path
            "C://testing-root////testing-dir\\\\testing-file")]))
 
+;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Make sure `write-byte` and `write-char` don't try to test
+;; a non-supplied argument:
+
+(parameterize ([current-output-port (open-output-string)])
+  (let ([s (if (zero? (random 1)) "a" "b")])
+    (string-append s s) ; causes a clear operation on the runstack for second argument
+    (write-byte 65)))
+
+(parameterize ([current-output-port (open-output-string)])
+  (let ([s (if (zero? (random 1)) "a" "b")])
+    (string-append s s) ; causes a clear operation on the runstack for second argument
+    (write-char #\A)))
+
 ;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
 (report-errs)
diff --git a/racket/src/racket/src/portfun.c b/racket/src/racket/src/portfun.c
index 86d9ef9568..cadf4ee4cd 100644
--- a/racket/src/racket/src/portfun.c
+++ b/racket/src/racket/src/portfun.c
@@ -4171,6 +4171,7 @@ write_byte (int argc, GC_CAN_IGNORE Scheme_Object *argv[]) XFORM_ASSERT_NO_CONVE
   if (SCHEME_INTP(argv[0])
       && (SCHEME_INT_VAL(argv[0]) >= 0)
       && (SCHEME_INT_VAL(argv[0]) <= 255)
+      && (argc > 1)
       && SCHEME_OUTPUT_PORTP(argv[1])) {
     char buffer[1];
     buffer[0] = SCHEME_INT_VAL(argv[0]);
@@ -4215,6 +4216,7 @@ write_char (int argc, GC_CAN_IGNORE Scheme_Object *argv[]) XFORM_ASSERT_NO_CONVE
   if (argc
       && SCHEME_CHARP(argv[0])
       && (SCHEME_CHAR_VAL(argv[0]) < 128)
+      && (argc > 1)
       && SCHEME_OUTPUT_PORTP(argv[1])) {
     char buffer[1];
     buffer[0] = SCHEME_CHAR_VAL(argv[0]);