[Python-Dev] Bug in inspect module (original) (raw)

Ewan Mellor ewan at xensource.com
Sun Mar 18 11:49:03 CET 2007

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.

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