[issue12291] file written using marshal in 3.2 can be read by 2.7, but not 3.2 or 3.3

[Vinay Sajip]

New submission from Vinay Sajip <vinay_sajip at yahoo.co.uk>:

The attached file 'data.bin' was written using Python 3.2. It can be read by Python 2.7, but in 3.2 and 3.3, after the first object is read, the file pointer is positioned at EOF, causing an error on subsequent reads. A simple test script 'marshtest.py' is below:

import marshal
import sys

f = open('data.bin', 'rb')
t = marshal.load(f)
print('Python version:', sys.version)
print('Object just loaded was:\n%r' % (t,))
print('File position is now at %d' % f.tell())
t = marshal.load(f)
print('Object just loaded was:\n%r' % (t,))
print('File position is now at %d' % f.tell())

Results of running it under various Python versions:

vinay at eta-natty:~/projects/scratch$ python marshtest.py 
('Python version:', '2.7.1+ (r271:86832, Apr 11 2011, 18:05:24) \n[GCC 4.5.2]')
Object just loaded was:
(u'text', u'alfa', 202, 1.0, '\x00\x00\x00\x01]q\x00K\x03a')
File position is now at 52
Object just loaded was:
(u'text', u'alfa', 212, 1.0, '\x00\x00\x00\x01]q\x00K\x03a')
File position is now at 104

vinay at eta-natty:~/projects/scratch$ python3.2 marshtest.py 
Python version: 3.2 (r32:88445, Mar 25 2011, 19:28:28) 
[GCC 4.5.2]
Object just loaded was:
('text', 'alfa', 202, 1.0, b'\x00\x00\x00\x01]q\x00K\x03a')
File position is now at 53617
Traceback (most recent call last):
  File "marshtest.py", line 9, in <module>
    t = marshal.load(f)
EOFError: EOF read where object expected

vinay at eta-natty:~/projects/scratch$ python3.3 marshtest.py 
Python version: 3.3a0 (default:8d4d87dd73ae, Apr  2 2011, 14:25:31) 
[GCC 4.5.2]
Object just loaded was:
('text', 'alfa', 202, 1.0, b'\x00\x00\x00\x01]q\x00K\x03a')
File position is now at 53617
Traceback (most recent call last):
  File "marshtest.py", line 9, in <module>
    t = marshal.load(f)
EOFError: EOF read where object expected

Note the size of the file is 53617 bytes.

vinay at eta-natty:~/projects/scratch$ ls -l data.bin
-rw------- 1 vinay vinay 53617 2011-06-09 09:33 data.bin

----------
files: data.bin
messages: 137943
nosy: vinay.sajip
priority: normal
severity: normal
status: open
title: file written using marshal in 3.2 can be read by 2.7, but not 3.2 or 3.3
versions: Python 3.2, Python 3.3, Python 3.4
Added file: http://bugs.python.org/file22289/data.bin

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue12291>
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