[Python-Dev] Bug in inspect module

[Ewan Mellor]

On Sat, Mar 17, 2007 at 08:09:06PM -0500, Collin Winter wrote:

> On 3/17/07, Ewan Mellor <ewan at xensource.com> wrote:
> >I have a problem being reported (by Xen users) where inspect.stack() is
> >throwing IndexError.  I think that this is a bug in inspect.py -- 
> >findsource
> >generally throws IOError when it can't find a particular source file, but 
> >in
> >the case where it finds a source file, but that file is shorter than 
> >expected,
> >then findsource throws IndexError, and this is propagated all the way out 
> >of
> >inspect.stack().
> >
> >I'm not sure why inspect.py is finding source files that don't match the 
> >code
> >being executed -- it seems to be dependent upon the install environment,
> >because it's not affecting most people.  That said, I think that it's
> >reasonable to cope with a too-short source file in the same way as we cope
> >with missing source files -- by throwing IOError from findsource and 
> >handling
> >that exception later.
> 
> FYI: this has been reported at least once before: see bug #1628987
> (http://python.org/sf/1628987). The problem (in the bug report, at
> least) is that the source file changes between compilation and when
> findsource() is called, and findsource() picks up the modified
> version.

Thanks for that.

It's certainly a mismatch between the compiled code and the source file
subsequently found.  That said, I don't think that it only affects the case
when people are editing source files and not recompiling -- this isn't the
sort of thing that my users would be doing at this point.  I suspect that the
source file lookup is broken in some way, and so the wrong file ends up in the
line cache.  It's not affecting me, unfortunately, so I can't easily
investigate.

I see that you closed this bug as "Won't Fix".  My two line patch seems like a
reasonable workaround, and certainly more simple than the other proposals --
do you think it's worth dropping in?

Cheers,

Ewan.