[ python-Bugs-1174606 ] Reading /dev/zero causes SystemError

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Bugs item #1174606, was opened at 2005-04-01 04:48
Message generated for change (Comment added) made by arigo
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Category: Python Interpreter Core
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Adam Olsen (rhamphoryncus)
Assigned to: Nobody/Anonymous (nobody)
Summary: Reading /dev/zero causes SystemError

Initial Comment:
$ python -c 'open("/dev/zero").read()'
Traceback (most recent call last):
  File "<string>", line 1, in ?
SystemError: ../Objects/stringobject.c:3316: bad
argument to internal function

Compare with this two variants:

$ python -c 'open("/dev/zero").read(2**31-1)'
Traceback (most recent call last):
  File "<string>", line 1, in ?
MemoryError

$ python -c 'open("/dev/zero").read(2**31)'
Traceback (most recent call last):
  File "<string>", line 1, in ?
OverflowError: long int too large to convert to int

The unsized read should produce either MemoryError or
OverflowError instead of SystemError.

Tested with Python 2.2, 2.3, and 2.4.

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>Comment By: Armin Rigo (arigo)
Date: 2005-04-01 09:58

Message:
Logged In: YES 
user_id=4771

I think that file.read() with no argument needs to be more conservative.  Currently it asks and trusts the stat() to get the file size, but this can lead to just plain wrong results on special devices.  (I had the problem that open('/dev/null').read() would give a MemoryError!)

We can argue whether plain read() on special devices is a good idea or not, but I guess that not blindly trusting stat() if it returns huge values could be a good idea.

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