changeset:   68305:9e3b1d77b0f8
tag:         tip
user:        Victor Stinner <victor.stinner@haypocalc.com>
date:        Mon Mar 07 12:05:14 2011 +0100
files:       Lib/test/test_os.py Misc/NEWS Modules/_io/fileio.c
description:
Issue #11395: FileIO().write() clamps the length to 32,767 bytes

io.FileIO().write() clamps the data length to 32,767 bytes on Windows if the
file is a TTY to workaround a Windows bug. The Windows console returns an error
(12: not enough space error) on writing into stdout if stdout mode is binary
(python -u) and the length is greater than 66,000 bytes (or less, depending on
heap usage).


diff -r c6a8e7debbe5 -r 9e3b1d77b0f8 Lib/test/test_os.py
--- a/Lib/test/test_os.py	Sun Mar 06 09:06:34 2011 -0600
+++ b/Lib/test/test_os.py	Mon Mar 07 12:05:14 2011 +0100
@@ -97,6 +97,25 @@
             self.assertEqual(fobj.read().splitlines(),
                 [b"bacon", b"eggs", b"spam"])
 
+    def write_windows_console(self, *args):
+        retcode = subprocess.call(args,
+            # use a new console to not flood the test output
+            creationflags=subprocess.CREATE_NEW_CONSOLE,
+            # Use a shell to hide the console window (SW_HIDE)
+            shell=True)
+        self.assertEqual(retcode, 0)
+
+    @unittest.skipUnless(sys.platform == 'win32',
+                         'test specific to the Windows console')
+    def test_write_windows_console(self):
+        # Issue #11395: the Windows console returns an error (12: not enough
+        # space error) on writing into stdout if stdout mode is binary (python
+        # -u) and the length is greater than 66,000 bytes (or less, depending
+        # on heap usage).
+        code = "print('x' * 100000)"
+        self.write_windows_console(sys.executable, "-c", code)
+        self.write_windows_console(sys.executable, "-u", "-c", code)
+
 
 class TemporaryFileTests(unittest.TestCase):
     def setUp(self):
diff -r c6a8e7debbe5 -r 9e3b1d77b0f8 Misc/NEWS
--- a/Misc/NEWS	Sun Mar 06 09:06:34 2011 -0600
+++ b/Misc/NEWS	Mon Mar 07 12:05:14 2011 +0100
@@ -23,6 +23,12 @@
 - Issue #10829: Refactor PyUnicode_FromFormat(), use the same function to parse
   the format string in the 3 steps, fix crashs on invalid format strings.
 
+- Issue #11395: io.FileIO().write() clamps the data length to 32,767 bytes on
+  Windows if the file is a TTY to workaround a Windows bug. The Windows console
+  returns an error (12: not enough space error) on writing into stdout if
+  stdout mode is binary (python -u) and the length is greater than 66,000 bytes
+  (or less, depending on heap usage).
+
 - Issue #11246: Fix PyUnicode_FromFormat("%V") to decode the byte string from
   UTF-8 (with replace error handler) instead of ISO-8859-1 (in strict mode).
   Patch written by Ray Allen.
diff -r c6a8e7debbe5 -r 9e3b1d77b0f8 Modules/_io/fileio.c
--- a/Modules/_io/fileio.c	Sun Mar 06 09:06:34 2011 -0600
+++ b/Modules/_io/fileio.c	Mon Mar 07 12:05:14 2011 +0100
@@ -712,7 +712,14 @@
         errno = 0;
         len = pbuf.len;
 #if defined(MS_WIN64) || defined(MS_WINDOWS)
-        if (len > INT_MAX)
+        if (len > 32767 && isatty(self->fd)) {
+            /* Issue #11395: the Windows console returns an error (12: not enough
+               space error) on writing into stdout if stdout mode is binary
+               (python -u) and the length is greater than 66,000 bytes (or less,
+               depending on heap usage). */
+            len = 32767;
+        }
+        else if (len > INT_MAX)
             len = INT_MAX;
         n = write(self->fd, pbuf.buf, (int)len);
 #else