[ python-Bugs-1005248 ] new.code() not cleanly checking its arguments

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Bugs item #1005248, was opened at 2004-08-07 20:01
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: Armin Rigo (arigo)
Assigned to: Nobody/Anonymous (nobody)
Summary: new.code() not cleanly checking its arguments

Initial Comment:
new.code() does not check its arguments properly:

>>> new.code(1,1,1,0,"123",(None,),(5,),(5,),"123","321",2,"")
Fatal Python error: non-string found in code slot

Here the tuple (5,) is used for co_names and co_varnames.

More generally it looks like this part of compile.c could do with quite some cleaning up.

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>Comment By: Armin Rigo (arigo)
Date: 2004-08-09 10:54

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Why do you check for argcount<0 but not nlocals<0, which also raises a SystemError?

More to the point, why on earth does PyCode_New() check for negative values of argcount and nlocals and not the other values?  A negative stacksize, for example, is likely to crash the interpreter too.  On the other hand, validating these numbers more precisely is much more complex, and not something we're trying to do here.  So I don't understand why these two values in particular are checked for < 0.  We should as well drop the check altogether.

My position here is that calling new.code() shouldn't do anything bad to the interpreter; but actually executing the resulting code object is allowed to destroy the sun (provided, of course, that CPython runs in an environment that allows that).

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Comment By: Michael Hudson (mwh)
Date: 2004-08-09 10:40

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Maybe new is meant to be scary, but current behaviour is going 
well above and beyond the effort required.  new.code can mutate 
a tuple containing string subclasses into a tuple containing exact 
strings!

Armin, what do you think of the attached?

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Comment By: Anthony Baxter (anthonybaxter)
Date: 2004-08-08 13:58

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I thought there was a general concensus that many things in
the 'new' module could be used to make a mess, and that
trying to fix them all was a pretty much open-ended task?


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