[Python-bugs-list] [ python-Bugs-603509 ] MemoryError when eval'ing string

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Bugs item #603509, was opened at 2002-09-02 15:56
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Category: Python Interpreter Core
Group: Python 2.3
Status: Open
Resolution: None
Priority: 5
Submitted By: Tim Peters (tim_one)
Assigned to: Martin v. Löwis (loewis)
Summary: MemoryError when eval'ing string

Initial Comment:
eval("'label;home;encoding=quoted-printable:r.'")

dies with a bogus MemoryError.  Assigned to Martin 
because this minimal substring dies the same way:

eval("'coding=q'")

Of course the result should be the string

    coding=q

Somehow it looks like parsing a string literal is getting 
mixed up with searching for a source-file encoding.

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>Comment By: Martin v. Löwis (loewis)
Date: 2002-09-02 19:40

Message:
Logged In: YES 
user_id=21627

The attached patch fixes the problem. It is still possible
to trick this code, with

eval("'#coding=q'")

I'm not really sure how to deal with that; I see the
following options:
1. tighten PEP 263 to require that the encoding comment is
the only thing in a source line.
2. perform some minimal scanning of the line, to see whether
we are inside a string literal when we see the #. This can
probably be tricked with a multi-line string.
3. perform source encoding analysis after in the tokenizer
proper, where comments are detected. This would be a heavy
change.
4. Just apply this patch, and wait until somebody complains.

Directions appreciated.

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