[Python-checkins] cpython (3.3): Issue #17835: Fix test_io when the default OS pipe buffer size is larger than

[antoine.pitrou]

http://hg.python.org/cpython/rev/4b4ed1e11fd0
changeset:   83517:4b4ed1e11fd0
branch:      3.3
parent:      83512:601570064725
user:        Antoine Pitrou <solipsis at pitrou.net>
date:        Wed Apr 24 23:31:38 2013 +0200
summary:
  Issue #17835: Fix test_io when the default OS pipe buffer size is larger than one million bytes.

files:
  Lib/test/support.py |  10 ++++++----
  Lib/test/test_io.py |   4 ++--
  Misc/NEWS           |   3 +++
  3 files changed, 11 insertions(+), 6 deletions(-)


diff --git a/Lib/test/support.py b/Lib/test/support.py
--- a/Lib/test/support.py
+++ b/Lib/test/support.py
@@ -573,10 +573,12 @@
 IPV6_ENABLED = _is_ipv6_enabled()
 
 
-# A constant likely larger than the underlying OS pipe buffer size.
-# Windows limit seems to be around 512B, and many Unix kernels have a 64K pipe
-# buffer size or 16*PAGE_SIZE: take a few megs to be sure.  This
-PIPE_MAX_SIZE = 3 * 1000 * 1000
+# A constant likely larger than the underlying OS pipe buffer size, to
+# make writes blocking.
+# Windows limit seems to be around 512 B, and many Unix kernels have a
+# 64 KiB pipe buffer size or 16 * PAGE_SIZE: take a few megs to be sure.
+# (see issue #17835 for a discussion of this number).
+PIPE_MAX_SIZE = 4 *1024 * 1024 + 1
 
 
 # decorator for skipping tests on non-IEEE 754 platforms
diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -3061,7 +3061,7 @@
             # The buffered IO layer must check for pending signal
             # handlers, which in this case will invoke alarm_interrupt().
             self.assertRaises(ZeroDivisionError,
-                        wio.write, item * (support.PIPE_MAX_SIZE // len(item)))
+                        wio.write, item * (support.PIPE_MAX_SIZE // len(item) + 1))
             t.join()
             # We got one byte, get another one and check that it isn't a
             # repeat of the first one.
@@ -3160,7 +3160,7 @@
         select = support.import_module("select")
         # A quantity that exceeds the buffer size of an anonymous pipe's
         # write end.
-        N = 1024 * 1024
+        N = support.PIPE_MAX_SIZE
         r, w = os.pipe()
         fdopen_kwargs["closefd"] = False
         # We need a separate thread to read from the pipe and allow the
diff --git a/Misc/NEWS b/Misc/NEWS
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -132,6 +132,9 @@
 Tests
 -----
 
+- Issue #17835: Fix test_io when the default OS pipe buffer size is larger
+  than one million bytes.
+
 - Issue #17065: Use process-unique key for winreg tests to avoid failures if
   test is run multiple times in parallel (eg: on a buildbot host).
 

-- 
Repository URL: http://hg.python.org/cpython