[issue6198] test_float fails on Windows

[James Abbatiello]

New submission from James Abbatiello <abbeyj at gmail.com>:

test_float fails on Windows with:
======================================================================
FAIL: test_format_testfile (test.test_float.IEEEFormatTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "C:\Projects\python-trunk\lib\test\test_float.py", line 319, in
test_format_testfile
    self.assertEqual(fmt % float(arg), rhs)
AssertionError: '3' != '2'

----------------------------------------------------------------------


The problematic line from formatfloat_testcases.txt is:
%.0f 2.5 -> 2


On some systems *printf() uses round-to-even.  But the Windows CRT uses
round-half-away-from-zero.  Consider the following C code:
	printf("%+.1f -> %+.0f\n", -2.5, -2.5);
	printf("%+.1f -> %+.0f\n", -1.5, -1.5);
	printf("%+.1f -> %+.0f\n", +1.5, +1.5);
	printf("%+.1f -> %+.0f\n", +2.5, +2.5);

On Linux this will produce:
-2.5 -> -2
-1.5 -> -2
+1.5 -> +2
+2.5 -> +2

And on Windows:
-2.5 -> -3
-1.5 -> -2
+1.5 -> +2
+2.5 -> +3

----------
components: Tests, Windows
messages: 88922
nosy: abbeyj
severity: normal
status: open
title: test_float fails on Windows
versions: Python 2.7

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue6198>
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